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 A MANUAL OF PALEONTOLOGY
 
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 I. 
 
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 DUPLICATE 
 
 PEABODY MUSEUM, YALE UNIV. 
 A 
 
 MANUAL OF PALEONTOLOGY 
 
 FOR THE USE OF STUDENTS 
 
 WITH A GENERAL INTRODUCTION ON THE 
 PRINCIPLES OF PALAEONTOLOGY 
 
 HENRY ALLEYNE NICHOLSON 
 
 M.D. D.Sc. M.A. PH.D. F.R.S.E. F.G.S. &c. 
 
 PROFESSOR OF NATURAL HISTORY AND BOTANY IN UNIVERSITY COLLEGE, TORONTO ; 
 
 FORMERLY LECTURER ON NATURAL HISTORY IN THE MEDICAL SCHOOL 
 
 OF EDINBURGH ; ETC. ETC. 
 
 WILLIAM BLACKWOOD AND SONS 
 
 EDINBURGH AND LONDON 
 
 MDCCCLXXII 
 
 All Rights are reserved
 
 PREFACE. 
 
 THE object of the present work is to furnish the student 
 of Geology and the general reader with a compendious 
 account of the leading principles and facts of the vast 
 and ever-increasing science of Palaeontology. In carry- 
 ing out this object, all superfluous details have been 
 rigidly excluded, and the Author has endeavoured to 
 restrict himself entirely to those facts which are abso- 
 lutely necessary to any one who would study Palaeon- 
 tology as a department of science, sufficiently distinct 
 to stand alone, and yet most closely connected with the 
 sciences of Zoology and Botany on the one hand, and 
 with Geology on the other hand. 
 
 In the First Part of the work is given a general ac- 
 count of the principles upon which the palasontological 
 observer proceeds. 
 
 In the Second Part of the work, Palaeontology, or the 
 past history of the Animal Kingdom, is treated of ; and 
 here much more space has been devoted to the Inver- 
 tebrate than to the Vertebrate groups upon the ground 
 that it is chiefly, or almost exclusively, with the former 
 that the ordinary palaeontological student has to deal. 
 
 The Third Part of the work gives a brief and very 
 general view of Palseobotany, or the past history of the
 
 vi PREFACE. 
 
 Vegetable Kingdom. This department of the subject 
 has not been treated at any length, partly because the 
 remains of plants are comparatively rare in the stratified 
 series, and partly because nothing less than a special 
 treatise would suffice to handle satisfactorily this obscure 
 and difficult branch of the subject. 
 
 The fourth and concluding portion of the work treats 
 of Historical, or, as it might be called, Stratigraphical, 
 Palaeontology namely, of the application of Palaeon- 
 tology to the elucidation of the succession of the strati- 
 fied deposits of the earth's crust. This department of 
 the subject has also been very briefly disposed of, not 
 because its intrinsic importance does not warrant a 
 more extended treatment, but because it is the Author's 
 intention, as his leisure will permit, to devote a separate 
 treatise to the consideration of this wide and compara- 
 tively independent section of the science. 
 
 In conclusion, the Author would beg his readers to 
 remember that there is no science which is growing so 
 rapidly, and which is as yet so comparatively in its 
 infancy, as Palaeontology ; and that there is none in 
 which the conclusions of to-day are more liable to be 
 vitiated by the discoveries of the morrow. Even whilst 
 these sheets have been going through the press, facts 
 have been brought to light which ought to have found 
 their place in a Manual of this kind, but which have 
 been of necessity altogether passed over, or, at best, 
 have been merely alluded to. For all deficiencies, there- 
 fore, arising from this cause, the Author has to beg the 
 kind indulgence of his readers. 
 
 With regard to the Illustrations, the Author has 
 gratefully to acknowledge the kindness of Alfred R. C.
 
 PREFACE. Vli 
 
 Selwyn, Esq., Director of the Geological Survey of 
 Canada, who placed at the Author's disposal a number 
 of engravings of Silurian and Devonian fossils, from the 
 publications of the Survey. The Author has likewise 
 to acknowledge a similar obligation to Principal Daw- 
 son, of M'Gill' University, Montreal, who kindly per- 
 mitted the use of several of the illustrations of his 
 ' Acadian Geology.' A considerable proportion of the 
 engravings, however, are taken from D'Orbigny's beau- 
 tifully illustrated ' Cours Elementaire de Paleontologie,' 
 by an arrangement with the publishers of that work. 
 
 UNIVERSITY COLLEGE, TORONTO, 
 October 16, 1872.
 
 CONTENTS. 
 
 PART I. GENERAL INTRODUCTION. 
 
 CHAPTER I. 
 
 PAGE 
 
 Definition of Palaeontology Definition of the term " fossil " Pro- 
 cesses of Fossilisation Definition of "rock" Classification of 
 Rocks, 1-5 
 
 CHAPTER II. 
 
 Characters of the Sedimentary Rocks Mode of formation of the Sedi- 
 mentary Rocks Definition of the term "formation" Chief 
 divisions of the Aqueous Rocks Mechanically-formed Rocks 
 Chemically-formed Rocks Organically-formed Rocks Different 
 ages of the Aqueous Rocks Chronological Succession of the 
 Stratified Rocks, .". . 5-14 
 
 CHAPTER III. 
 
 Use of the term "contemporaneous," as applied to groups of beds 
 General sequence of phenomena at the close of each Geological 
 Period Migrations Differences between the fossils of known 
 contemporaneous strata Geological continuity Relations be- 
 tween the Chalk and the Atlantic Ooze Reappearance of similar 
 forms of life under similar conditions Doctrine of " Colonies," 14-27 
 
 CHAPTER IV. 
 
 Causes of the Imperfection of the Palseontological Record Causes of 
 the absence of certain animals as fossils Unrepresented time 
 Unconformity, sequence of phenomena indicated by Leading 
 examples of unconformity Thinning out of beds Sudden ex- 
 tinction of Animals Disappearance of fossils, . "". 27-39 
 
 CHAPTER V. 
 
 Conclusions to be drawn from Fossils Age of Rocks Mode of origin 
 of any Fossiliferous bed Fluviatile, lacustrine, and marine deposits 
 Conclusions as to Climate, 4-44 
 
 CHAPTER VI. 
 
 Primary divisions of the Animal Kingdom Impossibility of a linear 
 Classification Tabular view of the chief divisions of the Animal 
 Kingdom General succession and progression of organic types, 44-55
 
 CONTENTS. 
 
 PAST II. PALEOZOOLOGY. 
 
 CHAPTER VII. 
 
 Zoological characters and chief divisions of the Protozoa Relations of 
 the Protozoa to time Characters of the Foraminifera Variations 
 of the test of the Foraminifera Structure of Eozoon Distribu- 
 tion of the Forminifera in time Characters of the Radiolaria, and 
 their distribution in time Characters of the Sponges, and their 
 geological distribution Stromatopora Receptaculites, . 59- 72 
 
 CHAPTER VIII. 
 
 General characters and chief divisions of the Coelenterata Distribu- 
 tion in time of Ccelenterate animals Orders of Hydrozoa not 
 represented as fossils Fossil Medusae and Sea-blubbers General 
 characters of the Corynida Palaeocoryne Corynoides General 
 characters of the Thecaphora Dendrograpsus Dictyonema 
 Structure and probable affinities of Oldhamia General characters 
 and distribution of the Graptolitidae Structure of a simple Grapto- 
 lite Reproduction of Graptolites Monoprionidian and Diprion- 
 idian forms Characters of the genus Graptolites Didymo- 
 grapsus Tetragrapsus Dichograpsus Rastrites Diplograpsus 
 
 Climacograpsus Dicranograpsus Phyllograpsus, . . 73-85 
 
 CHAPTER IX. 
 
 General facts as to the distribution of the Actinozoa in time Divisions 
 of the Zoantharia Characters of Z. malacodermata Characters 
 of Z. sclerobasica, and their distribution in time Nature of a 
 Sclerodermic coral Structure of a simple coral Gemmation and 
 fission amongst corals Deep-sea corals and reef-builders 
 Ancient coral-reefs Divisions and distribution in time of the 
 Zoantharia sclerodermata Characters of the Rugosa Recent 
 Rugose corals Operculate corals Families and distribution in 
 time of the Rugosa Tabular view of the divisions of the Zoan- 
 tharia sclerodermata and Rugosa Characters of the Alcyonaria 
 
 Distribution of the Alcyonaria in time ..... 85-102 
 
 CHAPTER X. 
 
 Characters of the Annuloida Characters of the Echinodermata Dis- 
 tribution of Echinodermata in time General characters of the 
 Echinoidea Structure of the test in Echinoids Spines and 
 tubercles Apical disc Regular and irregular Echinoids Peris- 
 choechinidx Distribution of Echinoids in time Chief families of 
 Echinoidea, their characters and distribution, . . . 102-110 
 
 CHAPTER XI. 
 
 Characters of the Asteroidea Features distinguishing them from the 
 Echinodermata General structure of a Starfish Differences 
 among them Diagram and structure of a Goniaster The internal 
 and integumentary skeletons Distribution of the Asteroidea in 
 time Characters of the Ophiuroidea General structure of an 
 Ophiuroid Their distribution in time ..... 110-117
 
 CONTENTS. 
 
 CHAPTER XII. 
 
 Characters of the Crinoidea General structure of a Crinoid Structure 
 of the column of the Crinoids Structure of the calyx Distribu- 
 tion of the Crinoids in time Crinoidea articulata and tesselata 
 Characters of the Cystoidea Structure of the column, calyx, 
 and appendages of the Cystideans Pectinated rhombs Distribu- 
 tion of the Cystideans in time Chief genera of Cystoidea Cha- 
 racters of the Blastoidea Structure of Pentremites Distribution 
 of Blastoidea in time Characters and distribution in time of the 
 Holothuroidea, . . ' : .'''.- . ~ : '/"" '"^ ': .' . 118-135 
 
 CHAPTER XIII. 
 
 Characters of the Annulosa Characters of the Annelida Characters 
 of the Tubicola Distribution of the Tubicola in time Cornulites 
 Conchicolites Serpulites Trachyderma Spirorbis Serpula 
 Ditrupa Characters of the Errant Annelides Scolithus 
 Arenicolites Tracks of Errant Annelides; .... 136-143 
 
 CHAPTER XIV. 
 
 Characters of Arthropoda Distribution of Arthropoda in time Cha- 
 racters of Crustacea Morphology of a typical Crustacean General 
 facts as to the past existence of Crustacea Table of the divisions 
 of the Crustacea Characters and divisions of the Cirripedia 
 Structure of the shell in the Balanidae Distribution of the Balan- 
 idae in time Characters and distribution of the Verrucidse Struc- 
 ture of the Pedunculated Cirripedes Distribution of the Lepadida? 
 in time, ; . 143-155 
 
 CHAPTER XV. 
 
 Characters and orders of the Entomostracous Crustaceans Ostracoda 
 Distribution of the Ostracoda in time Estheria Characters 
 and distribution in time of the Phyllopoda Characters of the 
 Trilobita General structure of a Trilobite Appendages of Tri- 
 lobites Systematic position of Trilobites Distribution of Trilo- 
 bites in past time Leading families of the Trilobita Characters 
 and divisions of the Merostomata Characters and distribution in 
 time of the Eurypterida Characters and distribution in time of 
 the Xiphosura, 155-175 
 
 CHAPTER XVI. 
 
 Characters of the Malacostrata Characters of the Edriophthalmata 
 Characters and distribution in time of the Amphipoda Cha- 
 racters and distribution in time of the Isopoda Characters of the 
 Podophthalmata Characters and distribution of the Stomapoda 
 Characters and distribution of the Decapoda Macrura Ano- 
 mura Brachyura, i75- l % 
 
 CHAPTER XVII. 
 
 Characters of the Arachnida General distribution of the Arachnida in 
 time Characters and distribution of the Scorpionidae Characters
 
 xii CONTENTS. 
 
 and distribution of the Araneida Characters and distribution 
 of the Myriapoda Characters and distribution in time of the 
 Insecta, . 181-187 
 
 CHAPTER XVIII. 
 
 General characters of the Mollusca General characters of the shell of 
 the Molluscs General distribution of the Mollusca in time Divi- 
 sions of the Mollusca Characters of the Polyzoa Structure of 
 the polypides and colonies of the Polyzoa Divisions of the Poly- 
 zoa Distribution of the Polyzoa in time, .... 187-198 
 
 CHAPTER XIX. 
 
 General characters of the Brachiopoda Structure of the shell of the 
 Brachiopods Oral processes and their supports Divisions of the 
 Brachiopods General distribution of the Brachiopoda in time 
 Characters, distribution in time, and leading genera of the Tere- 
 bratulidae Thecididae Spiriferidae Kininckidoe Rhynchonel- 
 lidae Strophomenidae Productidse Craniadae Discinidae 
 Lingulidae 198-214 
 
 CHAPTER XX. 
 
 General characters of the Lamellibranchiata Shell of the Lamelli- 
 branchs General distribution of the Lamellibranchiata in time 
 Ostreidae Aviculidae Mytilidoe Arcadae Trigoniadae Union- 
 idae Chamidas Hippuritidae Tridacnidse Cardiadae Lucin- 
 idae Cycladidre Cyprinidae Veneridae Mactridae Tellinidae 
 
 Solenidae Myacidae Anatinidae Gastrochaenidae Pholad- 
 idae, 214-240 
 
 CHAPTER XXI. 
 
 General characters of the Gasteropoda Shell of the Gasteropods 
 Siphonostomatous and Holostomatous Univalves Table of the 
 divisions of the Gasteropoda General distribution of the Gastero- 
 poda in time Strombidae Muricidae Buccinidae Conidae 
 Volutidae Cypneidae Naticidae Pyramidellidae Cerithiadae 
 Melaniadac Turritellidae Littorinidae Paludinidse Neritidae 
 
 Turbinidae Haliotida: Fissurellidae Calyptrseidae Patel- 
 lidat Dentalidse Chitonidae Opisthobranchiate Gasteropods 
 Tornatcllida; Bullidae Aphysiadae Pleurobranchida;, . 240-262 
 
 CHAPTER XXII. 
 
 Heteropoda Firolidas Atlantidae Pulmonate Gasteropods Heli- 
 cidz Limacidae Limmcidae Auriculidae Cyclostomidae 
 Aciculid*, 262-268 
 
 CHAPTER XXIII. 
 
 General characters of the Pteropoda General distribution of the 
 Pteropoda in time Hyalea Theca Conularia Tenta- 
 culites, i . 269-272
 
 CONTENTS. 
 
 CHAPTER XXIV. 
 
 General characters of the Cephalopoda Mandibles of the Cephalo- 
 pods Ink-sac, shell, and internal skeleton Divisions General 
 distribution of the Cephalopoda in time, . .' . . 272-277 
 
 CHAPTER XXV. 
 
 General characters of the Tetrabranchiata Anatomy of the Pearly 
 Nautilus Shell of the Tetrabranchiata Distribution of the 
 Tetrabranchiata in time Nautilidse Orthoceratidse Ammoni- 
 tidse Shell of the Ammonitidae Distribution in time of the 
 Ammonitidse Genera of the Ammonitidae, . . . 277-293 
 
 CHAPTER XXVI. 
 
 General characters of the Dibranchiate Cephalopods Distribution of 
 the Dibranchiata Octopoda Argonautidse Octopodidse De- 
 capoda Teuthidse Sepiadse Spirulidae Belemnitidae, . 293-299 
 
 CHAPTER XXVII. 
 
 General characters of the Vertebrata General structure of the Verte- 
 brate skeleton Classes of the Vertebrata General distribution 
 of Vertebrata in time, 299-306 
 
 CHAPTER XXVIII. 
 
 General characters of the Fishes Scales of Fishes Skeleton of 
 Fishes Limbs of Fishes Median fins of Fishes General dis- 
 tribution of Fishes in time, 306-315 
 
 CHAPTER XXIX. 
 
 Teieostean and Ganoid Fishes General characters of the Teleostei 
 Sub-orders of the Teleostei Malacopteri Anacanthini Acan- 
 thopteri Plectognathi - Lophobranchii General characters of 
 the Ganoidei General distribution of the Ganoids in time 
 Classification of the Ganoids Amiadee Lepidosteidse Lepi- 
 dopleuridae Crossopterygidae Families and distribution of the 
 Crossopterygious Ganoids Ostracostei Sturionidse, . . 315-333 
 
 CHAPTER XXX. 
 
 Elasmobranchii and Dipnoi General characters of the Elasmo- 
 branchii General distribution of the Elasmobranchii in time 
 Holocephali Plagiostomi, general characters and divisions of 
 Cestraphori Cestracionts of the Upper Ludlow Rocks Hybo- 
 donts and Acrodonts Selachii Batides General characters of 
 the Dipnoi Characters of the Barramunda Palseichthyes of Dr 
 Giinther, 334-345 
 
 CHAPTER XXXI. 
 
 Amphibia General characters of the Amphibia Distribution of 
 
 Amphibians in time Urodela Anoura Labyrinthodontia, 346-353
 
 CONTENTS. 
 
 CHAPTER XXXII. 
 
 Reptilia General characters of Reptiles Distribution of Reptiles- 
 Characters and geological distribution of the Chelonia Ophidia 
 Lacertilia Crocodilia, . .,.:..,.. , >'-. . , :. .. 353-368 
 
 CHAPTER XXXIII. 
 
 Extinct orders of Reptiles Characters and distribution of the Ichthy- 
 opterygia Sauropterygia Pterosauria Anomodontia Deino- 
 sauria, 368-381 
 
 CHAPTER XXXIV. 
 
 General characters of the Birds Skeleton Pectoral limbs Hind 
 limbs General distribution in time Foot-prints of Birds 
 General characters and geological history of the Natatore? Gral- 
 latores Cursores Rasores Scansores Insessores Raptores 
 Saurune, 381-396 
 
 CHAPTER XXXV. 
 
 General characters of Mammals Osteology of Mammals Limbs 
 
 Teeth General distribution of Mammals in time, . . 397-406 
 
 CHAPTER XXXVI. 
 
 Orders of Mammalia Characters and distribution of Monotremata 
 
 Marsupialia Edentata, 406-417 
 
 CHAPTER XXXVII. 
 
 Orders of Mammalia continued Characters and distribution in time 
 of the Sirenia Cetacea Calaenidae Catodontidae Delphinidae 
 Rhynchoceti Zeuglodontidae, . . . . . 417-422 
 
 CHAPTER XXXVIII. 
 
 Orders of Mammalia continued Characters and distribution of the 
 Ungulata Perissodactyles Rhinoceridoe Tapiridae- Palaeother- 
 idae Solidungula Artiodactyles Hippopotamidae Sinda 
 Anoplotheridae Ruminant ia Camelida; Moschidre Cervidae- 
 Camelopardalidx Cavicornia, 423-441 
 
 CHAPTER XXXIX. 
 
 Orders of Mammalia continued Characters and distribution in time 
 of the Hyracoidea Proboscidea Elephas Mastodon Deino- 
 therium, . . . . . . . . . . 441-447 
 
 CHAPTER XL. 
 
 Orders of Mammalia continued Characters and distribution in time 
 of the Carnivora Pinnigrada Plantigrada Ursidae Melidse 
 Digitigrada Mustelidae Viverridae Hysenidae Canidae 
 Felidas, . . :-i -<fl ..--.: . . . 447-456
 
 CONTENTS. XV 
 
 CHAPTER XLI. 
 
 Orders of Mammalia continued Characters and distribution in time 
 of Rodentia Leporidas . Cavidae - Hystricidae Castoridse 
 Muridae Dipodidse Myoxidae Sciuridae Cheiroptera Insec- 
 tivora Talpidae Soricidae Erinaceidae, . . < . . 456-463 
 
 CHAPTER XLII. 
 
 Orders of Mammalia continued Characters and distribution in time 
 of the Quadrumana Strepsirhina Platyrhina Catarhina 
 Characters and distribution in time of the Bimana, . . 464-469 
 
 PART IIL-PAL^OBOTANY. 
 
 CHAPTER XLIII. 
 
 Palaeobotany Divisions of the Vegetable Kingdom General Rela- 
 tions of Plants to time, 473*477 
 
 CHAPTER XLIV. 
 
 Pre-Carboniferous Floras Cambrian Plants Silurian Plants De- 
 vonian Plants, ,477-484 
 
 CHAPTER XLV. 
 
 Carboniferous Plants Origin and structure of Coal Ferns Calamites 
 Calamodendron Lepidodendroids Sigillarioids Coniferae 
 Cycadaceae Angiospermous Exogens Monocotyledons Per- 
 mian Plants, 485-496 
 
 CHAPTER XLVI. 
 
 Floras of the Secondary and Tertiary Periods Triassic Plants 
 Jurassic Plants Cretaceous Plants Eocene Plants Miocene 
 Plants Pliocene Plants, 496-503 
 
 PART IV. HISTORICAL PALEONTOLOGY. 
 
 CHAPTER XLVI I. 
 
 Historical Palaeontology Synopsis of the fossiliferous formations 
 Rocks of the Laurentian Period Life of the Period Rocks of 
 the Huronian Period Rocks of the Cambrian Period Lower 
 Cambrian Upper Cambrian Life of the Cambrian Period 
 Primordial Zone Skiddaw and Quebec Groups, . . 507-514 
 
 CHAPTER XLVIII. 
 
 Rocks of the Silurian Period Divisions of the Silurian Rocks in 
 
 Britain In North America Life of the Silurian Period, . 515-520
 
 xvi CONTENTS. 
 
 CHAPTER XLIX. 
 
 Rocks of the Devonian Period Old Red Sandstone Devonian 
 
 Rocks of N. America Life of the Devonian Period, . . 520-523 
 
 CHAPTER L. 
 
 Rocks of the Carboniferous Period Life of the Carboniferous Period 
 
 Rocks of the Permian Period Life of the Permian Period, 524-530 
 
 CHAPTER LI. 
 
 Rocks of the Triassic Period Rhaetic beds Life of the Triassic 
 
 Period, 530-535 
 
 CHAPTER LII. 
 Rocks of the Jurassic Period Life of the Jurassic Period, . . 535-539 
 
 CHAPTER LIII. 
 Rocks of the Cretaceous Period Life of the Cretaceous Period, 540-546 
 
 CHAPTER LIV. 
 
 Pakeontological break between the Secondary and Tertiary Rocks 
 Classification of the Tertiary Rocks Rocks of the Eocene 
 Period Life of the Eocene period, 546-552 
 
 CHAPTER LV. 
 Rocks of the Miocene Period Life of the Miocene Period, . 552-554 
 
 CHAPTER LVI. 
 
 Rocks of the Pliocene Period Life of the Pliocene Period Post- 
 Pliocene Period Pre-Glacial Deposits Pre-Glacial Mammals 
 Glacial Deposits Glacial Shells Post-Glacial Deposits Post- 
 Glacial Mammals, ........ 554-562 
 
 GLOSSARY, 563-585 
 
 INDEX, 586-601
 
 PART I. 
 
 GENERAL INTRODUCTION
 
 PAL^ONTO LOGY. 
 
 CHAPTER I. 
 
 INTRODUCTION. 
 
 DEFINITION OF PALAEONTOLOGY. 
 
 PALAEONTOLOGY (Gr. palaios, ancient ; onta, beings ; logos, dis- 
 course) is the science which treats of the living beings, whether 
 animal or vegetable, which have inhabited this globe at past 
 periods in its history. It is the ancient life-history of the earth, 
 and if its record could ever be completed, it would furnish us 
 with an account of the structure, habits, and distribution of all 
 the animals and plants which have at any time flourished upon 
 the land-surfaces of the globe or inhabited its waters. From 
 causes, however, which will be subsequently discussed, the 
 palaeontological record is most imperfect, and our knowledge 
 is interrupted by gaps which not only bear a large proportion 
 to our solid information, but which in many cases are of such 
 a nature that we can never hope to have them filled. 
 
 As Zoology, then, treats of the animals now inhabiting the 
 earth, and as Botany treats of the now existing plants, 
 Palaeontology may be considered as the Zoology and Botany 
 of the past. Regarding it from this, the only true point of 
 view, some knowledge of Zoology and Botany is essential to a 
 prosecution of the study of Palaeontology, and such details of 
 these sciences as may be deemed requisite will be introduced 
 in the proper place. The materials, again, which fall to be 
 studied by the palaeontologist, are derived entirely from the 
 proper province of the geologist. fossils are derived from 
 rocks. It will therefore be necessary to trespass to some ex- 
 A
 
 2 INTRODUCTION. 
 
 tent upon the peculiar domain of the geologist, and to obtain 
 some knowledge of the origin, composition, and mode of 
 occurrence of the rocks from which Palaeontology derives its 
 materials. Lastly, Palaeontology, apart from its own import- 
 ance as an independent science, is employed by the geologist 
 to assist him in his determination of the chronological succes- 
 sion of the materials which compose the crust of the earth. 
 Palaeontology, therefore, must be separately studied in its rela- 
 tion to historical Geology. 
 
 DEFINITION OF FOSSILS. 
 
 All the natural objects which come to be studied by the 
 palaeontologist are termed " fossils " (Lat. fossus, dug up). In 
 most cases, fossils, o'r, as they are often termed, " petrifactions," 
 are actual portions of animal or vegetable organisms, such as 
 the shells of Molluscs, the skeletons of Corals, the bones of Ver- 
 tebrate animals, the wood, bark, or leaves of plants, &c. ; and 
 these may be preserved very much in their original condition, 
 or may have been very much altered by changes subsequent to 
 their burial. Strictly speaking, however, by the term " fossil " 
 is understood " any body, or the traces of the existence of any 
 body, whether animal or vegetable, which has been buried in 
 the earth by natural causes " (Lyell). We shall find, therefore, 
 that we must include under the head of fossils objects which at 
 no time themselves formed parts of any animal or vegetable, 
 but which, nevertheless, point to the former existence of such 
 organisms, and enable us to reason as to their nature. Under 
 this head come such fossils as the moulds or " casts " of shells 
 and the footprints left by various animals upon sand or mud. 
 
 In the great majority of cases fossils are the remains of 
 animals or plants which are now extinct that is to say, which 
 no longer are in existence, but have entirely disappeared from 
 the earth's surface. In some cases, however, fossils are the 
 remains of recent animals that is, of animals which are still 
 found in a living condition upon the globe. The term " sub- 
 fossil," sometimes applied to these, has been more appropriately 
 applied in another sense, and is best discarded in this con- 
 nection. The terms " fauna " and " flora " are employed in 
 Palaeontology much as they are by the naturalist, to mean 
 the entire assemblage of the animals or of the plants respect- 
 ively belonging to a particular region or a particular time. 
 Thus we may speak of the " fauna " of the Carboniferous 
 Period, or the "flora" of the Tertiary Epoch, or the fauna of 
 the Chalk, or of any other set of beds.
 
 FOSSILISATION. 
 
 FOSSILISATION. 
 
 Fossilisation may be applied in a general sense to all the 
 processes through which an organic body passes in order to 
 become a fossil. Here we need only consider the three lead- 
 ing forms in which fossils present themselves. In the first 
 instance, the fossil is to all intents and purposes an actual 
 organic remain, being itself a fragment of an animal or plant. 
 Thus we may meet with fossil bones, shells, or wood, which 
 may have undergone certain changes, such as would be pro- 
 duced by pressure, by the deprivation of organic matter origi- 
 nally present, or by more or less complete infiltration with 
 mineral matter, but which, nevertheless, are practically the real 
 bodies they represent. As a matter of course, it is in the more 
 modern formations that we find fossils least changed from their 
 primitive condition, but all formations almost contain some 
 fossils in which the original structure is more or less com- 
 pletely retained. 
 
 In the second place, we very frequently meet with fossils in 
 the state of " casts " or moulds of the original organic body. 
 What occurs in this case will be readily understood if we ima- 
 gine any common bivalve shell, as an Oyster, or Mussel, or 
 Cockle, embedded in clay or mud. If the clay were sufficiently 
 soft and fluid, the first thing would be that it would gain access 
 to the interior of the shell and would completely fill up the 
 space between the valves. The pressure, also, of the surround- 
 ing matter would insure that the clay would everywhere ad- 
 here closely to the exterior of the shell. If now we suppose 
 the clay to be in any way hardened so as to be converted into 
 stone, and if we were to break 
 up the stone, we should obvi- 
 ously have the following state of 
 parts. The clay which filled the 
 shell would form an accurate 
 cast of the interior of the shell, 
 and the clay outside would give 
 us an exact impression or cast 
 of the exterior of the shell (fig. 
 
 l). We Should have, then, tWO Fig. i. 7 ngonia lotiga, showing casts 
 
 casts, an interior and an exterior, <L&^ " d interior of the shelL 
 and the two would be very dif- 
 ferent to one another, since the inside of a shell is very unlike 
 the outside. In the case, in fact, of many univalve shells, the 
 interior cast is so unlike the exterior or unlike the shell itself, 
 that it maybe difficult to determine the true origin of the former.
 
 4 INTRODUCTION. 
 
 It only remains to add that there is sometimes a further 
 complication. If the rock be very porous and permeable by 
 water, it may happen that the original shell is entirely dissolved 
 away, leaving the interior cast loose, like the kernel of a nut, 
 within the case formed by the exterior cast. Or it may happen 
 that subsequent to the attainment of this state of things, the 
 space thus left vacant between the interior and exferior cast 
 the space, that is, formerly occupied by the shell itself may 
 be filled up by some foreign mineral deposited there by the 
 infiltration of water. In this last case the splitting open of the 
 rock would reveal an interior cast, an exterior cast, and finally 
 a body which would have the exact form of the original shell, 
 but which would be really a much later formation, and which 
 would not exhibit under the microscope the minute structure 
 of shell. 
 
 In the third class of cases we have fossils which present with the 
 greatest accuracy the external form, and even sometimes the in- 
 ternal minute structure, of the original organic body, but which, 
 nevertheless, are not themselves truly organic, but have been 
 formed by a " replacement " of the particles of the primitive 
 organism by some mineral substance. The most elegant ex- 
 ample of this is afforded by fossil wood which has been " silici- 
 fied " or converted into flint. In this case we have a piece of 
 fossil wood, which presents the rings of growth and fibrous 
 structure of wood, and which under the microscope exhibits 
 even the minutest vessels which characterise ligneous tissue. 
 The whole, however, instead of being composed of the original 
 carbonaceous matter of the wood, is now converted into pure 
 flint. The only explanation which can be given of this by no 
 means very rare phenomenon, is that the wood must have 
 undergone a slow process of decay in water holding silica or 
 flint in solution. As each particle of the wood was removed 
 by decay, its place was taken by a particle of flint deposited 
 from the surrounding water, till ultimately the entire wood was 
 silicified. The replacing substance is by no means necessarily 
 flint, but may be iron-pyrites, oxide of iron, sulphur, &c. ; and it 
 is not uncommon to find many other fossils besides wood pre- 
 served in this way, such as shells, corals, or sponges. 
 
 DEFINITION OF ROCK. 
 
 The crust of the earth consists of various different materials, 
 produced at different successive periods, occupying certain 
 definite spaces, and not confusedly mixed together, but, on the 
 contrary, exhibiting a definite and discoverable order of arrange-
 
 CLASSIFICATION OF ROCKS. 5 
 
 ment. All these materials, however different in appearance, 
 texture, or mineral composition, are called "rocks" by the 
 geologist. The term " rock," then, is to be understood as ap- 
 plying to all the materials which compose the crust of the 
 earth. In the language of geology, the finest mud, the loosest 
 sand, and the most incoherent gravel, are just as much rocks as 
 are the hardest and most compact granites or limestones. 
 
 CLASSIFICATION OF ROCKS. 
 
 For the purposes of the palaeontologist all the rocks which 
 enter into the composition of the solid exterior of the earth 
 may be divided into two great classes : i. The Igneous 
 Rocks, which are formed within the body of the earth itself, 
 and which owe their structure and origin to the action of heat; 
 and 2, the Aqueous or Sedimentary Rocks, which are formed 
 at the surface of the earth, and which owe their structure and 
 origin to the mechanical action of water. The Igneous Rocks 
 are formed below the surface of the earth, are as a general rule 
 destitute of organic remains or fossils, and are mostly in the 
 form of unstratified masses. The Aqueous and Sedimentary 
 Rocks are formed at the surface by the disintegration and re- 
 construction of previously existing rocks, are mostly fossilifer- 
 ous, and are stratified i.e., are arranged in distinct layers or 
 " strata." The Sedimentary Rocks, as containing fossils, are the 
 only rocks which it is essential for the palaeontologist to be 
 acquainted with, and we shall very briefly consider their lead- 
 ing physical characters, their chief varieties, their mode of ori- 
 gin, and their historical succession. 
 
 CHAPTER II. 
 
 SEDIMENTARY ROCKS. 
 
 THE Sedimentary or Fossiliferous Rocks form the greater por- 
 tion of that part of the earth's crust which is open to our 
 examination, and are distinguished by the fact that they are 
 regularly " stratified," or arranged in distinct and definite layers 
 or " strata." These layers may consist of a single material, 
 as in a block of sandstone, or they may consist of different 
 materials. When examined on a large scale, they are always 
 found to consist of alternations of layers of different mineral
 
 6 INTRODUCTION. 
 
 composition. We may examine any given area, and find in it 
 nothing but one kind of rock sandstone, perhaps, or lime- 
 stone. In all cases, however, if we extend our examination 
 sufficiently far, we shall ultimately come upon different rocks ; 
 and, as a general rule, the thickness of any particular set of 
 beds is comparatively small, so that different kinds of rock 
 alternate with one another in comparatively small spaces. 
 
 As regards the origin of the Sedimentary Rocks, they are 
 for the most part " derivative" rocks, being derived from the 
 wear and tear of pre-existent rock. Sometimes, however, they 
 owe their origin to chemical or vital action, when they would 
 more properly be spoken of simply as Aqueous Rocks. As to their 
 mode of deposition, we are enabled to infer that the materials 
 which compose them have formerly been spread out by the 
 action of water, from what we see going on every day at the 
 mouths of our great'rivers, and on a smaller scale wherever there 
 is running water. Every stream, where it runs into a lake or 
 into the sea, carries with it a burden of mud, sand, and rounded 
 pebbles, derived from the waste of the rocks which form its bed 
 and banks. When these materials cease to be impelled by the 
 force of the moving water they sink to the bottom, the heaviest 
 pebbles, of course, sinking first, the smaller pebbles and sand 
 next, and the finest mud last. Ultimately, therefore, as might 
 have been inferred upon theoretical grounds, and as is proved 
 by practical experience, every lake becomes a receptacle for a 
 series of stratified rocks produced by the streams flowing into 
 it. These deposits may vary in different parts of the lake, 
 according as one stream brought down one kind of material, 
 and another stream contributed another material ; but in all 
 cases the materials will bear ample evidence that they were 
 produced, sorted, and deposited by running water. The finer 
 beds of clay or sand will all be arranged in thicker or thinner 
 layers or laminse ; and if there are any beds of pebbles these will 
 all be rounded or smooth, just like the water-worn pebbles of 
 any brook-course. In all probability, also, we should find in 
 some of the beds the remains of fresh-water shells or plants or 
 other organisms which inhabited the lake at the time these 
 beds were being deposited. 
 
 In the same way large rivers such as the Ganges or 
 Mississippi deposit all the materials which they bring down at 
 their mouths, forming in this way their "deltas." Whenever 
 such a delta is cut through, either by man or by some channel 
 of the river altering its course, we find that it is composed of a 
 succession of horizontal layers or strata of sand or mud, varying 
 in mineral composition, in structure, or in grain, according to
 
 CHIEF DIVISIONS OF THE AQUEOUS ROCKS. 7 
 
 the nature of the materials brought down by the river at 
 different periods. Such deltas, also, will contain the remains 
 of animals which inhabit the river, with fragments of the plants 
 which grew on its banks, or bones of the animals which lived 
 in its basin. 
 
 Lastly, the sea itself irrespective of the materials delivered 
 into it by rivers is constantly preparing fresh stratified de- 
 posits by its own action. Upon every coast-line the sea is 
 constantly eating back into the land and reducing its compo- 
 nent rocks to form the shingle and sand which we see upon 
 every shore. The materials thus produced are not, however, 
 lost, but are ultimately deposited elsewhere in the form of new 
 stratified accumulations, in which are buried the remains of 
 animals inhabiting the sea at the time. 
 
 Whenever, then, we find anywhere in the interior of the land 
 any series of beds having these characters composed, that is, 
 of distinct layers, the particles of which, both large and small, 
 show distinct traces of the wearing action of water whenever 
 and wherever we find such rocks, we are justified in assuming 
 that they have been deposited by water in the manner above 
 mentioned. Either they were laid down in some former lake 
 by the combined action of the streams which flowed into it ; 
 or they were deposited at the mouth of some ancient river, 
 forming its delta ; or they were laid down at the bottom of the 
 ocean. In the first two cases, any fossils which the beds 
 might contain would be the remains of fresh-water or terres- 
 trial organisms. In the last case, the majority, at any rate, of 
 the fossils would be the remains of marine animals. 
 
 The term "formation" is employed by geologists to express 
 " any group of rocks which have some character in common, 
 whether of origin, age, or composition " (Lyell) ; so that we 
 may speak of stratified and unstratified formations, aqueous 
 or igneous formations, fresh-water or marine formations, and 
 so on. 
 
 CHIEF DIVISIONS OF THE AQUEOUS ROCKS. 
 
 The Aqueous Rocks maybe divided into two great sections, 
 the Mechanically-formed and the Chemically-formed, includ- 
 ing under the last head all rocks which owe their origin to 
 vital action, as well as those produced by ordinary chemical 
 agencies. 
 
 A. MECHANICALLY-FORMED ROCKS. These are all those 
 Aqueous Rocks of which we can obtain proofs that then- 
 particles have been mechanically transported to their present
 
 8 INTRODUCTION. 
 
 site. Thus, if we examine a piece of conglomerate or pudding- 
 stone, we find it to be composed of a number of rounded 
 pebbles embedded in an enveloping paste or matrix. The 
 pebbles are worn and rounded, and thus show that they have 
 been subjected to much mechanical attrition, whilst they have 
 been mechanically transported for a greater or less distance 
 from the rock of which they originally formed part. In the 
 case of an ordinary sandstone, the component grains of sand 
 are equally the result of mechanical attrition, and have been 
 equally transported from a distance. In the case of still finer 
 rocks, such as shale, the particles have been so much water- 
 worn that their source cannot be recognised, though a micro- 
 scopical examination would reveal that their edges were all 
 worn and rounded. It follows from this that the mechanically- 
 formed Aqueous Rocks are such as can be proved to have been 
 derived from the abrasion of other pre-existent rock : hence 
 they are often spoken of as " Derivative Rocks." Every bed, 
 therefore, of any mechanically-formed rock, is an exact equiva- 
 lent of a corresponding amount of destruction of some older 
 rock. 
 
 The Mechanically-formed Rocks may be divided into the 
 two groups of the Arenaceous or Siliceous Rocks, and the 
 Argillaceous or Aluminous Rocks. In the Arenaceous group 
 are those Aqueous Rocks which are mainly composed of 
 smaller or larger grains of flint or silica. The chief varieties 
 are the various kinds of sand and sandstone, grits, and most 
 conglomerates and breccias. In the Argillaceous, group are 
 those Aqueous Rocks which contain a certain amount of clay 
 or hydrated silicate of alumina. Under this head come clays, 
 shales, marls, clay-slate, and most flags or flag-stones. 
 
 B. CHEMICALLY-FORMED ROCKS. In this section are com- 
 prised all those Aqueous Rocks which have been formed by 
 chemical agencies. As many of these chemical agencies, how- 
 ever, are exerted through the medium of living beings, whether 
 animals or plants, we get into this section a number of what 
 may be called " organically-formed" rocks. The most import- 
 ant of the Chemically-formed Rocks are the so-called Calcare- 
 ous Rocks, comprising all those which contain a large propor- 
 tion of carbonate of line, or are wholly made up of this substance. 
 We may also shortly notice coal and gypsum. 
 
 Chalk is merely a limestone which is soft and pulverulent, 
 with an earthy fracture. It is nearly pure carbonate of lime, 
 and is to a great extent an organically-formed rock, consisting 
 mainly of the minute calcareous shells of Foraminifcra, with 
 the calcareous shells of molluscs, sea urchins, sea-mosses, and
 
 CHIEF DIVISIONS OF THE AQUEOUS ROCKS. 9 
 
 the like. The nearest approach which we have at the present 
 day to chalk is probably to be found in the deposit called "ooze," 
 which forms a considerable portion of the bed of the deep At- 
 lantic, and which will be afterwards noticed at greater length. 
 
 Limestone is a hard and compact rock, and its many 
 varieties are formed in different ways, and differ from one 
 another in more or less important points. Though the sea 
 contains carbonate of lime in solution, no marine limestones 
 appear to be formed by chemical agency alone, but in all these 
 the lime is abstracted from the sea-water by the agency of 
 marine animals. Primarily, therefore, marine limestones are 
 organically-formed rocks, consisting almost entirely of corals, 
 shells, Crinoids, and other calcareous organisms. Such lime- 
 stones may fairly be compared to the great coral-reefs of the 
 Pacific and other warm seas. It is to be remembered, how- 
 ever, that many marine limestones are secondarily mechani- 
 cally-formed rocks. In these cases, the calcareous matter of 
 the rock has been originally separated by living beings, but 
 has then been transported by the waves, or by currents, to 
 certain localities at a distance, where it has been heaped up to 
 form a bed of limestone. 
 
 Other limestone deposits, such as the stalactites and stalag- 
 mites of caves, and the "calcareous tufa" and "travertine" of 
 some hot springs, are purely chemical in their origin, and owe 
 nothing to the operation of living beings. 
 
 Gypsum, in chemical composition, consists of sulphuric acid 
 in combination with lime and two atoms of water ; or, in other 
 words, it is a hydrated sulphate of lime. It commonly occurs 
 as a whitish or yellowish-white rock, something like loaf-sugar 
 to look at, generally arranged in distinct beds, but sometimes 
 in irregular cakes or veins. It is palaeontologically important 
 as occasionally yielding well-preserved fossils ; but its exact 
 mode of origin has not yet been fully worked out. 
 
 Coal is, in all those forms to which the name would ordin- 
 arily be applied, an organically-formed rock, and may be re- 
 garded as formed of compressed vegetable matter. In all its 
 varieties such as bituminous coal, anthracite, and lignite or 
 brown coal, it approximates more or less closely in chemical 
 composition to wood. It consists, namely, of from seventy 
 to eighty per cent of pure carbon, with varying quantities 
 of hydrogen and oxygen, and a small amount of earthy or 
 mineral matter which constitutes the ash. All coals occur in 
 the form of beds, intercalated with other stratified rocks ; and 
 there are innumerable gradations between pure coal, earthy 
 coal, and carbonaceous shale, till we reach ordinary shale.
 
 10 INTRODUCTION. 
 
 DIFFERENT AGES OF THE AQUEOUS ROCKS. 
 
 The two principal tests by which the age of any particular 
 bed, or group of beds, may be determined, are superposition 
 and organic remains a third test sometimes being afforded by 
 mineral characters. The first and most obvious test of the 
 age of any aqueous rock is rts relative position to other rocks. 
 Any bed or set of beds of sedimentary origin is obviously and 
 necessarily older than all the strata which surmount it, and 
 younger than all those upon which it rests. It is to be remem- 
 bered, however, that superposition can at best give us but the 
 relative age of a bed as compared with other beds of the same 
 region. It cannot give us the absolute age of any bed ; and if 
 we are ignorant of the age of any of the beds with which we 
 may be dealing, we have to appeal to other tests to learn 
 more than the mere order of succession in the particular 
 region under examination. 
 
 The second, and in the long-run more available, test of the 
 ages of the different sedimentary beds, is that afforded by their 
 organic remains. Still, this test is also by no means univer- 
 sally applicable, nor in all cases absolutely conclusive. Many 
 aqueous rocks are unfossiliferous through a thickness of 
 hundreds, or even thousands, of feet of little altered sediments ; 
 and even amongst beds which do contain fossils, we often 
 meet with strata of a few feet or yards in thickness, which are 
 wholly destitute of any traces of life. Many fossils, again, 
 range vertically through many groups of strata, and in some 
 cases even through several formations. Such fossils, there- 
 fore, if occurring by themselves, or considered apart from 
 other associated organisms, are not conclusive as to the age of 
 any particular set of beds. As the result, however, of com- 
 bined palaeontological and geological researches, it is now pos- 
 sible for us to divide the entire series of stratified deposits into 
 a number of definite rock-groups or formations, each of which 
 is characterised by possessing an assemblage of organic 
 remains which do not occur in association in any other 
 formation. Such an assemblage of fossils, characteristic of 
 any given formation, represents the life of the particular period 
 in which the formation was deposited. It follows from this, 
 that whenever we can get a group or collection of fossils from 
 any particular bed or set of beds, there is rarely any difficulty 
 in determining the precise geological horizon of the beds in 
 which the fossils occur. 
 
 With certain limitations, however, we may go much further 
 than this. Not only are the great formations characterised by
 
 CHRONOLOGICAL SUCCESSION OF AQUEOUS ROCKS. 1 1 
 
 special and characteristic assemblages of animals and plants ; 
 but, in a general way, each subdivision of each formation has 
 its own peculiar fossils, by which it may be recognised by 
 a skilled worker in paleontology. Whenever, for instance, 
 we meet in Britain with the fossils known as Graptolites, we 
 may be sure that we are dealing with Silurian Rocks. We 
 may, however, go much further than this. If the Graptolites 
 belong to certain genera, we may be sure that we are dealing 
 with Lower Silurian Rocks. Furthermore, if certain special 
 forms are present, we may be even able to say to what exact 
 part or subdivision of the Lower Silurian series they belong. 
 
 All these conclusions, however, would have to be accom- 
 panied by a tacit but well-understood reservation. No Grap- 
 tolites have ever been found in Britain out of rocks known 
 upon other grounds to be Silurian ; but there is no reason why 
 they might not at any time be found in younger deposits. In 
 the same way, the species and genera which we now regard as 
 characteristic of the Lower Silurians, might at any time be 
 found to have survived into the Upper Silurian period. We 
 should never forget, therefore, in determining the age of a rock 
 by palaeontological evidence alone, that we are always reason- 
 ing upon generalisations which are the result of experience 
 alone, and which may at any time be overthrown by fresh 
 discoveries. 
 
 CHRONOLOGICAL SUCCESSION OF THE AQUEOUS ROCKS. 
 
 , As the result of observations made upon the superposition of 
 rocks in different localities, from their mineral characters, and 
 from their included fossils, geologists have been able to divide 
 the entire stratified series into a number of different divisions 
 or formations, each characterised by a general uniformity of 
 mineral composition, and by a special and peculiar assemblage 
 of organic forms. Each of these primary groups is in turn 
 divided into a series of smaller divisions, characterised and 
 distinguished in the same way. It is not pretended for a mo- 
 ment that all these primary rock-groups can anywhere be seen 
 surmounting one another regularly. There is no region upon 
 the earth where all the stratified formations can be seen to- 
 gether; and, even when most of them occur in the same 
 country, they can nowhere be seen all succeeding each other 
 in their regular and uninterrupted succession. The reason of 
 this is obvious. There are many places to take a single ex- 
 ample where one may see the Silurian Rocks, the Old Red 
 Sandstone, and the Carboniferous Rocks succeeding one an-
 
 12 INTRODUCTION. 
 
 other regularly, and in their proper order. This is because 
 the particular region where this occurs was always submerged 
 beneath the sea while these formations were being deposited. 
 There are, however, many more localities in which one would 
 find the Carboniferous Rocks resting unconformably upon the 
 Silurians without the intervention of any strata which could be 
 referred to the Old Red Sandstone. This might arise from 
 one of two causes : i. The Silurians might have been elevated 
 above the sea immediately after their deposition, so as to form 
 dry land during the whole of the Old Red period, in which 
 case, of course, no strata of the age of the Old Red Sandstone 
 could possibly be deposited. 2. The Old Red Sandstone might 
 have been deposited upon the Silurian, and then the whole 
 might have been elevated above the sea, and subjected to an 
 amount of denudation sufficient to remove the Old Red Sand- 
 stone entirely. In this case, when the land was again sub- 
 merged, the Carboniferous Rocks, or any younger formation, 
 might be deposited directly upon Silurian strata. From one 
 or other of these causes, then, or from subsequent disturbances 
 and denudations, it happens that we can rarely find many of 
 the primary formations following one another consecutively 
 and in their regular order. 
 
 In no case, however, do we ever find the Old Red Sand- 
 stone resting upon the Carboniferous, or the Silurian Rocks 
 reposing on the Old Red. We have therefore, by a com- 
 parison of many different areas, an established order of succes- 
 sion of the stratified formations, as shown in the subjoined 
 ideal section of the crust of the earth (fig. 2). 
 
 The main subdivisions of the Stratified Rocks are -known by 
 the following names : 
 
 1. Laurentian. 
 
 2. Cambrian (with Huronian?). 
 
 3. Silurian. 
 
 4. Devonian or Old Red Sandstone. 
 
 5. Carboniferous. 
 
 8. Jurassic or Oolitic. 
 
 9. Cretaceous. 
 
 10. Eocene. 
 
 11. Miocene. 
 
 12. Pliocene. 
 
 13. Post-tertiary.
 
 IDEAL SECTION OF THE CRUST OF THE EARTH. I 3 
 
 IDEAL SECTION OF THE CRUST OF THE EARTH. 
 
 Fig. 2 . 
 
 ) Post-tertiary and Recent. 
 Pliocene. 
 
 Devonian or Old Red Sandstone. 
 
 Cambrian. 
 Huronian. 
 
 Laurentian.
 
 14 INTRODUCTION. 
 
 Of these primary groups, the Laurentian, Cambrian, Silu- 
 rian, Devonian, Carboniferous, and Permian are collectively 
 grouped together under the name of Primary or Paleozoic 
 Rocks (Gr. palaios, ancient ; zoe, life), because of the entire 
 divergence of their animals and plants from any now existing 
 upon the globe. The Triassic, Jurassic, and Cretaceous 
 systems are grouped together as the Secondary or Mesozoic 
 formations (Gr. mesos, intermediate; zoe, life), because their 
 organic remains are intermediate between those of the Pal- 
 aeozoic period, and those of more modern strata. The Eocene, 
 Miocene, Pliocene, and Post-tertiary Rocks are grouped together 
 under the head of Tertiary or Kainozoic Rocks (Gr. kainos, new ; 
 zoe, life), because their organic remains approximate in char- 
 acter to those now existing upon the globe. 
 
 CHAPTER III. 
 
 CONTEMPORANEITY OF STRATA AND 
 GEOLOGICAL CONTINUITY. 
 
 WHEN groups of beds in different parts of the earth's surface, 
 however widely separated from one another, contain the same 
 fossils, or rather an assemblage of fossils in which many iden- 
 tical forms occur, they are ordinarily said to be " contempora- 
 neous ; " that is to say, they are ordinarily supposed to belong 
 to the same geological period, and to have been formed at the 
 same time in the history of the earth. They would therefore 
 be unhesitatingly regarded as "geological equivalents," and 
 would be classed as Silurian, Devonian, Carboniferous, and so 
 on. It is to be remembered, however, that it is not necessary, 
 to establish such a degree of equivalency between widely 
 separated groups of strata, that the fossils of each should be 
 to any great extent specifically identical. It is sufficient that, 
 whilst some few species are identical in both, the majority of 
 the fossils should be "representative forms," or, in other words, 
 nearly allied species. It will be shown, however, that groups 
 of strata widely removed from one another in point of distance 
 can only exceptionally be " contemporaneous," in the strict 
 sense of this term. On the contrary, in so far as we can judge 
 from the known facts of the present distribution of living beings, 
 the occurrence of exactly the same fossils in beds far removed 
 from one another is primd, facie evidence, that the strata are
 
 CONTEMPORANEITY OF STRATA. 15 
 
 not exactly contemporaneous, but that they succeeded one 
 another in point of time, though by no long interval geologi- 
 cally speaking. 
 
 Most of the facts bearing upon this question may be elicited 
 by a consideration of such a widely extended and well-known 
 formation as the Mountain Limestone or Sub-Carboniferous 
 Limestone. This formation occurs in localities as remote 
 from one another as Europe, Central Asia, North America, 
 South America, and Australia ; and it is characterised by an 
 assemblage of well-marked fossils, amongst which Brachiopods 
 belonging to the genus Producta may be specially singled out. 
 Now, if we believe that the Carboniferous Limestone in all 
 these widely distant localities was strictly contemporaneous, 
 we should be compelled to admit the existence of an ocean 
 embracing all these points, and, in spite of its enormous ex- 
 tent, so uniform in temperature, depth, and the other condi- 
 tions of marine life, that beings either the same or very nearly 
 the same inhabited it from end to end. We can, however, 
 point to no such uniformity of conditions and consequent uni- 
 formity of life over any such vast area at the present day ; and 
 we have therefore no right to assume that this is the true 
 explanation of the facts. Indeed, this explanation would 
 almost necessarily lead us to the now abandoned theory that 
 each period in geological history was characterised by a special 
 group of organisms spreading over the whole globe, and that 
 there took place at the close of each period a general destruc- 
 tion of all existing forms of life, and a fresh creation of the new 
 forms characteristic of the next period. 
 
 In our inability, then, to accept this view, we must seek for 
 some other explanation of the observed facts. The most pro- 
 bable view, and the one which is supported most strongly both 
 by what we see at the present day and by what we learn from 
 numerous examples in past time, is this : The Carboniferous 
 Limestone was not deposited all over the world in one given 
 period, by one sea, or at exactly the same time ; so that it 
 cannot be said to be strictly " contemporaneous " wherever it 
 is found. This would imply a uniformity of conditions over 
 vast distances, such as exists nowhere at the present day, and 
 such as we have no right to assume ever existed. On the 
 contrary, the deposition of the Carboniferous Limestone must 
 have first taken place in one comparatively limited area say 
 in Europe where fitting conditions were present both for the 
 animals which characterise it, and for the formation of beds of 
 its peculiar mineral and physical characters. How wide this 
 area may have been, signifies very little. It may have been as
 
 16 INTRODUCTION. 
 
 large as the area now covered by the Pacific, or larger, and yet 
 it could not include all those localities in which strata of Car- 
 boniferous age with identical or representative fossils are 
 already known to exist At the close of the deposition of 
 the Carboniferous Limestone in its original area, the condi- 
 tions there present must be supposed to have become unsuit- 
 able for the further existence in that area of the assemblage of 
 animals which had been its inhabitants, or, at any rate, for a 
 great many of them. The change from suitable to unsuitable 
 conditions must, it is hardly necessary to say, have been an 
 extremely slow and gradual one ; and would doubtless be con- 
 nected with the progressive shallowing of the sea, the diversion 
 of old currents of heated water or the incoming of new currents 
 of cold water, or other physical changes tending to alter the 
 climatic conditions of the area. What, then, would be the 
 effect of such a change of conditions as we have supposed 
 upon the animals inhabiting the area? a. Some of them 
 would, doubtless, be sufficiently hardy and accommodating to 
 bear up under the new state of things ; and these would per- 
 sist into the ensuing period, without any perceptible change, it 
 might be, or more probably in the form of varieties or species 
 allied to the old ones. In this case, therefore, we should get 
 a certain number of species which would pass from the Car- 
 boniferous Limestone up into the Yoredale Series, the Mill- 
 stone Grit or the Coal-measures ; or, if we did not find any 
 species exactly the same in all these groups, we should still find 
 in the later groups some forms which would be varieties of those 
 of the older, or which would be allied or representative species. 
 
 l>. There would, in the second place, be a certain number of 
 species which would be utterly unable to withstand the altered 
 conditions of the area ; and these would gradually die out and 
 become wholly extinct. We should thus get a certain number 
 of fossils which would be either exclusively confined to the 
 Carboniferous Limestone in general, or which, perhaps, might 
 not be found out of the Carboniferous Limestone of a single 
 region, or even a single particular locality. 
 
 c. Lastly, some species would yield so far to the altered 
 conditions of the area that they would "migrate," and seek 
 elsewhere a more congenial home. This term is apt to convey 
 false impressions ; and it will be well here to consider what is 
 meant by the " migration " of species or groups of animals. It 
 is quite obvious that only animals like birds, mammals, insects, 
 &c., which enjoy when grown up the power of active locomo- 
 tion, can actually " migrate " in person, supposing they find 
 themselves placed under unfavourable conditions. There are
 
 CONTEMPORANEITY OF STRATA. I/ 
 
 many animals, however, such as most shell-fish, corals, sea- 
 urchins, &c., which have, when adult, either no power of chang- 
 ing their place, or at best a very limited one. Still in these 
 cases even, though the individual has no means of removing 
 his quarters to some more favoured spot, there may be a "migra- 
 tion " of the species from an unsuitable to a suitable locality. 
 This is effected through the medium of iheyottng, which have 
 the power of choosing where they will settle, and are endowed 
 with vigorous powers of locomotion. If, for example, a bed of 
 oysters should become placed under conditions unsuitable for 
 the development of these molluscs, it is clear that the old 
 oysters cannot change their location. The young oysters, 
 however, swim about freely; and these will move away from the 
 original bed till they find a place which will suit them. By a 
 repetition of this process there may be in course of time a re- 
 moval or " migration " of a species to almost any distance, irre- 
 spective of the fact that the adult is permanently rooted. 
 
 To return, then, to the case which we have been consider- 
 ing : When the conditions of life in the seas of the Carbonifer- 
 ous Limestone became unfavourable for the further existence of 
 their fauna, some species would migrate to a more congenial 
 area. In this way a greater or less number of the species 
 characteristic of the Carboniferous Limestone would ultimately 
 be transferred to some other area. Here they would mingle 
 with the forms already inhabiting that area, perhaps more or 
 less completely supplanting these, perhaps merely succeed- 
 ing in maintaining a more or less precarious existence. In 
 either case, their remains would be preserved in the sedimen- 
 tary deposits of the new area. When, ages afterwards, we come 
 to examine the crust of the earth geologically, we should find 
 these identical and characteristic species of fossils in the rocks 
 of the two areas, and we should say " these rocks are contem- 
 poraneous." It is clear, however, that we should be wrong in 
 so saying. The rocks in question would belong to the same 
 geological period, but they would belong to different stages of 
 the same period, and they would not be strictly contemporan- 
 eous. For deposits of this nature, believed to hold this relation 
 to each other, the term of " homotaxeous" has been proposed, 
 in place of the term " contemporaneous." 
 
 What has just been said about the Carboniferous Rocks 
 would apply with equal justice to all the great formations, and 
 to many of the smaller rock-groups all over the world. The 
 Silurian Rocks of Europe, North America, South America, 
 Australia, &c., contain very similar fossils, and are undoubtedly 
 " homotaxeous." Nothing, however, that we see at the present 
 B
 
 1 8 INTRODUCTION. 
 
 day can justify us in believing that these widely separated de- 
 posits are strictly " contemporaneous," in the sense that they 
 were deposited at exactly the same period of time. We should 
 have to believe, if this conclusion is to be justified, that in Silu- 
 rian times the ocean spread over a much larger area of the 
 earth's surface than it does now, and that its temperature and 
 depth were unnaturally uniform : and there are, perhaps, some 
 who would accept this view. What has been said about the Silu- 
 rian Rocks as a whole applies with still greater force to certain 
 of the minor subdivisions of the same, which contain many of 
 exactly the same specific forms in parts of the globe very 
 widely removed from one another. It is the very identity of 
 the fossils, however, which proves that the beds in question, 
 from their geographical position, cannot have been deposited 
 at exactly the same time, though they doubtless belong to the 
 same period, and may even be said to be related to one an- 
 other, as far as the identical fossils are concerned, by lineal 
 descent. Similar remarks might be made about the Devonian, 
 Permian, Triassic, Jurassic, Cretaceous, and other formations ; 
 but it is not necessary further to multiply examples. 
 
 If we consider the present state of things upon the globe, we 
 shall be further convinced of the justice of these views, which 
 were first prominently brought forward by Professor Huxley. 
 If we could suddenly remove the sea from the earth, we should 
 find at various points of the earth's surface deposits of different 
 kinds, now concealed from us by the ocean, or only partially 
 known by dredgings or soundings. Thus, we should find vast 
 accumulations of calcareous matter, in the form of coral-rock 
 and coral-reef, where now rolls the Pacific Ocean. In high 
 northern and low southern latitudes we should find great de- 
 posits of sand and mud, with angular blocks of stone, the 
 whole derived from the ice-clad regions of the poles. Over 
 vast areas, again, in the deep Atlantic, we should find an im- 
 palpable chalky mud, or "ooze." All these different deposits 
 are obviously and necessarily " contemporaneous," not only in 
 the geological acceptation of the word, but in its most literal 
 sense. In spite of this fact they would not contain the same 
 fossils ; and, indeed, they would be characterised by organic 
 remains which would be wholly different in each case. The 
 coral-reefs of the Pacific would be essentially characterised by 
 the abundance of the remains of reef-building corals, though 
 they would also present other tropical forms of life, especially 
 Brachiopods and Echinoderms. The glacial mud of the Polar 
 regions would contain the remains of Arctic molluscs, along 
 with such other animals as delight in severe cold. Lastly, the
 
 CONTEMPORANEITY OF STRATA. 19 
 
 ooze of the deep Atlantic would contain innumerable Foram- 
 inifera, along with siliceous Sponges, Sea-urchins, and Crinoids. 
 We learn, therefore, from this, that contemporaneous deposits 
 not only do not necessarily contain the same fossils, but that, 
 if widely separated geographically, they may be characterised 
 by wholly dissimilar assemblages of organisms. 
 
 It may happen, again, as pointed out by Sir Charles Lyell, 
 that deposits belonging to different geographical and zoological 
 provinces may, as regards space, be nearly approximated, and, 
 as regards time, may be actually contemporaneous, and yet 
 may not contain any fossils in common, or only a very few. If, 
 for example, any sudden upheaval were to lay bare what is now 
 the floor of the Red Sea together with that of the Mediter- 
 ranean, we should find the two areas to contain deposits actu- 
 ally synchronous as regards the time of their deposition, and 
 very near to one another in point of distance, and yet contain- 
 ing, upon the whole, entirely distinct groups of organic remains. 
 We learn, therefore, from this, that owing to the existence of 
 geographical barriers, it is possible for contemporaneous de- 
 posits to be found in close contiguity, in a single region, and 
 yet to contain very different fossils. 
 
 Again, we know from the researches of Professors Carpenter 
 and Wyville Thomson and Mr Gwyn Jeffreys, that deposits may 
 be formed, side by side, in a single ocean, and may yet differ 
 from one another altogether, both in mineral characters and in 
 their included fossils, though strictly contemporaneous in point 
 of time. Thus, in parts of the deep Atlantic where the tem- 
 perature of the bottom water is comparatively high, we have 
 the calcareous deposit of the ooze, abounding in Foraminifera, 
 Sponges, and Echinoderms. In certain other areas in the 
 same ocean, and in comparatively close contiguity with the 
 preceding, we have the temperature lowered by cold currents, 
 and we find a sandy deposit in process of formation, with a 
 fauna much more scanty than that of the ooze, and wholly 
 distinct from it. We thus learn that sedimentary deposits may 
 be strictly contemporaneous, and may be placed very near to 
 one another in point of distance, and yet may contain very 
 different fossils. 
 
 Lastly, synchronous deposits necessarily contain wholly dif- 
 ferent fossils, if one has been deposited by fresh water, and the 
 other has been laid down in the sea. The fresh-water deposits 
 of one period are obviously contemporaneous with the marine 
 formations of the same period, and they may not be far 
 removed from one another in point of distance, but they must 
 contain altogether different organic remains. The former will
 
 20 INTRODUCTION. 
 
 contain remains of the fresh-water and terrestrial animals of 
 the period, and of these only ; whilst the latter will principally, 
 if not exclusively, be characterised by the remains of marine 
 forms of life. In this way, there is reason to believe, may be 
 explained the differences between the fossils of the Old Red 
 Sandstone and of the Devonian Rocks, strictly so called. Both 
 are believed to have been deposited in the same geological 
 period, and to be truly " contemporaneous ; " but they do not 
 contain the same fossils. This may be readily explained, how- 
 ever, if we suppose the former to represent the fresh-water 
 deposits of the Devonian period, or to have been laid down in 
 an inland sea, whilst the latter is the true marine formation of 
 the same period. 
 
 We are now in a position very briefly to discuss the question 
 of what may be called "geological continuity." It has already 
 been stated that the entire series of Fossiliferous or Sedi- 
 mentary Rocks may be naturally divided into a certain num- 
 ber of definite rock-groups or " formations," each of which is 
 characterised by the possession of a peculiar and characteristic 
 assemblage of fossils, constituting, or rather representing, the 
 "life" of the "period" in which the formation was deposited. 
 The older geologists held, what probably every one would be 
 tempted to think at first, that the close of each formation was 
 characterised by a general destruction of the forms of life of 
 the period, and that the commencement of each new formation 
 was accompanied by the creation of a number of new animals 
 and plants, destined to figure as the characteristic fossils of 
 the same. This theory, however, not only invokes forces and 
 processes which it can in no way account for, but overlooks 
 the fact that most of the great formations are separated by 
 lapses of time, unrepresented perhaps by any deposition of 
 rock, or represented only in some particular area, and yet, 
 perhaps, as great as, or greater than, the whole time occupied 
 in the production of the formation itself. 
 
 Nowadays, most geologists hold that there was no such 
 sudden destruction of life at the close of each great geological 
 epoch, and no such creation of fresh forms at the commence- 
 ment of the next period. On the contrary, they hold that 
 there is a geological "continuity," such as we see in other 
 departments of nature, and that the lines which we draw 
 between the great formations merely mark periods of time in 
 which no rocks were laid down, or the rocks deposited in 
 which are at present unknown to us. 
 
 What are we to believe occurred at the close of any great 
 geological period say, the Cretaceous period? If we reject
 
 CONTEMPORANEITY OF STRATA. 21 
 
 the view that the close of the period was marked by a sudden 
 and universal extinction and destruction of the characteristic 
 Cretaceous forms of life, there is only one other view which 
 we can take. Confining our attention solely to those seas of the 
 period of which alone we know enough for safe reasoning, 
 we know that the close of the Cretaceous period in Europe 
 was accompanied, or rather caused, by an upheaval of the 
 Cretaceous area, and an obliteration of the Cretaceous sea. 
 This upheaval was, of course, effected with extreme slowness, 
 or, at any rate, not suddenly, and it must have completely 
 changed the life-conditions or "environment" of the animals 
 which swarmed in the Cretaceous seas. Some of these would 
 doubtless be unable to accommodate themselves to their 
 altered surroundings, and would simply die out. Others, we 
 may presume, would migrate to some more favourable area, 
 and some of these might accomplish their migration without 
 undergoing any change. Most, however, of the forms which 
 migrated, in the process of migration, and by reason of coming 
 into contact with strange neighbours and untried conditions, 
 would probably undergo more or less modification. Ulti- 
 mately, therefore, many characteristic Cretaceous forms might 
 be transferred to some sea far distant from their original home. 
 Not only so, but some of the transferred species might have 
 suffered so much modification that they would no longer be 
 regarded as specifically identical Avith the original Cretaceous 
 forms, but would be looked upon simply as allied or " repre- 
 sentative " species, though really the lineal descendants of the 
 animals of the Chalk. 
 
 It is perfectly clear that the process of rock - deposition 
 which was going on in Europe towards the close of the 
 Cretaceous period was not, and could not be, abolished by 
 the elevation of the European area, and the obliteration of the 
 Cretaceous sea, but was simply transferred to some other area. 
 In this particular case, we do not happen to know where the 
 new area of deposition may have been. It is quite certain, 
 however, that in whatever area the Cretaceous animals took 
 refuge, there rocks must have been deposited in course of 
 time, as they are in all seas, though it does not in the least 
 follow that the rocks of this new area should have the smallest 
 likeness in mineral composition to the Cretaceous sediments. 
 If we should at any time discover these rocks, it may pretty 
 safely be predicted what we should find in them in the way of 
 fossils. We should find, namely, some Cretaceous species, 
 probably unchanged ; with these there would be forms allied 
 to the Cretaceous species, but differing from them to a greater
 
 22 INTRODUCTION. 
 
 or less extent ; in addition, there would be a certain proportion 
 of forms of life wholly unknown in the Cretaceous Rocks ; and, 
 lastly, there would be a conspicuous absence of certain charac- 
 teristic species of the Chalk period. In other words, such 
 deposits as we have been speaking of would contain an assem- 
 blage of fossils more or less intermediate in character between 
 those of the true Cretaceous period and those of the lowest 
 Tertiary beds (Eocene), which rest upon the Chalk, or they 
 would present an intermixture of Cretaceous with Eocene 
 types. In point of fact, we have fragments of such interme- 
 diate deposits (in the Maastricht beds of Holland, the Pisolitic 
 Limestone of France, the Faxoe Limestone of Denmark, and 
 the Thanet Sands of Britain), and we find in them traces of 
 such an intermixture. 
 
 We may pause here to consider how it is that we may never 
 hope to find a complete series of deposits linking on one great 
 formation to another, as, for example, the Chalk to the Eocene 
 Rocks. In the first place, only a limited portion of the earth 
 has as yet been properly examined, and we have therefore no 
 right to expect that we have as yet hit upon the area, or areas, 
 to which the process of rock-forming was transferred at the 
 close of the Cretaceous period proper in Europe. We have, 
 however, the full right to expect that we shall ultimately find 
 formations which will have to be intercalated in point of time 
 between the White Chalk and the Eocene ; and, as before 
 said, traces of such are already known to us. In the second 
 place, we have every reason to suppose that many of these 
 intermediate deposits have been destroyed at some period sub- 
 sequent to their formation by what is technically called 
 " denudation," or, in other words, by the action of rain, rivers, 
 ice, and the sea. In the third place, many of the missing 
 deposits may have been concealed since their formation by 
 the deposition upon them of other newer rocks ; or they may 
 be situated in areas which are at present covered by the 
 ocean. Lastly, we must not forget that there may have been 
 times in which great changes in life were actively progressing 
 in areas in which there might be little or no contemporaneous 
 deposition of rock, so that the extreme terms of a series might 
 be preserved to us whilst all the intermediate links might have 
 escaped record. 
 
 From these and similar causes, it is almost certain that we 
 shall never be able to point to a complete series of deposits 
 linking one great geological period, such as the Cretaceous, to 
 another, such as the Eocene. Still, we may well have a strong 
 conviction that such deposits must exist, or must have existed,
 
 CONTEMPORANEITY OF STRATA. 23 
 
 as memorials of, at any rate, part of the time which elapsed 
 between the close of the one formation and the commence- 
 ment of the next. Upon any theory of " evolution," at any 
 rate, it is certain that there can be no total break in the great 
 series of the stratified deposits, but that there must have been 
 a complete continuity of life, and a more or less complete 
 continuity of deposition, from the Laurentian period to the 
 present day. There was, and could have been, no such con- 
 tinuity in any one given area ; but the chain could never have 
 been snapped at one point and taken up at a wholly different 
 one. The links must have been forged in different places, 
 but the chain, nevertheless, remained unbroken. From this 
 point of view, there would be little impropriety in saying that 
 we are living in the Silurian period ; but we could only say so 
 in a very limited sense. While most geologists will readily 
 admit that there must have been such an actual continuity of 
 the great geological periods, from the earliest times up to the 
 present day, it remains certain that we can never dispense with 
 the division of the stratified series into definite rock-groups 
 and life-periods. We can never hope to discover all the lost 
 links of the geological chain, and the great formations will 
 always be separated from one another by more or less evident 
 physical or palaeontological breaks, or by both combined. The 
 utmost we can at present do is to arrive at the conviction that 
 the lines of demarcation between the great formations only 
 mark gaps in our knowledge, and that there can be in nature 
 no hiatus in the long series of fossiliferous deposits. 
 
 The theory of " geological continuity," then, may in practice 
 be carried so far as to be useless, or even injurious to the progress 
 of science. This would seem to be the case with the attempt 
 to show that we " are still living in the Cretaceous period," 
 and that the ooze now forming at the bottom of the deep 
 Atlantic is merely a continuation in point of time of the great 
 and well-known formation of the White Chalk. The points of 
 resemblance by which this is sought to be established are 
 these: i. The Atlantic ooze or "abyssal mud" is a whitish 
 or grayish-looking mud, containing about sixty per cent of 
 carbonate of lime, with from twenty to thirty per cent of silica, 
 and a variable quantity of alumina. When dry, and espe- 
 cially if consolidated, it may fairly be compared in mineral 
 composition to some varieties of Chalk or to Chalk-marl. 2. 
 The abyssal mud of the Atlantic is to a very large extent com- 
 posed of the microscopic shells of Foraminifera, some of which 
 are specifically identical with Cretaceous forms, whilst White 
 Chalk is known to be very largely composed of the debris
 
 24 INTRODUCTION. 
 
 of these minute organisms. 3. The ooze contains siliceous 
 sponges, in many respects comparable to the sponges which 
 are so characteristic of the Cretaceous period. 4. The ooze 
 contains Echinoderms, especially Sea-urchins and Crinoids, 
 such as abounded in the Chalk period ; whilst one of the latter 
 is related to a Cretaceous type hitherto believed to be extinct. 
 5. We have reason to believe that the conditions under which 
 the Chalk was formed were very similar to those now present 
 in the Atlantic at great depths. 
 
 On the other hand, as pointed out by Sir Charles Lyell and 
 Mr Prestwich, the differences between the Atlantic ooze and 
 and the Chalk are, to say the least of it, quite as weighty as 
 the resemblances, if not more so. Chalk is composed of from 
 eighty to as much as ninety-nine per cent of carbonate of lime, 
 and has therefore a very small proportion of any siliceous 
 or aluminous impurity. Secondly, the occurrence of identical 
 species of Foraminifera in the two formations amounts to very 
 little ; for it is well known that such lowly organised forms of 
 life have an extraordinary power of persistence, surviving geo- 
 logical changes which are fatal to higher organisms. Lastly, 
 the most characteristic of the Chalk fossils, such as the various 
 forms of Cephalopoda and Bivalve Molluscs, are entirely want- 
 ing in the Atlantic ooze. 
 
 Mr Prestwich concludes that although it is probably true 
 that " some considerable portion of the deep sea-bed of the 
 mid-Atlantic has continued submerged since the period of 
 our Chalk, and although the more adaptable forms of life 
 may have been transmitted in unbroken succession through 
 this channel, the immigration of other and more recent faunas 
 may have so modified the old population that the original 
 Chalk element is of no more importance than is the original 
 British element in our own English people. As well might it 
 have been said in the last century that we were living in the 
 period of the early Britons, because their descendants and 
 language still lingered in Cornwall, as that we are living in the 
 Cretaceous period, because a few Cretaceous forms still linger 
 in the deep Atlantic. Period in Geology must not be con- 
 founded with ' system ' or ' formation.' The one is only 
 relative, the other definite. A formation is deposited or takes 
 place during a certain time, and that time is the period of the 
 formation ; but a geological period may include several forma- 
 tions, and is defined by the preponderance of certain orders, 
 families, or genera, according to the extent of the period 
 spoken of; and the passage of some of the forms into the next 
 geological series does not carry the period with them, any more
 
 CONTEMPORANEITY OF STRATA. 2$ 
 
 than would any particular historical epoch be delayed until the 
 survivors of the preceding one had died out. Period is an 
 arbitrary time-division. The Chalk or the ' London Clay ' 
 formations mark definite stratigraphical divisions. We may 
 speak of the period of the London Clay, or we may speak of 
 the Tertiary period. It merely refers to the ' time when ' 
 either were in course of construction. The occurrence of 
 Triassic forms in the Jurassic series, of Oolitic forms in the 
 Cretaceous series, and of Cretaceous forms in the Eocene, in 
 no way lessens the independence of each series, although it 
 may sometimes render it difficult to say where one series ceases 
 and the other commences. The land and littoral faunas are 
 necessarily more liable to change than a deep-sea fauna, 
 because an island or part of a continent may be submerged, 
 and all on it destroyed, while the fauna of the adjacent oceans 
 would survive ; and as we cannot suppose the elevation of 
 entire ocean-beds at the same time, the maritime fauna of one 
 period must be in part almost necessarily transmitted to the 
 next." 
 
 In accordance, therefore, with the principles here laid down, 
 we may conclude that it is not correct to say that we " are 
 living in the Cretaceous period," in any other sense than one 
 might say that we are living in the Silurian period, with this 
 difference, that the Cretaceous period is much nearer to us in 
 point of time than the Silurian, and that we can therefore trace 
 a relationship between certain Cretaceous types and certain 
 living forms that we can not hope to establish in the case of 
 Silurian fossils. 
 
 It is to be observed, lastly, that certain classes of animals 
 are always likely to flourish in places and times in which 
 favourable conditions are present, wholly irrespective of any 
 genetic connection between successive faunas. Thus, the con- 
 ditions present in the deep Atlantic are such as favour the 
 existence of numerous Foraminifera, Sponges, Echinoderms, 
 &c. Similar conditions existed in the seas in which the Chalk 
 was deposited ; and we need not, therefore, be surprised at the 
 predominance of similar organisms in the Cretaceous period. 
 In the same way, there are portions of the Carboniferous 
 Limestone fairly comparable to the Chalk in mineral characters 
 (making due allowance for difference of age), and containing 
 forms of life which may be regarded as representative of the 
 Cretaceous fauna such as Foraminifera, smooth Terebratulce, 
 Crinoids, and Sea-urchins. The conditions, however, present 
 in the deep Atlantic are not exactly similar to those under which 
 the Chalk was deposited, for there are certain great classes,
 
 26 INTRODUCTION. 
 
 such as the Cephalopoda, which abounded in the Cretaceous 
 seas, but which seem to have no representative in the abyssal 
 mud of the Atlantic. 
 
 DOCTRINE OF COLONIES. It only remains in this connec- 
 tion to consider very briefly the doctrine . of " colonies," laid 
 down by M. Barrande, the eminent Bohemian palaeontologist. 
 It has been laid down as a law that when once a species dis- 
 appears it never again makes its appearance in the geological 
 record. This is unquestionably true, so long as we remember 
 that it can only apply to cases in which a species has entirely 
 and totally disappeared from the earth, and that it is often 
 very difficult, or altogether impossible, to obtain evidence as 
 to the exact time at which a given species has thus become 
 actually extinct. There are plenty of cases in which a species 
 seemingly disappears in a particular set of rocks, to reappear 
 in some higher and later set of rocks in the same region, whilst 
 its remains are wanting in all the intermediate deposits of the 
 area. It also often occurs that a species, having disappeared 
 in one region, is found in deposits of a later age in another 
 area. The above-mentioned law, therefore, can obviously only 
 hold good of cases in which a species has definitely and finally 
 become extinct ; and this implies an amount of knowledge on 
 our part which we seldom or never possess. M. Barrande, 
 however, has pointed out that there are other cases in which 
 groups of species peculiar to one set of beds may appear in a 
 temporary and sporadic manner in a much earlier set of beds, 
 the two deposits thus characterised being separated by beds 
 containing fossils peculiar to the earlier and older series. 
 Thus, the Upper and Lower Silurian Rocks of Bohemia are 
 characterised by very distinct assemblages of fossils. It is 
 found, however, that the Lower Silurian Rocks contain in 
 places a group of fossils characteristic of the Upper Silurian 
 series. The beds containing this "colony" of Upper Silurian 
 forms are succeeded by strata filled with Lower Silurian fossils ; 
 and it is only after several alternations of this kind that the 
 Upper Silurian fauna comes in definitely and generally. These 
 temporary appearances of a later fauna in the midst of an older 
 fauna are termed by M. Barrande " colonies," and he explains 
 their occurrence as follows : If we suppose the seas of the 
 Bohemian area to have been peopled with Lower Silurian 
 animals at a time when other portions of Europe were covered 
 by a sea containing Upper Silurian animals, and suppose the 
 former area to have been shut off from the latter by a land- 
 barrier, we can readily understand how the " colonies" were 
 produced. If, from any cause, a channel of communication
 
 IMPERFECTION OF PAL^EONTOLOGICAL RECORD. 2/ 
 
 were opened between the Bohemian area and the general area 
 of Northern Europe, an immigration of species would take 
 place from the latter into the former area. The Upper 
 Silurian species of the latter area would thus be imported, in 
 greater or less numbers, into the midst of the general Lower 
 Silurian fauna of Bohemia, and would be preserved in the 
 Lower Silurian Rocks. If, however, the channel of com- 
 munication were speedily closed, so that the new-comers 
 could not be constantly reinforced by fresh immigrants, the 
 " colonial " species would die out, and the general Lower 
 Silurian fauna would again reign supreme. A reopening of 
 the channel of communication would allow of a fresh immigra- 
 tion and the formation of a fresh " colony," and the process 
 might be indefinitely repeated. Finally, however, we must 
 suppose that the Bohemian area was permanently thrown open 
 to immigration from the general European area, when the 
 Upper Silurian fauna of the latter would succeed in per- 
 manently and completely displacing the old Lower Silurian 
 fauna of the former region. The phenomenon, therefore, of 
 " colonies," may be defined as "the coexistence of two general 
 faunas, which, considered in their entirety, are nevertheless 
 distinct ; " and it is to be regarded as merely a case of migra- 
 tion under certain peculiar and exceptional circumstances. 
 
 CHAPTER IV. 
 
 THE IMPERFECTION OF THE PAL^ONTOLOGICAL 
 RECORD. 
 
 As has been already pointed out, the series of the stratified 
 formations is an imperfect one, and is likely ever to remain so. 
 The causes of this " imperfection of the geological record," as it 
 has been termed by Darwin, are various ; but it is chiefly to be 
 ascribed to our as yet incomplete knowledge of the geology of 
 vast areas of the earth's surface, to denudation, and to the fact 
 that many of the missing groups are buried beneath other de- 
 posits, whilst more than half of the superficies of the globe is 
 hidden from us by the waters of the sea. The imperfection of 
 the geological record necessarily implies an equal imperfection 
 of the " palaeontological record;" but, in truth, the record of 
 life is far more imperfect than the mere physical series of de- 
 posits. As we are here chiefly concerned with the biological
 
 28 INTRODUCTION. 
 
 aspect of the question, we may advantageously consider some 
 of the main causes of the numerous breaks and gaps in the 
 palaeontological record at some length. 
 
 I. CAUSES OF THE ABSENCE OF CERTAIN ANIMALS IN 
 FOSSILI FERGUS DEPOSITS. In the first place, even if the series 
 of the stratified deposits had been preserved to us in its entirety, 
 and we could point to the sedimentary accumulations belong- 
 ing to every period of the earth's history, there would still be 
 enormous deficiencies in the palaeontological record, owing to 
 the differences in the facility with which different animals may 
 be preserved as fossils. This subject is sufficiently important 
 to render it advisable to consider each of the primary groups 
 of the animal kingdom separately from this point of view : 
 
 a. Protozoa. As regards the sub-kingdom of the Protozoa, 
 the entire classes of the Gregarinidtz and Infusorian Animal- 
 cules, from their absence of hard parts, must ever remain un- 
 represented in a fossil condition. One or two of the latter, 
 however, possess an integumentary covering capable under 
 favourable circumstances of being preserved in rocks of recent 
 age. The Monera present no structures capable of fossilisa- 
 tion ; and the same may be said of the Amoebea, though one or 
 two of the latter have a carapace which might possibly be pre- 
 served. The remaining Rhizopodous orders viz., the Fora- 
 minifera, Radiolaria, and Spongida almost invariably develop 
 hard structures of lime or flint ; and all these orders, therefore, 
 have left abundant traces of their existence in past time. 
 
 b. Ccelenterata. Amongst the Ccelenterate animals, the 
 Fresh-water Polypes (Hydra), the Oceanic Hydrozoa, the Jelly- 
 fishes (Medusidce), the Sea -blubbers (Luccrnarida), the Sea- 
 anemones (Actinida), and the Ctenophora are destitute of hard 
 parts which could be preserved as fossils. The Sea-blubbers, 
 however, supply us with an instance of how a completely soft- 
 bodied creature may leave traces of its past existence; for there 
 is no doubt that impressions left by the stranded carcasses of 
 these animals have been detected in certain fine-grained rocks 
 (the Lithographic Slate of Solenhofen). On the other hand, 
 the coralligenous Zoophytes or "corals" (comprising the /.oan- 
 tharia sclerodermata and sclerobasica, and most of the Aleyonaria} 
 possess hard parts capable of preservation, and the same is the 
 case with most of the Hydroid Zoophytes. Accordingly, there 
 are few more abundant fossils than corals ; whilst the large ex- 
 tinct group of the Graptolitcs is generally placed in the vicinity 
 of the Sea-firs (Sertularians). 
 
 c. Annuloida. In this sub-kingdom the great class of the 
 Echinodermata may be said to be represented more or less
 
 IMPERFECTION OF PAL^ONTOLOGICAL RECORD. 29 
 
 completely by all its orders. In the Sea-cucumbers (Holothur- 
 oidea), however, the calcareous structures so characteristic of 
 the integuments of the other Echinoderms are reduced to their 
 minimum ; and accordingly the evidence of the past existence 
 of these creatures is of the most scanty description. The other 
 great class of the Annuloida (viz., the Scoledda) comprises 
 animals almost without exception destitute of hard parts, and 
 which mostly live parasitically in the interior of other animals 
 (e.g., the Tape -worms, Suctorial -worms, Round -worms, &c.) 
 We are therefore without any geological evidence of the former 
 existence of Scoledda, though no doubt can be reasonably 
 entertained but that the group dates back to a time long an- 
 terior to the present fauna. 
 
 d. Anmdosa. Many of the lower Annulose animals, such 
 as Leeches, Earth-worms, and Errant Annelides, possess no 
 structures by which we could expect to get direct evidence of 
 their past existence. The last of these, however, have left 
 ample traces of their former presence in the form of burrows 
 or "tracks" upon the mud and sand of ancient sea-bottoms; 
 and the so-called " Tubicolar " Annelides are well represented 
 by their investing tubes. In the case of the higher Annulosa, 
 another law steps in to regulate their comparative abundance 
 as fossils. Most, in fact almost all, fossiliferous formations 
 have been deposited in water; and of necessity, therefore, most 
 fossils are the remains of animals whose habits are naturally 
 aquatic. As most deposits, further, are not only aqueous, but 
 are also marine, most fossils are those of sea -animals. It 
 follows, therefore, that the remains of air-breathing animals, 
 whether these be terrestrial or aerial, can only be preserved in 
 an accidental manner, so to speak ; except the animal inhabit 
 water (as the Cetaceans do), or except in the rare instances in 
 which old land-surfaces have been buried up by sediment, and 
 thus partially kept for our inspection. In accordance with this 
 law, the most important and abundant fossil Annulose animals 
 are Crustaceans ; since these not only have a resisting shell or 
 " exoskeleton," but are also generally aquatic in their habits. 
 The air-breathing classes of the Myriapoda (Centipedes and 
 Millipedes), the Arachnida (Spiders and Scorpions), and the 
 Insecta or true Insects, on the other hand, have been much 
 less commonly and completely preserved, though many of 
 them are perfectly capable of being fossilised. Almost all such 
 remains, however, as we have of these three great classes, are - 
 the remains of isolated individuals, which may have been 
 accidentally drowned; or else they occur in hollow trees, or in 
 fragments of ancient soils, or in vegetable accumulations such
 
 30 INTRODUCTION. 
 
 as coal and peat. There is, however, a considerable number 
 of aquatic insects (but exclusively in fresh water), and there 
 are many insects the larvae of which inhabit water, whether 
 this be fresh or salt ; so that instances of these occurring as 
 fossils are not very infrequent 
 
 e. Mollusca. This sub-kingdom requires little notice, since 
 the greater number of its members possess hard structures 
 capable of being preserved in a fossil condition. Thus, the 
 horny or calcareous polypidoms of many of the Polyzoa, the 
 shells of the Brachiopods, the true Bivalves, and most of the 
 Gasteropoda, the internal skeletons of the Cuttle-fishes, and 
 the chambered shells of the Tetrabranchiate Cephalopods, all 
 occur more or less abundantly as fossils. The entire class of 
 the Tunicaries, however, presents (with one or two exceptions) 
 no hard structures, and is hence not with certainty known by 
 any fossil representative. Amongst the Gasteropoda, again, 
 the Sea-slugs and their allies (Nudibranchiatd) possess no shell, 
 and are unknown to the paleontologist ; whilst the shell of the 
 Land-slugs is extremely minute, and has not been certainly 
 recognised as fossil. Lastly, the air-breathing terrestrial Mol- 
 luscs, from their habits, rarely occur as fossils ; whilst those 
 which inhabit rivers, ponds, and lakes are less largely repre- 
 sented than marine forms, owing to the preponderance of salt- 
 water deposits over those of fresh water. 
 
 f. Vertebrata. The majority of Vetebrate animals possess a 
 bony skeleton, so that their preservation in a fossil state so 
 far as this point is concerned is attended with no difficulty. 
 Some of the fishes, however (such as the Lancelet, the Hag- 
 fishes, and the Lampreys), have no scales, and either possess no 
 " endoskeleton " or have one which is almost wholly cartila- 
 ginous. The only evidence, therefore, which could be obtained 
 of the past existence of such fishes would be afforded by their 
 teeth ; but these are wanting in the Lancelet, and are very 
 small in the Lampreys : so that we need not wonder that these 
 fishes are unknown as fossils. The higher groups of the fishes, 
 however, taking everything into consideration, may be said to 
 be abundantly represented in a fossil condition by their scales, 
 bones, teeth, and defensive spines. 
 
 The Amphibians are tolerably well represented by their 
 bones and teeth, and, as regards one extinct order, by integu- 
 mentary plates as well. They have also left many traces of 
 their existence in the form of footprints. Most living Amphi- 
 bians, however, frequent fresh waters, or spend a great part of 
 their time upon the land ; and hence their remains would not 
 be apt to be preserved in marine deposits.
 
 IMPERFECTION OF PAL^EONTOLOGICAL RECORD. 31 
 
 The abundance of Reptiles as fossils naturally varies much, 
 according to the habits of the different orders. Of the living 
 orders, the Chelonians (Tortoises and Turtles) are by no means 
 rare ; since many of them are habitual denizens of fresh water 
 or of the sea, whilst all are provided with a hard integumentary 
 skeleton. The Snakes are mainly represented by forms which 
 frequented water, and especially by marine forms. The Lizards 
 (Laccrtiliat) live mainly upon the land, and do not therefore 
 abound as fossils ; but some extinct forms (the Mosasauroids) 
 were marine in their habits, and have consequently been pretty 
 fully preserved. The Crocodilia, again, are so essentially aquatic 
 in their habits, that their comparative frequency in aqueous 
 deposits is no matter of wonder, especially if we recollect that 
 many of the extinct members of this order seem to have fre- 
 quented the sea itself. Of the extinct orders of Reptiles, the 
 great Ichthyosauri and the Plesiosauri and their allies were 
 marine in their habits, and their remains occur in what may 
 fairly be called profusion. The Flying Reptiles, or Ptero- 
 dactyles, would not seem to have any better chance of being 
 preserved than Birds, if as good, yet their remains occur by 
 no means very rarely in certain formations. The terrestrial 
 Deinosaurs and Dicynodonts, again, come very much under the 
 laws which regulate the preservation of Mammals as fossils ; 
 and their remains are chiefly, but not exclusively, to be found 
 in fluviatile deposits. 
 
 As regards Birds, their powers of flight, as pointed out by 
 Sir Charles Lyell, would save them from many destructive 
 agencies, and the lightness of their bones would favour the 
 long floating of the body in water, and thus increase the 
 chances of its being devoured by predaceous animals. In ac- 
 cordance with these considerations the most abundant remains 
 of Birds are referable to large wingless forms, to which the 
 power of saving themselves from their enemies by flight was 
 denied, whilst most of their bones were filled with marrow in- 
 stead of air. Next in abundance after these come the remains 
 of birds which frequent the sea-shore, lakes, estuaries, or rivers, 
 or which delight in marshy situations. 
 
 Lastly, as regards Mammals, the record is far from being a 
 full one, and from obvious causes. The great majority of 
 Mammals live on land, and therefore are not likely to be 
 buried in aqueous, and especially in marine, accumulations. 
 That this cause is the chief one which has operated against the 
 frequent preservation of Mammalian remains is shown by the 
 fact that when we exhume an old land-surface, the remains of 
 Mammals may be found in tolerable plenty. The strictly
 
 32 INTRODUCTION. 
 
 aquatic Mammals such as Whales, Dolphins, and the like 
 are, of course, much more likely to have been preserved as 
 fossils than the strictly terrestrial forms; but their want of 
 integumentary hard structures places them at a disadvantage 
 in this respect as compared with fishes. In a general way, we 
 may conclude that the preservation of the terrestrial Mam- 
 mals as fossils is due to the comparatively rare occurrence of a 
 stray individual being killed whilst swimming a river or some 
 other piece of water, or being mired in a bog, or to the bones 
 of one that had died on land being washed into some stream 
 by floods ; but there are other cases for which a different ex- 
 planation must be sought. 
 
 II. UNREPRESENTED TIME. In the second place, we have 
 seen that the geological record is very imperfect, and this of 
 necessity causes vast gaps in our palasontological knowledge. 
 In this connection we may briefly consider the evidence which 
 we possess as to the immensity of the "unrepresented time" 
 between some of the great formations, and no better example 
 can be chosen than that of the Cretaceous and Eocene Rocks. 
 In considering such a case, the evidence may be divided into 
 two heads, the one palaeontological, the other purely physical, 
 and each may be looked at separately. 
 
 The Chalk, as is well known, constitutes in Britain the 
 highest member of the Cretaceous formation, and is the highest 
 deposit there known as appertaining to the great Secondary or 
 Mesozoic series. It is directly overlaid in various places by 
 strata of Eocene age, which form the base of the great Tertiary 
 or Kainozoic series of rocks. The question, then, before us is 
 this, What evidence have we as to the lapse of time repre- 
 sented merely by the dividing-line between the highest beds of 
 the Chalk and the lowest beds of the Eocene ? 
 
 Taking the palsontological evidence first, it is found that 
 out of five hundred species of fossils known in the Upper Cre- 
 taceous beds, only one Brachiopod and a few Foraminifera 
 have hitherto been detected in the immediately overlying 
 Eocene beds. These latter, on the contrary, are replete with 
 organic remains wholly distinct from those of the Cretaceous 
 beds. It may be said, therefore, that the very extensive as- 
 semblage of animals which lived in the later Cretaceous seas 
 of Britain had entirely passed away and become a thing of the 
 past, before a single grain of the Eocene Rocks had been de- 
 posited. Now, it is of course open to us to believe that the 
 animals of the Chalk sea were suddenly extinguished by some 
 natural agencies unknown to us, and that the animals of the 
 Eocene sea had been in as sudden and as obscure a manner
 
 IMPERFECTION OF PAL^ONTOLOGICAL RECORD. 33 
 
 introduced en masse into the same waters. This theory, how- 
 ever, calls upon the stage forces of which we know nothing, 
 and is contradicted by the whole tenor of the operations which 
 we see going on around us at the present day. It is prefer- 
 able, therefore, to believe that no such violent processes of 
 destruction and re-peopling took place, but that the marked 
 break in the life of the two periods indicates an enormous 
 lapse of time. The Cretaceous animals, in consequence of the 
 elevation of the British area at the close of the Cretaceous 
 period, must have mostly migrated, some doubtless perishing, 
 and others probably becoming modified in the process. When 
 the British area became once more submerged beneath the 
 sea, and became again a fitting home for marine life, an immi- 
 gration into it would set in from neighbouring seas. By this 
 time, however, the Cretaceous animals must have mostly died 
 out, or must have become greatly changed in their characters ; 
 and the new immigrants would be forms characteristic of the 
 Lower Eocene. How long the processes here described may 
 have taken, it is utterly impossible to say, even approximately. 
 Judging, however, from what we can observe at the present 
 day, the palaeontological break between the Chalk and the 
 Eocene indicates a perfectly incalculable lapse of time; for 
 all species change or die out slowly, marine species especially 
 so ; and we have here the disappearance of a large fauna almost 
 in its entirety, and its replacement by another wholly distinct. 
 In the second place, to come to the physical evidence, the 
 Eocene strata are seen to rest upon an eroded and denuded 
 surface of Chalk, filling up " pipes " and winding hollows 
 which descend far below the general surface of the latter. Not 
 only so, but the base of the Eocene Rocks is commonly com- 
 posed of a bed of rolled and rounded flints, derived from the 
 Chalk, affording incontestable proof that the Chalk had been 
 greatly worn down and removed by denudation, before the 
 Eocene beds were deposited upon its surface. In short, the 
 Eocene Rocks repose " unconformably " upon the Chalk, and 
 this, as is well known, indicates the following series of pheno- 
 mena : Firstly, the Chalk was deposited in horizontal layers 
 at the bottom of the Cretaceous sea. Secondly, at some wholly 
 indefinite time after its deposition, after it had become more 
 or less consolidated, the Chalk must have been raised by a 
 gradual process of elevation above the level of the sea, during 
 which it would inevitably surfer vast denudation. Thirdly, 
 after another wholly indefinite period, the Chalk was again 
 submerged beneath the sea, in which process it would be sub- 
 jected to still further denudation, and an approximately level 
 c
 
 34 
 
 INTRODUCTION. 
 
 surface would be formed upon it. Fourthly, strata of Eocene 
 age were deposited upon the denuded surface of the Chalk, 
 filling up all the hollows and inequalities of its eroded sur- 
 face (fig. 3). 
 
 Fig. 3. Section showing strata of Tertiary age (a), resting upon a worn and denuded 
 surface of White Chalk (b), the stratification of which is marked by lines of flints. 
 
 In the unconformability, then, between the Chalk and the 
 Eocene Rocks, we have unequivocal evidence irrespective of 
 anything that we learn from Palaeontology that the break 
 between the two formations was one of enormous length. In 
 Britain the interval of time thus indicated is not represented 
 by any deposits ; and in Europe generally there are but frag- 
 mentary traces of such. We may be quite sure, however, that 
 during the time represented in Britain by the mere line of un- 
 conformability between the Chalk and the Eocene, there were 
 somewhere deposited considerable accumulations of sediment. 
 Whether we shall ever succeed in discovering these, or any 
 part of these, is, of course, uncertain. We may be certain, 
 however, that such deposits, if ever discovered, will prove to 
 be charged with the remains of animals more or less inter- 
 mediate in character between those of the Cretaceous and those 
 of the Eocene period ; and the huge gap now existing between 
 these formations will thus be more or less completely bridged 
 over. 
 
 Amongst other well-known instances of more or less general 
 unconformity in the stratified series, may be mentioned that 
 between the Lower and Upper Silurian (not always present), 
 that between the Lower and Upper Old Red Sandstone (also 
 not universal), that between the Carboniferous and Permian 
 Rocks, that between the Permian and Triassic Rocks (not 
 universal), and that between the Lower and Upper Cretaceous
 
 IMPERFECTION OF FAL^ONTOLOGICAL RECORD. 35 
 
 Rocks. All these physical breaks are accompanied by more 
 or less extensive palseontological breaks as well. Other breaks 
 which are rendered less important by the absence or scarcity 
 of fossils, or which are as yet not thoroughly established, are 
 those between the Lower and Upper Laurentian Rocks, the 
 Upper Laurentian and Huronian, and the Upper Cambrian 
 and Lower Silurian. 
 
 It may not be out of place to point out that the unconforma- 
 bilities here indicated must in no way be confounded with the 
 common cases in which beds of one age rest unconformably 
 upon beds far older than themselves. When, for example, we 
 find beds of Carboniferous age reposing unconformably upon 
 Silurian strata, this merely indicates that, in the particular lo- 
 cality under examination, the Devonian or Old Red Sandstone 
 is amissing. This absence of a whole formation in any given 
 region merely indicates that the area was dry land during the 
 period of that formation, or that if any rocks of this age were 
 deposited in this locality, they were removed by denudation 
 before the higher group was laid down. The instances above 
 spoken of, as where the Carboniferous Rocks are succeeded 
 unconformably by the Permian, though essentially of the same 
 nature, are distinguished by an important point. In the former 
 case we know what formation is wanting, and we can intercal- 
 ate it from foreign areas, and thus complete the series. In the 
 latter case we have two successive formations in unconformable 
 junction, and we are not acquainted with any intermediate 
 group of strata which could be intercalated from any other 
 locality. 
 
 From the above facts, then, we learn that one of the chief 
 causes of the imperfection of the palseontological record is to 
 be found in the vast spaces of time which separate most of the 
 great " formations," and which, so far as we yet know, are not 
 represented by any formation of rock. In process of time we 
 shall doubtless succeed in finding deposits to account for more 
 or less of this " unrepresented time," but much will ever remain 
 for which we cannot hope to find the representative sediments. 
 It only remains to add that we have ample evidence within the 
 limits of each formation, and wholly irrespective of any want of 
 conformity, of such lengthened pauses in the work of deposi- 
 tion as to have allowed of great zoological changes in the 
 interim, and to have thus caused irremediable blanks in the 
 palasontological record. The work of rock-deposition is at best 
 an intermittent process ; the changes in a fauna, if slowly 
 effected, are continuous. Thus there are scores of instances in 
 which the fauna of a given bed, perhaps but a few inches in
 
 36 INTRODUCTION. 
 
 thickness, differs altogether from that of the beds immediately 
 above and below, and is characterised by species peculiar to 
 itself. In such cases we can only suppose, that though no 
 physical break can be detected, the deposition of sediment was 
 interrupted by pauses of incalculable length, during which no 
 additional material was added to the sea-bottom, whilst time 
 was allowed for the dying out of old species and the coming in 
 of new. The incessant repetition of such intervals of unrepre- 
 sented time throughout the whole stratified series is convincing 
 proof that the palaeontological record is, and ever must be, a 
 mere excerpt from the biological annals of the globe. 
 . III. THINNING OUT OF BEDS. Another cause by which the 
 continuity of the paloeontological record is affected is what is 
 technically called the " thinning out " of beds. Owing to the 
 mode in which sedimentary rocks are produced, it is certain 
 that there must be for every bed a point whence the largest 
 amount of sediment was derived, and in the neighbourhood of 
 which the bed will therefore be thickest. Thus, if we take a 
 series of beds, such as sandstones and conglomerates, which 
 are the product of littoral action, and are deposited in shallow 
 water near a coast-line, it will be found that these gradually 
 decrease in thickness, or " thin out," as we pass away from the 
 coast in the direction of deep water. On approaching deep 
 water, however, we might find that, though the sandstones 
 were rapidly dying out, the thickness of the entire series might 
 still be preserved, owing to the commencement now of some 
 deep-water deposit, such as limestone. The beds of limestone 
 
 Fig. 4. Diagram to show the " thinning out " of beds, a Sandstones and 
 Conglomerates ; b Limestones. 
 
 would at first be very thin, but in proceeding still in the direc- 
 tion of deeper water, we should find that they would gradually 
 expand, till they reached a point of maximum thickness, on 
 the other side of which they would gradually thin out. Each 
 individual bed, therefore, in any group of stratified rocks, may 
 be regarded as an unequal mass, thickest in the centre, and 
 gradually tapering off or " thinning out " in all directions to- 
 wards the circumference (fig. 4).
 
 IMPERFECTION OF PAL^ONTOLOGICAL RECORD. 37 
 
 In a general way this holds good, not only for any particular 
 bed, but for any particular aggregation or group of beds which 
 we may choose to take. In the case, namely, of every group 
 of beds, there must have been a particular point whither sedi- 
 ment was most abundantly conveyed, or where the other con- 
 ditions of accumulation were especially favourable. At this 
 point, therefore, the beds are thickest, and from this they thin 
 out in all directions. It need scarcely be pointed out, indeed, 
 that some such state of things is unavoidable in the case of 
 every bed or group of beds, since no sea is boundless, and 
 the sedimentary deposits of every ocean must come to an end 
 somewhere. 
 
 An excellent example of the phenomena above described 
 may be derived from the Lower Carboniferous Rocks of 
 Britain. Here we may start in South Wales and in Central 
 England with the Carboniferous Limestone as a great calcare- 
 ous mass over 1000 feet in thickness, and almost without a 
 single intercalated layer of shale. Passing northwards, some 
 of the beds of limestone begin to thin out, and their place is 
 taken by strata of a different mineral nature, such as sandstone, 
 grit, or shale. The result of this is, that by the time we have 
 followed the Carboniferous Limestone into Yorkshire and West- 
 moreland, in place of a single great mass of limestone, we have 
 an equivalent mass of alternating strata of limestone, sandstone, 
 grit, and shale, with one or two thin seams of coal the lime- 
 stones, however, still bearing a considerable proportion to the 
 whole. Passing still further northwards, the limestones go on 
 thinning out, till in Central Scotland, in place of the dense cal- 
 careous accumulations of Derbyshire, the Lower Carboniferous 
 series consists of a great group of sandstones, grits, and shales, 
 with thick and workable beds of coal, and with but few and 
 comparatively insignificant beds of limestone. 
 
 The state of things indicated by these phenomena is as fol- 
 lows : The sea in which the Lower Carboniferous Rocks of 
 Britain were deposited must have gradually deepened from north 
 to south. The land and coast-line whence the coarser mechani- 
 cal sediments were derived, must have been placed somewhere 
 to the north of Scotland, and the deepest part of the ocean 
 must have been somewhere about Derbyshire. Here the con- 
 ditions for lime-making were most favourable, and here conse- 
 quently we find the greatest thickness of calcareous strata, and 
 the smallest intermixture of mechanical deposits. 
 
 The palaeontological results of this are readily deducible. 
 The entire Lower Carboniferous series of Britain was probably 
 deposited in a single ocean, apparently destitute of land-bar-
 
 38 INTRODUCTION. 
 
 riers ; and consequently, taken as a whole, the fauna of this 
 series may be regarded as one and indivisible. The condi- 
 tions, nevertheless, which obtained in different parts of this 
 area were very different; and, as a necessary result, certain 
 groups of animals flourished in certain localities, and were 
 absent or but scantily represented in others. In the deeper 
 parts of the area we have an abundance of Corals, with Crinoids, 
 and at times Foraminifera. In the shallower parts of the area 
 there is, on the other hand, a predominance of forms which 
 affect water of no great depth. Still, there is no difference in 
 point of time between the deposits of different parts of the area; 
 and in order to obtain a true notion of the Lower Carbonifer- 
 ous fauna, we must add the fossils derived from one portion of 
 the area to those derived from another. 
 
 In many cases, however, we are acquainted with but one 
 class of deposits belonging to a given period. We may have 
 the deep-sea deposits of the period only, or we may know no- 
 thing but its littoral accumulations. In either case it is clear 
 that there is an imperfection of the palaeontological record ; 
 for we cannot have even a moderately complete record of the 
 marine animals alone of a particular period, unless we have 
 access to a complete series of the deposits laid down in the 
 seas of that period. 
 
 IV. SUDDEN EXTINCTION OF ANIMALS. Whilst there can 
 be little doubt but that the changes in animal life indicated by 
 Geology were in the main gradually effected, there still remain 
 cases in which individuals seem to have been suddenly de- 
 stroyed in great numbers, and others of a more obscure nature 
 in which allied species succeed one another with an inexpli- 
 cable rapidity. As an example of the first class of cases, we 
 may take the great Marine Reptiles of the Lias, which often 
 exhibit indications of having met a sudden death, whilst they 
 show no traces of mechanical injury. It has been suggested by 
 Sir Charles Lyell, with great probability, that the sudden death 
 of marine animals, in these and other similar cases, might have 
 been caused by the sudden "periodical discharge of large 
 bodies of turbid fresh water into the sea." 
 
 As an example of the second class of cases which more 
 especially bear upon the present question we may take the 
 existence in the Lias of zones characterised by particular species 
 of Ammonites. These zones are usually of small thickness, 
 and the Ammonite characterising each is usually confined to 
 that particular horizon ; whilst several of these zones have been 
 found to be persistent over very wide areas. As we know of 
 no reason why one species of Ammonite should flourish where
 
 IMPERFECTION OF PAIwEONTOLOGICAL RECORD. 39 
 
 another allied species would not, we cannot at present account 
 for this sudden disappearance of one species and its seeming 
 immediate replacement by another. We may be sure, however, 
 that we have here an imperfection of the palaeontological record, 
 and that in reality any two zones must have been separated by 
 a long period, in which one species became extinct, or was so 
 far modified as to appear as a new species. 
 
 V. DISAPPEARANCE OF FOSSILS. The last subject which 
 need be mentioned in connection with the imperfection of the 
 palseontological record is that of the disappearance of fossils 
 from rocks originally fossiliferous. This, as a rule, is due to 
 " metamorphism " that is to say, the subjection of the rock to 
 a sufficient amount of heat to cause a rearrangement of its 
 particles. When of at all a pronounced character, the result 
 of metamorphism is invariably the obliteration of any fossils 
 which might have been originally present in the rock. To this 
 cause must be set down many great gaps in the palasonto- 
 logical record, and the irreparable loss of much fossil evidence. 
 The most striking example which is to be found of this is the 
 great Laurentian series, which comprises some 30,000 feet of 
 highly metamorphosed sediments, but which, with one not 
 absolutely certain exception, has as yet yielded no remains of 
 life, though there is strong evidence of the former existence in 
 it of fossils. 
 
 Another not uncommon cause of the disappearance of organic 
 remains from originally fossiliferous deposits is the percolation 
 through them of water holding carbonic acid in solution. 
 By this means fossils of a calcareous nature are dissolved out 
 of the rock, and may leave no traces behind. This cause, 
 however, can only operate to any extent in more or less loose 
 and porous arenaceous deposits. 
 
 Lastly, " cleavage " may be mentioned as a common cause 
 of the disappearance of fossils. The cleavage, however, must 
 be very intense, if it actually prevents the recognition of the 
 deposit as one in which fossils formerly existed, though cases 
 are not uncommon in which this occurs through thousands of 
 feet of strata. As a more general rule, however, it is not very 
 difficult to determine whether a cleaved rock has ever con- 
 tained fossils or not, though it may be quite impossible to 
 make out the exact nature and character of the organic
 
 40 INTRODUCTION. 
 
 CHAPTER V. 
 CONCLUSIONS TO BE DRAWN FROM FOSSILS. 
 
 WE have already seen that geologists have been Jed by the 
 study of fossils to the all-important generalisation that the vast 
 series of the Fossiliferous or Sedimentary Rocks may be divided 
 into a number of definite groups or " formations," each of which 
 is characterised by its organic remains. It may simply be re- 
 peated here that these formations are not properly and strictly 
 characterised by the occurrence in them of any one particular 
 fossil. It may be that a formation contains some particular 
 fossil, or fossils, not occurring out of that formation, and that 
 in this way an observer may identify a given group with toler- 
 able certainty. It very often happens, indeed, that some parti- 
 cular stratum, or sub-group of a series, contains peculiar fossils, 
 by which its existence may be determined in various localities. 
 As before remarked, however, the great formations are charac- 
 terised properly by the association of certain fossils, by the 
 predominance of certain families or orders, or by an assemblage 
 of fossil remains representing the " life" of the period in which 
 the formation was deposited. 
 
 Fossils, then, enable us to determine the age of the deposits 
 in which they occur. Fossils further enable us to come to very 
 important conclusions as to the mode in which the fossiliferous 
 bed was deposited, and thus as to the condition of the parti- 
 cular district or region occupied by the fossiliferous bed at the 
 time of the formation of the latter. If, in the first place, the 
 bed contain the remains of animals such as now inhabit rivers, 
 we know that it is " fluviatile " in its origin, and that it must at 
 one time have either formed an actual river-bed, or been de- 
 posited by the overflowing of an ancient stream. Secondly, if 
 the bed contain the remains of shell-fish, minute crustaceans, 
 or fish, such as now inhabit lakes, we know that it is " lacus- 
 trine," and was deposited beneath the waters of a former lake. 
 Thirdly, if the bed contain the remains of animals such as now 
 people the ocean, we know that it is " marine " in its origin, 
 and that it is a fragment of an old sea-bottom. 
 
 We can, however, often determine the conditions under 
 which a bed was deposited with greater accuracy than this. 
 If, for example, the fossils are of kinds resembling the marine 
 animals now inhabiting shallow waters, if they are accompanied 
 by the detached relics of terrestrial organisms, or if they are 
 partially rolled and broken, we may conclude that the fossili-
 
 CONCLUSIONS TO BE DRAWN FROM FOSSILS. 4! 
 
 ferous deposit was laid down in a shallow sea, in the immediate 
 vicinity of a coast-line, or as an actual shore-deposit. If, again, 
 the remains are those of animals such as now live in the deeper 
 parts of the ocean, and there is a very sparing intermixture of 
 extraneous fossils (such as the bones of birds or quadrupeds, 
 or the remains of plants), we may presume that the deposit is 
 one of deep water. In other cases, we may find, scattered 
 through the rock, and still in their natural position, the valves 
 of shells such as we know at the present day as living buried 
 in the sand or mud of the sea-shore or of estuaries. In other 
 cases, the bed may obviously have been an ancient coral-reef, 
 or an accumulation of social shells, like Oysters. Lastly, if we 
 find the deposit to contain the remains of marine shells, but 
 that these are dwarfed of their fair proportions and distorted 
 in figure, we may conclude that it was laid down in a brackish 
 sea, such as the Baltic, in which the proper saltness was want- 
 ing, owing to its receiving an excessive supply of fresh water. 
 
 In the preceding, we have been dealing simply with the 
 remains of aquatic animals, and we have seen that certain con- 
 clusions can be accurately reached by an examination of these. 
 As regards the determination of the conditions of deposition 
 from the remains of aerial and terrestrial animals, or from 
 plants, there is not such an absolute certainty. The remains 
 of land-animals would, of course, occur in "sub-aerial" deposits 
 that is, in beds, like blown sand, accumulated upon the land. 
 Most of the remains of land-animals, however, are found in 
 deposits which have been laid down in water, and they owe 
 their present position to having been drowned in rivers or 
 lakes, or carried out to sea by streams. Birds, Flying Reptiles, 
 and Flying Mammals might also similarly find their way into 
 aqueous deposits ; but it is to be remembered that many birds 
 and mammals habitually spend a great part of their time in the 
 water, and that these might therefore be naturally expected to 
 present themselves as fossils in Sedimentary Rocks. Plants, 
 again, even when undoubtedly such as must have grown on 
 land, do not prove that the bed in which they occur was 
 formed on land. Many of the remains of plants known to 
 us are extraneous to the bed in which they are now found, 
 having reached their present site by falling into lakes or rivers, 
 or being carried out to sea by floods or gales of wind. There 
 are, however, many cases in which plants have undoubt- 
 edly grown on the very spot where we now find them. Thus 
 it is now generally admitted that the great coal-fields of the 
 Carboniferous age are the result of the growth in situ of the 
 plants which compose coal, and that these grew on vast
 
 INTRODUCTION. 
 
 marshy or partially submerged tracts of level alluvial land. 
 
 We have, however, distinct evidence of old land-surfaces, both 
 in the Coal-measures and in 
 other cases (as, for instance, 
 in the well-known "dirt-bed" 
 of the Purbeck series). When, 
 for example, we find the erect 
 stumps of trees standing at 
 right angles to the surround- 
 ing strata, we know that the 
 surface through which these 
 send their roots was at one 
 time the surface of the dry 
 land, or, in other words, was 
 an ancient soil (fig. 5). 
 
 CONCLUSIONS AS TO CLI- 
 MATE. In many cases fossils 
 enable us to come to impor- 
 tant conclusions as to the 
 climate of the period in which 
 they lived, but only a few in- 
 stances of this can be here 
 adduced. As fossils in the 
 majority of instances are the 
 
 Fijj. 5. Erect Tree conta 
 remains. Coal-measures, No 
 Dawson). 
 
 ng Reptilian 
 Scotia (after 
 
 remains of marine animals, it 
 is mostly the temperature of 
 the sea which can alone be determined in this way ; and it is 
 important to remember that, owing to the existence of heated 
 currents, the marine climate of a given area does not neces- 
 sarily imply a correspondingly warm climate in the neighbour- 
 ing land. Land-climates can only be determined by the 
 remains of land-animals or land-plants, and these are com- 
 paratively rare as fossils. It is also important to remember 
 that all conclusions on this head are really based upon the 
 present distribution of animal and vegetable life on the globe, 
 and are therefore liable to be vitiated by the following 
 considerations : 
 
 a. Most fossils are extinct, and it 'is not certain that the 
 habits and requirements of any extinct animal were exactly 
 similar to, or even at all resembling, those of its nearest living 
 relative. 
 
 b. When we get very far back in time, we meet with groups 
 of organisms so unlike anything we know at the present day as 
 to render all conjectures as to climate founded upon their sup- 
 posed habits more or less uncertain and unsafe.
 
 CONCLUSIONS TO BE DRAWN FROM FOSSILS. 43 
 
 c. In the case of marine animals, we are as yet very far from 
 knowing the exact limits of distribution of many species within 
 our present seas ; so that conclusions drawn from living forms 
 as to extinct species are apt to prove incorrect. For instance, 
 it has recently been shown that many shells formerly believed 
 to be confined to the Arctic Seas have, by reason of the ex- 
 tension of Polar currents, a wide range to the south ; and this 
 has thrown doubt upon the conclusions drawn from fossil 
 shells as to the Arctic conditions under which certain beds 
 were supposed to have been deposited. 
 
 d. The distribution of animals at the present day is certainly 
 dependent upon other conditions beside climate alone ; and 
 the causes which now limit the range of given animals are 
 certainly such as belong to the existing order of things. But 
 the establishment of the present order of things does not date 
 back in many cases to the introduction of the present species 
 of animals. Even in the case, therefore, of existing species of 
 animals, it can often be shown that the past distribution of the 
 species was different formerly to what it is now, not necessarily 
 because the climate has changed, but because of the alteration 
 of other conditions essential to the life of the species or con- 
 ducing to its extension. 
 
 Still, we are in many cases able to draw completely reliable 
 conclusions as to the climate of a given geological period, by 
 an examination of the fossils belonging to that period. Among 
 the more striking examples of how the past climate of a region 
 may be deduced from the study of the organic remains con- 
 tained in its rocks, the following may be mentioned : It has 
 been shown that in Eocene times, or at the commencement 
 of the Tertiary period, the climate of what is now Western 
 Europe was of a tropical or sub-tropical character. Thus the 
 Eocene beds are found to contain the remains of shells such 
 as now inhabit tropical seas, as, for example, Cowries and 
 Volutes; and with these are the fruits of palms, and the 
 remains of other tropical plants. It has been shown, again, 
 that in Miocene times, or about the middle of the Tertiary 
 period, Central Europe was peopled with a luxuriant flora 
 resembling that of the warmer parts of the United States, and 
 leading to the conclusion that the mean annual temperature 
 must have been at least 30 hotter than it is at present. It 
 has been shown that, at the same time, Greenland, now buried 
 beneath a vast ice-shroud, was warm enough to support a large 
 number of trees, shrubs, and other plants, such as inhabit the 
 temperate regions of the globe. Lastly, it has been shown, 
 upon physical as well as palagontological evidence, that the
 
 44 INTRODUCTION. 
 
 greater part of the North Temperate Zone, at a comparatively 
 recent geological period, has been visited with all the rigours 
 of an Arctic climate, resembling that of Greenland at the pre- 
 sent day. This is indicated by the occurrence of Arctic shells 
 in the superficial deposits of this period, whilst the Musk-ox 
 and the Reindeer roamed far south of their present limits. 
 
 CHAPTER VI. 
 
 DIVISIONS OF THE ANIMAL KINGDOM, AND 
 SUCCESSION OF ORGANIC TYPES. 
 
 IT seems hardly necessary to remark that Palaeontology, as 
 a science, is based upon the kindred sciences of Zoology and 
 Botany, and that no satisfactory acquaintance with the former 
 can be arrived at without the previous acquisition of some 
 knowledge of the latter. It cannot be pretended to teach here 
 even the rudiments of these sciences, but there are a few points 
 which may be noticed as having a special bearing upon the 
 study of Palaeontology. 
 
 CLASSIFICATION OF THE ANIMAL KINGDOM. Leaving the 
 vegetable kingdom till we come to speak of fossil plants, a 
 few remarks may be made on the classification of the animal 
 kingdom. Vast as is the number of known animals, all, 
 whether living or extinct, may be classed under some five or 
 six primary divisions or "morphological types," which are 
 technically spoken of as the " sub-kingdoms." All the animals 
 in any one sub-kingdom agree with one another in their 
 structural type, or in the fundamental plan upon which they 
 are constructed ; and they differ from one another simply in 
 the modifications of this common plan. No comparison, 
 therefore, is possible between an animal belonging to one sub- 
 kingdom, and one belonging to another, since their distinguish- 
 ing characters are the result of the modification of two essen- 
 tially different ground-plans. Hence, it is possible to arrange 
 the animals of any one sub-kingdom in something like a linear 
 series, in which the lowest of the series most closely approaches 
 the primitive or ideal form of the sub-kingdom, whilst the 
 highest exhibits the greatest amount of complexity and special- 
 isation of this type. But it is not possible to establish any 
 such linear classification for the animal kingdom as a whole. 
 Given an animal of a lower "sub-kingdom" than another
 
 CHIEF DIVISIONS OF THE ANIMAL KINGDOM. 4$ 
 
 animal, no amount of complexity, no specialisation of organis- 
 ation, can raise the former above the latter. The one may be 
 the result of the high evolution of a low morphological type, 
 the other may be the result of the low evolution of a higher 
 morphological type, but the superiority of the ground-plan 
 gives the latter the higher place. We must therefore abandon 
 the idea that it is possible to establish a linear classification of 
 the animal kingdom. 
 
 The following synoptical table gives briefly the leading 
 divisions of the animal kingdom, and the chief characters of 
 these : 
 
 TABULAR VIEW OF THE CHIEF DIVISIONS OF THE 
 ANIMAL KINGDOM. 
 
 INVERTEBRATE ANIMALS. 
 
 SUB-KINGDOM I. PROTOZOA. 
 
 Animal simple or forming colonies, usually very minute ; the body com- 
 posed of the structureless, jelly-like, albuminous substance called "sar- 
 code ; " not divided into regular segments ; having no nervous system ; no 
 regular circulatory system ; usually no mouth ; no definite body-cavity or 
 digestive system, or at most but a short 'gullet. 
 
 CLASS A. GREGARINID^. Minute Protozoa which inhabit the interior 
 of insects and other animals, and which have not the power of throwing 
 out prolongations of their substance (pseud opodia). No mouth. 
 
 CLASS B. RHIZOPODA (Root-footed Protozoa). Protozoa which are 
 simple or compound, and have the power of throwing out and retracting 
 prolongations of the body-substance (the so-called "pseudopodia"). No 
 mouth, in most, if not in all. 
 
 Order i. Monera. Ex. Protogenes. 
 
 Order 2. Amcebea. Ex. Proteus Animalcule (Amceba). 
 
 Order 3. Foraminifera. Ex. Lagena, Nodosaria, Globigerina. 
 
 Order 4. Radiolaria. Ex. Thalassicolla, Polycystina. 
 
 Order 5. Spongida. Ex. Fresh-water Sponge (Spongilla), Venus's 
 Flower-Basket (Euplectella). 
 
 CLASS C. INFUSORIA (Infusorian Animalcules). Protozoa with a mouth 
 and short gullet ; destitute of the power of emitting pseudopodia ; furnished 
 with vibratile cilia or contractile filaments ; the body usually composed of 
 three distinct layers. 
 
 Order i. Ciliata. Ex. Bell-animalcule (Vorticella), Paramcecium. 
 
 Order 2. Flagellata. Ex. Peranema. 
 
 Order 3. Suctoria. Ex. Podophyra. 
 
 SUB-KINGDOM II.C(ELENTERA TA. 
 
 Animals whose alimentary canal communicates freely with the general 
 cavity of the body ; body composed essentially of two layers or membranes, 
 an outer layer or "ectoderm," and an inner layer or "endoderm." No 
 circulatory system or heart, and -in most no nervous system. Skin fur- 
 nished with minute stinging organs or "thread-cells." Distinct reproduc- 
 tive organs in all. 
 
 CLASS A. HYDROZOA. Walls of the digestive sac not separated from
 
 4 6 
 
 INTRODUCTION. 
 
 those of the general body-cavity, the two coinciding with one another. 
 Reproductive organs external. 
 Sub-class I. HYDROIDA (Hydroid Zoophytes). 
 
 Order I. Hydrida.Ex. Fresh-water Polype (Hydra). 
 Order 2. Corynida. Ex. Pipe-coralline (Tubularia). 
 Orders. Sertularida.Ex. Sea-firs (Sertularia). 
 Sub-class II. SIPHONOPHORA (Oceanic Hydrozoa). 
 Order 4. Calycophoridce. Ex. Diphyes. 
 
 Order 5. Physophorida. Ex. Portuguese Man-of-War (Physalia). 
 Sub-class III. DISCOPHORA (Jelly-fish). 
 
 Order 6. Medusida Ex. Trachynema. 
 Sub-class IV. LUCERNARIDA (Sea-blubbers). 
 Order 7. Lucernaridce. Ex. Lucernaria, 
 OrderS. Pelagidce.Ex. Pelagia. 
 Order 9. Rhizostomida. Ex. Rhizostoma. 
 Sub-class V. GRAPTOLITIDJE (extinct). 
 
 CLASS B. ACTINOZOA. Stomach opening below into the body-cavity, 
 which is divided into a number of compartments by a series of vertical par- 
 titions or " mesenteries." Reproductive organs internal. 
 
 Order I. Zoantharia. Tentacles simply rounded, in multiples of 
 five or six. Ex. Sea-Anemones (Actinidas), Star- 
 corals (Astrreidae), Brain-corals (Meandrina), Madre- 
 pores (Madreporidae). 
 
 Orders. Alcyonaria. Tentacles fringed, in multiples of four. 
 Ex. Dead-man's-toes (Alcyonium), Organ-pipe Coral 
 (Tubipora), Sea-rods (Virgularia), Sea-pens (Penna- 
 tula), Red Coral (Corallium). 
 Order 3. Rngosa (extinct). 
 
 Order 4. Ctenophora. Animal oceanic, swimming by means of 
 bands of cilia or " ctenophores." Ex. Pleurobrachia, 
 Venus's Girdle (Cestum). 
 
 SUB-KINGDOM HI.ANNULOIDA. 
 
 Animals in which the alimentary canal is completely shut off" from the 
 general cavity of the body, and in which there is a distinct nervous system. 
 A true blood-circulatory system may or may not be present. In all there 
 is a peculiar system of canals, which usually communicate with the exterior, 
 and which constitute what is called the "water-vascular system." The 
 body of the adult is never composed of a succession of definite rings, or pro- 
 vided with successive pairs of appendages disposed symmetrically on the 
 two sides of the body. 
 
 The Annuloida are divided into two great classes : 
 
 A. EcHlNODERMATA. Integument composed of numerous calcareous 
 plates joined together, or leathery and having grains, spines, or tubercles 
 of calcareous matter developed in it. Water-vascular system (ambulacra! 
 system) mostly employed in locomotion, and generally communicating with 
 the exterior. Adult generally more or less starlike or " radiate " in shape ; 
 young mostly showing more or less complete " bilateral symmetry," that is, 
 showing similar parts on the two sides of the body. Nervous system 
 radiate. 
 
 Order I. Crinoidm (Sea-lilies). Ex. Feather-star (Comatula), Me- 
 dusa-head Crinoid (Pentacrinus), Stone-lily (Encri- 
 nus. ) 
 
 Order 2. Blastoidea (extinct). 
 Order 3. Cystoidea (extinct).
 
 CHIEF DIVISIONS OF THE ANIMAL KINGDOM. 47 
 
 Order 4. Ophiuroidea (Brittle-stars) Ex. Sand-stars (Ophiura), 
 
 Brittle-stars (Ophiocoma). 
 
 Order 5. Asteroidea (Star-fishes). Ex. Cross-fish (Uraster), Sun- 
 star (Solaster), Cushion-star (Goniaster). 
 Order 6. Echinoidea (Sea-urchins). Ex. Sea -eggs (Echinus), 
 
 Heart-urchins (Spatangus). 
 Order 7. Holothuroidea (Sea-cucumbers). Ex. Trepangs (Holo- 
 
 thuria). 
 
 B. SCOLECIDA. Body usually flattened, or cylindrical and worm-like ; 
 integument soft, without lime. Water-vascular system not assisting in 
 locomotion. Nervous system consisting of one or two ganglia or little 
 masses, and not disposed in a radiate manner. 
 
 Order I. Taniada.Ex. Tape-worm (Tsenia). 
 
 Order 2. Trematoda (Suctorial worms). Ex. Liver-fluke (Dis- 
 
 toma). 
 Order 3. Turbellaria. Ex. Planarians (Planaria), Ribbon-worms 
 
 (Nemertes). 
 Order^ Acanthocephala (Thorn-headed worms). Ex. Echino- 
 
 rhynchus. 
 
 Order 5. Gordiacea (Hair-worms). Ex. Gordius. 
 Order 6. Nematoda (Thread- worms). Ex. Round-worm (Ascaris), 
 
 Guinea-worm (Filaria), Vinegar-eel (Anguillula) . 
 Order 7. Rotifera (Wheel-animalcules). Ex. Builder-animalcule 
 
 (Melicerta), Flexible Creeper (Notommata). 
 
 SUB-KINGDOM IV.ANNULOSA. 
 
 Animal composed of numerous definite segments or " somites," arranged 
 longitudinally, one behind the other. Nervous system always present, con- 
 sisting typically of a double chain of nervous masses, or ganglia, which are 
 placed along the lower surface of the body, and form a collar around the 
 gullet. Limbs (when present) turned toward that side of the body on 
 which the main masses of the nervous system are situated. 
 
 DIVISION A. ANARTHROPODA. Locomotive appendages, when pre- 
 sent, not distinctly jointed or articulated to the body. 
 CLASS I. GEPHYREA. Ex. Spoon-worms (Sipunculus). 
 CLASS II. ANNELIDA (Ringed-worms). 
 
 Order I. Hirudinea. Ex. Leeches (Sanguisuga, Hirudo). 
 Order 2. OligochcEla. Ex. Earth - worms (Lumbricus), Water- 
 worms (Nais). 
 
 Order 3. Tubicola. Ex. Tube-worms (Serpula). 
 Order 4. Errantia. Ex. Sand-worms and Sea-centipedes (Nereis), 
 
 Lob-worm (Arenicola), Sea-mouse (Aphrodite). 
 CLASS III. CH^TOGNATHA ( Arrow- worms). Ex. Sagitta. 
 DIVISION B. ARTHROPODA. Locomotive appendages jointed or articu- 
 lated to the body. 
 
 CLASS I. CRUSTACEA. Respiration aquatic, mostly by gills. Two 
 pairs of antennas. Limbs more than four pairs in number, carried upon the 
 thorax, and generally the abdomen also. 
 
 Order I. Ichthyophthira. Ex. Lerasea. 
 
 Order 2. Rhizocephala.Ex. Peltogaster. 
 
 Order 3. Cirripedia.Ex. Barnacles (Lepas), Acorn-shells (Bal- 
 
 anus). 
 
 Order 4. Ostracoda.Ex. Water-fleas (Cypris). 
 Order 5. Copepoda. Ex. Cyclops. 
 Order 6. Cladocera.Ex. Branched -horned Water-fleas (Daphnia).
 
 48 INTRODUCTION. 
 
 Order 7. Phyllopoda. Ex. Brine-shrimp (Artemia). 
 
 Order 8. Trilobita (Extinct). 
 
 Order 9. Merostomata. Ex. King-crabs (Limulus). 
 
 Order IO. Ltcmodipoda. Ex. Whale-louse (Cyamus). 
 
 Order n. Isopoda. Ex. Wood-lice (Oniscus), Slaters (Ligia). 
 
 Order 12. Amphipoda. Ex. Sandhopper (Talitrus), Fresh-water 
 
 Shrimp (Gammarus). 
 
 Order 13. Stomapoda. Ex. Locust-shrimp (Squilla). 
 Order 14. Decapoda. Ex. Lobster (Homarus), Cray-fish (Astacus), 
 Shrimps (Crangon) ; Hermit-crabs (Pagurus) ; Crabs 
 (Cancer, Carcinus), Land-crabs (Gecarcinus). 
 
 CLASS II. ARACHNIDA. Respiration aerial, by pulmonary chambers or 
 air-tubes (tracheae) in the higher forms. Antennae converted into jaws. 
 Head and thorax amalgamated. Four pairs of legs. Abdomen without 
 limbs. 
 
 Order I. Podosomata (Sea-spiders). Ex. Pycnogonum. 
 
 Order 2. Monomerosomata. Ex. Mites (Acarus), Water-mites (Hy- 
 
 drachna), Ticks (Ixodes). 
 Order 3. Adelartkrosomata. Ex. Harvest-spiders (Phalangidae), 
 
 Book-scorpions (Chelifer). 
 
 Order 4. Pfdipalpi. Ex. Scorpions (Scorpio). 
 Order 5. Araneida. Ex. House-spiders (Tegenaria), Field-spiders 
 
 (Epeira). 
 
 CLASS III. MYRIAPODA. Respiration aerial, by tracheae (air-tubes) or 
 by the skin. Head distinct ; remainder of body composed of nearly simi- 
 lar segments. Legs more than eight pairs in number, and borne partly 
 upon the abdomen. One pair of antennae. 
 
 Order I. Chilopoda.Ex. Centipedes (Scolopendra). 
 Order 2. Chilognatha.Ex. Millipedes (lulus). 
 Order 3. Pauropoda. Ex. Pauropus. 
 
 CLASS IV. INSECTA. Respiration aerial, by tracheae. Head, thorax, 
 and abdomen distinct. One pair of antennae. Three pairs of legs, and 
 generally two pairs of wings on the thorax. No locomotive limbs on the 
 abdomen. 
 
 Order I. Anoplura.Ex. Lice (Pediculus). 
 
 Order 2. Mallophaga (Bird-lice). 
 
 Order 3. Thysanura (Springtails). 
 
 Order 4. Hemiptera.Ex. Plant-lice (Aphides), Field-bug (Pen- 
 
 tatoma), Cochineal Insects (Coccus). 
 Order 5. Orthoptera. Ex. Locusts (Acrydium), Grass-hoppers 
 
 (Gryllus), Crickets (Achetina), Cockroach (Blatta). 
 Order 6. Neuropttra. Ex. White Ants (Termes), Dragon-flies 
 
 (Libellulidae), May-flies (Ephemerida;). 
 Order 7. Aphaniptera. Ex. Fleas (Pulex). 
 Order 8. Diptera.Ex. Gnats (Culex), Crane-flies (Tipula), 
 
 House-flies and Flesh-flies (Musca). 
 Order 9. Lepidoptera (Butterflies and Moths). 
 Order 10. Hymenoptera. Ex. Bees (Apidae), Humble-bees (Bom- 
 bidae), Wasps (Vespidae), Ants (Formicida), Saw-flies, 
 (Tenthredinidae). 
 
 Order II. Strepsiptcra.Ex. Stylops. 
 Order 12. Coleoptera (Beetles). 
 
 SUB-KINGDOM V.MOLL USCA. 
 Animal soft-bodied, generally with a hard covering or shell. Nervous
 
 CHIEF DIVISIONS OF THE ANIMAL KINGDOM. 49 
 
 system consisting of a single ganglion or of scattered pairs of ganglia. A 
 distinct heart and breathing-organ, or neither. 
 
 The Mollusca may be divided into the two following primary divisions, 
 containing the following classes : 
 
 A. MOLLUSCOIDA. Nervous system consisting of a single ganglion or of 
 a principal pair of ganglia. No heart, or an imperfect one. 
 
 CLASS I. POLYZOA. Animal always forming compound growths or 
 colonies. No heart. The mouth of each zooid surrounded 
 by a circle or crescent of ciliated tentacles. Ex. Sea- 
 mats (Flustra), Lace-coral (Fenestella). 
 
 CLASS II. TUNICATA. Animal simple or compound, enclosed in a 
 leathery or gristly case. An imperfect heart. Ex. Sea- 
 squirts (Ascidia). 
 
 CLASS III. BRACHIOPODA. Animal always simple ; the body enclosed 
 in a bivalve shell. Mouth furnished with two long fringed 
 processes or "arms." Ex. Lamp-shells (Terebratula). 
 
 B. MOLLUSCA PROPER. Nervous system consisting of three principal 
 pairs of ganglia. Heart well developed, consisting of at least two chambers. 
 
 CLASS IV. LAMELLIBRANCHIATA (Bivalve Shell -fish). No distinct 
 head ; no teeth. Body enclosed in a shell which is " bi- 
 valve," or composed of two distinct pieces. One or two 
 leaf-like gills on each side of the body. Ex. Oyster 
 (Ostrea), Scallop (Pecten), Mussel (Mytilus). 
 
 CLASS V. GASTEROPODA. A distinct head and toothed tongue. Shell 
 absent in some, but mostly present, and usually consisting 
 of a single piece ("univalve"). Locomotion effected by 
 creeping about on the flattened under surface of the body 
 (" foot "), or by swimming by means of a fin-like modifi- 
 cation of the same. Ex. Whelks (Buccinum), Limpets 
 (Patella), Sea-lemons (Doris), Land-snails (Helix), Slugs 
 (Limax). 
 
 CLASS VI. PTEROPODA. Animal oceanic, swimming by means of two 
 wing-like appendages, one on each side of the head. Size 
 minute. Ex. Cleodora. 
 
 CLASS VII. CEPHALOPODA. Animal with eight or more arms, placed 
 in a circle round the mouth. Mouth armed with jaws, and 
 and a toothed tongue. Two or four plume-like gills. In 
 front of the body, a muscular tube ("funnel") through 
 which is expelled the water which has been used in respira- 
 tion. An external shell in some, an internal skeleton in 
 others. Ex. Calamaries (Loligo), Cuttle-fishes or Poulpes 
 (Octopus), Paper-Nautilus (Argonauta), Pearly Nautilus 
 (Nautilus). 
 
 VERTEBRATE ANIMALS. 
 
 6" UB - KINGDOM VI. VER TEBRA TA . 
 
 Body composed of a number of definite segments arranged longitudinally, 
 or one behind the other. The main masses of the nervous system are 
 placed on the dorsal aspect of the body, and are completely shut off from 
 the general body-cavity. The limbs (when present) are turned away from 
 that side of the body on which the main nervous masses are situated, and 
 are never more than four in number. In most cases a backbone, or 
 "vertebral column," is present in the fully-grown animal. 
 D
 
 50 INTRODUCTION. 
 
 CLASS I. PISCES (Fishes). Breathing-organs in the form of gills. Heart 
 usually of two chambers, rarely of three. Blood cold. Limbs, when present, 
 converted into fins. 
 
 Order I. Pharyngobranchii. Ex. Lancelet (Amphioxus). 
 
 Order 2. Marsipobranchii, Ex. Lamprey (Petromyzan), Hag-fish 
 
 (Afyxine). 
 
 Orders. Teleostei (Bony Fishes). Ex. Eels (Munenidae), Her- 
 rings (Clupeidae), Salmon and Trout (Salmonidae), Cod 
 and Haddock (Gadidae), Flat-fishes (Pleuronectidae), 
 Perch (Percidae), Mackerel (Scomberidae). 
 Order 4. Ganoidei. Ex. Bony Pike (Lepidosteus), Paddle-fish 
 
 (Spatularia), Sturgeon (Sturio). 
 
 Order 5. Elasmobranchii. Ex. Sharks (Carcharidse), Dog-fishes 
 (Scylliadse), Saw-fishes (Pristis), Rays and Skates 
 (Raiidse). 
 
 Order 6. Dipnoi. Ex. Mud-fish (Lepidosiren). 
 
 CLASS II. AMPHIBIA (Amphibians). Breathing-organs in the young in 
 the form of gills alone, afterwards lungs, either alone or associated with gills. 
 Skull joined to the backbone by two articulating surfaces ("condyles"). 
 Limbs never converted into fins. Heart in the young of two chambers 
 only, in the adult of three chambers. Blood cold. 
 Order I. Labyrinthodontia (extinct). 
 Order 2. Ophiomorpha.Ex. Caecilia. 
 
 Order 3. Urodela (Tailed Amphibians). Ex. Water - newts 
 (Triton), Salamanders (Salamandra), Axolotl (Sire- 
 don), Mud-eel (Siren). 
 
 Order^ Anoura (Tailless Amphibians). Ex. Frogs (Rana), 
 Tree-frogs (Hyla), Toads (Bufo), Surinam Toads (Pipa.) 
 CLASS III. REPTILIA (Reptiles). Respiratory organs in the form of 
 lungs, never in the form of gills. Heart three-chambered, rarely four-cham- 
 bered, the pulmonary and systemic circulations always connected together 
 directly, either in the heart itself or in its immediate neighbourhood. Blood 
 cold. Skull jointed to the backbone by a single articulating surface or 
 "condyle." Each half of the lower jaw composed of several pieces. 
 Appendages of the skin in the form of scales or plates. 
 
 Order I. Chelonia. Ex. Turtles (Cheloniidae), Soft Tortoises 
 (Trionycidae), Terrapins (Emydidte), Land Tortoises 
 (Testudinidae). 
 
 Order 2. Ophidia.Ex. Vipers (Viperidae), Rattlesnakes (Crota- 
 lidae), Sea-snakes (Hydrophidae), Boas and Pythons 
 (Boidse). 
 
 Order 3. Lacertilia. Ex. Lizards (Lacerta), Iguanas (Iguanidae), 
 Monitors (Varanidae), Chameleons (Chamaeleontidae). 
 Order 4. Crocodilia. Ex. Crocodiles, Alligators, Gavials. 
 Order 5. Ichthyopterygia (extinct). Ex. Ichthyosaurus. 
 Order 6. Sauropterygiu (extinct). Ex. Plesiosaurus. 
 Order 7. Pttrosauria (extinct). Ex. Pterodactylus. 
 Order 8. Anomodontia (extinct). Ex. Dicynodon. 
 Order 9. Deinosauria (extinct). Ex. Iguanodon. 
 
 CLASS IV. AVES (Birds) Respiratory organs in the form of lungs, 
 
 never in the form of gills. Lungs connected with air-receptacles placed in 
 different parts of the body. Heart four-chambered. Blood warm. Skull 
 connected with the backbone by a single articulating surface or " condyle." 
 Each half of the lower jaw composed of several pieces. Appendages of 
 the skin in the form of feathers. Cavities of the chest and abdomen not
 
 CHIEF DIVISIONS OF THE ANIMAL KINGDOM. 51 
 
 separated by a complete partition (diaphragm). Fore-limbs converted into 
 wings. Animal oviparous. 
 
 Order I. Natatores (Swimmers). Ex. Penguins (Spheniscidae), 
 Gulls (Laridse), Ducks (Anatidse), Geese (Anserinae), 
 Flamingos (Phaenicopteridae). 
 
 Order 2. Grallatores (Waders). Ex. Rails (Rallidae), Water-hens 
 (Gallinulae), Cranes (Gruidae), Herons (Ardeidae), 
 Storks (Ciconinse), Snipes and Woodcock (Scolop- 
 acidse), Plovers, Oyster-catchers, and Turnstones 
 (Charadriidae). 
 
 Order 3. Cursores (Runners). Ex. Ostrich (Struthio), American 
 Ostrich (Rhea), Emeu (Dromaius), Cassowary (Casu- 
 arius), Apteryx. 
 
 Order 4. Rasores (Scratchers). Ex. Grouse, Ptarmigan, Par- 
 tridges, Pheasants, Turkey, Guinea-fowl, Domestic 
 Fowl, Pea-fowl (Gallinacei) ; Doves, Pigeons, Ground- 
 pigeons (Columbacei). 
 
 Order 5. Scansores (Climbers). Ex. Cuckoos (Cuculidae), Wood- 
 peckers (Picidae), Parrots, Cockatoos, Parrakeets 
 (Psittacidse), Toucans (Rhamphastidae), Trogons 
 (Trogonidae). 
 
 Order 6. Insessores (Perchers). Ex. Crows, Magpies, and Jays 
 (Corvidae), Starlings (Sturnidas), Finches, Grosbeaks, 
 Larks (Fringillidae), Thrushes, Blackbirds, Orioles 
 (Merulidae), Creepers and Wrens (Certhidae), Hum- 
 ming-birds (Trochilidae), Swallows and Martins 
 (Hirundinidse), Swifts (Cypselidse), King-fishers (Al- 
 cedinidae). 
 
 Order 7. Raptores (Birds of Prey). Ex. Owls (Strigidaa), Fal- 
 cons and Hawks (Falconidae), Eagles (Aquilina), Vul- 
 tures (Vulturidse). 
 
 Order 8. Saurum (extinct). Ex. Archaeopteryx. 
 
 CLASS V. MAMMALIA (Mammals or Quadrupeds). Respiratory organs 
 in the form of lungs, which are never connected with air-sacs placed in 
 different parts of the body. Heart four-chambered. Blood warm. Skull 
 united to the backbone by two articulating surfaces or "condyles." Each 
 half of the lower jaw composed of a single piece. Appendages of the skin 
 in the form of hairs. Young nourished by means of a special fluid the 
 milk, secreted by special glands the mammary glands. Animal vivipa- 
 rous. 
 
 A. NON-PLACENTAL MAMMALS. The young not provided with a 
 placenta. 
 
 Order I. Monotremata. Ex. Duck-mole (Ornithorhynchus), Spiny 
 Ant-eater (Echidna). 
 
 Order 2. Marsupialia. Ex. Kangaroos (Macropodidae), Kan- 
 garoo-bear (Phascolarctos), Phalangers (Phalangis- 
 tida), Opossums (Didelphidae), Tasmanian Devil 
 (Dasyurus). 
 
 B. PLACENTAL MAMMALS. The young provided with a placenta. 
 
 Order 3. Edentata. Ex. Sloths (Bradypodidae), Armadillos (Dasy- 
 podidae), Hairy Ant-eaters (Myrmecophagidae), Scaly 
 Ant-eaters (Manis). 
 
 Orders Sirenia. Ex. Manatee (Manatus), Dugong (Halicore). 
 
 Order^. Cetacea. Ex. Whalebone-whales (Balasnidoe), Sperm- 
 whales (Physeteridae), Dolphins and Porpoises (Del- 
 phinidae).
 
 52 INTRODUCTION. 
 
 Order 6. Ungulata (Hoofed Quadrupeds). Ex. Rhinoceros; 
 Tapir ; Horse, Ass, and Zebra (Equidae) ; HipjKipota- 
 mus ; Hogs and Peccaries (Suida) ; Camels and 
 Llamas (Camelidce) ; Giraffe ; Stags, Elk, Reindeer 
 (Cervidae) ; Antelopes (Antilopidce) ; Sheep and Goats 
 (Ovidas) ; Oxen and Buffaloes (Bovidae). 
 
 Order 7. Hyracotdea. Ex. Hyrax. 
 
 Order 8. Proboscidea. Ex. Elephants (Elephas). 
 
 Order 9. Carnivora. Ex. Seals (Phocidae), Bears (Ursidae), 
 Racoons (Procyon), Badgers (Melidae), Weasels and 
 Otters (Mustelidae), Civets and Genettes (Viverridae), 
 Dogs, Wolves, and Foxes (Canidaej ; Hyaenas 
 (Hyaenidae), Cats, Lynxes, Leopards, Tigers, Lions 
 (Felidae). 
 
 Order IO. Rodentia. Ex. Hares and Rabbits (Leporidae), Porcu- 
 pines (Hystricidae), Beavers (Castoridae), Mice and 
 Rats (Muridae), Dormice (Myoxidae), Squirrels and 
 Marmots (Sciuridas). 
 
 Order II. Cheiroptera. Ex. Common Bats (Vespertilionidae), 
 Horseshoe-bats (Rhinolophidae), Vampire-bats (Phyl- 
 lostomidas), Fox-bats (Pteropidae). 
 
 Order 12. Insectivora. Ex. Moles (Talpidae), Shrew-mice (Sori- 
 cidae), Hedgehogs (Erinaceidae). 
 
 Order 13. Quadrumana. Ex. Aye-aye (Cheiromys), Lemurs (Le- 
 muridae), Spider-monkeys (Ateles), Howlers (My- 
 cetes), Macaques (Macacus), Baboons (Cynocephalus), 
 Gibbons (Hylobates), Orang (Simla), Gorilla and 
 Chimpanzee (Troglodytes). 
 
 Order 14. Bimana. Man (Homo Sapiens). 
 
 GENERAL SUCCESSION AND PROGRESSION OF ORGANIC 
 TYPES. Whilst admitting the impossibility of arranging the 
 animal kingdom upon any linear plan, no doubt obtains as to 
 the fact that some of the fundamental " morphological types," 
 or plans upon which animals have been constructed, are higher 
 than others. Every one admits, for example, that the Verte- 
 brate type is higher than the Molluscan or the Articulate type, 
 an admission which is not affected by the fact that the highest 
 Molluscs and Articulates are superior in point of organisation 
 to the lowest Vertebrates. In the same way, within the limits 
 of each sub-kingdom, every one admits that some of the groups 
 are higher than the others. Every one, for example, would 
 admit that a Mammal is a superior animal to a Fish. It fol- 
 lows from this that a certain general arrangement of the animal 
 kingdom, as a whole, is possible, upon the comparative basis 
 of the morphological type of the sub-kingdoms. Similarly a 
 general and more exact arrangement of the classes and orders 
 of each sub-kingdom may be made by the degree of perfection 
 in which the type of the sub-kingdom is carried out in each. 
 
 No generalisation of Palaeontology seems to stand on a
 
 GENERAL SUCCESSION OF ORGANIC TYPES. 53 
 
 firmer basis than that which asserts that there has been a 
 general succession of organic types, and that the appear- 
 ance of the lower forms of life has in the main preceded that 
 of the higher forms in point of time. In other words, it is 
 one of the generalisations of Palaeontology that there has 
 not only been a succession, but also a progression, of organic 
 types in proceeding from the earliest fossiliferous deposits 
 up to the present day. Whilst this general law remains, as 
 we believe, unassailable, there are some important considera- 
 tions which must not be lost sight of. In the first place, it is 
 very doubtful if we are as yet acquainted with the absolute time 
 of the first appearance upon the globe of even one of the sub- 
 kingdoms. Future discoveries, therefore, are almost certain to 
 push back still further into the remote vistas of the past the 
 point of time at which each morphological type first made its 
 appearance upon the globe. Still, there is little likelihood that 
 the relative times of appearance of the great groups, as com- 
 pared with one another, will be affected by the researches of 
 the future. It remains almost certain that we shall find that 
 the lower types were followed in point of time by the higher. 
 In the second place, we find all the primary types in exist- 
 ence before the close of the Silurian period ; and he would be 
 rash indeed who would dogmatically deny that they might all 
 have been present in the earlier Cambrian period. This, at 
 first sight, might seem almost to negative the above generalisa- 
 tion, but it does not affect its value if fairly examined. The 
 lower sub-kingdoms of the Invertebrate animals appeared so 
 early that their origin is lost in the mists of antiquity, and we 
 can say nothing positively as to the time when each came into 
 existence. The Cambrian deposits are underlaid by the vast 
 series of the Laurentian deposits, representing an incalculable 
 lapse of time. These ancient sediments, with one exception, 
 have hitherto proved barren of life, owing to the intense meta- 
 morphism to which they have been subjected, and they conse- 
 quently yield no evidence bearing on the question in hand. 
 They serve to show us, however, by their presence alone, that 
 we must in the meanwhile leave the Invertebrate sub-kingdoms 
 out of account altogether as bearing upon the question of the 
 succession and progression of organic types. We do not know 
 when these sub-kingdoms commenced, and hence we have no 
 right to assert either that they were all introduced simultane- 
 ously, or that they came into being successively. We may be 
 sure, however, of one thing they did not commence at the 
 points where now we find their earliest traces. There remains, 
 then, only the sub-kingdom of the Vertebrate animals which can
 
 54 INTRODUCTION. 
 
 reasonably be appealed to as evidence on this question. The 
 stratified series is long enough to render it certain that it con- 
 tains traces of the first appearance of, at any rate, the higher 
 classes of these, though we doubtless are ignorant of the abso- 
 lute moment at which each appeared. If, therefore, it can be 
 shown that there has been a progression as far as this sub- 
 kingdom is concerned, then there would, by analogy, be the 
 greatest probability that a similar progression has taken place 
 in all the sub-kingdoms. 
 
 So far as our present knowledge goes, it would appear that 
 there is such a progression in the Vertebrate sub-kingdom. 
 The classes of Vertebrates make their appearance, on the 
 whole, in the order indicated by their zoological position, the 
 lowest first and the highest last. Not only does this hold 
 good for the classes of the Vertebrates, but the same general 
 statement may be made as to the orders of each class. Where 
 apparent exceptions occur, a reasonable explanation can be 
 given, or our knowledge can be shown to be defective. Space 
 will not allow a discussion of this question, but a single ex- 
 ample may be taken. So far as we know at present, the earliest 
 remains of vertebrate animals are those of Fishes the lowest 
 class of the sub-kingdom and these appear in the Upper 
 Silurian Rocks for the first time. Granting the probability that 
 Fishes may some day be found in the Lower Silurian Rocks, 
 or even in Cambrian deposits, there still seems no likelihood 
 that they will be deprived by any future discoveries of their 
 position as being the earliest of their sub-kingdom. The oldest 
 remains of Fishes, however, are by no means those which would 
 be expected, but belong to two of the higher orders of the class. 
 This seeming anomaly, however, disappears when we consider 
 that the two lowest orders of Fishes possess no structures by 
 which we can reasonably expect to find them recorded in a 
 fossil state. They may therefore have been in existence long 
 before the Ganoids and Placoids of the Upper Silurian Rocks, 
 and we have no right to assume that they were not. As to the 
 remaining great order of Fishes (the Teleostean Fishes), it is 
 certain that their appearance was much later, and they are gen- 
 erally regarded as inferior to the Ganoids and Placoids in zoo- 
 logical position. This, however, is a matter of opinion, and 
 reasons are not wanting for regarding them as the highest of 
 their class. 
 
 It only remains to add that nothing further is contended for 
 here than the general fact of there having been a progression 
 of morphological types, the lowest presenting themselves first, 
 the highest being the last to appear upon the scene. It is by no
 
 GENERAL SUCCESSION OF ORGANIC TYPES. 55 
 
 means contended that the Ganoid fishes of the Upper Silurian 
 Rocks were in any way degraded members of their order, or 
 inferior in point of organisation to the Ganoids of the present 
 day. On the contrary, there is reason to think that many 
 types early presented a development more varied than that 
 exhibited by their successors. It is simply contended that, on 
 the whole, there has been a zoological progression as we ascend 
 from the Cambrian period to the present day. It is also to 
 be remembered, that though the commencement of the Inver- 
 tebrate sub-kingdoms may be unknown to us, a similar pro- 
 gression can be in many cases shown as regards the orders and 
 classes of these, even more completely than in the case of the 
 Vertebrate sub-kingdom.
 
 PART II.
 
 PART II. 
 
 CHAPTER VII. 
 
 6- UB-KINGD OM I. PRO TOZOA . 
 
 SUB - KINGDOM I. PROTOZOA. Animal simple or composite, 
 generally of very minute size, composed of a structureless, jelly-like, 
 albuminoid substance (termed " sarcode"\ showing no composition 
 out of definite parts or segments, having no definite body -cavity, 
 presenting no traces of a nervous system, and having either no ali- 
 mentary apparatus, or but a very rudimentary one. 
 
 TABLE OF THE DIVISIONS OF THE PROTOZOA. 
 
 CLASS A. GREGARINID^E. Parasitic Protozoa, which are destitute of a 
 mouth, and do not possess the power of emitting processes of their body- 
 substance (pseudopodia). 
 
 CLASS B. RHIZOPODA. Protozoa, which are destitute of a mouth, and 
 have the power of emitting extensile and contractile processes of the body- 
 substance (pseudopodia). 
 
 Order I. Monera. Ex. Protogenes. 
 Order 2. Anixbea. Ex. Amoeba. 
 Order 3. Foraminifera. Ex. Nummulites. 
 Order 4. Radiolaria. Ex. Haliomma. 
 Order 5. Spongida. Ex. Spongilla. 
 
 CLASS C. INFUSORIA (Infusorian Animalcules). Protozoa mostly with 
 a mouth, and rudimentary digestive canal ; destitute of the power of emit- 
 ting pseudopodia; furnished with vibratile cilia or contractile filaments; 
 the body usually with a distinct cuticle covering a layer of firm sarcode. 
 
 Regarded palaeontologically, we may eliminate from the Pro- 
 tozoa the entire class of the Gregarinidce, with the Rhizopodous 
 orders of the Monera and Amosbea, no trace of the past exis- 
 tence of which has yet been obtained, or, from their soft-bodied 
 nature, is ever likely to be. For all practical purposes the 
 same may be said of the large and universally-distributed class 
 of the Infusorian Animalcules. Some of these, however, possess 
 horny or membranous cases which might possibly be preserved 
 in a fossil state ; and it has been alleged that the genus Peri-
 
 6o 
 
 PROTOZOA. 
 
 dinium has been thus detected in the Cretaceous formation. 
 With this doubtful exception, however, no Infusorian animal- 
 cule has ever been detected in the fossil state, though the class 
 has doubtless existed from the most remote antiquity. There 
 remain, then, only the three Rhizopodous orders of the Fora- 
 minifera, Radio/aria, and Spongida, all of which secrete hard 
 structures, and all of which are more or less extensively repre- 
 sented as fossils, so that they demand our attention separately 
 and in detail. 
 
 I. FORAMINIFERA. 
 
 The Foraminifera may be denned as Rhizopoda in which the 
 body is protected by a sJiell or " test" which is usually composed 
 of carbonate of lime, but which may consist of particles of sand 
 cemented together by some animal cetnent, or may be simply horny 
 (chitinous). The animal may be simple, or may repeat itself inde- 
 finitely by budding, and the body-substance gives out long and 
 thread-like processes (pseudopodia), which interlace with one an- 
 other to form a network, and often coalesce at their bases to form a 
 continuous layer of sarcode outside the shell. The pseudopodia 
 reach the exterior either by perforations in the walls of the shell, or 
 simply by the mouth of the latter (fig. 6, c b}. 
 
 Fig. 6. Morphology of Foraminifera. a Lagena vulgarfs, a monothalamous Fora- 
 minifer ; b Miliola (after Schultze), showing the pseudopodia protruded from the oral 
 aperture of the shell ; c Discorbina (after Schultze), showing the nautiloid shell with 
 the foramina in the shell-wall giving exit to pseudopodia ; d Section of Xodosaria 
 (after Carpenter) ; * Kodosaria hisfitda ; / Globigerina bulloides.
 
 
 FORAMINIFERA. 6l 
 
 From a palaeontological point of view the only part of a 
 Foraminifer with which we have to deal is the shell or " test," 
 and there are several points to notice in this connection. 
 Firstly, as regards the actual composition of the shell, it is in 
 the majority of cases calcareous, or composed of carbonate of 
 lime, but it is rarely membranous, and it is not uncommonly 
 " arenaceous " that is, composed of particles of sand cemented 
 together by some animal substance. Secondly, the shells of the 
 Foraminifera may be divided into two natural groups, accord- 
 ing as their walls are, or are not, perforated by apertures or 
 "foramina" through which the pseudopodia are protruded. In 
 those calcareous shells in which the walls are not perforated 
 the substance of the test is " porcellanous," homogeneous, and 
 opaque-white when viewed by reflected light. In those calcar- 
 eous shells in which the walls are perforated by pseudopodial 
 foramina, the substance of the test is "vitreous," transparent, and 
 glassy. The arenaceous shells may or may not be perforated, 
 their texture in either case remaining the same. Thirdly, there 
 are some convenient, though arbitrary, distinctions to be drawn 
 from the form of the shell. The simplest form amongst the 
 Foraminifera, and that in which all alike primitively commence 
 their existence, is that of a single spheroid of sarcode capable 
 of secreting for itself a hard covering, as in Lagena (fig. 6, a) 
 and Orbnlina (fig. 7). This simple state of things is rarely 
 retained throughout life, but the primitive 
 mass of sarcode usually repeats itself by bud- 
 ding, till a compound mass is produced, con- 
 sisting of a number of little spheres of sarcode, 
 surrounded by a common calcareous or are- 
 naceous envelope or test. Each bud of the 
 compound Foraminifer is surrounded by its 
 own shell, so that the whole comes to be com- 
 posed of a number of chambers, each contain- 
 ing a mass of sarcode. The partitions, how- Apennine beds) of 
 ever, or "septa," between the different cham- 
 bers, are perforated by one or more apertures (fig. 6, d], through 
 which pass connecting bands of sarcode ; so that the sarcode 
 occupying the different chambers is united into a continuous 
 and organic whole. Each member of the colony may give out 
 its own pseudopodia through perforations in its investing wall 
 (fig. 6, c), or the pseudopodia may be simply emitted from the 
 mouth of the shell by the last segment only (fig. 6, b). In any 
 case the direction in which the buds are thrown out by the 
 primordial spherule of sarcode is -governed by a determinate 
 law, and differs in different species, the form ultimately assumed
 
 62 
 
 PROTOZOA. 
 
 by the shell depending wholly upon this. The forms, however, 
 assumed by the shells of Foraminifera are extremely variable, 
 even within the limits of a single species, and it would be im- 
 possible to notice even the chief types in this place. There 
 are, however, two or three important variations which may 
 be noticed. If the buds are thrown out from the primitive 
 spherule in a linear series so as to form a shell composed of 
 numerous chambers arranged in a straight line, we get such 
 a type as Nodosaria (fig. 6, e). When the new chambers are 
 added in a spiral direction, each being a little larger than the 
 one which preceded it, and the coils of the spiral lying in the 
 same plane, we get such a form as Discorbina (fig. 6, <r), or 
 Robnlina (fig. 8). These are the so-called " nautiloid " Fora- 
 minifera, from the resem- 
 blance of the shell in figure 
 to that of the Pearly Nauti- 
 lus. From this resemblance 
 the nautiloid Foraminifera 
 were originally placed in the 
 same class as the Ammonites 
 ( Cephalopoda), but their true 
 position was shown by the 
 examination of their soft 
 
 Fig. %.Kobulinaechinata, a "nautiloid' 
 Foraminifer. D'Orbigny. 
 
 parts. In the typical nauti- 
 loid shell the convolutions 
 
 of the spiral all lie in one plane ; but in other cases, as in 
 Rotalia (fig. 9) the shell becomes turreted or top-shaped, in 
 consequence of the coils of the spiral passing obliquely round 
 a central axis. In other forms, such as Numnntlites (fig. 13), 
 
 Fig. <). Rotalia Bone 
 
 D'Orbigtiy. 
 
 Orbitolites, and Orbitoides, the shell, though consisting essen- 
 tially of a succession of chambers arranged in a spiral series, is 
 of a much more complex nature. Lastly, in addition to these 
 symmetrical forms, there are others, such as Globigcrina (fig. 6, 
 /), in which the arrangement of the segments is very irregular. 
 Remains of Foraminifera have been found in all the great
 
 FORAMINIFERA. 63 
 
 formations into which the stratified series is divided, from the 
 Laurentian period to the present day. In one of the limestones 
 of the vast Laurentian series of Canada occurs a singular body 
 which has been described as a gigantic Foraminifer, under the 
 name of Eozoon Canadense (fig. 10). Some observers doubt 
 the true organic nature of Eozob'n, but the weight of authority 
 is decidedly in favour of the belief that the above is its real 
 character. If this be the case, Eozoon is not only the oldest of 
 the Foraminifera, but is the earliest fossil of any kind as yet 
 discovered. Eozoon consists of a chambered calcareous skele- 
 
 a -\?'? ...... '; .." 
 
 A 
 
 Fig. io. Diagram of a portion of Eozoon (after Carpenter). A, B, C, Three tiers of 
 chambers communicating with one another by constricted apertures ; a a The true shell- 
 wall, perforated by numerous pseudopodial foramina; b b Intermediate skeleton ; c Pas- 
 sage of communication (stolon-passage) from tier to tier ; d Ramifying tubes in the inter- 
 mediate skeleton. 
 
 ton infiltrated by certain silicates in solution. These silicates 
 are chiefly white pyroxene, serpentine, and Loganite, and they 
 are now found occupying all the spaces in the fossil which were 
 formerly filled with the sarcode of the animal. When, there- 
 fore, a specimen of Eozoon is treated with acid, the calcareous 
 matter is dissolved out, and what we have left consists of a 
 cast in the above silicates of the chambers formerly occupied 
 by the sarcode of the animal, together with the various passages 
 by which these chambers are connected, and the tubes by 
 which the pseudopodia were conducted to the exterior. That 
 such a replacement of an animal body by silicated minerals 
 is not an impossibility is shown by the occurrence of casts of 
 living Foraminifera (such as Amphistegina) in which the sarcode 
 is replaced by a green silicate (probably glauconite), which 
 forms an accurate cast of the interior of the shell. Eozoon 
 consists essentially of a series of chambers placed in tiers 
 (fig. io, A, B, C) which are arranged one above the other.
 
 64 PROTOZOA. 
 
 Sometimes its growth was very regular, but sometimes extremely 
 irregular. The chambers are more or less perfectly marked off 
 from one another by inflections of the test or " septa," per- 
 forated for the passage of bands of sarcode, by which the 
 chambers are brought into organic connection. The sarcode 
 occupying the tiers of chambers is bounded by a thin "proper 
 wall" (fig. 10, a a), perforated by numerous minute tubes by 
 which the pseudopodia reached the exterior. It is obvious, 
 however, that only the chambers of the uppermost tiers could 
 thus have the power of giving out pseudopodia. The various 
 tiers of chambers are connected with one another by a canal- 
 system, and are separated from one another by the develop- 
 ment of supplementary layers of calcareous matter, constituting 
 what is called the " intermediate skeleton." Eozoon appears 
 to have grown in reef-like masses, often of very great extent, 
 and it finds its nearest living allies in the recent Polytrema and 
 Carpenteria. Its shell-structure also shows points of affinity 
 with the extinct Nummulites and the recent Calcarina. Eozoon 
 has been detected, not only in the Laurentian series of Canada, 
 but in other rocks supposed to be of the same age in Bavaria 
 and in other parts of Europe. It also occurs in the Lower 
 Silurian marbles of Connemara in Ireland ; and it is said to 
 have been detected in rocks of Liassic age. 
 
 Having given a somewhat detailed account of the singular 
 Eozoon justified by its importance it will not be necessary 
 to speak at any length of the more modern representatives of 
 the order. In the Silurian Rocks remains of Foraminifera 
 have been detected in various localities, some of the forms 
 apparently being identical with existing types. Thus, Ehren- 
 berg showed that the Lower Silurian sandstones of the 
 neighbourhood of St Petersburg contained casts of Forami- 
 niferous shells in glauconite, some of which were referable 
 to the living genera Rotalia and Textularia. Over wide 
 areas in the Southern Alps, Russia, Spain, Armenia, and the 
 United States, beds of Carboniferous limestone are charged 
 
 with the shells of Fusnlina 
 (fig. n). Whole beds are 
 made up of the remains of 
 this minute fossil, and the 
 Fusulina limestone has been 
 Fig. n.-F***u*a cyiindrica. justly paralleled with the 
 
 Carboniferous, Russia. NummulitlC Limestone of 
 
 Eocene times. 
 
 In the Secondary Rocks, Foraminifera occur in great abun- 
 dance, but they are not specially noticeable except for the part
 
 FORAMINIFERA. 
 
 they play in the formation of Chalk. The great formation of 
 the White Chalk forming the well-known chalk-cliffs of the 
 south of England, and attaining sometimes a thickness of not 
 less than 1000 feet is to a very large extent composed of the 
 debris of the microscopic shells of Foraminifera. As already 
 pointed out, therefore, the White Chalk is to some extent 
 comparable with the ooze of the deep Atlantic, which is also 
 largely made up of the skeletons of these minute organisms. 
 Amongst the Foraminifera of the Chalk are the genera Globi- 
 gerina (fig. 6, f), Rotalia (fig. 9), and Textularia (fig. 12), all 
 of which are represented by living species, no difference being 
 distinguishable in the case of 
 the first between the Creta- 
 ceous and the modern form. 
 In the Cretaceous formation 
 (Upper Greensand) we have 
 also the gigantic Arenaceous 
 Foraminifer which consti- 
 tutes the genus Parkeria, 
 the shell of which attains a 
 diameter of two and a quarter 
 inches. 
 
 In the Kainozoic period the Foraminifera attained their 
 maximum of development, both as regards their size and the 
 number of generic types. The Eocene formation especially is 
 remarkable for the profusion of its Foraminiferous fauna. The 
 Middle Eocene in particular is characterised by the possession 
 of a very widely spread and easily recognised formation, known 
 as the Nummulitic Limestone, from the occurrence in it of a 
 large coin-shaped Foraminifer, the Nwnmulite (fig. 13). Num- 
 mulites attain a size of as much as three inches in circumference, 
 and their structure is very complex. According to Sir Charles 
 
 Fig. 12. Textularia Meye> 
 D'Orbigny. 
 
 Fig. 13. Nummulites Icevigatus. Eocene. 
 
 Lyell, " the Nummulitic Limestone, with its characteristic 
 fossils, plays a far more conspicuous part than any other
 
 66 PROTOZOA. 
 
 Tertiary group in the solid framework of the earth's crust, 
 whether in Europe, Asia, or Africa. It often attains a thick- 
 ness of many thousand feet, and extends from the Alps to the 
 Carpathians, and is in full force in the north of Africa, as in 
 Algeria or Morocco. It has also been traced from Egypt, 
 where it was largely quarried of old for the building of the 
 Pyramids, into Asia Minor, and across Persia, by Bagdad, to 
 the mouths of the Indus. It occurs not only in Cutch, but in 
 the mountain-ranges which separate Scinde from Persia, and 
 which form the passes leading to Cabul ; and it has been fol- 
 lowed still further eastwards into India, as far as Eastern 
 Bengal and the frontiers of China." Another important 
 member of the Eocene Rocks is the Miliolite Limestone of 
 the Paris basin, so called because of the abundance in it of the 
 shells of a species of Miliola, of which a living form is shown 
 in fig. 6, b. 
 
 II. RADIOLARIA. 
 
 The order Radiolaria is denned as comprising those members 
 of the Rhizopoda which possess a siliceous test or siliceous spicules, 
 and are provided -with pseudopodia which stand out from the body 
 like radiating filaments, and occasionally run into one another 
 (fig. 14)- 
 
 Fig. 14. Recent Radiolaria. a Acanthometra; b Haliomma, one of the Poly- 
 cystina, showing the siliceous test and radiating pseudopodia. 
 
 All the Radiolaria possess hard structures in the form of sili- 
 ceous spicules or a siliceous test ; but only one group, viz., 
 that of the Polycystina, has as yet been detected in a fossil 
 condition. The Polycystina (fig. 14, b} are all microscopic 
 organisms very closely allied to the Foraminifera, from which 
 they differ chiefly in the siliceous nature of their skeleton. 
 The test is glassy, composed of flint, perforated by numerous
 
 SPONGIDA. 67 
 
 foramina for the emission of pseudopodia, and often provided 
 with spine-like projections. The Polycystina are best known 
 as occurring in the so-called " Infusorial Earth " of Barbadoes. 
 This is a Tertiary deposit, and consists largely of the shells of 
 Polycystina. They have not as yet been detected in any 
 Palaeozoic formation, but they are known to occur in the 
 Mesozoic series. 
 
 III. SPONGIDA. 
 
 The Sponges may be defined as Rhizopoda composed of 
 numerous amxbiform masses of sarcode united into a composite 
 mass, which is traversed by canals opening on the surface, and is 
 almost always supported by an internal skeleton or framework of 
 horny fibres or of calcareous or siliceous spicula. 
 
 The only portion of the Sponges with which the palaeonto- 
 logist is concerned, is the skeleton. Whatever the nature of 
 this skeleton may be, it is so arranged that its parts surround 
 two sets of apertures which open on the surface of the sponge, 
 and which are connected with one another by a system of 
 canals ramifying in its deeper portions. Of the apertures 
 which penetrate the substance of the sponge in every direc- 
 tion, one set consists of large chimney-like openings, which are 
 called " oscula," or " exhalant apertures." There maybe only 
 a single osculum, or many may be present. The other set 
 consists of very much smaller openings, which are always very 
 numerous, and which are termed the " pores," or " inhalant 
 apertures." The pores and oscula are connected by a system 
 of canals excavated in the substance of the sponge, and a con- 
 stant circulation of water can be kept up through the whole 
 mass, the former serving for the incoming currents, the latter 
 for the outgoing. 
 
 The Sponges are divided into three groups according to the 
 nature of the skeleton : i. Keratosa, comprising the ordinary 
 sponges of commerce, in which the skeleton is composed of 
 a horny substance called "keratode;" 2. Calcarea, or Calci- 
 spongia, in which the skeleton is composed of carbonate of 
 lime ; and 3. Silicea, or Vitrea, in which the skeleton is com- 
 posed of flint or silex. 
 
 The Horny Sponges, from the nature of their skeleton, are 
 not certainly known as fossils ; but traces of their past exist- 
 ence are said to have been obtained in the form of the spicules 
 with which the horny skeleton is sometimes furnished. The 
 Calcareous and Siliceous Sponges are both well represented in 
 a fossil condition, though the true nature of some of the more
 
 68 
 
 PROTOZOA. 
 
 ancient examples is perhaps somewhat dubious. As far as 
 we know at present, the Calcispongix commence in the Silurian 
 Rocks, attain their maximum in the Secondary Rocks, and are 
 diminished in numbers at the present day ; though Haeckel's 
 recent discoveries have rendered this last assertion more than 
 problematical. The Silirispongia seem to have come into 
 existence during the Secondary period, attaining a great de- 
 velopment during the Cretaceous epoch, and being well repre- 
 sented at the present day. 
 
 As regards Palaeozoic sponges, one of the earliest known 
 forms is the Archceocyathns (fig. 15) of Mr Billings, species of 
 which have been obtained from the Potsdam Sandstone and 
 Calciferous Sand-rock (Upper Cambrian?) of Canada. The 
 
 general form in this genus 
 is that of a hollow cone or 
 hollow cylinder, enclosing a 
 large cup-shaped cavity, and 
 tapering towards one ex- 
 tremity, which was presum- 
 ably fixed to some foreign 
 body. Specimens appear to 
 have reached a very large 
 size, a length of two or three 
 feet and a diameter of three 
 or four inches being some- 
 times attained. The sponge 
 consists of an outer wall, 
 usually perforated with nu- 
 merous small irregular aper- 
 tures, and a thin inner wall 
 pierced with many open- 
 ings (fig. 15, a). The space 
 between the outer and inner 
 wall is subdivided into a 
 
 number of vertical radiating partitions, thus very closely simu- 
 lating the structure of one of the septate corals. The genus, 
 however, is shown truly to belong to the Spongida by the 
 occurrence of numerous branching, cylindrical, or fusiform 
 siliceous spicula within the substance of the organism. In the 
 same geological horizon, and also in higher strata, occurs the 
 somewhat allied genus Calathium, in which the skeleton also 
 assumed a turbinate form. 
 
 Amongst the Lower Silurian genera of Sponges may be 
 mentioned Palceospongia, Acanthospongia, Eospongia, Palceo- 
 manon, and Astylospongia (fig. 16). In the last, we have a 
 
 Fig. 15. Restoration of the lower part of 
 rclurocyathus Minganensis ; a the pores of 
 
 Arc 
 
 the inner wall of the cup. 
 
 (After Billings.)
 
 SPONGIDA. 69 
 
 globular sponge, provided with a cup-shaped cavity, on which 
 the oscula open, whilst the pores open upon the external sur- 
 face of the sphere. It was a calcareous sponge, enjoying a 
 free mode of existence, and it presents points of decided 
 affinity to the recent genus 
 Grantia. In the Upper Silurian 
 Rocks occur many sponges, -,vy 
 
 one of the most interesting .^ - ^p 
 
 genera being Amphispongia, '. ''.'' ^ 
 comprising calcareous sponges, 
 oblong or sub-clavate in shape, 
 
 containing a central cavity, and / 
 
 probably opening above by a 
 single osculum. On this hori- 
 zon occurs also the genus Favo- 
 spongia ; and here, as well as in 
 the Lower Silurians, we have -. 
 
 . ' tig. 16. Section of ..-,, 
 
 the Singular genUS StromatO- pra-morsa, a lower Silurian 
 
 pora, which will be spoken of (after 
 immediately. In the Devonian Rocks, the genus Sparsispongia 
 may be noted ; but the Carboniferous series has hitherto 
 proved singularly destitute of sponges. In the Permian Rocks 
 it is worthy of notice that there occurs a genus described by 
 Geinitz under the name of Spongillopsis, and believed by him 
 to be most nearly allied to the recent fresh-water sponges 
 (Spongilla}. This is a remarkable fact as bearing upon Pro- 
 fessor Ramsay's view, that the Permian Rocks were deposited 
 in inland waters of great extent. 
 
 Leaving the Palseozoic series, the sponges of the Triassic 
 and Jurassic formations call for no special remark, except that 
 the latter series abounds with examples of the Calcispongia. 
 It is in the Cretaceous system, however, in which we meet with 
 the greatest development of the sponges. The flints which 
 form such a characteristic feature in the White Chalk are, in 
 some measure at any rate, "connected with the periodic 
 growth of large crops of the sponges " (Owen) ; and in some 
 sections of flint are found minute " spherical bodies, covered 
 with radiating and multicuspid spines," which have been 
 termed Spiniferites or Xanthidia, and are probably the " gem- 
 mules " of sponges. (By some, however, these are regarded 
 as being the " sporangia " of the Desmidice, an order of the 
 Protophyta.) The two most notable genera of Cretaceous 
 Sponges are Siphonia and Ventriculites. The Siphonice (fig. 17) 
 belong to a group of sponges termed Petrospongiada, from 
 their possession of a stony reticulate skeleton without spicula.
 
 PROTOZOA. 
 
 They consist of a pear-shaped mass, supported upon a longer 
 or shorter stem, which breaks up at its base into a number of 
 root-like processes of attachment. At the summit of the pyri- 
 form head is a single chimney-like osculum. In many respects 
 
 Fig. 17. Siphonia 
 ficus, a Cretaceous 
 Sponge. D'Orbigny. 
 
 Fig. i%.Ventriculites 
 radiatns. White Chalk. 
 (After Lyell.) 
 
 the Siphonia present a curious resemblance to the Holtenia 
 of the Atlantic ooze, and, like these, they probably were 
 denizens of a deep sea. The genus, however, is not known 
 to occur in strata younger than the Chalk. 
 
 Still more closely allied to the living Holtenia are the Ven- 
 triculites of the Chalk (fig. 18). These "have usually the 
 form of graceful vases, tubes, or funnels, variously ridged or 
 grooved, or otherwise ornamented on the surface, frequently 
 expanded above into a cup-like lip, and continued below into 
 a bundle of fibrous roots. The minute structure of these 
 bodies shows an extremely delicate tracery of fine tubes, some- 
 times empty, sometimes filled with loose calcareous matter 
 dyed with peroxide of iron " (VVyville Thomson). Like the 
 Siphonia, the genus Ventriculites is not known to occur above 
 the Chalk. 
 
 The Tertiary Sponges call for no special comment ; but it 
 may be noticed that the great apparent predominance of the
 
 SPONGIDA. 7 1 
 
 Horny Sponges in our present seas, may be explained by the 
 _ fact that the members of this group cannot be recognised in a 
 ' fossil state except by their siliceous spicula, and that these are 
 only sometimes present, and are necessarily very difficult of 
 detection. The genus Cliona alone, comprising the singular 
 boring sponges, has managed to survive from the commence- 
 ment of the Palaeozoic period to the present day. Shells 
 mined by species of this genus occur in the Silurian Rocks, 
 and the genus is well represented in recent seas. 
 
 FOSSILS OF DOUBTFUL AFFINITIES. Before leaving the Pro- 
 tozoa, there are two fossils of doubtful relationships which may 
 be briefly noticed viz., Stromatopora and Receptaculites. These 
 show points of affinity to the Foraminifera on the one hand, 
 and the Sponges on the other hand, whilst the former ap- 
 proaches the Corals in some respects. Both, however, may, 
 with the greatest probability, be regarded as peculiar types of 
 Sponges. 
 
 Stromatopora (fig. 19) forms hemispherical, globular, or 
 irregular masses, often of very considerable size, and sometimes 
 
 Fig. 19. A small and perfect specimen of Stromatopora. rugosa (Hall). 
 From the Memoirs of the Geological Survey of Canada. 
 
 demonstrably attached to shells. In its structure, Stromato- 
 pora consists of numerous thin, concentric laminae, penetrated 
 by minute tubes, the mouths of which appear on the surface
 
 72 PROTOZOA. 
 
 of each lamina as minute pores. Species of the genus occur 
 in both Lower and Upper Silurian strata, and in the Devonian 
 series, apparently not completely disappearing till towards the 
 close of the Triassic period. 
 
 Rueptaatlites (fig. 20), in its most perfect condition, is 
 described by Mr Billings as being " of a discoid, cylindrical, 
 
 ovate, or globular shape, 
 hollow within, and usually, 
 if not always, with an 
 aperture in the upper side. 
 Irl or near the centre of 
 the lower side there is 
 generally to be seen a 
 small rounded protuber- 
 ance, indicating, most pro- 
 bably, the position of the 
 primitive cell or nucleus 
 from which the animal 
 commenced its growth. 
 . . . The body-wall is of 
 a somewhat complex struc- 
 
 tacitlitcs, as it Would be shown by a vertical se'c- ture. It Consists of three 
 tion of a perfect specimen, a The aperture at the t j 
 
 summit ; b The inner integument ; c The outer parts an external and an 
 
 rtff^tttfj^fiftBI intemal ^tegument, and, 
 
 bands running from the outer to the inner integu- between theSC, 3. peculiar 
 
 tubular or spicular skele- 
 ton." The inner and outer integuments are composed of 
 numerous rhomboidal calcareous plates, closely fitting together, 
 and arranged in peculiar curved rows, giving fragments of the 
 fossil very much the appearance of the engine-turned case of a 
 watch. The inner integument differs from the outer in being 
 pierced by numerous small apertures, which open into the 
 central cavity, an aperture being placed at every junction of 
 four plates. Lastly, the inner and outer integuments are con- 
 nected together by a number of small straight cylindrical tubes 
 or hollow spicula. The late Mr Salter regarded Rcceptaculitcs 
 as belonging to the Foraminifera, and finding its nearest living 
 ally in Orbitolites. Mr Billings, however, points out that it 
 has some curious points of resemblance to the little seed-like 
 "gemmule" of the Fresh-water Sponge; and he regards it as 
 being on the whole a Sponge, having relationships with the 
 Foraminifera. Reccptaculites occurs in both Lower and Upper 
 Silurian strata, as does the nearly-allied or identical genus 
 Ischadites.
 
 CCELENTERATA. 73 
 
 CHAPTER VIII. 
 
 SUB-KINGDOM IL CCELENTERATA. 
 FOSSIL HYDROZOA. 
 
 SUB-KINGDOM II. CCELENTERATA. Animals whose alimen- 
 tary canal communicates freely with the general cavity of the body 
 (" somatic cavity "), so that the body-cavity communicates with the 
 outer world through the mouth. Body composed of tivo funda- 
 mental layers, an outer layer or " ectoderm" and an inner layer or 
 " endoderm" The parts of the body, and especially the organs 
 round the mouth, arranged in a star-like or radiated form. 
 
 TABLE OF THE DIVISIONS OF THE CCELENTERATA. 
 
 CLASS A. HYDROZOA. The walls of the digestive sac not separated 
 from those of the general body-cavity, the two coinciding with one another. 
 Reproductive organs in the form of external processes of the body-wall. 
 Sub-class I. HYDROIDA (Hydroid Zoophytes). 
 Order I. Hydrida.Ex. Hydra. 
 Order 2. Corynida. Ex. Tubularia. 
 Order 3. Thecaphora. Ex. Sertularia, Campanularia. 
 Sub-class II. SIPHONOPHORA (Oceanic Hydrozoa). 
 Order 4. Calycophoridce. Ex. Diphyes. 
 Order 5. Physophoridce, Ex. Physalia. 
 Sub-class III. DISCOPHORA (Jelly-fishes). 
 
 Order 6. Medusidce. Ex. ^Egina. 
 Sub-class IV. LUCERNARIDA (Sea-blubbers). 
 Order 7. Lucernariadcz. Ex. Lucernaria. 
 Order 8. Pelagidce.Ex. Pelagia. 
 Order 9. Rhizostomida Ex. Rhizostoma. 
 Sub-class V. GRAPTOLITID^ (Graptolites.) 
 
 CLASS B. ACTINOZOA. Animal with a differentiated digestive sac open- 
 ing below into the body-cavity, but separated from it by an intervening 
 " perivisceral space," which is divided into compartments by a series of 
 radiating vertical partitions or "mesenteries," to the faces of which the re- 
 productive organs are attached. 
 
 Order I. Zoantharia. Ex. Sea-anemones, Star-corals, Brain- 
 corals. 
 
 Order 2. Alcyonaria. Ex. Sea-pens, Fan-corals, Sea-shrubs, Red- 
 coral. 
 
 Order 3. Rugosa. Ex. Cyathophyllum. 
 Order 4. Ctenophofa Ex. Venus's Girdle. 
 
 The Coelenterata appear to have commenced their existence 
 in the Cambrian period, at which time both the great classes 
 of the sub-kingdom were differentiated from one another. So 
 far as we can judge, the Ccelenterate animals have attained 
 their greatest development at the present day; but two large
 
 74 
 
 CCELENTERATA. 
 
 groups (the Graptolitida and Rugosa) are wholly extinct, whilst 
 the group of the Tabulate Corals is now much reduced in 
 numbers. The above conclusion is further rendered uncertain 
 by the existence in the sub-kingdom of some groups which, 
 from their absence of hard parts, have left no traces of their 
 past existence. 
 
 FOSSIL HYDROZOA. 
 
 Of the living orders of Hydrozoa, the Fresh-water Polypes 
 (Hydrida) and the Oceanic Hydrozoa (Calycophorida and 
 Physophorida) have left no traces of their former presence, as 
 might have been anticipated from their want of hard structures. 
 The order of the Medusida and the sub-class Lucernarida 
 (Jelly-fishes and Sea-blubbers) are equally destitute of hard 
 parts, and their absence from the 
 palaeontological record might have 
 been confidently predicted. Curi- 
 ously enough, however, traces of 
 both groups have been detected in 
 the fine-grained lithographic slates 
 of Solenhofen and Eichstadt. Of 
 the Medusida, the two living families 
 of the dEqiioridce and Trachyne- 
 mida have been recognised by 
 their impressions ; and an ancient 
 member of the order Rhizostomida 
 represents the Lucernarida in the 
 same formation/ With these ex- 
 ceptions, however, the only living 
 orders of Hydrozoa which have 
 fossil representatives are the Cory- 
 nida and Thecaphora, both of which 
 possess a chitinous or horny in- 
 tegumentary skeleton. In neither 
 case, however, can the evidence be 
 said to be wholly free from sus- 
 picion. 
 
 I. CORYNIDA Or TUBULARIDA 
 
 (Pipe-Corallines.) Animal simple, 
 consisting of a single polypite; or 
 compound, consisting of sei'eral poly- 
 
 pites united to one another by a common flesh or ccenosarc. The 
 cxnosarc generally secretes a hard chitinous outer covering or 
 " polypary ; " but the separate polypites are never protected by cup- 
 
 Fig. ai. Coryniila. 
 f Tubularia indivisa. 
 
 Fragment 
 atural size.
 
 FOSSIL HYDROZOA. 
 
 75 
 
 like expansions of the polypary. Type of the order, Tubularia 
 
 (fig. 21). 
 
 Two genera, viz., Pal&ocoryne and Corynoides, have been re- 
 ferred to the Corynufa, but in neither case is the reference free 
 from doubt. Palaocoryne (fig. 22) is a minute organism which 
 
 Fig. 22. Palceocoryiie radiatum, enlarged fifteen diameters. 
 (After Duncan and Jenkins.) 
 
 was discovered by Dr Martin Duncan and Mr Jenkins grow- 
 ing attached to the margins of Lace-corals (Fenestella) in the 
 Carboniferous Rocks of Scotland. Its base is expanded, with 
 finger-like processes of attachment. From the base rises a 
 short robust stem, which is marked with flutings and super- 
 ficial granulations. The stem terminates in a single polypite, 
 the mouth of which is surrounded by a single whorl of slender 
 processes or " tentacles," in the centre of which is the mouth. 
 The entire polypary, as above described, is " calcareous, dense, 
 and ornamented." In one living form only (viz., Bimeria) is 
 the polypary continued along the tentacles and upper part of 
 the body of the polypite, and in this case the polypary is simply 
 of the consistence of parchment. This peculiarity, therefore, 
 with the possession of a calcareous polypary, renders the refer-
 
 CCELENTERATA. 
 
 ence of Palaocoryne to the order Corynida not wholly free from 
 doubt. 
 
 The genus Corynoidcs was proposed by the author for some 
 singular fossils from the Lower Silurian 
 . Rocks of Scotland. Each consists of 
 
 C/^V a cylindrical corneous tube (fig. 23), 
 I J tapering towards the base, where it is 
 /' / furnished with two small spines, and 
 
 expanding above into a species of 
 toothed cup. Corynoides consists of a 
 single polypite, and in this respect may 
 M be compared with some living Cory- 
 
 11 nida. It would seem, however, not to 
 
 have been attached to any foreign 
 body as all living Corynids are 
 and its true affinities are thus rendered 
 uncertain. 
 
 II. THECAPHORA (or Sertularida and Campanularidd). 
 Animal compound, rooted and plant-like, consisting of numerous 
 
 Fig. 23. Corynoides cali- 
 cularis, enlarged. (Origi- 
 nal.) 
 
 Fig. 24. a Sertularta (Difihasia) pimtata, natural size: 4 Fragment of the same en- 
 larged, carrying a male capsule (o), and showing the hydrothecse (AJ ; f> Fragment of 
 Campanularin neglecta (after Hincks), showing the polypites contained in their hydro- 
 thecae (h), and also the point at which the coenosarc communicates with the stomach of 
 the polypite (o). 
 
 polypites united by common flesh or coenosarc. The avnosarc is 
 more or less branched, and secretes a strong chitinous investment or 
 The polypites are also protected -within " hydro-
 
 FOSSIL HYDROZOA. 
 
 77 
 
 or little cup-like expansions derived from the polypary. 
 The process of reproduction is carried on by the development of 
 the reproductive elements within horny urn-like sacs, which are of 
 larger size than the " hydrotheca" and are known as " ovarian 
 capsules" or "gonothecce" (often called " gonophores"). Type of 
 the order, the Sea-fir (Sertularia., fig. 24). 
 
 As in the case of the Corynida, there is some uncertainty as 
 to the existence of any fossil representatives of this order. No 
 undoubted Sertularian, at any rate, is as yet known to the 
 palaeontologist ; but there are several genera which may with 
 more or less probability be referred to this place. The most 
 important of these as being those in which the reference is 
 probably correct are certain forms usually referred to the 
 
 Fig 25 Dendrograpsus Hallianus. 
 tion of a branch, enlarged ; c The footstalk 
 size. (After Hall.) 
 
 a Portion of the frond, natural size ; b Por- 
 and some of the principal branches, natural 
 
 GraptoUtidce, of which the genera Dendrograpsus and Dicty- 
 onema may be noticed in particular. The forms referred to 
 Dendrograpsus are exclusively confined to the Upper Cam- 
 brian and Lower Silurian formations. They consist of plant- 
 like spreading and branched growths, which are furnished with 
 a strong footstalk (fig. 25). In all probability the organism 
 was attached by the base of the footstalk to some foreign 
 body, but no actual demonstration of this has as yet been 
 obtained. The branchlets carry upon one side a series of
 
 78 CCELENTERATA. 
 
 little chitinous cups or " cellules," each of which must have 
 contained a polypite, and which agree with the similar struc- 
 tures of the Graptolites in partially overlapping one another ; 
 thus differing from the " hydrothecae " of the Sertularians. 
 
 In Dictyonema (fig. 26) we have organisms resembling 
 Dendrograpsus in many respects, but not possessing any foot- 
 
 Fig. rt.Dictyonenta rctiforme, Hall. (After Hall.) 
 
 stalk. The frond is branched and plant-like, and is fan-shaped 
 or funnel-shaped in form. It is not certainly known whether 
 the organism was attached by its base or not ; but there is the 
 strongest probability in favour of its having been fixed. The 
 branches radiate from the base, running nearly parallel with 
 one another, and often bifurcating. They are united to one 
 another at short intervals by numerous, irregular, slender, 
 transverse processes or dissepiments, and they bear small 
 horny cups or " cellules " like those of the Graptolites. Dic- 
 tyonema ranges from the Upper Cambrian to the Middle 
 Devonian. The genus bears a close superficial resemblance 
 to the Fenestellce or Lace-corals (belonging to the Polyzod) ; 
 but the latter have a calcareous skeleton, and have no " cel- 
 lules." Besides the above-mentioned genera, Callograpsna 
 and Ptilograpsus may with great probability be referred to the 
 Sertularida ; as may, perhaps, be the obscure fossils Bntho- 
 grapsus and Thamnograpsus. All these genera are Silurian or 
 Upper Cambrian in age.
 
 FOSSIL HYDROZOA. 79 
 
 OLDHAMIA. The singular fossils described under the genus 
 Oldhamia may be noticed here, as they have been referred to 
 the Hydrozoa ; though their true nature is altogether uncertain. 
 Oldhamia occurs in certain green and purple grits of Lower 
 Cambrian age, at Bray Head, in Wicklow, Ireland. They 
 occur in great abundance, matted together, and spreading over 
 the surfaces of the strata. Old- 
 hamia antiqua, the commonest 
 species, consists of a central 
 thread-like axis from which 
 spring bundles or umbels of 
 short radiating branches (fig. 27), 
 at regular intervals. Each branch 
 " is formed of a series of articu- 
 lations marking the positions of 
 minute cells" (E. Forbes). Old- 
 hamia has been variously refer- 
 red to the Sertularian Zoophytes, 
 to the Polyzoa, and to the vege- 
 table kingdom. The most pro- 
 bable conjecture would refer the 
 genus to the calcareous sea- 
 weeds (Salter). 
 
 III. SUB-CLASS GRAPTOLITID^E 
 (Graptolites). The Graptolites 
 form a very large and important 
 family of fossils which usually present themselves in the shape 
 of horny linear bodies, toothed or serrated upon one or both 
 sides, and often combined into more or less complex systems. 
 If we disregard the genus Dictyonema, which is best referred 
 elsewhere, the Graptolites have an extremely definite range in 
 point of time, being exclusively confined to the Upper Cam- 
 brian and Silurian deposits. They attain their maximum of 
 development in the Upper Cambrian Rocks (Quebec group of 
 Canada and Skiddaw Slates of England), are abundantly re- 
 presented in the Lower Silurian, and die out altogether before 
 the close of the Upper Silurian period. 
 
 Excluding the genera Dictyonema, Dendrograpsus, Ptilograp- 
 MS, and Callograpsus, the GraptolitidcB may be defined by the 
 possession of a compound polypary, consisting of a tubular 
 chitinous investment enclosing the ccenosarc, giving origin to 
 numerous cup-like " cellules " or " hydrothecae," each of which 
 protected a polypite. The polypary was free, and was not at- 
 tached to any foreign body ; and the polypites were not sepa- 
 rated from the coenosarc by any partition. Lastly, the poly-
 
 8o 
 
 CCELENTERATA. 
 
 pary was almost always strengthened by a chitinous rod or fibre, 
 which is termed the " solid axis," and which is somewhat analo- 
 gous to the chitinous rod described by Dr Allman in the 
 singular Polyzoon, Rhabdopleura. 
 
 From the above definition, it will be seen that the Grapto- 
 lites agree with the living Sertulari- 
 ans in possessing a corneous poly- 
 pary, which not only invests the cceno- 
 sarc, but is expanded into little cups 
 or " hydrothecae, " within which 
 each polypite is protected. The 
 Graptolites, however, differ from the 
 Sertularians in the fact that the poly- 
 pary was unattached, and apparently 
 free-floating, whilst it has not, except 
 in a few cases, anything like the plant- 
 like appearance of the latter. Further, 
 the hydrothecae of the Graptolites, 
 except in the genus Rastrites, always 
 more or less overlap one another ; 
 whereas those of the Sertularians are 
 not in contact. Lastly, no Sertula- 
 rian exhibits any structure which can 
 be compared with the " solid axis " 
 of the Graptolites. 
 
 Taking such a simple Graptolite 
 o as G. priodon (fig. 28), or G. sagitta- 
 
 i&X^t^Sn^. rius (fig. 29, A), as the type of the sub- 
 
 odo,t, Bronn, preserved in relief : c l ass> tne polypary IS Seen tO Consist 
 
 Clements, ^ 
 
 ment of th 
 largcd. D, 
 
 lateral viewsHghtivn f > 
 
 Dorsal view of a fragment of the ot three elements, which are known 
 
 viewof bl a y fr a e : *s the solid axis," the common 
 
 e, showing the canal," and the " Cellules." The 
 
 ve^ s^on'of " solid axis " is a cylindrical fibrous 
 rod which gives support to the cor- 
 neous and flexible polypary. The 
 term " solid" is probably a misnomer; for it was almost certainly 
 hollow, and filled with living material. It appears to be absent in 
 the genus Rastrites, and in Retiolitcs Gcinitzianus, but some un- 
 certainty rests upon this point. As a very general rule, it is 
 prolonged as a longer or shorter naked rod beyond one or both 
 ends of the polypary, and either extension may be more or less 
 dilated. Its basal prolongation, with or without an accom- 
 panying extension of the common canal, is termed the "radicle," 
 or " initial point," as marking the organic base of the frond. 
 The " common canal " is the tube in which the crenosarc
 
 FOSSIL HYDROZOA. 
 
 Si 
 
 was enclosed ; but it commonly appears, in compressed speci- 
 mens, merely as a vacant space between the "cellules" and 
 the solid axis. The common canal gives origin, by a process 
 of budding, to the " cellules " or " hydrothecae," which are little 
 horny cups for the reception of the polypites. Each cellule 
 
 Fig. 29. A, Young individual of Graptolitcs Sagittarius, His., showing the slender 
 curved base of the frond, and the extension of the axis beyond its opposite end ; B, Base of 
 another individual of the same, in which there is an extremely long " radicle ; " C, Frag- 
 ment of G. Sagittarius, much enlarged to show the cellules from a specimen in relief ; 
 D, Specimen of Graptolites Clingani, Carr., showing the distal and proximal extensions 
 of the axis. 
 
 rests by its base upon the common canal, is separated from its 
 neighbours by " cell-partitions," and opens at its apex by a 
 distinct aperture or "cell-mouth," through which the polypite 
 could exsert its tentaculate head. 
 
 The reproductive process appears, in some cases, at any rate, 
 to have been carried on by the formation at certain seasons of 
 horny capsules, of much greater size than the cellules, within 
 which the generative elements were matured. In some cases 
 these " ovarian vesicles" have been found actually attached to 
 the fronds of Graptolites. In other cases, as described by the 
 writer, we find numerous bell-shaped horny capsules (fig. 30), 
 each with a little spine at its summit, scattered through the 
 rock in which the Graptolites occur, but only doubtfully 
 attached to the fronds of the latter. These we may infer to 
 have been " ovarian vesicles ; " but they differ from the bodies 
 so called in the Sertularians in becoming detached from the 
 parent colony. 
 
 Two leading types may be distinguished amongst the Grap-
 
 82 
 
 CCELENTERATA. 
 
 tolites, which are termed respectively " monoprionidian " and 
 "diprionidian." The monoprionidian graptolites, such as G. 
 priodon (fig. 28), are distinguished by the fact that the polypary, 
 
 Fig. 30. Supposed " Ovarian Capsules" or reproductive buds of Graptolites. 
 
 whether simple or branched, possesses but a single row of cel- 
 lules or " hydrothecae." In the diprionidian forms, on the other 
 hand, as in Diplograpsus (fig. 35), the polypary possesses a row 
 of cellules on each side. It is noticeable that the diprionidian 
 graptolites, with rare exceptions, are confined to the Lou>er 
 Silurian and Cambrian Rocks; whilst the monoprionidian forms 
 range from the Cambrian to the summit of the Upper Silurian 
 series. 
 
 At least sixteen genera of Graptolites, as here restricted, are 
 known to science ; but it will be 
 sufficient to give the diagnostic 
 characters of a few of the com- 
 monest and more important 
 types. In the genus Graptolites 
 (figs. 28, 29), the polypary is 
 simple, linear, possessing but a 
 single row of cellules on one 
 side, and commencing by an at- 
 tenuated, usually curved, base. 
 
 Fig. 32 TetrnrrafiSMS quadribrachia- 
 Fig. 31. Didymografisus V-fractus. tus (after Hall). Upper Cambrian (Skid- 
 Upper Cambrian (Skiddaw Slates). daw and Quebec groups). 
 
 Species of this genus are found from near the base of the
 
 FOSSIL HYDROZOA. 
 
 Lower Silurian series to the very summit of the Upper Silurian 
 deposits. 
 
 In the genus Didymograpsus (fig. 31), the polypary con- 
 sists of two simple monoprionidian branches, which spring 
 from a common point, which is almost invariably marked by 
 a small spine-like " radicle." The genus attains its maximum 
 in the Quebec group of Canada and Skiddaw slates of Eng- 
 land (Upper Cambrian), and is well represented in the earlier 
 portion of the Lower Silurian period (Llandeilo Rocks) ; but 
 no species of the genus is known as late as the Upper Silurian 
 period. 
 
 In the genus Tetragrapsus (fig. 32), the polypary consists of 
 four simple monoprionidian branches, springing from a central 
 
 non-celluliferous connecting 
 process, which bifurcates at 
 each end. The celluliferous 
 branches do not subdivide, 
 and the base may be en- 
 veloped in a peculiar cor- 
 neous "disc," as will be im- 
 mediately described in the 
 genus Dichograpsus. The 
 species of Tetragrapsus are 
 exclusively confined to the 
 Skiddaw and Quebec groups 
 (Upper Cambrian). 
 
 In the genus Dichograp- 
 sus there are more than four 
 (usually eight) simple mono- 
 prionidian branches, which 
 arise from the same number 
 of divisions of a non-cel- 
 luliferous basal process. In 
 many cases the divisions of 
 the basal connecting pro- 
 cess (fig. 33), are enveloped 
 
 Fig. 33- Dichograpsus octobrachiatus, showing the central disc (after Hall). 
 Skiddaw and Quebec groups.
 
 8 4 
 
 CCELENTERATA. 
 
 in a species of corneous " disc" or plate, which is believed 
 to have been composed of two laminae. The functions of 
 this disc are doubtful ; but it has been compared with the 
 " float " or buoy of the Physophorida, an order of the Oceanic 
 Hydrozoa. 
 
 In the genus Rastrites (fig. 34), the polypary consists of a 
 
 Fig. 34. Morphology of Rastrites. A, Rastrites peregrinus, Barr., from the Mud- 
 stones of the Coniston Series, enlarged. B, Rastrites capillaris. Can-., from the Upper 
 Llandeilo Shales of Dumfriesshire, enlarged. C, Fragment of Rastrites Linruri, Barr., 
 from the Coniston Mudstones, enlarged. D, Fragment of R. peregrimis, greatly en- 
 larged, showing the impressed line running up the centre of each cellule. (Original.) 
 
 slender axial tube, giving off on one side a series of linear tubu- 
 lar cellules or " hydrothecse," which are free throughout their 
 entire length. The genus differs from all the other Graptolites, 
 in the fact that the cellules do not overlap one another, but are 
 free through their whole length, whilst it is very doubtful if a 
 true " solid axis " is present. In Britain and North America 
 the species of Rastrites are exclusively confined to the Lower 
 Silurian Rocks, but in Bohemia they pass up into the lowest 
 beds of the Upper Silurian. 
 
 In the genus Diplograpsus (fig. 35), the polypary consists of 
 two simple monoprionidian stipes, firmly united to one another, 
 back to back. The frond, therefore, is "diprionidian," or carries 
 cellules on both sides. The solid axis is usually prolonged 
 beyond the base of the polypary as a longer or shorter process 
 or " radicle," which is often flanked by lateral spines. The 
 solid axis is also almost invariably prolonged beyond the op- 
 posite or " distal " end of the polypary as a naked rod. In the 
 nearly-allied genus Climacograpsus, the structure is much as 
 above described, but the cellules have such a structure that
 
 FOSSIL ACTINOZOA. 
 
 their mouths appear to be sunk below the general surface of 
 the polypary, forming a row of rounded or quadrangular open- 
 ings on each side. Both Dip- 
 lograpsus and Climacograpsus 
 range in Britain and North 
 America from the Upper Cam- 
 brian to the summit of the 
 Lower Silurian series ; but in 
 Bohemia they rise into the 
 lower portion of the Upper 
 Silurian deposits. In the genus 
 Dicranograpsus the polypary is 
 at first diprionidian, but soon 
 splits into two monoprionidian 
 branches which carry the cel- 
 lules along their outer margins. 
 The genus is exclusively Lower 
 Silurian. Lastly, the beautiful 
 genus Phyllograpsus may be 
 regarded as composed of two 
 Diplograpsi placed at right 
 angles to one another. It is 
 exclusively confined to the 
 Skiddaw and Quebec Rocks.* 
 
 * The Student, desirous of fuller 
 information on this subject, may con- 
 sult the author's ' Monograph of 
 the British Graptolitidae, ' Part I., 
 General Introduction ; where full de- 
 tails are given as to the morphology 
 and affinities of these singular fossils. 
 
 Fig- 35- A, Diplograpsus pristis, 
 His., slightly enlarged, showing the 
 
 _pines ; C, Another of the same, 
 larged, 
 
 proximi , _., , 
 
 (Original.) 
 
 nes ; C, Another of the same, en- 
 ged, showing lateral spines, succeeded 
 )ximally by a small bulb, but showing 
 true radicle. (Original.) 
 
 CHAPTER IX. 
 FOSSIL ACTINOZOA. 
 
 OF the living groups of the Actinozoa (see Table, p. 73), the 
 Ctenophora and the Sea-anemones (Zoantharia malacodermata), 
 from their absence of hard parts, are unknown in a fossil con- 
 dition. The remaining groups viz., faz Zoantharia sderobasica, 
 Zoantharia sclerodermata, Alcyonana, an&Rugosa secrete a hard 
 skeleton, which is known by the general name of the " coral "
 
 86 
 
 CCELENTERATA. 
 
 or "corallum." All these groups, therefore, are known as 
 fossils ; but they are of very unequal importance. The Zoan- 
 tharia sclerobasica and Alcyonaria are known by very few fossil 
 representatives, and require to be little more than mentioned. 
 The Zoantharia sclerodcrmata and Rugosa, on the other hand, 
 have left very numerous and interesting traces of their former 
 existence the latter being almost altogether extinct, and 
 both will require to be noticed at some length. Regarded 
 as a whole, the class of the Actinozoa appears, so far as we yet 
 know, to have commenced its existence in the Upper Cam- 
 brian period, and to have attained its maximum 6f develop- 
 ment at the present day. 
 
 ORDER I. ZOANTHARIA. 
 
 Tentacles simple, rounded ; soft parts in multiples of five or six. 
 
 Sub-order I. Zoantharia malacodermata. Ex. Sea-anemone. 
 ,, 2. Zoantharia sclerobasica. Ex. Antipathes. 
 ,, 3. Zoantharia sclerodermata. Ex. Reef-building Corals. 
 
 A. ZOANTHARIA MALACODERMATA. Though, from their soft 
 nature, unknown in a fossil condition, the Sea-anemones merit 
 a brief description here, as they may be taken as the types of 
 the order, and as the somewhat complicated structure of the 
 sclerodermic coral will thereby be rendered much more intel- 
 ligible. 
 
 Fig. 36. A, Actinia mesentbryantliemutti, one of the Sea-anemones (after Johnston). 
 B, Section of the same, showing the mouth (a), the stomach (b), and the body-cavity (c). 
 
 The body of a Sea-anemone (fig. 36) is a truncated cone, or 
 a short cylinder, termed the " column," and is of a soft,
 
 FOSSIL ACTINOZOA. 8/ 
 
 leathery consistence. The two extremities of the column are 
 termed respectively the " base " and the " disc," the former 
 constituting the sucker, whereby the animal attaches itself at 
 will, whilst the mouth is situated in the centre of the latter. 
 In a few cases ( Cerianthus and Peachid) the centre of the base 
 is perforated, but the object of this arrangement is unknown. 
 Between the mouth and the circumference of the disc is a flat 
 space, without appendages of any kind, termed the " peris- 
 tomial space." Round the circumference of the disc are 
 placed numerous tentacles, usually retractile, arranged in alter- 
 nating rows, and amounting to as many as 200 in number in 
 the common Actinia. The tentacles are tubular prolongations 
 of the ectoderm and endoderm, containing diverticula from 
 the somatic chambers, and sometimes having apertures at 
 their free extremities. The mouth leads directly into the 
 stomach, which is a wide membranous tube, opening by a 
 large aperture into the general body-cavity below, and extend- 
 ing about half-way between the mouth and the base. The 
 wide space between the stomach and column-wall is sub- 
 divided into a number of compartments by radiating vertical 
 lamellae, termed the " primary mesenteries," arising on the one 
 hand from the inner surface of the body-wall, and attached on 
 the other to the external surface of the stomach. As the 
 stomach is considerably shorter than the column, it follows 
 that the inner edges of the primary mesenteries below the 
 stomach are free ; and these free edges, curving at first out- 
 wards and then downward and inwards, are ultimately attached 
 to the centre of the base. Besides the primary mesenteries, 
 there are other lamellae which also arise from the body-wall, 
 but which do not reach so far as the outer surface of the 
 stomach, and are called "secondary" and "tertiary" mesen- 
 teries, according to their breadth. The reproductive organs 
 are in the form of reddish bands, which contain ova and sper- 
 matozoa, and are situated on the faces of the mesenteries. 
 
 B. ZOANTHARIA ScLEROBASiCA. The members of this 
 group are all composite organisms, consisting of numerous 
 polypes, each of which has essentially the structure of a small 
 Sea-anemone, united together by a common organised medium 
 or "ccenosarc" (fig. 37). Each polype has six tentacles, 
 and the entire organism is supported by an internal skeleton 
 or " corallum." The coral is horny, and it is what is called 
 " sclerobasic ; " that is to say, it forms an internal axis, over 
 which the ccenosarc is spread, much as the bark encloses the 
 wood of a tree. As the polypes are sunk in the ccenosarc, 
 and as this simply forms a rind for the coral, it follows that
 
 88 CCELENTERATA. 
 
 the polypes are outside the corallum. In other words, the 
 polypes take no part in the secretion of the corallum; but this 
 is deposited solely by the coenosarc o'r common flesh by which 
 the polypes are connected together. 
 
 Fig. 37. Part of a living stem of A tit if at/if s anguina, of the natural size. 
 (After Dana.) 
 
 The Zoantharia sclerobasica are not known as occurring in 
 either the Palaeozoic or Mesozoic period. They appear for 
 the first time in Tertiary deposits, and the genus Antipathes 
 is represented in strata of Miocene age. 
 
 C. ZOANTHARIA SCLERODERMATA. This group includes 
 most of the so-called " corals," and is of very high geological 
 importance. All the members of this group secrete a skeleton 
 or " corallum," and this is necessarily the only part of the 
 animal with which the palaeontologist has to deal ; so that it 
 becomes necessary to enter into its structure at some length. 
 The animal itself, in the Zoantharia sclerodermata, in its essen- 
 tial structure resembles a sea-anemone ; but it very often has 
 the power of repeating itself by budding (gemmation) or cleav- 
 age (fission), so that from a simple it becomes a compound 
 organism. It may therefore consist of a single " polype," or 
 of many similar polypes united by a common flesh or " cceno- 
 sarc." The corallum is what is called " sclerodermic," its 
 essential peculiarity being that it is secreted by the polype or 
 polypes. The sclerodermic coral, in fact, is an actual calcifi- 
 cation of part of the tissues of the polype. When, therefore, 
 we have a simple coral, produced by a simple member of this 
 group (as in fig. 38), we have clearly to do with nothing but 
 skeletal structures produced in the interior of the polype itself. 
 When, on the other hand, we have a compound sclerodermic 
 coral to deal with, we have usually more than this. We have, 
 namely, two parts or elements of the coral to consider: i. 
 The parts of the coral secreted by each individual polype; and, 
 2. The parts secreted by the ccenosarc which unites all the 
 polypes into an organic whole. A compound coral may be 
 theoretically regarded, therefore, as consisting of a greater or 
 less number of simple corals, such as the preceding, united 
 together by a greater or less quantity of calcareous matter
 
 FOSSIL ACTINOZOA. 
 
 secreted by the coenosarc (fig. 40). The entire compound 
 corallum consists, therefore, of a greater or less number of 
 
 Fig. Tfr.Petraia calicula. 
 Lower Silurian. 
 
 Fig. 
 
 aphrentis Stokesi. 
 
 39. apren 
 Lower Siluri 
 
 " corallites " bound together by a calcareous basis, which is 
 secreted by the coenosarc, and is called the " coenenchyma." 
 
 Fig. 40. Synhelia Sharpeana. 
 
 Iii practice, however, this theoretical view of the subject is not 
 always borne out. The compound corallum may. and often 
 does, consist (as in fig. 41) of a number of corallites produced
 
 90 CCELENTERATA. 
 
 by budding or cleavage from a primitive corallite, having their 
 outer walls closely amalgamated, but not sunk in any general 
 ccenenchyma. In other cases, the coenenchyma, though not 
 actually absent, is very much reduced in quantity. 
 
 Fig. v.- 
 
 i eonvexa (D'Orbigny). A compound sclerodermic Coral. 
 Devonian. 
 
 To comprehend the more intimate structure of a sclero- 
 dermic coral, we may take a single 
 " corallite" of a composite form or, 
 better, the simple corallum secreted by 
 a form which never repeats itself by 
 gemmation or cleavage (fig. 42). Such 
 a coral consists of an outer wall, which 
 encloses an internal space or chamber, 
 and which assumes very various forms. 
 We may, however, take the simplest 
 and commonest form, in which the coral 
 is conical or turbinate in shape (fig. 42). 
 The outer wall of this cone is called the 
 " theca," and it encloses a space which 
 is variously subdivided below, but which 
 has the form of a shallower or deeper 
 conical cup towards its summit. This 
 vacant space is called the " calice," and 
 in the living state it contains the sto- 
 machal sac of the polype. The space below the calice is 
 broken up into a number of vertical compartments or "loculi," 
 
 Fig. 42. Cjatktixonia. 
 Dalmani. A simple sclero- 
 dermic coral, showing the 
 theca, with its costs, the 
 calice, with the columella 
 in its centre, and the septa. 
 A portion of wall of the 
 theca is broken, in order 
 to show the interior of the
 
 FOSSIL ACTINOZOA. 9 1 
 
 by a series of upright partitions or " septa," which spring from 
 the inner surface of the theca, and advance toward its centre. 
 Very commonly some of the septa unite centrally with a 
 median calcareous rod, which extends vertically from the 
 bottom of the theca to the bottom of the calice (sometimes 
 projecting into the latter), and which is called the " columella." 
 The columella, however, is often wanting, or a spurious one 
 may be formed by the twisting together or coalescence of the 
 inner edges of the septa. In rare cases, also, the septa them- 
 selves are wanting. The septa, further, are of different 
 breadths. A certain number (fig. 43) extend quite to the 
 
 Fig. 43. Diagrammatic sections of corals. A, Section of sclerodermic coral, showing 
 five primary septa, the columella, and costse (<r) ; B, Section of Rugose coral, showing 
 four primary septa. Between the primary septa are seen the secondary and tertiary 
 septa. 
 
 centre of the coral, where they meet the columella (when this 
 is present). These are called the " primary septa.' ; Others, 
 however, fall short of the columella by a greater or less dis- 
 tance ; and these are called "secondary" and "tertiary" 
 septa, according to their breadth. 
 
 The above is the essential structure of the typical form of a 
 simple sclerodermic coral, and it is easy to see that it is pro- 
 duced by the calcification, or conversion into carbonate of 
 lime, of the lower portion of a polype similar in structure to 
 an ordinary Sea-anemone. The " theca" of the coral corre- 
 sponds to, and is secreted by, the " column-wall " or general 
 wall of the body of the polype. The " septa," again, corre- 
 spond with the " mesenteries," and, like them, are " primary," 
 " secondary," or " tertiary," according as they reach the centre 
 or fall short of it by a greater or less distance. We must re- 
 member, however, that it is only the inferior half of the body 
 of the polype which is thus calcified. The tentacular disc and 
 mouth are placed at some distance above the upper margin of 
 the theca, and the digestive sac occupies the calice; whilst
 
 CCELENTERATA. 
 
 the whole ot the space comprised within the theca is lined by 
 the endoderm, and the whole of its outer surface is covered 
 by the ectoderm. 
 
 Whilst the above gives the fundamental structure of a simple 
 sclerodermic corallum, there are some ad- 
 ditional details which are of sufficient im- 
 portance to demand special notice. The 
 septa in the coralla of the Zoantharia 
 sderodermata, like the mesenteries of the 
 living animal, are in multiples of five or 
 six. It is not common, however, to find 
 the septa so few as would be represented 
 by these fundamental numbers. Com- 
 monly, in progress of growth, fresh septa 
 are formed between those originally pre- 
 sent, until there may be several " cycles " 
 of septa (fig. 43). 
 
 The septa may be considered as being 
 continued, in many cases, through the 
 theca, and beyond its external surface. 
 The outer surface of the theca thus comes 
 to be covered with a series of vertical 
 ridges or ribs, which are termed the " cos- 
 tae" (fig. 43, c, and fig. 44). The costae 
 vary much as to the distance by which 
 they are separated from one another, and 
 as to their breadth, their solidity, and 
 their ornamentation with spines, tuber- 
 cles, or teeth. 
 
 In some cases the outer surface of the 
 theca is more or less covered by a thicker 
 or thinner envelope of calcareous matter, 
 constituting what is termed the "epi- 
 theca." In some cases, as in the genus 
 Montlivaltia (fig. 45), the epitheca is very 
 highly developed, and forms a dense 
 covering, but it is often extremely thin. It varies much as 
 to the extent to which it is applied to the theca ; and it may 
 be smooth, or may be marked by concentric or encircling 
 ridges. 
 
 The chief remaining structures which may be noticed are 
 what are called " pali," " dissepiments," and " tabulae." Pali 
 are "small processes which exist between certain septa and 
 the columella. They generally arise from the base of the vis- 
 ceral cavity, or close to it, and pass upwards, united by one 
 
 Fig. 44. Tnrbinolia 
 rulcata. The upper figure 
 shows the exterior of the 
 theca with the costae. The 
 lower figure shows the ca- 
 lice, with the columella 
 and primary and second- 
 ary septa. Eocene.
 
 FOSSIL ACTINOZOA. 
 
 93 
 
 edge to the columella, and by the other to the inner end or 
 margin of the septa. When there is no columella, they are 
 adherent to the septa, present a free edge 
 to the cavity in the axis of the corallum, 
 and arise with the septa" (Duncan). 
 The dissepiments are incomplete hori- 
 zontal plates which grow from the sides 
 of the septa, stretching from one septum 
 to another, and more or less interfering 
 with the continuity of the loculi, and 
 breaking them up into a series of cells. 
 The loculi may thus, when the dissepi- 
 ments are numerous, become more or 
 less completely vesicular. Lastly, the 
 tabula (fig. 46) are transverse plates or 
 floors running at right angles to the axis 
 of the corallite, and dividing the theca 
 into so many horizontal compartments or 
 stories, each of which is vertically subdivided by the septa, 
 when these exist. Very generally, however, the septa are 
 absent when the coral is " tabulate." 
 
 Fig. ^.Montlivaltia 
 caryophyllata, showing 
 the greatly-developed epi- 
 theca covering the lowe 
 
 Ooii 
 
 rt of the coral. Great 
 
 Fig. 46. Columnaria alveplata, showing the corallites partitioned off 
 into stories by tabulas. Silurian. 
 
 GEMMATION AND FISSION AMONGST CORALS. Compound 
 Corals, as before remarked, are produced by a process of 
 budding (gemmation) or cleavage (fission) from an originally 
 simple form, or by a combination of both these processes. 
 Most commonly, the compound sclerodermic coral consists of 
 a number of " corallites," each produced by a separate polype, 
 and of a common calcareous basis, or " ccenenchyma," secreted 
 by the coenosarc. There may, however, be no coenosarc, and
 
 94 
 
 CCELENTERATA. 
 
 consequently no coenenchyma ; and the compound coral may 
 consist simply of a congeries of corallites directly united to, 
 or springing from, one another. 
 
 Three chief forms of gemmation may be distinguished 
 amongst the compound Zoantharia viz., basal, parietal, and 
 calicular. 
 
 In basal gemmation the mode of increase is by means of 
 a rudimentary coenosarc, which is put forth by the original 
 polype, and from which the young polype-buds are produced. 
 It " affords very different products according as the coenosarc 
 remains soft, or deposits a coenenchyma ; appears under the 
 form of stolons, or of stouter connecting stems ; or even 
 spreads out in several directions as a continuous horizontal 
 expansion ; " in which last case the youngest polypes are, of 
 course, those nearest to the periphery of the mass. 
 
 The parietal mode of gemmation is the commonest, and 
 it gives rise chiefly to dendroid, or tree-like, corals. In this 
 method the buds are produced from the sides of the original 
 polype, and they often repeat the process indefinitely. 
 
 Calicular gemmation is not known to occur in any recent 
 coral, but it was a common mode of increase amongst extinct 
 forms. In this method "the 
 primitive polype sends up from 
 its oral disc two or more simi- 
 lar buds ; these, in their turn, 
 produce other young polypes, 
 and thus the process is repeated 
 until an inverted pyramidal mass 
 of considerable size is produced, 
 al1 the P arts of which rest 
 upon the narrow base of the 
 first budding polype" (fig. 47). 
 Fission in the Actinozoa differs 
 from gemmation chiefly in the 
 fact, that the polypes produced 
 fissiparously resemble one an- 
 ? ther in organisation, and often 
 m size, as soon as they become 
 distinct. In gemmation, on 
 
 the other hand, the polype-bud consists primarily of a mere 
 process of ectoderm and endoderm, enclosing a cascal process 
 of the somatic cavity, and a mouth and other structures are at 
 first wanting. Amongst the coralligenous Actinozoa fission is 
 usually effected by " oral cleavage," the divisional groove com- 
 mencing at the oral disc, and deepening to a certain extent,
 
 FOSSIL ACTINOZOA. 95 
 
 the proximal extremity always remaining undivided. More 
 rarely, fission " is effected by the separation of small portions 
 from the attached base of the primitive organism, whose form 
 and structure they subsequently, by gradual development, tend 
 to assume." 
 
 " The coral structures which result from a repetition of the 
 fissiparous process are of two principal kinds, according as 
 they tend most to increase in a vertical or in a horizontal 
 direction. In the first of these cases the corallum is ccsspitose, 
 or tufted, convex on its distal aspect, and resolvable into a 
 succession of short diverging pairs of branches, each resulting 
 from the division of a single corallite." In the second case 
 the coral becomes lamellar. " Here the secondary corallites 
 are united throughout their whole height, and disposed in a 
 linear series, the entire mass presenting one continuous theca." 
 Both these forms of corallum " are liable to become massive by 
 the union of several rows or tufts of corallites throughout the 
 whole or a portion of their height. An illustration of this is 
 afforded by the large gyrate corallum of Meandrina, over the 
 surface of whose spheroidal mass the calicine region of the 
 combined corallites winds in so complex a mariner as at once 
 to suggest that resemblance to the convolutions of the brain 
 which its popular name of Brain-stone Coral has been devised 
 to indicate." (Greene, ' Manual of Coelenterata,' p. 185 et seq.} 
 
 Fig. 48. Phillipsastrcea Verneuilli. From the Devonian (Corniferous Limestone) 
 of N. America. 
 
 DEEP-SEA CORALS AND REEF-BUILDERS. At the present 
 day, as has been specially insisted on by Dr Martin Duncan, 
 we find two great groups of the Sclerodermic Zoantharia viz., 
 those which inhabit tolerably deep water, and those which 
 build the great masses of coral which are known as " coral- 
 reefs." The deep-sea corals, though often attaining, as in- 
 dividuals, a considerable size, and though often compound,
 
 96 CCELENTERATA. 
 
 never form massive aggregations or " reefs;" This is due to 
 the fact that, when composite, the separate corallites are not 
 united together by a lax cellular coenenchyma, so that the 
 colony cannot increase to an indefinitely large size. The 
 deep-sea corals seem to have existed in all the great geological 
 periods, from the Silurian upwards. The chief genera of this 
 group at the present day are Caryophyllia, Balanophyllia, 
 Flabcllum, Desmophyllum, and Sphenotrochus, amongst the sim- 
 ple forms ; and Lophohelia, Amphihdia, Dendrophyllia, and 
 Astrangia, amongst the compound forms. 
 
 The reef-building corals, when simple, are provided with 
 special structures which enable the polypes to grow rapidly. 
 The great majority of the reef-builders, however, are com- 
 pound, and owe the large size to which they attain to the 
 fact that the corallites are mostly united by a loose cellular 
 coenenchyma. The chief genera of reef-building Zoantharia 
 in Mesozoic, Kainozoic, and Recent times, are M&andrina, 
 Madrepora, Forties, Astraa, Millepora, Hcliopora, Cycloseris, 
 Trochoseris, Heliastrcea, Soleiiastraa, Pachyseris, Turbinaria, 
 and Astraopora ; but many others might be mentioned. 
 
 Amongst the more ancient examples of coral-reefs may be 
 mentioned the Wenlock Limestone of the Upper Silurians in 
 England, some of the Devonian Limestones in North America, 
 and parts of the Carboniferous Limestone in various parts of 
 the world. In Mesozoic times coral-reefs existed towards the 
 close of the Trias in Western Europe, and largely in Oolitic 
 times both in Western Europe and in England. In the earlier 
 portion of the Tertiary period, again, vast coral-reefs were 
 formed in Central and Southern Europe, in Egypt, Syria, and 
 Arabia, and in parts of India. 
 
 DIVISIONS AND DISTRIBUTION IN TIME OF THE ZOANTHARIA 
 SCLERODERMATA. The Zoantharia sclerodermata are divided 
 into the four following groups, founded upon the characters of 
 the corallum : 
 
 1. Tabulata. Septa rudimentary, or entirely absent ; tabulae 
 well developed and dividing the space included within the 
 theca (the " visceral chamber ") into a number of stories 
 (fig. 46). 
 
 2. Perforata. Septa well developed ; dissepiments rudi- 
 mentary ; no tabulae ; calcareous tissue of the coral (" scler- 
 enchyma ") porous. 
 
 3. Aporosa. Septa well developed, lamellar ; no tabulse ; 
 calcareous tissue of the corallum (" sclerenchyma ") compact 
 and imperforate. 
 
 4. Tubulosa. Septa indicated by mere strias ; thecae pyri- 
 form, occasionally united by a basal ccenenchyma (fig. 94).
 
 FOSSIL ACTINOZOA. 97 
 
 As regards the distribution in time of the above four groups, 
 the Tabulate Corals attain their maximum in the Palaeozoic 
 period, being well represented in the Silurian, Devonian, and 
 Carboniferous formations. The family Thecida is exclusively 
 Silurian ; but the familiar Seriatoporidce, Favositidce, and Mille- 
 poridiz survived to the present day; though there are many 
 breaks in our knowledge of their course. 
 
 The Perforata are, on the whole, most abundant in Mesozoic 
 and Cainozoic strata, and attain their maximum at the present 
 day. In the Palaeozoic series the group is represented by 
 Protarea (Silurian) and Pleurodictyum (Devonian), both belong- 
 ing to the family of the Poritidce. The great family of the 
 MadreporidcR, on the other hand, did not make its appearance 
 till the Cretaceous period. 
 
 The Aporosa are almost exclusively confined to the Meso- 
 zoic, Kainozoic, and recent periods, attaining their maximum 
 at the present day. In the Palaeozoic period the group is 
 only represented by the Silurian genus Palceocydus, belonging 
 to the Fungida. At the commencement of the Mesozoic 
 period, in the Trias, appears for the first time the great family 
 of the Astrceidce, so largely represented at the present day. 
 Almost all the Jurassic Corals belong to the Aporosa, and 
 the two families of the Turbinolidce and Oculinidtz make their 
 first appearance here. In the Cretaceous Rocks the Aporosa 
 are largely represented, the family Astraidcz being particularly 
 rich in generic forms. In the Tertiary period the group is also 
 well represented. 
 
 The Tubtilosa, comprising the single 
 family of the Auloporidce, are exclusively 
 Palaeozoic. In the Devonian period, 
 and doubtfully in the Silurian, we have 
 the genus Aiilopora (fig. 49); and in the 
 Carboniferous Rocks occurs the genus 
 Pyrgia. There is, however, reason to 
 believe that these genera have been 
 founded upon the young and immature lg ' 49 'lvom^? 
 forms of other corals. 
 
 ORDER II. RUGOSA. The members of this order are almost 
 entirely extinct, and, with the exception of Holocystis elegans 
 from the Lower Cretaceous rocks, and a few more modern 
 forms, are not known to occur in deposits younger than the 
 Palaeozoic epoch. With the soft parts of the Rugosa we are, 
 for the most part, entirely unacquainted, and the definition of 
 the order must therefore be founded upon the characters of 
 the corallum. The corallum in the Rugosa is highly de- 
 G
 
 98 CCELENTERATA. 
 
 veloped, sclerodermic, with a true theca, and often presenting 
 both septa and tabulae combined. The septa are in multiples 
 of four (fig. 43), unlike the recent sclerodermic coralla, in which 
 they are in multiples of five or six. There is, further, no true 
 coenenchyma. Some of the Rugosa are simple; but others are 
 composite, increasing either by parietal or by calicular gemma- 
 tion. 
 The Palaeozoic corals (figs. 50-55), with hardly an exception, 
 
 PALEOZOIC CORALS. 
 
 Fig. y>.Syringcipora retifom 
 A Silurian Tabulate Coral. 
 
 Fig. 51. Sytingopora verticillata. 
 Silurian. 
 
 Fig. 52. Syringopora Dalmani. Fig. ^.Syringopora compacta. 
 
 Silurian. Silurian. 
 
 Fig. 54. Stromboties featagonus. 
 A Silurian Rugose Coral. 
 
 Fig. 55. Strombodts gracilu. 
 Silurian. 
 
 belong either to the Rugosa or to the Tabulate division of the 
 Zoantharia sclerodermata. The former are readily distinguish- 
 able from the latter in having well-developed septa, as a rule, 
 and in invariably having their septa in multiples of four. Until
 
 FOSSIL ACTINOZOA. 99 
 
 quite recently it was believed that all the Rugosa were Palaeo- 
 zoic, with the exception of the genus Holocystis, represented in 
 the Cretaceous period (Upper Greensand) by the single species 
 H. elegans. Recent researches, however, have brought to 
 light the existence in our present seas of at least two genera 
 (Haplophyllia and Guynia) which belong to the Rugose family 
 of the Cyathaxonidtz ; and certain Tertiary Rugose Corals 
 have also been described (Martin Duncan). As the Rugosa 
 are in no fundamental structural character to be distinguished 
 from the Zoantharia sderodermata, save in the number of their 
 septa, there would thus seem to be no good ground for main- 
 taining that there is any essential difference between the Palaeo- 
 zoic corals and those of more modern times. 
 
 Recently it has been shown that some very abnormal Ru- 
 gose corals were provided with a lid or operculum, closing the 
 mouth of the calice. In the genus Calceola (fig. 56), formerly 
 referred to the Brachiopoda, and very abundant in certain parts 
 of the Devonian system, the operculum consisted of a single 
 valve or piece. In Goniophyllum four valves were present, and 
 in Cystiphyllum prismaticum there were four or more valves in 
 the operculum. It is worthy of notice that some recent corals 
 (species of Primnoa, Paramuricea, and others) exhibit also a 
 more or less complete operculum. According to Professor 
 Agassiz, the Rugosa and the Tabulate 
 division of the Zoantharia ought not 
 to be considered as belonging to the 
 Actinozoa, but should be placed amongst 
 the Hydrozoa. This radical change, how- 
 ever, cannot be accepted without the 
 production of very conclusive evidence in 
 its favour. A strong argument against re- 
 ferring the Rugose and Tabulate Corals, Fig . s6 _^ iceola sanda . 
 as proposed by Agassiz, to the Hydrozoa, &** An opercuiate Rugose 
 is their possession in most cases of well- Cc 
 developed septa, implying, of course, the existence in the living 
 animal of mesenteries, structures which are wholly wanting in 
 the Hydrozoa. 
 
 As regards the distribution in time of the families of the 
 Rugosa, the most important group is that of the Cyathophyllidce, 
 which is abundantly represented in the Silurian, Devonian, and 
 Carboniferous Rocks. The family Cyathaxonidce is Silurian 
 and Carboniferous, and is represented by two living genera. 
 The family Cystiphyllidcz is Silurian and Devonian. Lastly, 
 the family Stauridcz is represented in the Silurian Rocks by 
 the genus Stauria, in the Devonian Rocks by the genus
 
 100 CCELENTERATA. 
 
 Metriophyllum, in the Permian Rocks by the genus Polycceha, 
 and in Tertiary deposits by the genus Conosmilia. 
 
 APPENDIX GIVING A TABULAR VIEW OF THE DIVISIONS OF THE 
 
 ZOANTHARIA SCLERODERMATA AND RUGOSA (AFTER 
 
 MILNE-EDWARDS AND JULES HAIME). 
 
 A. The Zoantharia Sclerodermata are defined by the possession of a 
 sclerodermic corallum, the parts of which are arranged in multiples of five 
 or six. Septa generally well developed, but not combined, as a rule, with 
 tabulae. 
 
 The following chief divisions of the Zoantharia Sclerodermata are, with 
 few alterations, those adopted by the above-mentioned authorities : 
 
 I. TABULATA. Septa rudimentary or absent ; tabulae well developed, 
 
 dividing the visceral chamber into a series of stories. 
 
 1. Thccidtz. Corallum massive ; a dense spurious coenenchyma formed 
 
 by the lateral union of the septa ; tabulae numerous. 
 
 2. FavositidtE. Septa and corallites distinct ; little or no true coenen- 
 
 chyma. 
 
 3. SeriatoporidcE. Corallum arborescent ; sclerenchyma abundant and 
 
 compact ; tabulae few. 
 
 4. Milkporida:. Corallum massive or foliaceous ; septa not numerous; 
 
 sclerenchyma tabular or cellular. 
 
 II. PERFORATA. Septa well developed ; no tabulae ; dissepiments rudi- 
 
 mentary ; sclerenchyma porous. 
 
 5. Eupsammida:. Corallum simple or composite ; septa well developed 
 
 and lamellar ; columella spongiose. 
 
 6. Poritida. Corallum composed of spongy, reticulated sclerenchyma. 
 
 Septa never lamellar, but consisting wholly of a more or less definite 
 series of trabeculae ; no tabulae. 
 
 7. Madreporida. Corallum usually composite ; coenenchyma abundant 
 
 and spongy ; thecae porous, not distinct from the coenenchyma ; 
 septa distinct, but slightly perforate. 
 
 III. APOROSA. Septa well developed, completely lamellar, and primi- 
 
 tively consisting of six elements ; no tabulae ; sclerenchyma imper- 
 forate. 
 
 8. Fungidte. Corallum simple or compound ; thecae ill developed, and 
 
 somewhat porous ; no dissepiments or tabulae ; synapticulae numer- 
 ous. 
 
 9. Astrteida. Corallum simple or compound ; no proper coenenchyma ; 
 
 numerous dissepiments; no synapticulae. Corallites well denned, 
 and separated from one another by perfect walls. 
 
 10. OfulinidtT. Corallum composite ; coenenchyma abundant and com- 
 pact ; dissepiments few in number. Walls of the corallites without 
 perforations, not distinct from the coenenchyma. 
 
 11. Turbinolida. Corallum usually simple; no coenenchyma; septa 
 well developed ; no dissepiments, nor synapticuke. 
 
 IV. TUBULOSA. Septa indicated by mere striae ; thecae pyriform ; coral- 
 
 lites sometimes connected by a creeping basal coenenchyma. 
 
 12. Autoporida. This being the only family in the Ttibulosa, its charac- 
 ters are necessarily the same as those of the division itself. 
 
 B. ORDER RUGOSA. Characterised by the possession of a sclerodermic 
 corallum, usually with septa and tabulae combined, the former being in 
 multiples of four. The corallites are always distinct, and are never united
 
 FOSSIL ACTINOZOA. IOI 
 
 together by a true ccenenchyma. The septa are usually incomplete, but 
 are never porous, and never bear synapticulse. The order is divided into 
 the following four families : 
 Family I. Stauridcz. 
 
 Corallum simple or composite ; septa incomplete, united by lamellar 
 
 dissepiments ; four large primary septa, forming a cross. 
 Family 2. Cyathaxonida. 
 
 Corallum simple; septa complete; no dissepiments or tabulae; with- 
 out four primary septa. 
 Family 3. Cyathophyllidce. 
 
 Corallum simple or composite ; septa incomplete ; tabulae generally 
 
 present. 
 Family 4. Cystiphyllidte. 
 
 Corallum simple, composed chiefly of a vesicular mass with but 
 slight traces of septa. 
 
 ORDER III. ALCYONARIA. The Alcyonarian Zoophytes 
 differ from the Zoantharia in the fact that the polypes have eight 
 pinjiately fringed tentacles, the mesenteries also being some multiple 
 of four. The Alcyonaria thus differ from the Zoantharia, and 
 agree with the Rugosa in the numerical proportion of their soft 
 parts. The Alcyonaria, however, differ from the Rugosa in 
 never possessing a sclerodermic coral divided by septa. When 
 they have a sclerodermic corallum at all, it either consists 
 simply of scattered spicules (as in Alcyoniuni), or, if thecal, 
 consists of simple tubes which are not subdivided by vertical 
 partitions or septa (as in the Tubiporida). We have, however, 
 nothing to do with these forms, as they are unknown in a 
 fossil condition. The only members of the Alcyonaria which 
 have left any traces of their past existence, are those which 
 possess a " sclerobasic " coral, in the form of a simple or 
 branched internal axis, which may be calcareous or corneous, 
 or partly the one and partly the other. Such forms are well 
 represented at the present day by the Sea-pens (Pennatulida), 
 the Sea-shrubs and Red Coral (Gorgonida?}, the Fan -corals 
 (Rhipidogorgia}, and the like. They are, however, of very small 
 palaeontological importance. 
 
 The genus Protovirgularia has been constituted for the 
 reception of an obscure Silurian fossil, from its supposed 
 affinity to the living Sea-rods ( Virgularia}. This problematical 
 organism, however, is almost certainly not one of the Alcyona- 
 ria, and may, perhaps, belong to the Hydrozoa. With this 
 exception, and the still more dubious examples of Gorgonidcz 
 from the Silurian Rocks, no Alcyonarian Zoophyte has been 
 detected in deposits older than the Chalk. One of the Pen- 
 natulidce (viz., Graphularid) has been found in the London 
 Clay (Lower Eocene) ; and the same formation has likewise 
 yielded two species of Gorgonida (Mopsea and Websteria).
 
 102 ANNULOIDA. 
 
 The genus Corallium (including the living Red Coral) has 
 likewise been found in deposits of Miocene age. 
 
 CHAPTER X. 
 
 SUB-KINGDOM III. ANNULOIDA. 
 ECHINODERMA TA. 
 
 SUB-KINGDOM III. ANNULOIDA. Animals in which the 
 alimentary canal is completely shut off from the general cavity of 
 the body. Nervous system distinct. A peculiar system of canals, 
 usually communicating with the exterior and containing water 
 derived from the outside, and termed the "water-vascular" or 
 " aquiferous" system, is present in all. In none is the body of the 
 adult composed of definite segments, or provided with " bilaterally 
 disposed successive pairs of appendages" 
 
 This sub-kingdom was proposed by Huxley, as a provisional 
 arrangement, to include the two groups of the Echinodermata 
 (Sea-urchins, Star-fishes, &c.) and the Scoledda (Tape-worms, 
 Round-worms, Wheel-animalcules, &c.) Whether this arrange- 
 ment be ultimately retained or not, matters not at all to the 
 palaeontologist, as no member of the Scoledda is known in the 
 fossil condition. The palaeontologist, therefore, has simply to 
 deal with the Echinodermata, the complete distinctness of 
 which, as a group, is beyond question. 
 
 CLASS ECHINODERMATA. 
 
 The class Echinodermata comprises the animals known com- 
 monly as Sea-urchins, Star-fishes, Brittle-stars, Sea-lilies, and 
 Sea-cucumbers, and is distinguished by the fact that the external 
 envelope of the body (" perisome ") has the power of secreting 
 calcareous matter to a greater or less extent. The integument is, 
 therefore, either composed of calcareous plates articulated farther, 
 or is coriaceous, and has granules or spicules of lime developed in 
 it. The water-vasailar system usually communicates with the 
 exterior, and generally subserves locomotion. The adult animal 
 exhibits more or less distinctly a " radial symmetry" or star-like 
 arrangement of its parts, but the young animal is more or less 
 bilaterally symmetrical. 
 
 The Echinodermata are divided into the following seven 
 orders :
 
 ECHINOIDEA. lOJ 
 
 1. Echinoidea. Ex, Heart-urchin (Spatangus). 
 
 2. Asteroidea. Ex. Star-fish (Uraster). 
 
 3. Ophiuroidca. Ex. Brittle-star (Ophiura). 
 
 4. Crlnoidea. Ex. Stone-lily (Encrinus). 
 
 5. Cystoidea. Ex, Hemicosmites. 
 
 6. Blastoidea. Ex. Pentremites. 
 
 7. Holothuroidea. Ex. Trepang (Holothuria). 
 
 The above is not a true or natural arrangement of the orders 
 of the Echinodennatct) but it is convenient for many reasons to 
 consider them in this sequence. As regards the general dis- 
 tribution of the class, the Echinodermata are represented more 
 or less abundantly in all the great formations from the Upper 
 Cambrian to the present day. The orders Cystoidea and Blas- 
 toidea are not only extinct, but are exclusively Palaeozoic ; in the 
 Crinoidea we have an order which has passed its prime, and ap- 
 pears to be verging on extinction. On the other hand, the orders 
 Echinoidea, Asteroidea, Ophiuroidea, and Holothuroidea appear 
 to have attained their maximum of development at the present 
 day. The Asteroidea and Ophiuroidea commence in the Silu- 
 rian period. The Echinoids commence in the Upper Silurian, 
 but reach no marked development till we enter upon Mesozoic 
 deposits. Lastly, the Holothurians , as might be expected from 
 the soft nature of their integuments, are hardly known as fossils, 
 though they seem to have existed in the Mesozoic period. 
 
 ORDER I. ECHINOIDEA. 
 
 The members of this order commonly known as Sea- 
 urchins are characterised by the possession of a more or less 
 globular, heart-shaped, discoidal or depressed body, encased in a 
 " test" or shell, which is composed of numerous calcareous plates, 
 immovably connected together. The intestine is convoluted, and 
 there is a distinct anus. The mouth is usually armed with cal- 
 careous teeth, and is always situated on the inferior aspect of the 
 body, but the position of the vent varies. 
 
 As a matter of course, the palseontological student has to 
 deal with nothing except the test of the Echinoids and its 
 appendages, and these must be described in some detail. 
 The " test " of the Echinoidea may be regarded as essentially 
 composed of the so-called " corona" and of the " apical disc," 
 though other less important elements are present as well. The 
 " corona " is the main element of the test, and includes all 
 the calcareous covering of the animal except the scattered 
 plates round the mouth and anus and the " apical disc." The 
 test is composed of numerous calcareous plates, firmly united
 
 104 
 
 ANNULOIDA. 
 
 to one another by their edges, arranged in rows (fig. 57), and 
 bearing different names according to their position and func- 
 tion. In one or two exceptional cases the plates are so thin 
 
 Fig. 57. Morphology of Echinoidea. i. Portion of the test of Galerites kemisfihericus 
 enlarged, showing an inter-ambulacra! area (a), and an ambulacra! area (). 2. Galentes 
 liemisphericus viewed from above, a Inter-ambulacra ; b Ambulacra. 3. Genital and 
 ocular disc of Hemicidaris intermedia enlarged, c Ocular plate ; d Genital plate; e 
 Anal aperture ; f Madreporiform tubercle. 4. Spine of the same. (After Forbes.) The 
 tubercles are mostly omitted on figs 2 and 3 for the sake of clearness. 
 
 and are so united together that the entire test becomes flexible 
 and soft. As a rule, however, the corona forms an immovable 
 case or box, within which the animal is contained ; and its 
 growth is carried on by means of additions made to the edge 
 of each individual plate, by means of an organised membrane 
 which passes between the sutures, or the lines where the plates 
 come in contact with one another. 
 
 In all recent and most fossil Echinoids, the test is composed 
 of twenty rows of calcareous plates, which are arranged in ten 
 alternating zones or areas (fig. 58). Each zone, therefore, is 
 composed of two rows of plates. In five of these zones (fig. 
 57, i, and fig. 58) the plates are of large size, and are not 
 perforated by any apertures. These zones are called the " in- 
 ter-ambulacral areas." The remaining five zones alternate 
 with the former, and are composed of very much smaller 
 plates, which are perforated by minute apertures or pores. 
 Through these apertures are emitted the little suctorial tubes 
 of the water-vascular system the so-called " ambulacral tubes" 
 or " tube-feet" by means of which the animal moves. Hence 
 these zones of perforated plates are termed the " ambulacral 
 areas" or "poriferous zones."
 
 ECHINOIDEA. 
 
 105 
 
 In one great group of the Echinoids, the ambulacral areas 
 pass from the centre of the base of the shell to its summit 
 (fig. 58), when they are said to be " perfect" (ambulacra per- 
 fecta) or " simple." In another great group the ambulacral 
 
 Fig. t$.Galerites albogalerus. The first figure shows the under surface with the 
 mouth and anus. The middle figure is a side view : and the right-hand figure shows 
 the upper surface, with the ambulacral areas converging to the apical disc. White 
 Chalk. 
 
 areas are not thus continuous from pole to pole, but simply 
 form a kind of rosette upon the upper surface of the shell 
 (fig. 59). In these cases as in the common Heart-urchins 
 
 Fig. 59. Scutella subrotunda, showing petaloid ambulacra. Miocene. 
 
 the ambulacral zones are said to be "circumscript" (ambulacra 
 circumscriptd) or " petaloid." 
 
 The most important external structures of the corona are 
 the tubercles and spines. The tubercles are rounded eleva- 
 tions upon which the spines are carried (fig. 60). They vary 
 much in their dimensions, and receive special names accord- 
 ing to their size or position on the test. Ordinarily the tuber- 
 cle consists of a rounded ball or hemisphere (the " mamelon ") 
 supported upon a conical process (the "boss") which arises 
 from the plate. The ball of the tubercle may or may not be 
 perforated for the insertion of a ligament which is attached to 
 the articular surface of the spine. In many cases (as in fig. 
 60) the base of the tubercle is surrounded a round or oval 
 smooth and excavated space which is termed the " areola." 
 
 The spines are movable appendages which are jointed
 
 106 ANNULOIDA. 
 
 to the tubercles by a sort of "ball-and-socket" or "uni- 
 versal" joint. They are used defensively and in locomotion, 
 and vary much in length and shape. Sometimes they are very 
 minute ; at other times they attain a length considerably ex- 
 ceeding the diameter of the test Sometimes they are slender, 
 
 Fig. 60. Hemicidaris crenularis, showing tubercles, the larger of which are 
 perforated, and are surrounded by an areola. Oolite. 
 
 tapering, and truly spine-like ; at other times they are thick- 
 ened, ovate, or almost globular (fig. 61). The spine fits on 
 the rounded head of the tubercle by a concave 
 articular surface ("acetabulum"), and there may 
 or may not be a pit at the bottom of this, for 
 the attachment of the ligament before spoken 
 of. Above the acetabulum or socket of the 
 spine there is a prominent ridge or ring, more or 
 less " milled," for the attachment of the muscular 
 fibres which move the spine. 
 
 The " apical disc " or " genital disc " occupies 
 the summit of the test, and is generally composed 
 Fig. .61. spine of ten plates (fig. 57, 3). Five of these plates 
 We slan are of comparatively large size, and are termed 
 the "genital plates," each being perforated by 
 the duct of an ovary or testis. Each genital plate occupies 
 the summit of one of the interambulacral areas. One of the 
 genital plates (the right antero-lateral plate) is larger than the 
 others, and supports a spongy tubercle, perforated with many 
 apertures, like the rose of a watering-pot, and termed the 
 " madreporiform tubercle" (fig. 57). This structure protects 
 the mouth of the canal by which water is admitted from the 
 exterior to the water-vascular system. Wedged in between 
 the genital plates, and occupying the summits of the ambulacral 
 areas, are five smaller, heart-shaped, or pentagonal plates, each 
 of which is perforated for the reception of an " ocellus " or 
 eye, and which are therefore termed the " ocular plates."
 
 ECHINOIDEA. 
 
 107 
 
 An important division of the Echinoids is constituted by the 
 position of the anal aperture. In one great group of Echinoids 
 the mouth is situated in the centre of the base (fig. 62), and 
 the vent is placed at the summit of the test, surrounded by the 
 genital disc. These are the so-called " regular " Sea-urchins 
 
 
 
 Fig. 62. Salenia personata, a " regular" Echinoid. The left-band figure represents 
 the upper surface of the shell, and shows the anus surrounded by the apical disc. The 
 right-hand figure shows the mouth in the centre of the base. 
 
 (Echinoidea endocydica?). They have a test which is almost 
 always circular, or spheroidal, or, it may be, depressed ; and 
 the mouth is armed with a complicated masticatory apparatus. 
 In the second great group the mouth is situated on the lower 
 surface of the test, and is sometimes central, sometimes excen- 
 tric in position. The anus varies in position, but is never 
 placed on the summit of the test, opposite to the mouth. The 
 anus, therefore, is not surrounded by the genital disc. Most 
 commonly the anus is marginal, or is sub-marginal, coming to 
 be placed in this last case on the lower surface of the test near 
 the mouth (fig. 63). The Sea-urchins in which this state of 
 
 Fig. 63. Discoidea cylindrica, an "irregular" Echinoid. The right-hand figure shows 
 the summit of the shell, with the genital disc. The left-hand figure shows the base of 
 the shell, on which are situated both the mouth and anus. 
 
 parts obtains are termed the " irregular " Echinoids (Echinoidca 
 exocyclica). They are further distinguished by being mostly 
 oblong, pentagonal, heart-shaped, or discoidal in form, by 
 being mostly destitute of any masticatory apparatus, and by 
 having only four perforated genital plates. 
 
 Another group must be constituted for the reception of the 
 Sea-urchins of the Palaeozoic Rocks, which differ materially 
 from the Mesozoic, Kainozoic, and Recent Echinoids. Only
 
 108 ANNULOIDA. 
 
 two genera are known in the Palaeozoic series, viz., Archao- 
 cidaris and Falcechinus, but these differ from all the modern 
 forms in the fact that the corona of the test was composed of 
 more than twenty rows of plates. The test was divided into 
 five ambulacral and five interambulacral areas, and the in- 
 crease in the number of plates arises from the fact that each 
 interambulacral area consists of three, five, or more rows of 
 plates (fig. 64). From this peculiarity the Palaeozoic urchins 
 
 Fig. 64. Archaocidaris elliptic. The left-hand figure shows a portion of an 
 ambulacral area enlarged. The right-hand figure exhibits a single plate. 
 
 were placed in a separate sub-order by M'Coy, under the 
 name of Pcrischoechinida (the Tesselata of Pomel). The five 
 interambulacral areas are surmounted dorsally by the genital 
 plates, which are five in number, and in Pal&chinus are doubly 
 perforated. The five ambulacral areas are " simple," or are 
 continuous from pole to pole, being surmounted by the ocular 
 plates. These are said by Baily to be triply perforated in 
 Palcechinus, but they are said by De Koninck to be wanting. 
 The test in both genera appears to be " regular." 
 
 As regards the distribution of the Echinoidea in time, the 
 genera Archaocidaris and Paleechimts (the Perischoechinida) are 
 exclusively Palaeozoic, the former being confined to the Devo- 
 nian, Carboniferous Limestone, and Permian, whilst the latter 
 occurs both in the Carboniferous and in the Upper Silurian. 
 The normal Echinoids abound in the Mesozoic series, espe- 
 cially in the Oolitic and Cretaceous Rocks, and are also well 
 represented in the Tertiary Rocks. Their distribution will be 
 shortly noticed under the head of each family. 
 
 The Echinoidea are divided into the following more im- 
 portant families, with their leading characters, distribution in 
 time, and a few illustrative genera : - 
 
 i. Ananchytida. Mouth excentric, in front; anus behind,
 
 ECHINOIDEA. 109 
 
 marginal, or supramarginal. Ambulacra composed of simple 
 pores, not petaloidal. Apical disc of four perforated genital 
 plates and five ocular plates. Spines minute. No masticatory 
 apparatus. Distrib. Jurassic and Cretaceous. ///. Gen, Ana- 
 nychytes. 
 
 2. Spatangidce (Heart-urchins). Test oval, oblong, or com- 
 monly heart-shaped, exhibiting distinct bilateral symmetry. 
 Mouth excentric. Anus posterior and supramarginal. Am- 
 bulacra petaloid, the anterior one unpaired, usually lodged in 
 a groove or " sulcus." Four genital pores. Mouth toothless. 
 Spines minute and hair-like. Distrib, Cretaceous to Recent. 
 ///. Gen. Spatangtts, Micraster, Eupatagus, Amphidetus. 
 
 3. Colly ritida or Dysasteridce (sometimes placed with the 
 Ananchytida, sometimes in the following order of the Echino- 
 neidce). Test circular or oval. Mouth excentric ; anus supra- 
 marginal. Ambulacra not petaloidal, meeting at two points 
 on the upper surface, which are more or less apart. Four 
 generative pores. Mouth toothless. Distrib, Oolitic and 
 Cretaceous. ///. Gen. Colly rites (Dysaster}. 
 
 4. EchinoneidcB. Test oval. Mouth nearly central ; anus 
 basal or marginal. Ambulacra not petaloidal, continuous from 
 mouth to apical disc. Four generative pores. Mouth tooth- 
 less. Distrib, Cretaceous to Recent. ///. Gen. Echinoneus, 
 Pyrina. 
 
 5. Cassidulidce. Mouth central, or nearly so; anus supra- 
 marginal or infra-marginal. Ambulacra more or less petaloidal, 
 similar or dissimilar. Four generative pores. Apical disc 
 sometimes excentric. Mouth toothless. Distrib. Oolitic to 
 Recent. ///. Gen. Clypeus, Pygattlus, Pygurus. 
 
 6. ClypeasteridcB. Mouth central ; anus marginal or infra- 
 marginal, posterior. Dorsal portions of the ambulacra petaloid. 
 Five genital plates surrounding the madreporiform tubercle. 
 Mouth toothed. Distrib. Cretaceous to Recent. ///. Gen, 
 Clypeaster, Scntella (fig. 59), Echinocyamus. 
 
 7. Echinoconida. Mouth central ; anus on the upper sur- 
 face behind, or on the lower surface, sometimes mounting so 
 high as to enter into the genital disc. Ambulacra simple, 
 narrow. Apical disc with five genital plates. Spines small. 
 Mouth toothed. Distrib. Oolitic and Cretaceous. ///. Gen. 
 Galerites (fig. 58), EMnoconus, Pygaster, Holectypus. 
 
 8. Cidarida. Test regular, spheroidal. Mouth central; 
 anus opposite the mouth, surrounded by the genital disc. 
 Ambulacra narrow, straight, or flexuous. Spines large, mostly 
 club-shaped. Mouth toothed. Distrib, Triassic to Recent. 
 ///. Gen. Cidaris, Temnoddaris.
 
 1 10 ANNULOIDA. 
 
 9. Echinidx. Test regular, spheroidal. Mouth central ; 
 anus opposite the mouth, surrounded by the genital disc. 
 Ambulacra wide or narrow, usually wide centrally, diminish- 
 ing towards the mouth and anus. Mouth toothed. Spines 
 varied in length and shape. 
 
 Section a. Salenida. Apical disk of more than ten 
 plates, large, with the anus placed excentrically in it. 
 Distrib. Oolitic to Tertiary. ///. Gen. Salenia (fig. 62), 
 Acrosalenia. 
 
 Section b. Diademada. Ambulacral areas with two or 
 four rows of large tubercles. Distrib. Jurassic to Recent. 
 III. Gen. Diadema, Astropyga. 
 
 Section c. Hemicidarida. Interambulacra with two 
 rows of large tubercles. Distrib. Triassic to Cretaceous. 
 ///. Gen. Hemicidaris (fig. 60). 
 
 Section d. Echinidcz Proper. Ambulacral and inter- 
 ambulacral areas with large tubercles. Distrib. Jurassic 
 to Recent. III. Gen. Echinus, Temnopleurus. 
 
 10. Pcrischoechinida. Test regular. Mouth central, infe- 
 rior ; anus opposite to the mouth, surrounded by the genital 
 disc. Ambulacra simple, perfect. Corona composed of more 
 than twenty rows of plates, each interambulacral area consist- 
 ing of from three to six rows. Distrib. Upper Silurian to 
 Carboniferous. ///. Gen. Archaocidaris and Palczchinus. 
 
 CHAPTER XI. 
 
 ASTEROIDEA AND OPHIUROIDEA. 
 ORDER II. ASTEROIDEA. 
 
 THE order Asteroidea or Stellerida comprises the ordinary 
 " star-fishes," and is defined by the fact that the body (fig. 65) 
 is star-sliaped or pentagonal, and consists of a central " disc" 
 surrounded by five or more lobes or " arms" The arms are 
 truly prolongations of the body, are hollow, and contain prolonga- 
 tions of the stomach in their interior. The arms are, further, 
 grooved on their under surface for the reception of the ambulacral 
 or water-vascular vessels. From these grooves the tube-feet are 
 protruded in two or four rows. The integument (perisome) is 
 leathery, but is more or less calcified by the development in it of 
 plates, granules, and spines of carbonate of lime. The mouth is
 
 ASTEROIDEA. 1 1 1 
 
 inferior in position, and is toothless. An anus is usually present, 
 but may be absent. 
 
 The two most striking features which distinguish the Star- 
 fishes from the Sea-urchins are the star-like figure of the 
 former, and the fact that the body is not enclosed in an 
 immovable calcareous box or " test," as it is in the latter. 
 The integument of the Asteroidea is, however, so richly pro- 
 vided with calcareous matter, that though more or less soft 
 and flexible during life, it is quite capable of being preserved 
 in a fossil condition. It is, of course, wholly with the cal- 
 careous secretions of the animal that the palaeontologist has to 
 deal ; and we may, therefore, dispense with any further account 
 of the soft parts, beyond what is contained in the above defini- 
 tion. 
 
 In their form the Star-fishes differ considerably, though in 
 most the figure is markedly stellate. The animal consists of 
 a central body or " disc," which gives off radiating processes 
 or " arms," but the size of the disc is very different in different 
 species, and the arms vary greatly in length and in number. 
 In many living and extinct forms the " disc " is inconspicuous, 
 and appears to be formed simply by the junction of the bases 
 of the arms, which in this case are normally five in number. 
 The living Urasters and Cribella, 
 and the extinct Palceasters (fig. 65), 
 may be taken as examples of this 
 state of parts. In other forms, as 
 in the Sun-stars (Solaster) and the 
 extinct Lepidasters and Plumasters, 
 the disc is very broad, exceeding or 
 equalling the length of the arms in its 
 diameter; whilst the rays vary in num- 
 ber, from eight or ten up to thirty 
 or more. In the Cushion-stars 
 (Goniaster and Goniodiscus), again, 
 the body is pentagonal, disc-shaped, 
 and flattened on the two sides, and the arms can only be 
 recognised by the ambulacral grooves on the lower surface 
 (fig. 66). 
 
 On the upper surface of the body, placed nearly in the 
 centre of the disc, is the aperture of the anus, when this is 
 present; but the genera Astropecten, Ctenodiscus, and Luidia 
 are destitute of a vent. Also on the upper surface is the 
 " madreporiform tubercle," in the form of a spongy or striated 
 disc placed at the angle of junction of two rays. It has the 
 same function as in the Echinoids, serving to protect the
 
 112 
 
 ANNULOIDA. 
 
 entrance to the water-vascular system. Ordinarily there is a 
 single madreporiform tubercle, but in some genera there are 
 two, three, or more tubercles ; and there seems in some cases 
 to be a correspondence between the number of the arms and 
 the number of madreporic plates. 
 
 Placed in the centre of the lower surface is the mouth, at 
 the angles of which are the so-called " oral plates " (fig. 66). 
 Radiating from the mouth are a series of furrows, varying in 
 number with the arms, and termed the " ambulacral grooves." 
 Each ambulacral groove is continued along the lower surface 
 of one of the arms, tapering gradually towards the extremity 
 of the latter. The floor of each groove is constituted by a 
 double row of minute calcareous pieces the " ambulacral 
 ossicles" which are movably articulated to one another at 
 their inner ends. At the bottom of each groove is lodged one 
 
 of the radiating canals of the 
 water-vascular system or am- 
 bulacral system, from which 
 are given off the rows of suc- 
 torial feet, or " tube feet." 
 It follows from this that the 
 radiating vessels of the am- 
 bulacral system are outside 
 the chain of ambulacral os- 
 sicles, so that these latter 
 are to be regarded as an 
 internal skeleton, and they 
 do not correspond with any 
 part of the skeleton of Echi-, 
 noids * at least they do 
 not correspond with the per- 
 forated ambulacral plates of 
 the Sea-urchins. The am- 
 bulacral ossicles, however, of the Star-fishes are of such a form 
 that by their apposition an aperture or pore is formed between 
 each pair. By means of these pores (fig. 66, a) the tube-feet 
 communicate with a series of little bladders placed above the 
 chain of ossicles. These perforations, however, do not corre- 
 spond with the perforated plates of the Echinoid test, and the 
 tube-feet of the Star-fishes pass through no " poriferous " plates 
 on their way to the exterior. 
 
 This may be rendered more intelligible by examining a 
 
 * The structures in the Echinus, which are truly homologous with the 
 ambulacral ossicles of the Asteroidea and Ophiuroidea, are the so-called 
 "auriculae. " 
 
 Fig. 66. Diagram ef a Star-fish (Goniasier), 
 (lowing the under surface, with the mouth 
 nd ambulacral grooves, a, Ambulacral os- 
 
 sides, with the ambulacral pores betwee 
 them. b, Adambulacral plates, bounding 
 the ambulacral grooves ; in. Marginal plates 
 iwanting in many species); o, Oral plates, 
 placed at the angles of the mouth.
 
 ASTEROIDEA. 113 
 
 section of the arm of a Star-fish from which the soft parts have 
 been removed (fig. 67). In such a section the ambulacral 
 ossicles (a, a] are seen in the centre of the lower surface, 
 united along the middle line by their inner extremities. They 
 are so placed as to form a kind of elongated pent-house, and 
 immediately beneath the line where the ossicles of one side 
 are articulated with those of the other side is placed the 
 ambulacral vessel (fr). Superficial to this, again, is a nerve- 
 cord ; so that the whole chain of ambulacral ossicles is placed 
 in the midst of the soft parts of the animal, and is thus clearly 
 an internal skeleton. At their outer extremities the ambulacral 
 ossicles are articulated by the intervention of the " adambulac- 
 ral plates " (fig. 66, ), with plates belonging to the external 
 or integumentary skeleton, to be immediately described. As 
 before said, the shape of the ambulacral ossicles is such that a 
 
 Fig. 67. Section of the ray of Uraster nibens. a, a Ambulacral ossicles ; b Position 
 of the ambulacral vessel; c , c Plates of the external skeleton; n Nerve-cord. The 
 dotted lines show the tube-feet proceeding from the ambulacral vesseL 
 
 pore is formed by the apposition of each pair; and by these 
 apertures each tube-foot communicates with a vesicle placed 
 internal to the chain of ossicles. It will be seen, however, 
 that the tube-feet (indicated by the dotted lines in the figure) 
 do not pass through these apertures, or through any other 
 pores of the skeleton, on their way to the surface. The 
 "poriferous zones" of the Sea-urchins are part of the external 
 skeleton, and are not represented in the Star-fishes. On the 
 other hand, the integumentary skeleton in the Star-fishes is 
 absent along the ambulacral areas, or along the areas occupied 
 by the ambulacral grooves. 
 
 Leaving the ambulacral ossicles or internal skeleton of the 
 Asteroidea, we come now to the integumentary skeleton. This 
 consists of a vast number of small calcareous pieces, or " os- 
 sicles," united together so as to form a species of chain-armour. 
 H
 
 114 
 
 ANNULOIDA. 
 
 The ossicles are united with one another in a reticulated man- 
 ner, and the interspaces between them are filled by the coria- 
 ceous integument. In some genera there is a single or double 
 row of large plates round the borders of the disc and arms 
 (fig. 66, m). These are termed the " marginal plates." The 
 integument in the Star-fishes is also furnished with spines, 
 tubercles, and granules of calcareous matter. The spines 
 vary in their development and in their position in different 
 Star-fishes ; but there is commonly a row of spines along each 
 side of each of the ambulacral grooves. In some genera (as 
 in Solaster, Luidia, Ctenodiscns, &c.) there are spines the 
 summits of which carry bunches or tufts of minute calcareous 
 processes. These are termed " paxillae." Lastly, in Asteroidea, 
 as in Echinoidea, there are the modified pincer-like spines 
 which are known by the name of " pedicellariae." 
 
 As regards their geological distribution, the Asteroidea have 
 a long vertical range, extending from the Lower Silurian Rocks 
 to the present day. In Silurian seas Star-fishes abounded, 
 and the Upper Silurian Rocks especially contain their remains 
 in what may be considered as plenty. The leading Silurian 
 genera are Palaaster, Stenaster, Palasterina, Palceocoma (Salter), 
 Palaodiscus, and Petraster. Some of the more familiar Silurian 
 forms are figured below (fig. 68). The next period in which 
 
 Fig. 68. Silurian Star-fishes. A, Palasterina primerva. Upper Silurian ; B, Pala- 
 aster Ruthveni, Upper Silurian ; C, PaUeoconta Colvini, Upper Silurian 
 Salter.) 
 
 (After 
 
 Star-fishes abound is the Oolitic or Jurassic (Mesozoic), the 
 more important genera being Uraster, Luidia, Astropcctcn, and 
 Goniastcr. All the Oolitic species are extinct, but the genera 
 have mostly survived to the present day. In the Cretaceous 
 period, also, many Star-fishes occur, the genera Orcaster, Go- 
 niodiscus, and Stellaster being the most noticeable. In the 
 Tertiary Rocks remains of Star-fishes are not abundant, but 
 the genera Goniaster and Astropecten are represented in the 
 London Clay (Eocene).
 
 OPHIUROIDEA. 115 
 
 No thoroughly satisfactory classification of the Asteroidea 
 has been as yet proposed, but the following are the names of 
 the more important fossil genera, with their range in time : 
 
 Stenaster. Lower Silurian. 
 
 Petraster. 
 
 Palceaster. Lower Silurian to Carboniferous. 
 
 Palasterina. Upper Silurian. 
 
 Pal&ocoma (Salter). 
 
 Paltpodiscus. 
 
 Lepidaster. 
 
 Pleurasier. Trias. 
 
 Uraster. Jurassic to Recent. 
 
 Solaster. 
 
 Astrogonium. 
 
 Goniaster. 
 
 Astropecten. 
 
 Luidia. 
 
 Arthraster. Cretaceous. 
 
 Oreaster. 
 
 Stellaster. Cretaceous to Recent. 
 Goniodiscus. 
 
 ORDER III. OPHIUROIDEA. 
 
 The Ophiuroidea are often grouped with the Asteroidea, and 
 the living members of the order are known commonly as 
 Brittle-stars and Sand-stars. They are distinguished from the 
 true Star-fishes by the fact that the ""disc" contains all the 
 internal organs of the animal ; the " arms" are not grooved in- 
 feriorly for the emission of ambulacral tube-feet ; and the mouth 
 is provided with a masticatory apparatus. The Ophiuroids are 
 very conspicuously star-shaped, and consist of a central " disc " 
 and a series of radiating " arms " (fig. 69). The " disc " is 
 truly disc-shaped, and is covered with granules, spines, or 
 scales. From the disc proceed the arms, in the form of long 
 and slender processes, which may be simple or branched, but 
 which differ from the arms of Star-fishes in not containing any 
 prolongations from the stomach, and in never having their 
 under surfaces furrowed by ambulacral grooves. The arms, 
 in fact, are special processes superadded for the purposes of 
 prehension and locomotion, and rendered necessary by the 
 fact that the ambulacral system takes no part in the function 
 of locomotion, as it does in the Star-fishes. A madreporiform 
 tubercle, however, is present, and is placed on the inferior 
 surface of the body, being commonly concealed by one of the 
 plates surrounding the mouth. The mouth, as in the Star- 
 fishes, is placed in the centre of the lower surface of the disc ;
 
 Il6 ANNULOIDA. 
 
 but the stomach terminates blindly ; and there is, therefore, no 
 anal aperture. 
 
 Each arm is furnished with an internal and an external 
 skeleton. The internal skeleton consists, as in the star-fishes, 
 of a chain of " ambulacral ossicles," placed along the centre 
 of the arm. The ossicles are, however, now amalgamated in 
 pairs, each coalescing with its fellow on the opposite side ; so 
 that in place of a double row of movably articulated ossicles, 
 we have a single row of bilaterally symmetrical pieces. 
 
 Fig. 69. Recent Ophiuroids. a Opftiura. texturata, the common Sand-star ; 
 b Ophiocoma, neglecta, the grey Brittle-star (after ForbesX 
 
 The external skeleton of the arms is composed of four rows 
 of plates, one on the dorsal surface, one on the ventral, and 
 one on each lateral surface. The lateral plates generally carry 
 more less developed spines. In the extinct genus Protaster 
 it is said that the plates of the ventral row are double ; and 
 Ptilonaster is stated to possess four ventral rows of plates. 
 The disc, as before said, has a well-developed external skeleton 
 of scales, granules, and spines ; but there are never any of 
 those modified spines which are known as " pedicellariae," and 
 which occur in the Asteroids and Echinoids.
 
 OPHIUROIDEA. 117 
 
 As regards their distribution in time, the Ophiuroidea are 
 represented for the first time in the Upper Silurian Rocks by 
 the genus Protaster (fig. 70), unless Tceniaster be rightly re- 
 
 Fig. 70. Protaster Sedgwickii. Upper Silurian. A, Disc and bases of the arms, 
 magnified. B, Portion of an arm greatly enlarged. 
 
 ferred here, in which case the order begins in the Lower 
 Silurian. No other Palaeozoic genera have been satisfactorily 
 made out. In the Muschelkalk, the middle member of the 
 Trias, we have a well-marked species, the Aspidura loricata of 
 Goldfuss (fig. 71). In the Oolitic, Cretaceous, and Tertiary 
 
 Fig. 71. Aspidura loricata. Muschelkalk. 
 
 Rocks, Ophiuroids are by no means uncommon, and they be- 
 long for the most part to genera which exist at the present day. 
 Great uncertainty prevails as to the generic characters of these 
 animals ; but the Mesozoic forms are for the most part gene- 
 rally referred to the genera Ophiolepis, Ophioderma, Ophiocoma, 
 Amphiura, and Acroura.
 
 ANNULOIDA. 
 
 CHAPTER XII. 
 
 CRINOIDEA, CYSTOIDEA, AND BLASTOIDEA . 
 ORDER IV. CRINOIDEA. 
 
 THE Crinoids or Sea-lilies are Echinodermata in which Hie body 
 
 is fixed, during the whole or 
 a portion of the existence of 
 the animal, to the sea-bottom 
 by means of a longer or shorter 
 jointed or flexible stalk. The 
 body is provided with solid 
 arms which are primarily 
 five to ten in number, are 
 independent of the visceral 
 cavity, and are grooved on 
 their upper surface. The 
 arms are furnished with lat- 
 eral processes or "pinnula" 
 and the reproductive organs 
 are lodged beneath the integu- 
 ment on the ventral surf ace of 
 these, and are not placed in 
 the body-cavity. 
 
 If we take such a living 
 Crinoid as Rhizocrinus (fig. 
 72), we shall be able to ar- 
 rive at a comprehension of 
 the leading characters of this 
 order. Rhizocrinus is one 
 of those Crinoids which is 
 permanently rooted to some 
 foreign object by the base 
 of a stalk which is composed 
 of a number of calcareous 
 pieces or articulations. In 
 some cases (as in Apiocrinus, 
 fig. 81), the base of the stem 
 
 or " column " is consider- 
 ably expanded. In other 
 cases the column is simply 
 " rooted by a whorl of ter- 
 (Wyville Thomson). The joints of 
 the column are movably articulated to one another, the joint- 
 
 Fig. 73. Crinoidea : Rhizocrinia Lofoten- 
 sis, a living Crinoid (after Wyville Thomson), 
 four times the natural size, a Stem ; 6 Calyx ; 
 cc Arms. 
 
 minal cirri in soft mud
 
 CRINOIDEA. IIQ 
 
 surfaces often having a very elaborate structure, so that the 
 entire stem possesses in the living state a greater or less 
 amount of flexibility. Each joint is perforated centrally by a 
 canal, which is, very inappropriately, termed the " alimentary 
 canal/' but which in truth has nothing to do with the digestive 
 system of the animal. At the summit of the stem is placed 
 the body, which is termed the " calyx/' and which is usually 
 more or less cup-shaped, pyriform, bursiform, or discoidal. 
 The calyx exhibits two surfaces, a dorsal and a ventral, of 
 which the dorsal is composed of calcareous plates articulated 
 by their margins, whilst the former is composed of a more or 
 less leathery integument strengthened by the deposition in it 
 of numerous small plates of carbonate of lime. The ventral 
 surface exhibits the aperture of the mouth, which may be sub- 
 central or may be very excentric, and which in many extinct 
 forms is wholly concealed from view. The ventral surface also 
 exhibits the aperture of the anus, which is usually placed ex- 
 centrically in one of the spaces between the arms, and which 
 is generally, if not universally, carried at the end of a longer 
 or shorter tubular eminence or process, which is called the 
 " proboscis." Owing to the animal being supported on a stalk, 
 it is evident that the " ventral " surface is turned upwards, and 
 the " dorsal " surface downwards. The column springs from 
 the centre of the dorsal surface ; and a stalked Crinoid may, 
 therefore, be compared to a Star-fish turned upside down, with 
 its lower or ambulacral surface superior, and its dorsal surface 
 looking downwards. The calyx contains the digestive canal 
 and the central portions of 'the nervous and water- vascular 
 (ambulacral) systems ; but it does not contain the reproduc- 
 tive organs, as is the case with the visceral cavity of the other 
 Echinoderms. 
 
 From the margins of the calyx, where the dorsal and ventral 
 surfaces join one another, arises a series of longer or shorter 
 flexible processes, which are composed of a great number of 
 small calcareous articulations, and which are termed the "arms" 
 ( n g- 73)' The arms are usually primarily five in number, but 
 they generally divide almost immediately into two branches, 
 each of which may again subdivide ; the branches thus pro- 
 duced perhaps again dividing, until a crown of delicate graceful 
 filaments is formed. The arms carry smaller lateral branches 
 or " pinnulae " on both sides ; and they are not hollow like the 
 arms of the Star-fishes, nor do they contain any prolongations 
 of the stomach. The upper surface of the arms and pinnulae 
 is covered with a soft membrane, and below this are placed 
 the reproductive organs. The generative organs are, there-
 
 I2O 
 
 ANNULOIDA. 
 
 fore, not placed within the calyx, and it follows of necessity 
 that there is no generative opening or "ova- 
 rian aperture" in the walls of the calyx. 
 The ventral surfaces of the arms and pin- 
 nulse are furnished with grooves, which 
 in the living species are seen to be co- 
 vered with vibratile cilia. The brachial 
 grooves coalesce till they constitute five 
 primary grooves, which are continued from 
 the bases of the arms to the mouth. The 
 action of the cilia gives rise to a constant 
 current of sea-water, bearing organic mat- 
 ter in solution ; and this current proceeds 
 from the brachial grooves to the mouth. 
 In this way the animal obtains its food. 
 As the bases of the arms are separated 
 from the mouth by an intervening space, 
 it follows that the brachial grooves are 
 
 Fig- T>,.Platycrinus tricontadactylia. Carboniferous. The left-hand figure shows 
 the calyx, arms, and upper part of the stem, and the figure next this shows the surface 
 of one of the joints of the column. The right-hand figure shows the proboscis ; and 
 above is a magnified figure of part of one arm with its pinnula:. 
 
 continued over the ventral surface of the calyx, till they reach 
 the oral opening.
 
 CRINOIDEA. 1 2 1 
 
 There is no doubt that it is by the above arrangement that 
 the living Crinoids obtain their food, and the mechanism seems 
 to have been essentially the same in many extinct species. In 
 the Palaeozoic Crinoids, however, there seems to have been a 
 modification of this arrangement. In these forms, as in Actino- 
 crinus (fig. 75), the arms have much the structure of those of the 
 recent Crinoids, and are deeply grooved on theirventral surfaces. 
 The ventral surface of the calyx, however, exhibits no central 
 aperture, but only a proboscidiform tube, which arises from one 
 of the inter-radial spaces (i.e., one of the intervals between two 
 of the arms). This tube is often of great length, and a good 
 deal of controversy has taken place as to its nature. Without 
 entering into the conflicting views upon this subject, it may be 
 stated that the preponderance of authority is in favour of the 
 view that this " proboscis " is an anal tube, having the vent at 
 
 Fig. 74. Calyx of Fig. 75. Calyx of Fig. 76. Calyx of^. 
 
 Actinocrinus rotundus. Actinocrinus Konincki. Verneuillanus. The 
 
 arms are wanting, 
 and the apertures at 
 their bases are seen. 
 
 its extremity. Good observers, however, regard it as discharg- 
 ing the functions of both the mouth and the anus. Be this as 
 it may, the grooves on the ventral surfaces of the arms are 
 certainly not continued over the ventral surface of the calyx, 
 but, on the contrary, stop short at the bases of the arms. Their 
 further course was long a mystery ; but it is now known that 
 they are continued below the ventral surface of the calyx as a 
 series of covered passages or tunnels, the external apertures of 
 which are placed at the points where the arms spring from the 
 disc (see figs. 74-76). These covered channels are either 
 simply roofed over by the calcareous integument of the calyx, 
 or are rarely excavated in its walls ; and they converge to a 
 central point in the middle of the ventral surface of the disc. 
 Here, it is believed, is placed the mouth, concealed by the 
 calcareous plates of the perisome. From the known function 
 of the brachial grooves in the living Crinoids, this view would
 
 122 ANNULOIDA. 
 
 seem to be the most probable one ; but, as before remarked, 
 good authorities regard the excentric "proboscis" as the 
 mouth. 
 
 In another group of Crinoids, represented by the living 
 Feather-stars (Comatula) and the extinct Saccosoma (fig. 77), 
 
 Kig. 77. Saccosoma pectiitc ta, a free Crinoid. Jurassic. 
 
 the animal is only stalked when young, and in its adult con- 
 dition leads a free life. The young form in the members of 
 this group is supported upon a jointed calcareous column, by 
 which it is fixed to some foreign object ; and at this stage it in 
 no respect differs from the ordinary stalked Crinoids. At a
 
 CRINOIDEA. 123 
 
 certain period of its existence, however, the calyx drops off its 
 column, and becomes a locomotive animal. It now has a 
 near resemblance to one of the Brittle-stars (Ophiuroidea) ; 
 but is distinguished, not only by its developmental history, 
 but by the possession of lateral pinnae to the arms, and in 
 having the reproductive organs situated external to the body 
 proper. In the Feather-stars ( Comatula or Antedori) the dorsal 
 surface of the disc, at the point where the column was origi- 
 nally inserted, carries a series of jointed filaments or ".cirri," 
 by which the animal can moor itself to any foreign object. 
 These may be regarded as homologous with the " side-arms" 
 of the column of certain Crinoids. When the animal is thus 
 temporarily moored by its dorsal cirri, it is placed in the 
 ordinary position held by the Crinoids namely, with the 
 mouth and ventral surface of the disc looking upwards. When 
 creeping about, on the other hand, by means of the long and 
 flexible arms, the animal occupies the position held by the 
 Star-fishes and Ophiuroids namely, with the mouth and ven- 
 tral surface of the disc directed downwards, or towards the 
 ground. 
 
 Having now given a general account of the structure of the 
 Crinoids, it remains to consider some of their parts in greater 
 detail. In the first place, as regards the " column," we find 
 that the stem of attachment is composed of a great number of 
 separate plates or " articulations " placed one above the other, 
 and so jointed to one another that whilst the amount of move- 
 ment between any two pieces must be very limited, the entire 
 column acquires more or less flexibility. The column is per- 
 forated by a round or five-sided canal which pierces every 
 joint, and runs along the entire length of the stem. In the 
 Palaeozoic Crinoids, with few exceptions, the column was 
 round ; but in Platycrinus it is oval or elliptical (fig. 73). In 
 the genera Pentacrinus (fig. 78) and Extracrinus the column is 
 pentagonal in outline ; but much less markedly so in the 
 former than in the latter genus. The joints articulate with 
 one another by surfaces or facets which are differently marked 
 in different cases. In the Palaeozoic forms, as in Platycrinus 
 (fig. 73), the articulating facets are marked by more or less 
 numerous striae which radiate from near the centre of the joint. 
 In most of the Mesozoic genera, on the other hand, as in 
 Pentacrinus (fig. 78), the articulating facets are united by 
 crenated ridges arranged in a pentapetalous figure. In many 
 cases, as in Extracrinus and Pentacrinus, the column is fur- 
 nished with more or less numerous "auxiliary" arms, or "side- 
 arms," the function of which is not altogether clear.
 
 124 ANNULOIDA. 
 
 The dorsal surface of the cup or " calyx " is composed of a 
 number of calcareous plates accurately fitted together. The 
 number and arrangement of these vary much in different 
 
 Fig. 78. PentacrJHUS /asciciftosus, showing the form of the column, and one of the 
 facets of a joint The central figure shows the arms, and the summit of the column 
 
 with side-arms. 
 
 genera, and it will be sufficient to indicate here their general 
 disposition. Reposing directly upon the summit of the column
 
 CRINOIDEA. 
 
 125 
 
 is a series of plates which are termed " basal " from their 
 position, and which constitute the " pelvis " of Miller. The 
 "basals" may be five, four, or sometimes three in number, 
 and they form the lowest portion of the cup. In some cases 
 the "basals" are succeeded by a second row or cycle of plates, 
 which should properly be regarded, with Professor Beyrich, as 
 a second series of basals, but which are sometimes regarded 
 as something special, and are termed the " parabasals " or 
 " sub-radials." The basals (fig. 79, b) are succeeded by a 
 
 Fig. 79. Diagram to show the structure of the calyx in the fossil Crinoids ; I Basals; 
 r Radials ; i Inter-radials ; a Anal plates. Calyx of Forbesiocrinus. (After Pictet.) 
 
 series of two or three rows of plates, which are directly super- 
 imposed upon one another, and which form the foundations of 
 the arms (r, r). These are termed the "radials" (the "cos- 
 tas " of Miller), and are termed " primary," " secondary/' and 
 " tertiary," according to their distance from the basals. The 
 last radial plates, or those furthest from the column (some- 
 times called the " axillary radials "), give origin to the arms. 
 The radial plates are arranged in a series of vertical columns, 
 which extend from the summit of the basals to the bases of 
 the arms. Between the different columns of radial plates, 
 however, are intercalated certain other smaller plates, which
 
 126 ANNULOIDA. 
 
 alternate with one another, and which are termed "inter- 
 radials " (*). Lastly, one of the interradial spaces, correspond- 
 ing with the anus, is usually much wider than the others, and 
 is furnished with an additional series of plates, which are called 
 the " anal plates " (a). 
 
 As regards their general distribution in time, the Crinoidea 
 present us with an excellent example of a group which early 
 attained its maximum of development, and which has now 
 dwindled down to some half-dozen surviving species. With 
 one or two doubtful exceptions, the Crinoids appear, so far as 
 yet known, to have commenced their existence in the Lower 
 Silurian period, and they are represented by numerous and 
 very varied forms in the seas of the Upper Silurian period. 
 Amongst the commoner Silurian genera may be mentioned Cro- 
 talocrinus, Glyptocrinus, Ichthyocrinus, Periechocrinus, Rhodo- 
 crinus, Poteriocrinus, and Taxocrinus. In the Devonian Rocks, 
 also, Crinoids are plentiful, and the genera Cupressocrinus, Hap- 
 locrinus, and Melocrinus, may be mentioned as peculiar to this 
 period. It is in the earlier portion, however, of the Carbonifer- 
 ous period that the Crinoids attain their highest development. 
 The Carboniferous Limestone is in many places, over wide 
 areas, and for a thickness of many yards, almost entirely made 
 up of the debris of Crinoids; and in many places it is so 
 charged with the remains of these organisms as to deserve and 
 acquire the name of " crinoidal limestone " or " entrochal 
 marble." Amongst the commoner Carboniferous genera may 
 be mentioned Cyathocrinus, Actinocrinus (fig. 74), Platycrinus 
 (fig. 73), Poteriocrinus, and Taxocrinus. It is in the Palaeozoic 
 period, then, that the Crinoids attain their maximum, both 
 numerically and as regards the number of genera and species. 
 Taken as a whole, the Palaeozoic Crinoids are distinguished 
 by the characters already mentioned ; namely, by having the 
 brachial grooves conveyed to the mouth in concealed channels 
 or tunnels, in having mostly a rounded column, and in the 
 fact that the articular facets of the column-joints usually are 
 marked by numerous simple radiating striae. As a rule, also, 
 the Palaeocrinoids have a calyx, in which the dorsal surface has 
 a preponderating development as compared with the ventral 
 surface. 
 
 Coming to Mesozoic times, Crinoids are still abundant, 
 though certainly reduced in numbers as compared with their 
 development in the Palaeozoic period. Taken as a whole, the 
 Mesozoic Crinoids are characterised by having the brachial 
 grooves continued over the ventral surface of the disc, and by 
 having the ventral portion of the calyx more extensively de-
 
 CRINOIDEA. 
 
 127 
 
 veloped than the dorsal ; whilst the articular surfaces of the 
 column-joints are usually morticed to one another by means of 
 crenated ridges which have a flower-like arrangement. Neither 
 of these latter characters, however, is constant. In the Meso- 
 zoic Rocks, also, appear for the first time remains of the 
 free Crinoids allied to the living Comatulce. The genus Sacco- 
 soma (fig. 77) is exclusively Oolitic, and appears to form in 
 some respects a connecting link between the true Crinoids and 
 the Ophiuroidea. In the Chalk the genus Comatula seems to 
 be represented ; and the Cretaceous genus Marsupites (the 
 " Tortoise Encrinite ") presents us with a form which is inter- 
 mediate between the fixed Crinoids and the forms which lead 
 a free existence when adult. 
 
 Of the stalked Crinoids of the Mesozoic 
 period, the genera Encrinus, Pentacrinus, 
 Extracrinus, and Apiocrinus are especially 
 noticeable. In the genus Encrinus (fig. 
 80) the arms are composed of a double 
 series of alternating pieces, and carry pin- 
 nules on their inner surfaces. The joints 
 of the column are perforated by a small 
 round " alimentary canal. " The best-known 
 species is the famous Lily-encrinite (E. lilii- 
 formis, fig. 80), which is characteristic of 
 the Muschelkalk, the middle member of 
 the Trias. 
 
 In the genus Pentacrinus and the nearly 
 allied Extracrinus, the calyx is short and 
 composed of few plates (five basals and five 
 radials). The column is pentagonal, with 
 whorls of side-arms, and the articulating 
 surfaces of the joints are marked with pen- 
 tapetalous ridges. The arms are long, 
 slender, and branched. Amongst the best- 
 known species are the Pentacrinus fascicu- 
 losus of the Lias, and other nearly allied 
 forms of the same formation. 
 
 In the Apiocrinidce or " Pear-Encrinites " 
 (fig. 81), the animal was fixed to some 
 foreign object by a dilated base, and the 
 column was long and composed of numer- 
 ous joints. The articulating surfaces of the column-joints are 
 marked with simple ridges, and the stem is rounded and not 
 pentagonal. The last joints of the column gradually increase 
 in diameter, until they attain a size equal to the breadth of the 
 
 Fig. 80. Encrinus lilii- 
 formis. Muschelkalk.
 
 128 
 
 ANNULOIDA. 
 
 calyx. Upon the last of these developed column-joints rest 
 the basal plates of the calyx proper, and upon the margins ot 
 the calyx is inserted a circle of bifid and 
 pinnate arms. Although the calyx itself 
 is of large size, the internal cavity or vis- 
 ceral chamber, in which the soft parts of 
 the animal were contained, is comparatively 
 very small. The best- known species of 
 Apiocrinus are the A. rotundus of the 
 Great Oolite and the A. Roissyanus (fig. 
 81) of the Coral Rag. 
 
 In the Cretaceous period the Apiocrinida 
 are represented by the genus Bourgudi- 
 crinus, and the living genus Rhizocrinus 
 (fig. 72) would appear also to be a repre- 
 sentative of this family. The free Crinoids 
 are pretty well represented also in the 
 Cretaceous period, the White Chalk having 
 yielded the discs of Comatula, along with 
 the singular " Tortoise-encrinite " (Marsu- 
 pites), which would seem to connect the 
 stalked Crinoids with the free forms. 
 
 In the Tertiary period the Crinoids are 
 reduced, so far as is certainly known, to 
 the single genus Pentacrinus, which is re- 
 presented at the present day by the living 
 Pentacrinus Caput-Medusa of the Antilles. 
 The best -known species is the P. sub- 
 basaltiformis of the Eocene. 
 
 A good classification of the Crinoids is 
 still a desideratum. Commonly they have 
 been divided into two groups termed re- 
 spectively Articulata and Tessdata, accord- 
 ing as the radial plates of the calyx are 
 freely articulated to one another, or are 
 immovably joined together without articu- 
 lation. This arrangement is a far from 
 satisfactory one ; but if accepted, we should 
 have all the Mesozoic and Kainozoic 
 Crinoids (except Marsupites] in the divi- 
 sion of the Crinoidea articulata. On the 
 other hand, the division of the Crinoidea 
 tessdata would correspond with the Palaeo- 
 Apiocrinu* Crinoids, comprising all the species known 
 ' from the p al*ozoic formations.
 
 CYSTOIDEA. 129 
 
 The division of the Crinoidea into stalked and free forms is 
 in many respects inapplicable as a basis of zoological classifi- 
 cation. There can, however, be no doubt but that the free 
 Crinoids are structurally an advance upon the fixed forms. It 
 is, therefore, of interest to note that the stalked Crinoids had 
 attained their maximum in the Palaeozoic Rocks, and had even 
 commenced to decline before the free Crinoids first made their 
 appearance in the Mesozoic Series. 
 
 ORDER V. CYSTOIDEA. 
 
 The Cystoidea are Echinodermata in which the body was 
 enclosed in a series of calcareous plates accurately articulated by 
 fyeir edges, and was fixed to the sea-bottom by. a longer or shorter 
 flexible jointed stalk. There were rarely true arms, and if present, 
 these structures are much less developed than in the true Crinoids. 
 
 Fig. 82. Hemicosmites pyriformis, one of the Cystideans. The right-hand figure 
 shows the upper surface of the calyx. 
 
 In general form the Cystideans are globular, oval, pear- 
 shaped, conical, or sub-cylindrical, and they resemble the 
 Crinoids in consisting of a stem or " column " and a body or 
 "calyx." The column is composed of a succession of cal- 
 careous joints, and in no respect differs from the column of 
 the Crinoids. In Lepadocrinus (fig. 83, D), however, it is 
 doubtful if the column was affixed to any foreign body, for its 
 lower extremity is composed of a single, long, spindle-shaped 
 piece. The stalk also is asserted to be absent altogether in 
 Sph&ronites pomum and in the genus Agelacrinites. The calyx 
 consists of a number of polygonal calcareous plates accurately 
 fitted together, and enclosing all the viscera of the animal. 
 Sometimes the plates are indefinite in number and arrange- 
 ment ; but in other cases the number of plates is limited, and 
 they are arranged according to a definite plan. In other cases
 
 130 
 
 ANNULOIDA. 
 
 the number and arrangement of the plates may be definite on 
 one side of the calyx and indefinite on the other. 
 
 As regards the structure of the arms of the Cystideans, 
 there is a good deal of diversity. In some forms there were 
 no true arms, comparable with the arms of the Crinoids ; but 
 there were small jointed processes, which were attached to the 
 calyx, and which represent the " pinnulae " or lateral branches 
 of the arms of the Crinoids. In some cases, grooves cor- 
 responding with the brachial grooves of the Crinoids are 
 seen to extend from the point of attachment of each pinnula 
 
 Fig. 83. Cystideans. A, Caryocrinus ornatus ; a. Column ; *, Calyx ; c. Scars 
 where pinnulae were attached ; d, Valvular pyramid. B, Plturocyi tiles squamosus 
 (dorsal side) ; p, p, Two of the pectinated rhombs. C, Pseudocrinus bifasciatus. D, 
 Lcpadocnnus Gebhardi. 
 
 to the summit of the calyx. In other cases, as in Apiocysiitcs 
 and Callocystites, arms were present, but they were bent back- 
 wards and immovably soldered down to the surface of the 
 calyx. The arms spring in these cases from the apex of the 
 calyx, and are anchylosed by their dorsal surfaces to the body. 
 On their ventral surfaces the arms are grooved by furrows 
 which clearly correspond with the brachial grooves of the 
 Crinoids, and on each side of these grooves is a row of pin- 
 nulae. In one or two cases there is only a single row of pin- 
 nules, and the arm seems to have been fastened to the calyx
 
 CYSTOIDEA. 131 
 
 by one of the lateral surfaces, instead of by the dorsal surface. 
 In one Cystidean only (viz., Comarocystites punctatus, Billings) 
 are there free arms as in the true Crinoids ; but further re- 
 searches will doubtless show that these appendages existed in 
 other species as well. In Comarocystites, however, the arms 
 differ from those of the Crinoids in being only four in number, 
 in not subdividing (though they carry lateral pinnae), and in 
 arising directly from the summit of the calyx. 
 
 Upon the upper surface of the calyx in the Cystideans are 
 two, or sometimes three, apertures, the functions and nature 
 of which have given rise to considerable controversy. The 
 best known of these is a large opening which is pierced in one 
 side of the calyx, usually near the middle of the body, but 
 sometimes approximated to either the apex or the base. This 
 aperture is mostly defended by a "valvular pyramid;" or, in 
 other words, by a series of small plates, arranged in a pyra- 
 midal manner, and serving for the closure of the opening. 
 Much difference of opinion has prevailed as to the true nature 
 of this orifice. Von Buch believed that it was an " ovarian 
 aperture ; " Mr Billings regards it as discharging the functions 
 of both the mouth and anus ; whilst Professor Wyville Thom- 
 son, Mr Salter, and other high authorities, regard it as being 
 the anus, and as corresponding with the proboscis of the 
 Crinoids. That it is not an " ovarian orifice " may be re- 
 garded as certain, so that the question is narrowed to its 
 being the anus alone, or an " oro-anal" orifice. In the living 
 Le.tkia mirabilis, one of the Sea-urchins, both the mouth and 
 vent are closed by converging triangular valves, which doubt- 
 less correspond with the " pyramid " of the Cystideans. This 
 recent form, however, is not sufficient to decide the present 
 question, since in it both the mouth and the anus exhibit this 
 valvular apparatus. Upon the whole, therefore, this question 
 must be regarded as undecided, though the analogies of recent 
 forms would lead to the belief that the " pyramid " of the 
 Cystideans is truly the anus, and that the mouth must be 
 sought for between the bases of the arms, when these are 
 present. 
 
 A second aperture is placed near the centre of the summit 
 of the calyx, between the bases of the arms, when these exist. 
 This opening has not been universally detected, and its true 
 nature is doubtful. By Mr Billings it is believed to be what 
 he terms an "ambulacral orifice;" i.e., an aperture by which 
 the ambulacral vessels passed from the interior of the shell to 
 the exterior. The analogies of recent forms, however, would 
 support the view that this aperture is the mouth, in which case
 
 132 
 
 ANNULOIDA. 
 
 the " pyramid" must be the anus. There is, however, in some 
 cases a third aperture of small size, always placed near the 
 apex, and this has been regarded as being truly the anus. 
 
 Many Cystideans were further provided with a system of 
 minute pores or fissures, penetrating the plates of the calyx, 
 and usually arranged in definite groups. These groups are 
 termed " pectinated rhombs " (fig. 84), and their exact func- 
 tion is doubtful. By Messrs Billings and Rose, however, they 
 are believed, apparently with good reason, to have admitted 
 water to the body-cavity, and to have thereby subserved a 
 respiratory function. 
 
 Fig. 84. A, Pectinated rhomb of Glyptocystites mnltiporvs (Billings). B, Pectinated 
 rhomb of Pleurocystites (Billings). C, Two plates of Callocystites Jnuetti (Hall), show- 
 ing the pectinated rhombs (/). All enlarged. 
 
 As regards the distribution of the Cystideans in time, they 
 are not only wholly extinct, but they are exclusively confined 
 to the earlier portion of the Palseozoic period. They appear 
 to have commenced their existence in the Upper Cambrian 
 period, the earliest known examples being two extremely 
 simple forms (Trochocystites and Eocystitcs) from the "primor- 
 dial zone" of North America. Other forms have been de- 
 scribed as occurring in the " primordial zone " of Bohemia. 
 In the Chazy and Trenton Limestones of North America, of 
 Llandeilo-Caradoc age (Lower Silurian), and on the same 
 horizon in Russia, Scandinavia, and Bohemia, Cystideans are 
 found, often in vast numbers, though in a very fragmentary 
 condition. In the Bala Limestone (Lower Silurian) of Britain, 
 Cystideans are abundant fossils. In the Upper Silurian (Nia- 
 gara and Lower Helderberg) of North America, and on the 
 same horizon (Wenlock and Ludlow) of Britain, Cystideans 
 still occur, though their remains are not so plentiful. Lastly, 
 in the Devonian Rocks occur forms which have been doubt- 
 fully referred to Cystideans, but the real nature of which is 
 uncertain. Upon the whole, then, the Cystideans appear to 
 have commenced in the Upper Cambrian Rocks, to have
 
 CYSTOIDEA. 133 
 
 attained their maximum of development in the Lower Silurian 
 period, to have gradually diminished in numbers and in im- 
 portance during the Upper Silurian, and to have died out 
 at the commencement of the Devonian period, or shortly 
 thereafter. 
 
 Of the commoner genera, Hemicosmites (fig. 82), Caryocrinus, 
 and Echinospheerites have all the plates of the calyx perforated 
 by numerous pores. Spharonites has each calycine plate per- 
 forated by two pores, and Apiocystites, Callocystites, Prunocys- 
 tites, and Echinoencrinus have the calycine pores arranged in 
 rhombs upon two or three of the plates of the calyx. In 
 Glyptocystites there are from ten to thirteen of these " pecti- 
 nated rhombs." In Malocystites, Apiocystites, Callocystites, and 
 Psetidocrinus the arms are recumbent and soldered to the 
 calyx. In Comarocystites there were four free arms with pin- 
 nulae. In Lepadocrinus the last joint of the column is very 
 much elongated, and pointed at its extremity ; and in Agela- 
 crinites and some other forms the calyx appears to have been 
 directly attached to some foreign body, and a column seems 
 to have been wanting. 
 
 ORDER VI. BLASTOIDEA. 
 
 The Blastoidea or " Pentremites " are Echinodermata in 
 which the body is enclosed in an armour of closely-fitting calcareous 
 plates, and is fixed to some foreign object by a slender column. 
 From the summit of the calyx radiate five areas which are grooved 
 longitudinally, and striated across, and which carry a row of 
 jointed pinnula on each side, (Fig. 85.) 
 
 The Blastoidea nearly resembled the Cystideans in many 
 respects. The body or "calyx" is enclosed in a series of 
 articulated calcareous plates consisting of three large basals, 
 carrying five forked plates, which are usually regarded as 
 corresponding with the " radials " of the Crinoids. At the 
 angles of junction of the forked "radial" plates rest five 
 smaller plates the so-called " deltoid plates " which con- 
 verge towards the centre of the summit of the calyx. Between 
 these deltoid plates which are generally regarded as corre- 
 sponding with the " inter-radials " of the Crinoids are the so- 
 called " pseud -ambulacra." The pseud - ambulacra radiate 
 from the summit of the calyx, and the apex of each is re- 
 ceived into the cleft formed by the bifurcation of one of the 
 "radial" plates. Each pseud-ambulacrum is furrowed by a 
 longitudinal groove down its centre, and is of a somewhat 
 petaloid shape, the areas on each side of the central groove
 
 134 
 
 ANNULOIDA. 
 
 being transversely striated. Along the lateral margins of each 
 pseud-ambulacrum is a row of minute pores, which open into 
 internal sacs, and are believed to have had a respiratory func- 
 tion. Along each side of the longitudinal groove of each 
 pseud-ambulacrum there appears to have been attached a row 
 of small jointed processes or " pinnulae." The five pseud- 
 ambulacra, radiating from the summit of the calyx, give the 
 upper surface of the body somewhat the appearance of a 
 flower-bud ; hence the name applied to the order (Gr. blastos, 
 a bud ; eidos, form). Upon the whole, it would seem most 
 probable that the pseud-ambulacra of Pentremites represent 
 the arms of the Crinoids, anchylosed with the calyx, and that 
 the longitudinal furrows of the pseud-ambulacra represent the 
 " brachial grooves " of the Crinoids. 
 
 Fig. 85. Blastoidea. A, Pentremites ftriformU, side-view. B, Base of the same. 
 C, Summit ofPeHtnmiies conoideus. b, b, Basals ; d, d, Radials : /, /, Pseud-ambulacra. 
 C Shows the central pentagonal aperture, surrounded by the five openings at the summit 
 of the deltoid plates. Carboniferous. 
 
 At the summit of the calyx of the Blastoidea are usually six 
 apertures. One of these is larger than the others, and is 
 placed in the centre of the calyx, at the point towards which 
 the grooves of the pseud-ambulacra converge. This central 
 aperture has generally been regarded as the mouth, but Mr
 
 BLASTOIDEA. 135 
 
 Billings dissents from this view. The remaining five apertures 
 are placed at the summit of each deltoid plate, between two 
 pseud-ambulacra. Four of the apertures are equal in size, 
 and have generally been regarded as " ovarian ; " but they are 
 looked upon by the above-mentioned eminent authority as 
 being connected with the respiratory system. The fifth is of 
 larger size than the other four, and is usually regarded as 
 partly ovarian and partly anal ; but it is looked upon by Mr. 
 Billings as " oro-anal." 
 
 Like the Cystideans, the Blastoidea are not only extinct, 
 but are exclusively Palaeozoic. The Cystideans, however, 
 attained their maximum at a very early period of Palaeozoic 
 time; whereas the Pentremites flourished most abundantly in 
 the Carboniferous seas, towards the close of the Palaeozoic 
 period. The Cystideans had nearly died out, or had become 
 quite extinct, by the close of the Upper Silurian period ; and 
 it is a noteworthy fact that it is just at that point that the 
 Blastoidea seem to make their first appearance. Very spar- 
 ingly represented in the Upper Silurian Rocks, the Blastoidea 
 increase largely in numbers during the Devonian period ; but 
 they attain their maximum of development in the seas of the 
 earlier portion of the Carboniferous period. With one ex- 
 ceedingly problematical exception, no member of the order 
 is known to have survived the close of the Carboniferous 
 epoch. 
 
 ORDER VII. HOLOTHUROIDEA. 
 
 The last order of the Echinodermata is that of the Holothu- 
 rians or " Sea-cucumbers," in which the body is vermiform or 
 slug-shaped, and the calcareous matter secreted by the integument is 
 reduced to scattered spicules (Synapta), or rarely is present in the 
 form of imbricated scales (Psolus). 
 
 As might have been expected from the generally soft nature 
 of their integuments, the Holothuroids are hardly known as 
 fossils, and they merely require to be mentioned here. The 
 only remains referred with any probability to this order are 
 certain calcareous spicula which have been found in deposits 
 of both Mesozoic and Tertiary age, and which have been re- 
 garded as belonging to a Synapta, and the shield of a species 
 of Psolus which has been found in Post-Tertiary deposits in 
 Bute.
 
 136 ANNULOSA. 
 
 CHAPTER XIII. 
 
 SUB-KINGDOM IV. ANNULOSA. 
 FOSSIL ANNELIDA. 
 
 SUB-KINGDOM ANNULOSA. The Annulose animals are distin- 
 guished by the possession of a body which is composed of numer- 
 ous segments arranged longitudinally one behind the other. A 
 nen'ous system is always present, and consists of a double chain 
 of ganglia running along the ventral surface of the body and 
 traversed anteriorly by the gullet. The limbs (when present) are 
 turned towards that side of the body upon which tJie chief masses 
 of the nervous system are situated. 
 
 The sub-kingdom Annulosa may be divided into two primary 
 sections, according as the body is provided with articulated 
 appendages or not ; these divisions being known respectively 
 as the Arthropoda (or Articulata) and Anarthropoda. The 
 first of these comprises the Crabs, Lobsters, and the like (Crus- 
 tacea), the Spiders and Scorpions (Arachnida), the Centipedes 
 and Millipedes (Myriapodd), and the true Insects (Insecta). 
 The latter comprises the Spoon-worms (Gephyrea), the Leeches 
 (ffirudinea), the Earth-worms (Oligochceta), the Tube- worms 
 (Tubicola), and the Sand-worms or Sea-worms (Errantia); the 
 last four groups constituting the class of the Ringed Worms or 
 Annelida. 
 
 Regarded as a whole, the great Annulose sub-kingdom 
 seems to have commenced at least as early as the Echhioder- 
 mata and the Coelenterata. Both the Anarthropodous and 
 Arthropodous divisions of the sub-kingdom are represented in 
 the Upper Cambrian ; and the former, at any rate, is repre- 
 sented in the Lower Cambrian period, along with the earliest 
 traces of life known to us, except the Eozoon of the Laurentian 
 Series. 
 
 ANNELIDA, 
 
 In the Anarthropodous division of the Annulosa the loco- 
 motive appendages are never distinctly jointed or articulated 
 to the body ; and the integument, though usually capable of 
 secreting chitine or horny matter, is almost always quite soft 
 and flexible. The Spoon-worms (Gephyrea), and two orders 
 of the Annelides (viz., the Leeches and the Earth-worms), are 
 wholly unknown in the fossil condition, and need not be con- 
 sidered here. There remain only two orders of the Annelides
 
 ANNELIDA. 
 
 137 
 
 (viz., the Tubeworms or Tubicola, and the Sand-worms or 
 Errantia) which come under the notice of the palaeontologist, 
 and neither of these requires much notice. In both orders, as 
 throughout the division, the integument is more or less soft, 
 and there are no internal hard structures ; hence it is more 
 than doubtful if we have any example of the fossilised body of 
 these creatures, though such have been alleged to occur. The 
 Tubicolous Annelides, however, protect themselves by a tube 
 of lime, sand, or adventitious particles, and these investing 
 tubes are often preserved in the fossil condition. The Errant 
 Annelides, again, have left traces of their past existence in the 
 form of filled-up burrows or meandering trails upon the soft 
 sand and mud of the sea-bottom ; and from these we know 
 that the Annelides commenced their existence at least as early 
 as the Lower Cambrian period, obscure traces of their presence 
 having been even detected in the Laurentian Series. 
 
 ORDER TUBICOLA. The Tubicolous Annelides are distin- 
 guished by the fact that the body is protected by a tube within 
 which the animal can withdraw itself by means of tufts of bristles 
 carried on the sides of the body. The gills are placed on or near 
 the head, generally in two lateral tufts ; hence the name of 
 " Cephalobranchiate Annelides" applied to this order (fig. 86). 
 
 The protecting tube of the 
 Tubicolous Annelides may be 
 composed of carbonate of lime 
 (Serpula), of grains of sand 
 (Sabellaria), or of sand, pieces 
 of shell, and other adventitious 
 particles cemented together by 
 a glutinous secretion from the 
 body (Terebella) ; or it may be 
 simply membranaceous or lea- 
 thery (Sabella). Sometimes the 
 tube is free and non-adherent 
 (Pectinaria) more commonly it 
 is attached to some sub-marine 
 object by its apex or by one 
 side (Serpula and Spirorbis], 
 Sometimes the tube is single 
 
 (Spirorbis) ; sometimes the animal is social, and the tubes are 
 clustered together in larger or smaller masses (Sabellaria). 
 
 When the tube is calcareous, it presents certain resemblances 
 to the shells of some of the Molluscs, such as Vermetus and 
 Dentalium. In the living state it is easy to make a distinction 
 between these, for the Tubicolar Annelides are in no way 
 
 Fig. 86. Tubicola. a Serpula con- 
 tortuplicata, showing the branchiae and 
 operculum ; b Spirorbis communis.
 
 138 
 
 ANNULOSA. 
 
 organically attached to their tubes, whereas the Molluscs are 
 always attached to their shell by proper muscles. In the fossil 
 condition, however, it may be very difficult to refer a given 
 calcareous tube to its proper place. As a general rule, how- 
 ever, the calcareous tubes of Annelides, such as Serpula, are 
 less regular and symmetrical than those of Vermetus, whilst the 
 latter is partitioned by shelly septa, which do not exist in the 
 former. Again, the tube of Dentalium is open at both ends, 
 whereas it is closed at one extremity in the Serpulce. In the 
 Annelidous genus Ditrupa, however, the tube is open at 
 both ends, so that this distinction is one not universally appli- 
 cable. 
 
 Tubicolar Annelides are known from the Silurian Rocks 
 upwards, almost every great period having representatives of 
 the order, though many of the fossils referred to this group are 
 of a more or less problematical nature. The genus Spirorbis 
 has survived from the Upper Silurian period to the present 
 day; and forms very nearly allied to, if not actually identical 
 with, the recent Serpula, are found in almost all formations, 
 beginning with the Silurian. 
 
 The chief Palaeozoic genera of Tubicola are Cornulites, 
 Conchicolites, Serpulites, Trachydertna, Spirorbis (Microcon- 
 
 cAus), and Serpula. The 
 genus Cormtlites (fig. 87) 
 is Silurian, and the best 
 known species is C. serpu- 
 larius. In this singular 
 form the tube is of con- 
 siderable length often 
 three or four inches with 
 a wide aperture at one 
 end, and tapering gradu- 
 ally to its opposite extrem- 
 ity, which is often curved, 
 and seems to have been 
 attached to some solid 
 body. The tube is cal- 
 careous, with very thick 
 walls, the substance of 
 which is composed of a number of cellular cavities. Exter- 
 nally the tube is ringed with transverse annulations, and marked 
 with fine longitudinal striae. The internal cast of the tube has 
 the form of a series of inverted conical rings, of small width, 
 arranged in an imbricated manner. The tube appears to have 
 been solitary, and is rarely found attached. 
 
 Fig. ^.CornMtes serfularius. Upper 
 Silurian.
 
 ANNELIDA. 139 
 
 In the genus Conchicolites (fig. 88) we have a much smaller 
 Annelide, living socially, and forming masses of clustered tubes 
 growing attached to dead 
 shells in Lower Silurian 
 strata. As in Cornulites, 
 the tube of Conchicolites ap- 
 pears to have been calcare- 
 ous, but it is comparatively 
 thin, and has none of the 
 vesicular structure so char- 
 acteristic of the former. The 
 tube of Conchicolites is made 
 up of a series of short coni- 
 cal rings, inserted into one 
 another in an imbricated 
 
 -i -1 i j Fig. 88 -Conchicolites 
 
 manner, with their broader t f e s h e n of an om 
 ends turned away from the 
 
 mouth of the tube. It is worthy of notice that the casts of 
 Conchicolites, from their possession of the above structure, ex- 
 hibit a close resemblance to the shells of the Silurian genus 
 Tentaculites; whilst casts of the shells of some species of the 
 latter are absolutely undistinguishable, if fragmentary, from 
 casts of the tubes of the former. This is a remarkable fact, 
 since Tentaculites has often been regarded as a genus of Tubi- 
 colar Annelides ; but there are strong reasons for believing 
 that it is truly referable to the Mollusca, and belongs to the 
 order of the Pteropods. 
 
 The genus Serpulites was instituted by Murchison for certain 
 smooth semi-calcareous tubes, often of great length, and ap- 
 parently unattached, which occur in the Silurian series. These 
 tubes in some species reach a length of over a foot, with a 
 diameter of an inch, and their true nature is very doubtful. 
 The genus Trachyderma, again, was proposed by Phillips for the 
 casts of membranous flexible tubes which are found in the 
 Silurian rocks. These are transversely wrinkled or plaited, and 
 though the tube itself has disappeared, there can be little doubt 
 entertained as to their Annelidous nature. 
 
 The genus Spirorbis (fig. 89) is characterised by the posses- 
 sion of a shelly calcareous tube, which is coiled into a flat 
 spiral, one side of which is cemented to some foreign body. 
 The spiral may be either right-handed or left-handed, and the 
 shell generally occurs in numbers together, attached to dead 
 shells or to the remains of plants. The genus commences to 
 be represented in the Upper Silurian Rocks, in which S. Lewisii 
 is an abundant fossil. Other species occur in the Devonian,
 
 140 
 
 ANNULOSA. 
 
 and the little 6*. earbonarius (fig. 89) is a common species in 
 the Carboniferous Rocks, whilst more than one form has been 
 described from the Permian series. The genus continues to 
 
 Fig. 89. Spirorbis (Microconchus) earbonarius ; natural size, attached to a fossil plant, 
 and magnified. Carboniferous. (After Dawson.) 
 
 be well represented in both Mesozoic and Tertiary deposits ; 
 and living forms, apparently little different from the fossil ones, 
 abound in recent seas. 
 
 The genus Serpula (fig. 90) possesses a long shelly tube, 
 usually more or less tor- 
 tuous, sometimes solitary, 
 sometimes aggregated, and 
 fixed to some foreign body 
 by part of its surface. Spe- 
 cies of this genus have 
 been described from the 
 Upper Silurian, Devonian, 
 and Carboniferous forma- 
 tions. In the Trias some 
 species occur, and many 
 forms are known from the 
 Oolitic and Cretaceous 
 formations, whilst they are 
 equally numerous in the 
 Tertiary series. 
 
 Of the other fossils re- 
 ferred to the Tubicolar 
 Annelides, the only one 
 which needs notice is the 
 genus Ditrupa. The tube 
 in this genus is unattached, 
 open at both extremities, 
 and very closely resem- 
 bling the shell tf.z.Dcntalium, This genus does not seem to 
 
 Fig. 90. Serpula flagellun 
 'Jurassic.) 
 
 Oxford Clay.
 
 ANNELIDA. 
 
 141 
 
 have come into existence till the close of the Cretaceous 
 period ; but it is found in great abundance in the London Clay 
 (Eocene) and the Crag (Pliocene). 
 
 ORDER ERRANTIA. The Errant Annelides are character- 
 ised by the fact that the body is furnished with lateral tubercles 
 carrying tufts of bristles. The animal leads a free life, and is 
 not confined to a tube. The gills are placed along the back or sides 
 of the body ; hence the name of " Dorsibranchiate Annelides" often 
 applied to this order (fig. 91). 
 
 Fig. 91. Errant Annelides. A, Hairy-bait (Nephthys) ; B, Sea-mouse (Aphrodite] ; 
 C, Lob-worp (Arenicola). (After Gosse.) 
 
 Possessing no hard structures, the Errant Annelides are 
 hardly capable of being preserved in a fossil state. Certain 
 fossils, however, have been supposed to be the bodies of these 
 animals in a petrified state ; but it is very difficult to believe 
 that such is the true nature of the remains in question, and 
 it is almost certain that they are really nothing more than 
 the " tracks " of sea-worms. On the other hand, the Errant 
 Annelides are abundantly represented by their trails upon old 
 sea-bottoms or their burrows in sand or mud ; remains of which 
 occur in all formations, almost, from the Lower Cambrian up 
 to the present day. 
 
 The burrows of Annelides, as a matter of course, run in a 
 direction more or less opposed to the surfaces of the laminae 
 of the rock, being often quite vertical. Sometimes such bur- 
 rows are hollow, but they are more commonly filled up by the
 
 142 ANNULOSA. 
 
 matrix of the rock. The most important genera which have 
 been founded upon remains of this kind are Scolithus, Histio- 
 dcrma, and Arenuolites, all of which occur in rocks of Cam- 
 brian age. Scolithus is founded upon long burrows, which are 
 nearly straight, and descend vertically through the rock (fig. 
 92). Histioderma is a somewhat curved burrow, from one to 
 nearly four inches in length, terminating by a trumpet-shaped 
 opening, which is placed in the centre of a small mound. 
 Aretiicolites includes very small burrows which form loops, 
 opening on the surface by two apertures placed close to one 
 another. The mouths of these burrows are thus placed in 
 pairs, one being believed to be an aperture of entrance for the 
 worm, the other of exit. The nature of none of these fossils 
 
 Fig. 92. Annelide-burrows (Scolithus Canademis), from the Potsdam Sandstone (Upper 
 Cambrian). (After Billings.) 
 
 is wholly free from doubt ; but the other genera, which have 
 been regarded as formed by burrowing Annelides, are still 
 more obscure and uncertain. 
 
 As regards the surface-tracks and trails of Errant Annelides, 
 much difference of opinion exists, and the whole subject is 
 shrouded in obscurity. Many of these tracks were regarded 
 by their describers as being actually the body of the worm, as 
 in Crossopodia (fig. 93). Others, as Gordia and Myrianites y 
 are undoubtedly tracks of some animal, but there is no 
 evidence as to their having been produced by Annelides. 
 Others, again, such as Palceochorda, which are also almost cer- 
 tainly the trail of some marine animal, have been described as 
 the remains of plants. A few of these fossils may truly be of
 
 CRUSTACEA. 
 
 a vegetable nature, whilst as to others (such as Nereites) no 
 certain conclusion can be arrived at. Upon the whole, it 
 would be safest to adopt Mr. Sailer's proposal, and refer all 
 these remains provisionally to the artificial genus Helminthites, 
 
 Fig. 93. Crossopodia Scotica, an Annelide track. Silurian. (After M'Coy.J 
 
 retaining Scolithus for the burrows. As regards the distribu- 
 tion of these remains, it is sufficient to say that they occur 
 more or less abundantly in almost all strata of a suitable 
 mineral character from the Cambrian Rocks upwards. 
 
 CHAPTER XIV. 
 
 ARTHROPOD A. 
 
 CRUSTACEA. 
 
 DIVISION ARTHROPODA, or ARTICULATA. The members of 
 this division of the sub-kingdom Annulosa are distinguished 
 from the preceding division of the Anarthropoda by the pos- 
 session of jointed appendages, articulated to the body. The body 
 is composed of a series of segments or " somites" arranged along a 
 longitudinal axis; each segment occasionally, and some always, 
 being provided, at some period of life or other, with articulated 
 appendages. Both the segmented body and the articulated limbs
 
 144 ANNULOSA. 
 
 are more or less completely protected by an external skeleton 
 formed by the deposition of horny (chit incus) matter in the integu- 
 ment. 
 
 The division Arthropoda includes four great classes of 
 animals which are very generally spoken of as the " Arti- 
 culate Animals." These classes are the Crustacea (Lobsters, 
 Crabs, &c.), the Arachnida (Spiders, Scorpions, &c.), the 
 Myriapoda (Centipedes and Millipedes), and the Insecta (In- 
 sects). All these classes came into existence in the Palaeo- 
 zoic period, the division being represented by Crustaceans as 
 early as the Upper Cambrian at any rate, and doubtfully in 
 the Lower Cambrian. Owing to the fact that the Crustaceans 
 alone lead an habitually aquatic life, the remains of this class, 
 as might be expected, preponderate largely over those of the 
 other three. The air-breathing classes of the Arachnida, 
 Myriapoda, and Insecta, naturally, have not left abundant 
 traces of their existence in past time, a state of things which is 
 assisted by the nature of their integuments, which are rarely 
 as hard and resisting as those of the Crustaceans. 
 
 CLASS I. CRUSTACEA. 
 
 The Crustaceans are Articulate animals in -which the breath- 
 ing organs (when distinct) are in the form of gills, and the mode 
 of existence is almost always more or less aquatic. The body is 
 protected by a chitinous or sub-calcareous exoskeleton or "crust" 
 and the number of pairs of artiailated limbs is generally from five 
 to sei>en. Some of the locomotive appendages are often carried 
 upon the segments of the abdomen, and there are two pairs of 
 jointed feelers or " antennce" 
 
 The body of a typical Crustacean, such as a Lobster (fig. 
 94), consists of a definite number of somites placed one be- 
 hind the other, and divisible into three regions a head, thorax, 
 and abdomen. Most authorities regard the body as being 
 typically composed of twenty-one somites, of which seven go 
 to the head, seven to the thorax, and seven to the abdomen. 
 All these somites, except the last, may be provided with a pair 
 of appendages each. The last segment of the abdomen, how- 
 ever, never carries any appendages. This segment is known 
 as the "telson" (fig. 94, i, /), and it is variously regarded as 
 a somite without appendages, or as an unpaired appendage 
 placed in the middle line of the body. If this latter view be 
 adopted, the body of a typical Crustacean will consist of only 
 twenty segments, instead of twenty-one. The telson is very
 
 CRUSTACEA. 
 
 H5 
 
 greatly developed in some Crustaceans, such as the King- 
 crabs, and less so in the extinct Eurypterida. 
 
 Fig. 94. Morphology of Lobster, i. Lobster with all the appendages, except the 
 terminal swimmerets, removed, and the abdominal somites separated from one another. 
 ca Carapace ; t Telson. 2. The third abdominal somite separated, t Tergum ; s Ster- 
 num ; / Pleuron ; a Propodite ; b Exopodite ; c Endopodite. 3. One of the last pair 
 of foot-jaws or maxillipedes. e Epipodite ; g Gill ; the other letters as before. 
 
 Generally speaking, a greater or less number of the somites 
 are amalgamated together, rendering it difficult to recognise 
 their existence unless they bear appendages each pair of 
 appendages indicating a separate somite. Very commonly the 
 segments of the head and thorax are welded together into a 
 single mass, which is termed the " cephalothorax," and which
 
 146 ANNULOSA. 
 
 really consists of fourteen coalescent segments. The cephalo- 
 thorax is generally covered by a great shield or buckler, which 
 is termed the "carapace" (fig. 94, i, fa), which is produced 
 by an enormous development of the dorsal walls of one or two 
 of the cephalic somites. 
 
 Each segment of the body may be regarded as essentially 
 composed of a convex upper plate, termed the " tergum," 
 which is closed below by a flatter plate, called the " sternum," 
 the line where the two unite being produced downwards and 
 outwards into a plate which is called the " pleuron," or 
 " pleura " (fig. 94, 2). 
 
 Strictly speaking, the composition of the typical somite is considerably 
 more complex, each of the primary arcs of the somite being really com- 
 posed of four pieces. The tergal arc is composed of two central pieces, 
 one on each side of the middle line of the body, united together, and con- 
 stituting the "tergum" proper. The superior arc is completed by two 
 lateral pieces, one on each side of the tergum, which are termed the 
 "epimera." In like manner the ventral or sternal arc is composed of a 
 central plate, composed of two pieces united together in the middle line, 
 and constituting the "sternum" proper, the arc being completed by two 
 lateral pieces, termed the "episterna." These plates are usually more or 
 less completely anchylosed together, and the true structure of the somite 
 in these cases is often shown by what are called "apodemata." These 
 are septa which proceed inwards from the internal surface of the somite, 
 penetrating more or less deeply between the various organs enclosed by the 
 ring, and always proceeding from the line of junction of the different pieces 
 of the segment (fig. 95). 
 
 Each somite of the body may bear a pair of appendages, 
 and these appendages are very much modified in different 
 parts of the body, in order to fulfil 
 different functions. Usually, how- 
 ever, a common morphological type 
 may be recognised in the append- 
 ages of the Crustacea, though certain 
 elements of this type are often want- 
 J * ing or much modified. Typically, 
 
 Fig. 95 -Theoretical figure iiius- t h e appendages of the Crustacea 
 
 trating the composition of the tegu- . rr .. ' . . . , . . 
 
 mentary skeleton of the Crustacea COnSlSt Of an Undivided basal por- 
 
 tion or "propodite," giving origin 
 
 ral pieces; V Ventral arc; ssSter- tO tWO diverging joints, of which 
 
 ;/FnSn#the P l^ the inner is called the "endopo- 
 
 dite," whilst the outer is known 
 
 as the " exopodite." In such an appendage as the " swim- 
 meret " of a Lobster (fig. 94, 2), these fundamental parts are 
 readily recognisable ; but either the exopodite or endopodite, 
 or both, may be wanting, or they may be very much modified 
 in shape and form.
 
 CRUSTACEA. 147 
 
 It is impossible to give any general view of the appendages 
 of a Crustacean ; but it may be as well to name the appendages 
 which are present in one of the higher forms, such as the 
 Lobster, in which all the somites, except the telson, carry a 
 pair of appendages each. The somites of the head and thorax 
 are amalgamated into a single mass, termed the "cephalo- 
 thorax," which is protected above by the " carapace," and 
 carries the appendages on its lower surface. The first segment 
 of the head carries a pair of eyes, which are " compound," and 
 are borne upon long stalks, formed by the propodite of the 
 appendage. The second segment of the head carries a pair of 
 small jointed feelers, which are known as the " lesser antennae " 
 or " antennules." Each consists of a short propodite, and a 
 much-segmented endopodite and exopodite, which are nearly 
 of equal length. The third segment of the head carries a pair 
 of very long feelers, which are known as the " great antennas." 
 Each consists of a short propodite and a long and jointed 
 endopodite, with a rudimentary exopodite. Thefourt/i seg- 
 ment of the head carries a pair of jaws, which are known as the 
 ".mandibles." Each mandible consists of a large propodite, 
 with no exopodite, but with a small endopodite, which is known 
 as the " mandibular palp." Between the bases of the man- 
 dibles also is placed the aperture of the mouth, which is 
 bounded in front \yy a plate, known as the "labrum" (upper 
 lip) or " hypostoma." and behind by a forked plate, known as 
 the " labium " (lower lip) or " metastoma." Thefift/i segment 
 carries another pair of jaws, which are known as the first pair 
 of " maxillae ; " whilst the sixth segment carries another pair of 
 the same, known as the second pair of "maxillae." The 
 seventh and last segment of the head carries the first of three 
 pairs of what are generally known as " foot-jaws " or " maxilli- 
 pedes." Each foot-jaw is merely an ordinary limb, consisting 
 of propodite, exopodite, and endopodite, but modified to assist 
 in mastication. The eighth segment (the first of the thorax) 
 carries a second pair of foot-jaws, and the ninth segment (the 
 second of the thorax) bears a third pair of the same. The 
 tenth segment (the third of the thorax) carries a pair of jointed 
 limbs, consisting of propodite and endopodite alone, without 
 any exopodite. These limbs are greatly developed, and their 
 extremities form a pair of pincers or " chelae," so that they 
 constitute the " nipping-claws " of the Lobster. The eleventh 
 segment (the fourth of the thorax) carries a second pair of 
 limbs, also " chelate," but much smaller than the preceding ; 
 and the twelfth segment (the fifth of the thorax) carries another 
 pair of the same. The thirteenth segment (the sixth of the
 
 148 ANNULOSA. 
 
 thorax) carries a pair of limbs like the preceding, but with 
 simply-pointed extremities ; and the fourteenth segment (the 
 last of the thorax) carries another pair of the same ; so that 
 there are altogether five pairs of ambulatory limbs, carried 
 respectively by the loth, nth, i2th, i3th, and i4th somites of 
 the body ; or, in other words, by the last five segments of the 
 thorax. Of the seven segments of the abdomen completing 
 the total of twenty-one the first six carry each a pair of ap- 
 pendages, which are used as swimming organs, and which are 
 termed the "swimmerets." Each swimmeret (fig. 94, 2) con- 
 sists of a propodite and a flattened exopodite and endopodite; 
 and the last pair is greatly widened out and expanded, forming 
 with the telson a powerful swimming-tail. The telson or last 
 abdominal segment carries no appendages, and is simply 
 placed between the last pair of swimmerets. 
 
 As regards the general distribution of the Crustacea in time, 
 remains of the class are comparatively abundant in all forma- 
 tions except the very oldest ; as might have been expected 
 from the generally chitinous or sub-calcareous nature of their 
 integuments and their aquatic habits. Owing also to their 
 habit of periodically casting their shell, a single individual may 
 leave repeated traces of himself, and the number of fossils may 
 considerably exceed that of the individuals which actually 
 underwent fossilisation. The Crustaceans appear to have com- . 
 menced their existence in the Cambrian period, remains of 
 members of this class being tolerably abundant in the higher 
 portion of this formation. The Palaeozoic formations, taken 
 as a whole, are characterised by the predominance of the 
 orders Trilobita, Eurypterida, Ostracoda, and Phyllopoda, of 
 which the two former are exclusively confined to this period. 
 All the other orders of Crustacea, which have left any traces of 
 their past existence at all, appear to have come into existence 
 before the close of the Palaeozoic period. Upon the whole, 
 however, there has been a marked progression in proceeding 
 from the older formations to the present day. The Trilobites 
 and Eurypterids of the older Palaeozoic Rocks, though highly 
 organised so far as their type is concerned, are in many respects 
 inferior to later forms, whilst they present some striking points 
 of resemblance to the larval forms of the higher groups. The 
 great group of the Stalk-eyed Crustaceans undoubtedly the 
 highest of the entire class is not represented at all till we 
 reach the Carboniferous Rocks : and it is not till we come into 
 the Secondary period that we find any great development of 
 this group, whilst its abundance increases to a marked extent 
 in the Tertiary period, and it attains its maximum at the
 
 CRUSTACEA. 149 
 
 present day. Similarly, of the two sub-orders of the Merosto- 
 mata, the Eurypterida are confined to the earlier portion of the 
 Palaeozoic period, whilst the more highly organised and less 
 larval King-crabs (Xiphosurd) did not make their appearance 
 till the Eurypterids had disappeared, at the close of the Car- 
 boniferous period. 
 
 The following table shows the orders of the Crustacea, and 
 a short account will be given of the distribution in time of 
 those which are known to occur as fossils. The structure also 
 of the extinct groups will be shortly described. The orders 
 marked with an asterisk do not occur as fossils, or only doubt- 
 fully so, and will not be considered here. 
 
 TABULAR VIEW OF THE DIVISIONS OF THE CRUSTACEA. 
 Sub-class I. EPIZOA (Hausteliata). 
 Order I. Ichthyophthira* 
 
 ,, 2. Rhizocephala* 
 Sub-class II. CIRRIPEDIA. 
 
 ( Balanidse. 
 
 Order 3. Thoracica. < Verrucidse. 
 
 ( Lepadidse. 
 
 4. Abdominalia* 
 
 5. Apoda* 
 
 III. ENTOMOSTRACA. 
 
 Sub-class 
 
 Odei 
 
 8. Cladocera* \ 
 
 9. Phyllopoda. > Legion, Branchiopoda. 
 
 10. Trilobita. ) 
 
 11. Merostomata. 
 
 Sub-class IV. MALACOSTRACA. 
 
 Division A. EDRIOPHTHALMATA. 
 Order 12. Lcemodipoda* 
 ,, 13. Isopoda. 
 ,, 14. Amphipoda. 
 Division B. PODOPHTHALMATA. 
 Order 15. Stomapoda, 
 ,, 1 6. Decapoda. 
 
 Tribe a. Macrura. 
 b. Anomura. 
 ,, c. Brachynra. 
 
 SUB-CLASS CIRRIPEDIA. 
 
 Animal free when young, but permanently attached in the adult 
 condition to some foreign body by the anterior extremity of the 
 metamorphosed head. The visceral cavity of the adult protected 
 by a calcareous shell of several pieces, or by a coriaceous envelope. 
 Abdomen free. Thoracic segments usually carrying six pairs of 
 forked ciliated limbs.
 
 1 50 ANNULOSA. 
 
 The Cirripcdia include three orders, of which only the order 
 Thoracica has ever been found in a fossil condition, or is ever 
 likely to be so. In this order are the common Acorn-shells 
 (jBalanidce) and Barnacles (Lepadidce), in which the body is 
 protected by a more or less complete calcareous shell. The 
 Acorn-shells are generally known as the " Sessile Cirripedes," 
 because the shell is directly attached by its base to some 
 foreign body, whereas the Barnacles are commonly known as 
 the " Pedunculated Cirripedes," because the shell is supported 
 upon a stalk or " peduncle." Besides these, the order Thor- 
 acica comprises a third family, that of the Verritcida, in which 
 the shell resembles that of the Balanidce in being sessile, but 
 differs in being unsymmetrical, and in some other particulars. 
 
 It is with the shell of the Cirripedes that the palaeontologist 
 has to deal ; and we may, therefore, consider briefly the chief 
 parts of the shell in the Sessile and Pedunculated Cirripedes 
 respectively. It will not be necessary, however, to enter into 
 minute details on this complicated subject, and it will be 
 sufficient to indicate the leading facts of importance. 
 
 In the symmetrical Sessile Cirripedes or Balanidce, commonly 
 known as Acorn-shells, the animal is protected by a calcareous 
 shell formed by calcifications within the walls of the first three 
 cephalic segments. The animal is placed within the shell, 
 head downwards, and is fixed to the centre of a shelly or mem- 
 branous plate, which closes the lower aperture of the shell, and 
 which is termed the "basis" (fig. 96 A, I). The "basis" is 
 fixed by its outer surface to some foreign object, and is some- 
 times compact, sometimes porous. Above the basis rises a 
 limpet-shaped, conical, or cylindrical shell, which is op^n at 
 the top, but is capable of being completely closed by a pyra- 
 midal lid or " operculum." Leaving the operculum out of 
 consideration at present, the sides of the shell are seen to be 
 composed of from four to eight separate pieces, valves, or, as 
 they are technically called, compartments. These compart- 
 ments are usually closely contiguous by their lateral margins, 
 and are separated by lines of division or " sutures ; " but they 
 are sometimes anchylosed together. Each compartment con- 
 sists of a central portion, which is termed the "paries" (fig. 
 96, B/), which is attached by its base to the "basis" of the 
 shell. The "paries" grows downwards, so that the whole 
 shell increases by additions made round the base. The paries 
 of each compartment is flanked by wing-like portions, which 
 differ from the paries in appearance, and are called "radii" 
 and " alae," according to their shape (fig. 96, B, C). Some- 
 times the paries has a " radius " on both sides, sometimes
 
 CRUSTACEA. 151 
 
 "alee" on both sides, and sometimes an ala on one side and a 
 radius on the other. 
 
 The separate compartments of the shell receive special 
 names according to their position. The compartment at the 
 end of the shell where the animal thrusts out its cirrated limbs, 
 is called the " carina" (fig. 96, A) ; and the compartment im- 
 mediately opposite to this " rostrum." The remaining com- 
 partments are " lateral," the one nearest the carina " carino- 
 lateral," the one nearest the rostrum " rostro-lateral," and the 
 middle one simply " lateral " (fig. 96, A) ; but the three rarely 
 coexist. 
 
 Fig. 96. Shell of Balanidse. A, Diagram of the shell of Balamts ; I, I Basis ; c Carina ; 
 k Rostrum ; m Rostro-lateral compartment ; n Lateral compartment ; o Carino-lateral 
 compartment. B, Compartment with two radii (?, r) flanking the paries (^). C, 
 Compartment with a radius (r) on one side, and an ala (a) on the other side of the paries. 
 D, Internal view of the scutum. E, Internal view of the tergum, showing the spur (s) 
 and the beak (0. (After Darwin.) 
 
 The " operculum " or lid of the shell consists of two pairs of 
 valves, known as the " scuta " and " terga," forming a little 
 pyramid or cone, attached within the orifice of the shell by a 
 membrane. Each scutum opens and shuts against its fellow 
 along one margin (the " occludent " margin), and articulates 
 with one of the terga along the opposite margin. Similarly, 
 each tergum opens and shuts against its fellow along one mar- 
 gin (the "carinal" margin), and articulates with one of the 
 scuta along the opposite margin. The apex of the terga (fig. 
 96, E) often forms a prominent beak, and the basal margin is 
 furnished with a process or " spur." The scuta and terga are 
 not only movable, but are furnished with proper depressor 
 muscles.
 
 152 ANNULOSA. 
 
 As regards the distribution of the Balanida in time, the 
 oldest known representative of the family, so far as is certainly 
 known, has been indicated by Mr Seeley as occurring in the 
 Lias, and has been made the type of a new genus under the 
 name of Zoocapsa. So far as is known, no member of the 
 group occurs in any Palaeozoic deposit ; and negative evidence 
 is in this case of considerable value, as the Balani possess a 
 shell which is readily preserved, whilst they adhere to all 
 sorts of marine bodies. With the above-mentioned exception 
 (which may, perhaps, be referred to the Verrucidce), no fossil 
 Balanoid has hitherto been discovered in sediments older 
 than the commencement of the Tertiary period. The genus 
 Balanus is the earliest of the group, and appears under several 
 specific forms in the Eocene Rocks. In the Miocene and 
 Pliocene deposits, the Balanidce are abundantly represented 
 by Balanus itself, and in the latter by the genera Acasfa, 
 Pyrgoma, and Coronula. 
 
 The remaining family of the Sessile Cirripedes is that of the 
 Verruridce, comprising only the single genus Verruca. In many 
 respects the Verrucida approach the Balanidce, but the shell is 
 composed of six valves only, and is unsymmetrical, whilst the 
 scuta and terga (forming the operculum), though movable, 
 are not furnished with a depressor muscle. The Verrucida 
 appear, so far as is known, to have commenced their existence 
 towards the close of the Secondary period, the Chalk having 
 yielded one species. Verruca Stromia is found in the Coralline 
 and Red Crags (Pliocene), in Glacial deposits, and in existing 
 seas. 
 
 The third family of the Cirripedia Thoracica is that of the 
 Lepadidce or Pedunculated Cirripedes, commonly known as 
 " Barnacles." In these (fig. 97) the animal differs from the 
 Sessile Cirripedes in having its anterior extremity greatly 
 elongated, forming a stalk or " peduncle " by which the animal 
 is fixed to some foreign object. At its free extremity the 
 peduncle bears the "capitulum," which corresponds to the 
 shell of the Balanoids, and is composed of various calcareous 
 pieces, united by a membrane, moved upon one another by 
 appropriate muscles, and protecting in their interior the body 
 of the animal with its various appendages. The peduncle is 
 cylindrical, of varying length, flexible, and furnished with pro- 
 per muscles. In some species the peduncle is naked, and can- 
 not be preserved in the fossil condition ; but in other cases 
 the peduncle is furnished with calcareous scales (Loricula and 
 Turrilcpas, fig. 99), in which case it is readily preserved. The 
 " capitulum " (fig. 98), as before said, corresponds with the
 
 CRUSTACEA. 
 
 153 
 
 shell of the Balani, and is generally much flattened. It con- 
 sists ordinarily of five or more valves united to one another 
 by membrane, usually with marked interspaces ; but the valves 
 may be rudimentary or wanting, and 
 the entire capitulum may be mem- 
 branous. The parts of the capitu- 
 lum correspond ideally with the parts 
 of the shell in the Balanoids. In 
 the latter, however, the shell is for 
 the most part composed of the " com- 
 partments," and the " operculum " is 
 comparatively small and insignificant. 
 In the Lepadoids, on the other hand, 
 the valves which correspond with the 
 operculum of the Balanoids are dis- 
 proportionately developed, and the 
 valves which correspond with the 
 compartments of the Balanoids are 
 much less conspicuous, and are often 
 partially absent. The most important 
 and persistent of the valves are the 
 "scuta" (fig. 98, b], which protect the 
 front part of the body, and correspond 
 with the valves bearing the same name 
 in the operculum of the Balanoids. 
 The next most important are the 
 " terga" (fig. 98, a), which protect the 
 dorso-lateral surface. A pair of scuta 
 and a pair of terga are present, and 
 these are the largest of all the valves. 
 The " carina " and " rostrum " are 
 placed along the edges of the capitu- 
 lum, the former being much the most 
 important, and there may be a " sub- 
 carina " and " sub-rostrum." The re- 
 maining valves, with the carina and 
 rostrum, correspond with the proper 
 shell of the Balanoids ; but they are often wanting or rudi- 
 mentary, and they require no further consideration here. 
 
 As regards the distribution of the Pedunculated Cirripedes 
 in time, until recently no member of the family was certainly 
 known to have existed in the Palaeozoic period. Mr Henry 
 Woodward, however, has described a very interesting form 
 from the Upper Silurian Rocks, under the name of Turrilepas 
 (fig. 99, A). In this singular fossil the peduncle was furnished 
 
 Fig. 97. Anatifa lepas, a 
 recent Pedunculated Cirripede. 
 The lower figure shows the 
 scutum detached.
 
 154 
 
 ANNULOSA. 
 
 with intersecting rows of plates, as in Loricula. These plates, 
 when detached and occurring in an isolated condition, might 
 very readily be mistaken for the shells of Pteropods. The 
 genus is known both from the Wenlock Limestone of Dudley 
 and the Ludlow Rocks of the Pentland Hills near Edin- 
 burgh. The Devonian, Carboniferous, and Permian forma- 
 tions have as yet yielded no certain traces of Pedunculated 
 Cirripedes, if we reject, as we apparently must, the Aptychus 
 of the Carboniferous rocks, referred here by M. D'Orbigny. 
 
 Fig. 08. Capitulum of a Pedunculated Cirripede. a Tergum ; b Scutum ; c Carina ; 
 d Upper latus ; e Carino-latus ; f Rostrum ; g Sub-rostrum ; ft Rostral latus ; Infra- 
 median latus ; k sub-carina. (After Darwin.) 
 
 With the exception of the very ancient Turrilcpas, the oldest 
 pedunculated Cirripedes belong to the genus Pollicipcs, species 
 of which have been discovered in the Rhaetic beds (Upper Trias), 
 and in the Lower Oolites (Stonesfield Slate). In the Cretace- 
 ous period, " the Lepadidae arrived at their culminant point ; 
 there were then three genera, and at least thirty-two species, 
 some occurring in every stage of this system" (Darwin). In 
 the Tertiary rocks are a few species of Scalpdlum and Pollicipes ; 
 but no species of the now existing and widely distributed
 
 CRUSTACEA. 
 
 ISS 
 
 genus Lepas or Anatifa has as yet been certainly detected in a 
 fossil condition (Darwin), though D'Orbigny states that he has 
 
 Fig. 99. A, Turrilepas Wrightii. Upper Silurian. (After Woodward.) a A plate 
 of the same magnified. B, Loricula pulcltella. Chalk. (After Darwin.) 
 
 discovered a representative of this genus in the Miocene 
 
 Tertiary. 
 
 CHAPTER XV. 
 
 CR US TA CEA Continued. 
 SUB-CLASS ENTOMOSTRACA. 
 
 THE Entomostracous Crustaceans are defined by Professor 
 Rupert Jones as follows : " Animal aquatic, covered with a 
 shell, or carapace, of a horny consistency, formed of one or more 
 pieces, in some genera resembling a cuirass or buckler, and in others 
 a bivalve shell, which completely or in great part envelops the 
 body and limbs of the animal; in other genera the animal is in- 
 vested with a multivalve carapace, like jointed plate-armour ; the 
 branchice are attached either to the feet or to the organs of mastica- 
 tion ; the limbs are jointed, and more or less setiferous. The 
 animals, for the most part, undergo a regular moulting or change 
 of shell, as they grow ; in some cases this amounts to a species of 
 transformation. " 
 
 The orders commonly included in the sub-class Entomostraca 
 are the Ostracoda, Copepoda, Cladocera, Phyllopoda, Trilobita, 
 and Merostomata (comprising the sub-orders Xiphosura and 
 Eurypterida). Of these, the Copepoda and Cladocera may
 
 156 ANNULOSA. 
 
 be left out of consideration, as they are not certainly known to 
 occur in the fossil condition. There are also good reasons for 
 the belief that the Trilobites should be placed amongst the 
 Malacostracous Crustaceans, in or near the order Isopoda. In 
 the absence, however, of unassailable evidence, the Trilobites 
 may be safely retained in the vicinity of the Phyllopods, to 
 which they show undoubted affinities. 
 
 ORDER OSTRACODA. 
 
 Minute Crustaceans having the entire body enclosed in a shell or 
 carapace, which is composed of two valves united along the back by 
 a membrane. The valves are capable of being closed by an adduc- 
 tor muscle, the insertion of which is marked in the interior of each 
 valve by a tubercle, pit, or group of spots, or by both spots and a 
 pit. The branchice are attacJied to the posterior jaws, and there 
 are only two or three pairs of feet, which subscribe locomotion, but 
 are not adapted for swimming. 
 
 Of the living Ostracode Crustaceans, a great many inhabit 
 fresh waters (Cypris); others live in fresh or in brackish waters 
 (CandonaY, lastly, others are exclusively confined to the sea 
 ( Cythere and Cypridina). They generally swarm in the locali- 
 ties in which they occur, and from their habit of periodically 
 shedding their valves, considerable accumulations of their shells 
 may be formed under favouring circumstances. 
 
 It is only the carapace-valves of the Ostracode Crustaceans 
 that are preserved in the fossil condition; and the general form 
 of the carapace is often very similar in different genera. Hence, 
 the palaeontologist has to rely, in the discrimination of these 
 minute fossils, upon small variations of shkpe, differences in 
 the thickness of the valves, the characters of the edges of the 
 valves, or the manner in which they are hinged to one an- 
 other, or, lastly, the surface-ornamentation. Partly for this 
 reason, and partly because the number of known fossil Ostra- 
 coda is very large, it will not be advisable here to do more than 
 give an outline of the general distribution of the order in time. 
 
 The Ostracode Crustaceans appear to have been amongst 
 the earliest representatives of their class, abounding as they do 
 in many Lower Silurian deposits. Amongst the more import- 
 ant genera which are represented in the Silurian Rocks may 
 be mentioned Primitia (fig. 100, a}, Leperditia, Beyrichia, Ento- 
 mis, Cypridina, Cytherella, Cythere, and Bairdia. Of these the 
 genus Primitia is exclusively confined to the Silurian rocks, 
 whilst the great genus Leperditia arrived here at its greatest 
 development. On the other hand, the genera Cytherclla,
 
 CRUSTACEA. 
 
 157 
 
 Cythere, and Bairdia are represented by species now living. 
 Presumably all these genera were marine, and we know that 
 this was the case with many of them. The Devonian rocks 
 are comparatively poor in Ostracoda, all the known forms 
 (leaving Estheria out of consideration) belonging to the genera 
 Entomis, Leperditia, and Beyrichia. In the Carboniferous 
 
 Fig. 100. Fossil Ostracode Crustaceans : a Primitia strangulata, Lower Silurian ; 
 b Primitia Logani, Lower Silurian ; c Beyrichia Kloedeni, Upper Silurian ; d d 1 
 Cytherella iiiflata, Carboniferous; e Leperditia Anna, Lower Silurian ; f Leperditia. 
 Canadensis, Lower Silurian ; g Beyrichia impendens, Upper Silurian ; h Beyrichia 
 subarcuata, Carboniferous ; i Candona Tateana, Carboniferous. All enlarged. 
 
 Rocks no less than fifteen genera have been detected. Of 
 these the genera Leperditia, Bairdia, Beyrichia, Cythere, Cypri- 
 dina, Cypridella, and Entomis are the most important. The 
 Leperditia. were formerly referred to the genus Cypris, the 
 species of which are exclusively fresh-water in their habits. It 
 is noticeable, however, that some of the Carboniferous species 
 have been referred, apparently on good grounds, to the recent 
 genus Candona, all the forms of which inhabit fresh water. It 
 is also noticeable that the genera Beyrichia and Entomis 
 appear to die out in the Carboniferous Rocks, and have not 
 been detected in any later formations. In the Permian Rocks 
 we have only the genera Bairdia, Cythere, and Cypridina, of 
 which the two former are represented by living forms. In the 
 Secondary and Tertiary deposits, remains of Ostracode Crust- 
 aceans are abundant, often occurring in myriads in certain 
 strata, to which they sometimes impart a fissile character. The 
 chief genera which are represented in Mesozoic and Kainozoic 
 time, are Cypris, Candona, Bairdia, Cythere, Cytherella, and 
 Cypridina, all of which are represented by living species at the 
 present day.* 
 
 * The facts here summarised are mainly drawn from the Memoirs of 
 Professor Rupert Jones, and his admirable Monographs on the Ostracoda, 
 published by the Palseontographical Society.
 
 I $8 ANNULOSA. 
 
 ESTHERIA. Before going on to the order Phyllopoda, we 
 may briefly notice here the little fossils belonging to the genus 
 Estheria, as these are in some respects closely allied to the 
 Ostracoda, or are intermediate between these and the true 
 Phyllopods. Upon the whole, however, Estheria would seem 
 to be most nearly allied to the living Limnadia, in which case 
 it would be rightly referred to the Phyllopoda. The body in 
 Estheria is enclosed in a bivalve carapace (fig. 101, A), and 
 
 Fig. 101. A, carapace of Estheria ovata, magnified six diameters, Trias ; B, cara- 
 pace of Leaia Leidyi, magnified five diameters, Lower Carboniferous (after Rupert 
 Jones). 
 
 the feet are foliaceous. The valves of the carapace have a 
 well-marked beak or " umbo," and are hinged to one another 
 along a dorsal line. From these circumstances, and from their 
 being marked with numerous concentric lines of growth, the 
 carapace valves of Estheria very closely resemble the shells of 
 certain Bivalve Molluscs, for which they have often been mis- 
 taken. The valves are usually sub-triangulfr, ovate, or sub- 
 quadrate in form, and they possess a horny texture. 
 
 The living Estherice are, without exception, inhabitants of 
 fresh or, rarely, brackish water j and no one of the recent 
 twenty-four species has been detected in the sea. This would 
 afford a strong presumption that the deposits in which fossil 
 Estheria occur were deposited in fresh or brackish water ; but 
 they not uncommonly occur in conjunction with undoubted 
 marine remains. They appear, on the whole, to occur most 
 frequently in those accumulations that " have been decidedly 
 the result of brackish-water inundations, and of more perman- 
 ent lagoons " (Jones). Fossil Estheria occur in the Devonian, 
 Carboniferous, Permian, Triassic, Jurassic, Cretaceous, and 
 some Tertiary deposits; but they appear to have attained 
 their maximum development towards the close of the Triassic 
 period. 
 
 The genus Leaia (fig. 101) is very nearly allied to Estheria,
 
 CRUSTACEA. 159 
 
 and comprises small Bivalved Crustaceans, with " dark, horny, 
 sub-quadrate valves, obliquely ridged from umbo to angles, 
 and ornamented with distinct lines of growth parallel with the 
 border" (Jones). Leaia is a very widely distributed genus, 
 but all the known species belong to either the Carboniferous 
 or Permian Rocks. 
 
 ORDER PHYLLOPODA. 
 
 Crustacea, mostly of small size, the carapace protecting the head 
 and thorax, or the body entirely naked. Feet numerous, never less 
 than eight pairs, mostly foliaceous or leaf like, branchial in function. 
 
 Most of the living Phyllopods are inhabitants of fresh waters, 
 but some live in the sea (Nebalia), and others affect waters 
 which are abnormally salt (Artemid). The two most interest- 
 ing recent forms, as bearing on fossil examples of the order, 
 are Limnadia and Apus, both of which live in fresh water. In 
 Limnadia the body is enclosed in an oval bivalve carapace, 
 and there are from eighteen to thirty pairs of membranous 
 leaf-like feet. In Apus the carapace is clypeiform, and protects 
 a considerable portion of the abdomen ; and there are sixty 
 pairs of feet, of which all but the first pair are foliaceous. 
 
 Leaving out of sight the genera Estheria and Leaia, the 
 Phyllopods are almost exclusively palaeozoic in their distribu- 
 tion, and are chiefly, though not exclusively, known by their 
 carapace- valves. The best known genera are the Hymenocaris 
 of the Lingula flags, the Caryocaris of the Skiddaw slates, the 
 Peltocaris and Discinocaris of the Lower Silurian, the Ceratio- 
 caris of the Upper Silurian, and the Dithyrocaris of the Car- 
 boniferous Limestone. These forms have a general resem- 
 blance to one another, and are believed to be most nearly allied 
 to the recent Apus, whilst they are exclusively palseozoic. The 
 genus Aspidocaris, however, is allied to the preceding, and is 
 found in the Triassic period. 
 
 In Hymmocaris (fig. 102, b} the carapace is comparatively 
 large, sub-triangular, apparently not bivalved ; there are nine 
 free abdominal segments, and the last carries three pairs of 
 unequal lanceolate appendages. In Caryocaris ^Q. carapace is 
 bivalved, pod-shaped, and truncated behind, and the last ab- 
 dominal segment carries three spines. In Peltocaris and Dis- 
 cinocaris (fig. 102, c.} the carapace is rounded, with concentric 
 lines of growth, a dorsal furrow being present in the former, 
 but wanting in the latter. In both there is commonly a wedge- 
 shaped indentation in front, caused by the separation from the 
 carapace of the anterior portion of the head. In Ceratiocaris,
 
 i6o 
 
 ANNULOSA. 
 
 again, the carapace appears to be bent, but not divided or 
 hinged, along the dorsal line, and its shape is pod-like (fig. 
 102, a), with an abrupt posterior truncation. The surface of 
 the carapace is marked with " fine, obliquely longitudinal, im- 
 bricated striae " (M'Coy). 
 
 Fig. 102. Palaeozoic Phyllopods : a Ceratiocaris papill*. Upper Silurian (Salter). 
 b Hynttnocaris vertnicauda. Upper Cambrian (Salter). c i*)iscinocarif Brmimiana, 
 Lower Silurian (Original), d Peltocaris aptychoides, Lower Silurian (Woodward). 
 
 ORDER TRILOBITA. 
 
 Crustaceans in which the body is usually more or less distinctly 
 trilobed ; there is a cephalic shield, usually bearing a pair of sessile 
 compound eyes ; the thoracic somites are movable upon one another, 
 and are very variable in number ; the abdominal segments are 
 coalescent, attd form a caudal shield; there is a well-developed 
 tipper lip or " hypostome." 
 
 As regards the general structure of the Trilobites, the body 
 was protected by a well-developed chitinous shell or " crust," 
 which covered the whole dorsal surface of the body, and on 
 which no appendages have ever been discovered except the 
 eyes. The under surface of the body must, in many genera at
 
 CRUSTACEA. l6l 
 
 any rate, have been flexible and membranous; since many 
 species have the power of rolling themselves up into a ball like 
 the recent wood-lice (Oniscus). Other Trilobites, however, 
 never seem to have possessed any power of rolling up. The 
 dorsal crust usually exhibits more or less markedly a division 
 into three longitudinal lobes (fig. 103), from which the name 
 
 Fig. 103. Morphology of Trilobites. i. Angelina Sedgwickii, Upper Cambrian. 
 2. Diagram of a Trilobite fafter Salter) : a Glabella with its furrows: bb Free cheeks, 
 bearing the eyes (po) ; c c Fixed cheek, including the eye-lobe (d); ee Facial suture. 
 
 of the order is derived. In some cases, however, as in the 
 genera Homalonotus and Illanus, this trilobation is only ob- 
 scurely marked. The crust exhibits a well-marked division 
 into three regions, which are commonly found detached and 
 separate from one another. These three regions are i, a 
 cephalic shield; 2, a variable number of movable "body-rings" 
 or thoracic segments ; and 3, a caudal shield or "pygidium." 
 
 The cephalic shield or buckler (figs. 103 107) is generally 
 more or less semicircular in shape, and is composed of a central 
 and two lateral pieces, of which the two latter may or may not 
 be united in front of the former. The central portion of the 
 cephalic shield is usually elevated above the remainder. It is 
 termed the " glabella," and it protected the region of the 
 stomach. The form of the glabella varies a good deal. 
 Usually it is widest in front (fig. 105), but its width may be 
 nearly uniform (fig. 106), or it may be widest posteriorly, and 
 contracted in front, as in Calymene (fig. 107). The glabella 
 is bounded at the sides by two grooves, which are known as 
 the " axal furrows," and is marked off behind by a third 
 groove, which is termed the " neck-furrow." The surface of 
 the glabella may be quite smooth, but it is ordinarily divided 
 into lobes by grooves, which originate in the axal furrows, and 
 pass inwards towards the middle line (fig. 103, 2). These 
 L
 
 162 
 
 ANNULOSA. 
 
 furrows mark the position of the segments which compose the 
 glabella, and they are sometimes continuous from side to side. 
 Usually there are three pairs of 
 these furrows, a lower or basal, 
 a middle or ocular, and an upper 
 or frontal furrow ; but there may 
 be an additional pair of furrows 
 in front of these. In some cases, 
 as in Illanus (fig. 109), the gla- 
 bella is very indistinctly marked 
 off from the rest of the shield. 
 
 At each side of the glabella, 
 and continuous with it, is a small 
 semicircular area, which is 
 termed the " fixed cheek " (fig. 
 103, 2). The glabella, with the 
 " fixed cheeks," is separated 
 from the lateral portions of the 
 cephalic shield, termed the 
 "movable" or "free cheeks," 
 by a peculiar suture or line of 
 division, which is known as the 
 " facial suture" (fig. 103, 2, e t). 
 No such peculiar line of division 
 is known to exist in any recent 
 Crustacean ; but there is a faint 
 indication of it in Limn/us, and 
 some doubtful traces of it in certain other forms. The course 
 taken by the facial sutures differs in different cases, and 
 causes an important difference in the structure of the cephalic 
 shield. In some cases, the facial sutures, starting from the 
 posterior margins of the buckler, skirt the fixed cheeks, and 
 join one another in front of the glabella. In these cases 
 it is obvious that the free cheeks form a single piece, so that 
 the entire shield consists of but two portions i, the glabella 
 and fixed cheeks ; and 2, the amalgamated free cheeks. In 
 other cases, the facial sutures, instead of joining in front of the 
 glabella, are continued fonvard, till they cut the anterior mar- 
 gin of the shield separately. In these cases the free cheeks 
 are discontinuous, and the cephalic shield consists of three 
 portions. In a few genera (as in Trinuc/cus, Microdiscus, and 
 Agnostus), the facial suture is absent. 
 
 The posterior angles of the free cheeks are very commonly 
 prolonged into longer or shorter spines, and they bear the 
 eyes. The eyes are compound, and consist of an aggregation 
 
 Fig. io4-PAacofs (Dalmanites) 
 limulurus, Upper Silurian.
 
 CRUSTACEA. 163 
 
 of facets, covered by a thin cornea. They are generally cres- 
 centic or reniform in shape, and are invariably sessile, in the 
 sense that they are never supported upon movable stalks. In 
 some cases, however, they are carried upon longer or shorter 
 prominences. The eyes differ much in size, and they are 
 wanting in a few forms, such as the little Agnosti. 
 
 Fig. 105. Bronteus lunatus. Fig. 106. Cheirurus pleur- Fig. 107. Calymene 
 exanthemus. Blumenbachii. 
 
 Behind the cephalic shield comes the thorax, composed of 
 a variable number of segments which are not soldered to- 
 gether, but are capable of more or less movement upon each 
 other. The amount of movement thus allowed varies, but in 
 several genera (e.g., Calymene and Illcemis} it was sufficiently 
 great to allow of the animal completely rolling itself up after 
 the manner of a hedgehog. The number of body-rings or 
 segments in the thorax varies from no more than two (Agnos- 
 tits), to as many as twenty-six (Harpes ungula). Ordinarily the 
 thorax (fig. 108) is strongly trilobed, and each body-ring ex- 
 hibits the same trilobation, being composed of a central, more 
 or less convex portion, called the " axis," and of two flatter 
 side-lobes, termed the " pleurae." The pleurae are in one piece 
 with the axis, but are separated from it by a more or less pro- 
 nounced groove, the "axal furrow." Each pleura is grooved 
 longitudinally by a deep sulcus, and in many genera the ends 
 of the pleurae are furnished with facets, which have smooth 
 surfaces, and slide under the preceding pleura, in the act of 
 rolling up. In some genera, as in Illcznus (fig. 109), the axis 
 is very broad, the axal furrows are not marked, and the trilo-
 
 164 ANNULOSA. 
 
 bation of the thorax becomes very indistinct. This is likewise 
 the case, but to a less extent, in the genus Homalonotus. 
 
 Fig. 108. Asaphiis Canadensis (Chap- 
 man), Lower Silurian. 
 
 Fig. loa.Illefiius Barr- 
 iensis (Murchison), Lower 
 Silurian. 
 
 The caudal shield or " pygidium " commonly called the 
 tail " is composed of a greater or less number of segments 
 anchylosed or amalgamated. Commonly, the pygidium is tri- 
 
 Fig. i to. C-labella and pygidium of Diktloccpluilus inagnificus, Quebec Group 
 (Upper Cambrian). After Billings. 
 
 lobed (fig. no), like the thorax, and consists of a central 
 elevated " axis '' and of a marginal " limb." The limb is
 
 CRUSTACEA. 165 
 
 separated from the axis by axal furrows, and usually exhibits on 
 its surface the lines which indicate the component pleurae, as 
 well as the longitudinal furrows on the faces of these. The ex- 
 tremity of the pygidium is sometimes simply rounded ; but it 
 may be prolonged into a shorter or longer spine or "mucro," 
 and the ends of the pleurae may also be extended into spine- 
 like projections (fig. no). 
 
 Until recently, the only structure which had been discovered 
 on the under surface of any Trilobite was a broad plate situated 
 in front of the mouth, and doubtless corresponding with the 
 upper lip " labrum " or " hypostome " of living Crustaceans 
 (fig. in). The form of this hypostome very closely resembles 
 that of the lip-plate of the recent 
 Apus, one of the Phyllopods. Quite 
 recently, Mr Henry Woodward has 
 described a specimen of Asaphus 
 platycephalus, in which, in addition to 
 the lip-plate, there is a jointed fila- 
 ment (fig. 1 1 1,/), apparently springing 
 from a maxilla, and being the re- 
 mains of a maxillary "palpus." Mr 
 Woodward, who is one of the highest 
 
 ... i i ^ Fl & i. Buccal organs of 
 
 living authorities upon the Crustacea, Asaphus piatycepkaius. After 
 concludes that there is no reason to 
 doubt that Trilobites possessed an- 
 tennae and antennules, mandibles, and maxillae, and foot-jaws ; 
 though, with the exception of the above, no traces of these 
 organs have ever been detected. 
 
 Also recently, a specimen of the large Trjlobite, Asaphus 
 platycephalus (fig. 112), has been described by Mr Billings as 
 possessing organs which this distinguished palaeontologist re- 
 gards as being the remains of legs. The structures in question 
 are in the form of eight pairs of apparently jointed appendages, 
 which correspond with the eight segments of the thorax, arising 
 near the middle line, and curving forwards. Mr Henry Wood- 
 ward corroborates the view propounded by Mr Billings, that 
 these structures are of the nature of ambulatory legs. Pro- 
 fessors Dana and Verrill, on the other hand, regard these re- 
 mains as being "the semi-calcified arches in the membrane 
 of the ventral surface, to which the foliaceous appendages or 
 legs were attached." 
 
 Whichever view be adopted as to the nature of this specimen, 
 it seems tolerably certain that most Trilobites cannot have 
 possessed limbs which were furnished with a chitinous exo- 
 skeleton, and were thus capable of being preserved in a fossil
 
 166 
 
 ANNULOSA. 
 
 condition. The great abundance of Trilobites as fossils, and 
 their excellent preservation, as a general rule, render it pro- 
 bable that the limbs of most were of a soft and fleshy nature. 
 
 At the same time it is 
 very possible that some 
 forms were possessed of 
 chitinous jointed limbs, 
 as great variations exist 
 in the character of the 
 appendages even within 
 the limits of a single 
 order. The general view 
 which has up to the time 
 of this discovery been 
 held is, that the body of 
 the Trilobite occupied 
 the median lobe of the 
 crust, commencing with 
 the glabella in front, and 
 terminating with the py- 
 gidium behind, whilst the 
 axial lobes protected a 
 series of delicate, mem- 
 branous respiratory feet. 
 It is supposed, however, 
 by Mr Woodward, that 
 the branchiae were borne 
 on the under surface of 
 the caudal shield. 
 As regards the systematic position of the Trilobites, they 
 have very generally been placed in the neighbourhood of the 
 PhyUopoda, or of the much higher order of the Isopoda, They 
 have been placed near the Phyllopods chiefly from the posses- 
 sion of numerous (not definite) body-rings, from the resem- 
 blance of their hypostome to the lip-plate of the Phyllopodous 
 genus Apus, and from their supposed possession of membran- 
 ous gill-feet. The recent discoveries, however, of Messrs 
 Billings and Woodward would lead to the belief that the Tri- 
 lobites, if not actually belonging to the Isopoda, have at any 
 rate closer affinities with this order than with any other. They 
 agree with the Isopods in the possession of sessile compound 
 eyes, in having the abdominal somites coalescent, and in some- 
 times possessing the power of rolling themselves up into a 
 ball. They differ, however, from the Isopods in the very im- 
 portant character that the thoracic segments of the latter are 
 
 Fig. \\*.Asaphusplatycetlialus, Lower Silurian.
 
 CRUSTACEA. l6/ 
 
 always definite and are almost invariably seven in number. In 
 the meanwhile, therefore, it is safest to regard the Trilobita as 
 a peculiar order, the exact position of which in the Crustacean 
 class is still undetermined. 
 
 The general facts as to the distribution of the Trilobita in 
 past time are soon told. The Trilobites are exclusively Palaeo- 
 zoic, their range extending from the Upper Cambrian to the 
 Lower Carboniferous. If the Palceopyge Ramsayi of the Long- 
 mynd beds be a Trilobite, then the order has its commence- 
 ment in the Lower Cambrian. In the Upper Cambrian Rocks, 
 and especially in the strata which constitute the " Menevian 
 Group " of Salter, and the " Primordial Zone " of Barrande, is 
 a peculiar group of forms commonly spoken of as the " Prim- 
 ordial Trilobites." These belong mostly to the two families 
 Agnostida and Olenidtz, and to the genera Agnostus, Para- 
 doxides, Olenus, Dikdocephalns, Conocoryphe, Angelina, Ellipso- 
 cephalus, &c. 
 
 Many of these forms are distinguished by degraded char- 
 acters, such as the absence of eyes, the want of the facial 
 suture, the segmentation of the glabella, or the multiplication 
 or diminution of the number of body-rings. It should not be 
 omitted to be noticed that the singular tracks which have been 
 described from the Potsdam Sandstone (Upper Cambrian) of 
 Canada, under the names of Protichnites and Climactichnites, 
 are believed with good reason to be the tracks of Trilobites. 
 In the Lower and Upper Silurian Rocks the Trilobites attain 
 their maximum of development, the leading families being the 
 Asaphida, Phacopidce, Trinudeida, Cheiruridtz, and Calymenidce, 
 and the chief genera being Asaphus, Ogygia, Phacops, Trinu- 
 cleus, Ampyx, Cheirurus, Encrinurus, Calymene, and Homalo- 
 notus. In the Devonian Rocks, again, Trilobites are tolerably 
 abundant, though less so than in the preceding series. The 
 commonest Devonian genera are Phacops, Homalonotus, and 
 Brontcus. Lastly, the order seems to die out before the close 
 of the Carboniferous period, being represented in the Carbon- 
 iferous Limestone solely by the three genera, Phillipsia, 
 Brachymetopus, and Griffithides. 
 
 The following gives the leading characters of the more im- 
 portant families of Trilobites, with a few of the chief genera in 
 each family, and the range of the group in time : 
 
 i. AGNOSTID^E. Characterised by their small size, the head 
 and tail being covered by nearly equal and similar shields, and 
 the reduction of the body-rings to two in number (fig. 113). 
 There are no eyes, and the facial suture is wanting. The 
 family includes only one well-marked genus, viz. Agnostus,
 
 1 68 
 
 ANNULOSA. 
 
 which ranges from the Upper Cambrian to near the summit 
 of the Lower Silurian Rocks. 
 
 2. OLENIDJE OR PARADOXIDJE. Character- 
 ised by having long bodies, with numerous 
 free thoracic segments (from eight to twenty- 
 three in number). The caudal shield is small, 
 and generally consists of very few segments. 
 The pleurae are mostly prolonged into longer 
 or shorter spines, which are directed back- 
 wards. The family includes some of the 
 largest of the Trilobites, and is mainly char- 
 
 . F .- ^-AgnostHf acteristic of the " Primordial Zone " (Upper 
 Cambrian). It occurs, however, in the lower 
 
 Fig. i-n.-Par*do.Ti<les Micmat (?), Upper Cambrian. After Dawson. 
 
 Silurian, but appears to die out in the Caradoc period. The
 
 CRUSTACEA. 169 
 
 chief genera are Olenus, Paradoxides, Dikdocephalus, Cono- 
 coryphe, Sao, Angelina, and Ellipsocephalus. 
 
 3. AsAPHiDiE. Large Trilobites, generally oval, and never 
 furnished with spines or tubercles on their surface. The eyes 
 smooth, and the facial sutures terminating on the posterior 
 margin. The cephalic and caudal shields generally of large 
 size, the glabella of the former often obscure, and the latter 
 sometimes exhibiting no indication of its component segments. 
 The body-rings usually eight in number, sometimes more, rarely 
 fewer (six in sEglina). 
 
 The family Asaphida is characteristically Lower Silurian 
 in its distribution, commencing by a few forms in the Upper 
 Cambrian, and being hardly at all represented in Upper Silu- 
 rian strata. The most important genera are Asaphus, Ogygia, 
 Illtznus, sEglina, Barrandia, and Psilocephalus. 
 
 4. TRINUCLEIDJE. Cephalic shield large, the posterior angles 
 of the cheeks prolonged into long spines. Body-rings six 
 (sometimes five ?) in number. Facial suture sometimes absent 
 
 Fig. 115. Trinucleus P anger ardi, Lower Silurian. 
 
 (Trinudeus) -, eyes sometimes wanting (Ampyx). The Trinu- 
 deidce are exclusively Lower Silurian, though there are traces 
 of their existence in the higher portion of the Upper Cambrian. 
 The only genera referred to this family are Trinuckus, Ampyx, 
 and Dionide. 
 
 5. CHEIRURIDJE. Cephalic shield with the facial sutures 
 terminating on its exterior margins. Body-rings eleven. 
 Pleurae with free extremities. Caudal shield of few segments, 
 the ends of these being free. The family extends from the 
 Upper Cambrian to the Devonian, but it attains its greatest
 
 ANNULOSA. 
 
 development in the Silurian period. The chief genera are 
 CJuirurus, Amphion, Sphcerexochus, Staiirocephalus, Dciphon, 
 Encrinurus, and Cybele. 
 
 6. CALYMENID^;. Crust granulated, often tuberculated. 
 Body-rings thirteen in number. 
 Facial sutures ending at the 
 posterior angles of the cephalic 
 shield. Body sometimes very 
 indistinctly trilobed (ffotnalotw- 
 tus). The family appears to 
 commence at the base of the 
 Lower Silurian series or at the 
 summit of the Upper Cam- 
 brian, and ranges into the De- 
 vonian. The only genera are 
 Calymene and Homalonotus, 
 of which the former is mark- 
 edly trilobed, but the latter 
 very indistinctly so (fig. 116). 
 The best -known species are 
 Calymene Blumenbachii, which 
 ranges from the Caradoc (Lower 
 Silurian) to the Ludlow Rocks 
 (Upper Silurian), and Homa- 
 lonotus delphinocepJialus, which 
 is a well-known Upper Silurian 
 Trilobite. 
 
 7. PHACOPID^E. "Eyes 
 largely faceted, the cornea con- 
 vex over each facet, forming a 
 granulated, not a smooth eye. 
 Facial suture ending posteri- 
 orly on the outer margin of 
 the cheek. Thorax with eleven 
 rings " (Salter). This family includes the single genus, Phacops, 
 divided into the sub-genera Trimerocephaltis^ Phacops, Acaste, 
 Chasmops, Dalmania, and Cryphceus. The family Phacopida 
 ranges from the base of the Lower Silurian series (perhaps from 
 the Upper Cambrian) to the summit of the Devonian series. 
 Amongst the Upper Silurian species may be mentioned 
 Phacops caudatus and P. Downingia, as well-known fossils ; 
 whilst P. latifrons is a familiar and widely-distributed Devonian 
 species. 
 
 8. LICHAD/E. Cephalic shield small, the facial sutures 
 cutting its outer margins. Glabella large, deeply furrowed. 
 
 1 16. Hontalonotiis delphinoce~ 
 phalus. Upper Silurian.
 
 CRUSTACEA. 17 1 
 
 Body-rings eleven in number. Pygidium with an undefined 
 axis and broad limb. The family includes the single genus 
 Lichas, and extends from the Lower Silurian into the De- 
 vonian. 
 
 9. PROETID^E. Cephalic shield with the facial sutures not 
 uniting in front of the glabella. Body-rings nine or ten in 
 number. Axis elongated. This family ranges from the Lower 
 Silurian to the Carboniferous. Besides Proetus, this family in- 
 cludes Phillipsia and Griffithides. 
 
 10. ACIDASPIM;. Surface ornamented. Body-rings from 
 eight to ten in number. The ends of the pleurae extended into 
 spines, and directed backwards. Pygidium of from two to 
 three segments, small, furnished with prominent spines. The 
 genus Acidaspis ranges from the Lower Silurian into the De- 
 vonian. 
 
 11. BRONTEIM:. Body-rings ten in number. Pygidium 
 large, the axis extremely short, the margin entire. The family 
 includes only the genus Bronteus (fig. 105), and is confined to 
 the Upper Silurian and Devonian Rocks. 
 
 12. HARPEDID.E. Cephalic shield horse-shoe-shaped, its 
 lateral angles greatly prolonged. Facial suture cutting the 
 exterior margin of the buckler. Body-rings numerous, some- 
 times no less than twenty-six in number. Pygidium small. 
 This family comprises only the genus Harpes, all the species 
 of which belong to the Lower Silurian, Upper Silurian, and 
 Devonian. 
 
 13. CYPHASPID^E. Cephalic shield with the posterior angles 
 usually prolonged into spines, the facial suture cutting its ex- 
 terior margins. Body-rings from ten to twenty-two. Crust 
 spinulose or pitted. The chief genera of this family are 
 Cyphaspis and Aulacopkura (Arethusina], the former ranging 
 from the Lower Silurian to the Devonian, the latter exclusively 
 confined to the Silurian series. 
 
 ORDER MEROSTOMATA. 
 
 Crustaceans, often of large size, in which the mouth is furnished 
 with mandibles and maxillce, the terminations of which become 
 walking or swimming feet, or organs of prehension (figs. 117, 
 1 1 8). 
 
 The order Merostomata comprises the two sub-orders of the 
 Xiphosura and Eurypterida. The former appears to have 
 commenced its existence in the Upper Silurian period, and is 
 represented at the present day by the Limuli or King-crabs. 
 The latter is wholly extinct, and is exclusively Palseozoic, none
 
 172 
 
 ANNULOSA. 
 
 of its members being known out of the Silurian, Devonian, and 
 Carboniferous formations. 
 
 Fig. 117. Xiphosura. Limuluspoly- 
 fhcmns, viewed from below, c The 
 cephalic shield carrying the sessile eyes 
 upon its upper surface ; o " Operculum," 
 covering the reproductive organs ; b 
 Branchial plates , a First pair of anten- 
 nae (antennules) ending in chela. Below 
 these is the aperture of the mouth sur- 
 rounded by the spiny bases of the re- 
 maining five pairs of appendages, which 
 are regarded by Woodward as being 
 respectively, from before backwards, the 
 great antennae, the mandibles, the first 
 maxilla:, the second maxillae, and a pair 
 of maxillipedes. All have their extremi- 
 ties chelate. 
 
 Fig. 118. Eurypterida. Pttry- 
 Fotiis A it Aliens, restored (after H. 
 Woodward), c c Chelate antenna : 
 o o Eyes, situated at the anterior mar- 
 gin of the carapace ; nt m The mandi- 
 bles, and the first and second maxilla: ; 
 M n The maxillipedes ; the basal mar- 
 gins of these are serrated, and are 
 drawn as if seen through the metas- 
 toma or post-oral plate, which serves 
 as a lower lip. Immediately behind 
 this is seen the operculum or thoracic 
 plate, which covers the two anterior 
 thoracic somites. Behind this are five 
 thoracic and five abdominal somites, 
 and lastly, there is the tclsou (t). 
 
 SUB-ORDER I. EURYPTERIDA. 
 
 " Crustacea with numerous, free, thoracico-abdominal segments, 
 the first and second (?) of which bear one or more broad lamellar 
 appendages upon their ventral surface, the remaining segments 
 being devoid of appendages ; anterior rings united into a carapace, 
 bearing a pair of larval eyes (ocelli) near the centre, and a pair of 
 large, marginal, or sub-central eyes ; the mouth furnished with a 
 broad post-oral plate, or mctastoma, and five pairs of movable
 
 CRUSTACEA. 173 
 
 appendages, the posterior of which form great swimming-feet ; the 
 telson, or terminal segment, extremely "variable inform; the in- 
 tegument characteristically sculptured" (Henry Woodward.) 
 
 In the typical Eurypterids, such as Pterygotus (fig. 118) and 
 Eurypterus, the anterior portion of the body is covered by a 
 buckler or carapace, which bears a pair of minute larval eyes, 
 and a pair of large compound eyes placed marginally or sub- 
 centrally. On the under surface of the carapace are five pairs 
 of appendages. The first pair of these is usually regarded as 
 representing the antennae. The appendages of this pair are 
 mostly chelate, or converted into nipping-claws, but they are 
 sometimes simple, and they sometimes are spinous towards 
 their bases, and officiate as masticatory organs (Eurypterus 
 and Slimonid). The next three pairs of appendages are simply 
 pointed spinous organs (" pedipalps "), but the last pair is 
 sometimes converted into rowing-organs (Stylonurus}. The 
 last pair of appendages constitute two greatly-developed 
 swimming-feet, the bases of which are furnished with spines, 
 and form powerful jaws. The bases of these jaw-feet are covered 
 by a greatly-developed post-oral plate or " metastoma." Be- 
 hind the head come thirteen free segments, counting the telson 
 as one. The first two of these, immediately behind the cara- 
 pace, are covered below by a thoracic plate or " operculum," 
 which doubtless protected the reproductive organs. The 
 other somites carry no appendages, though it is probable that 
 some of them bore membranous branchiae. The " telson " or 
 terminal segment of the abdomen (fig. 118, t\ is sometimes 
 lanceolate or bilobate, as in Pterygotus and Slimoiiia, or some- 
 times narrow and sword-shaped, as in Eurypterus and Stylon- 
 urus. The surface of the crust is sculptured over the greater 
 part of its extent, with characteristic markings, which look 
 something like the scales of an ordinary Bony fish. These 
 " scale-marks," however, are often wanting over parts of the 
 surface. 
 
 The Eurypterids range from the Upper Silurian, where they 
 attain their maximum, through the Devonian, into the Car- 
 boniferous Rocks, where they appear to die out. Traces, how- 
 ever, of these large Crustaceans are by no means wanting in 
 the Lower Silurian, though as yet undescribed. Of the typical 
 genera, Pterygotus extends from the Upper Silurian to the 
 Upper' Devonian, and species of this genus seem to have 
 attained a gigantic size. (Pterygotus Anglicus is calculated to 
 have reached a length of six feet.) Slimonia is Upper Silurian, 
 and Stylonurus is both Upper Silurian and Devonian. Euryp- 
 terus is not known in the Silurian, but is represented by many
 
 1/4 ANNULOSA. 
 
 species in the Devonian, and extends into the Carboniferous 
 Rocks. Hemiaspis, with only nine segments and the telson 
 behind the carapace, is exclusively Upper Silurian. Lastly, 
 Pseudoniscus, with the same number of free segments, is found 
 in the passage-beds between the Upper Silurian and Devonian. 
 In conclusion, it is interesting to note that these ancient 
 Crustaceans present many larval features, resembling the larva? 
 of the Decapoda, especially in the fact that the hinder portion 
 of the body is composed of free segments, which carry no 
 appendages.* 
 
 SUB-ORDER II. XIPHOSURA (Pcedlopoda). 
 
 " Crustacea having the anterior segments welded together to 
 form a broad convex buckler, upon the dorsal surface of which are 
 placed the compound eyes and ocelli ; the former sub-centrally, the 
 latter in the centre in front. The mouth is furnished with a small 
 labrum, a rudimentary metastoma, and six pairs of appendages. 
 Posterior segments of the body more or less free, and bearing upon 
 their ventral surfaces a series of broad lamellar appendages ; the 
 telson, or terminal segment, ensiform." (Henry Woodward.) 
 
 The only living members of the Xiphosura are the Limuli, 
 commonly known as King-crabs or Horse-shoe Crabs. The 
 anterior portion of the body is covered by a broad horse-shoe- 
 shaped buckler (fig. 1 1 7), the upper surface of which bears a pair 
 of larval and a pair of compound eyes. On the lower surface 
 of the carapace is placed the aperture of the mouth, surrounded 
 by six pairs of limbs, the bases of which are spinous, and 
 officiate as jaws, whilst their terminations are converted into 
 chelae or nipping-claws. The first pair of appendages is placed 
 in front of the mouth, and represents the antennae, so that the 
 antennae of the King-crabs are chelate. Behind the cephalic 
 buckler comes a second shield, composed of six amalgamated 
 segments, below which are carried the reproductive organs and 
 branchiae, the former protected by a thoracic plate or " oper- 
 culum," the latter borne by five pairs of lamellar appendages. 
 Lastly, articulated to the posterior margin of the abdominal 
 shield, is a long sword-like spine or "telson" (fig. 117, t). 
 
 The Xiphosura seem to have commenced existence in the 
 Upper Silurian period, where they are represented by the 
 Neolimulus falcatus of Mr Henry Woodward. With this ex- 
 
 * The student desirous of fuller information on this subject, as on the 
 Xiphosura also, should consult the excellent memoirs by Mr Henry 
 Woodward, and especially his monograph of the Merostomata, published 
 by the Pabeontographical Society.
 
 CRUSTACEA. 
 
 175 
 
 ception, however, no Limuloid Crustaceans are known till the 
 Carboniferous Rocks are reached. Here we have the two 
 genera Prestwichia and Belinurus, the former represented by 
 two, the latter by four species. In Prestwichia (fig. 119), the 
 thoracic and abdominal segments are not separable from one 
 another, and the former 
 are anchylosed or amal- 
 gamated, as well as the 
 latter. In Jffc/zVz&ntt there 
 are five thoracic and three 
 abdominal segments (as 
 in the preceding), but the 
 thoracic somites are free 
 and movable, whilst the 
 abdominal ones are an- 
 chylosed. The only other 
 genus of the Xiphosura 
 is Limuhts itself. This 
 genus is represented by 
 forms doubtfully here re- 
 ferable as early as the 
 Permian Rocks. An- 
 other dubious form oc- 
 curs in the Trias. Seven 
 
 species have been described from the Lithographic slates of 
 Solenhofen (Middle Oolites). One doubtful form occurs in 
 the Chalk, a single Tertiary species has been described, and 
 four species are known as existing at the present day. 
 
 Fig. 119. Prestwichia (Limuhis) rotundata, 
 Coal-Measures. 
 
 CHAPTER XVI. 
 CR USTA CE A Concluded. 
 
 MALACOSTRACA. 
 
 THE Malacostracous Crustaceans are distinguished by the 
 possession of a definite number of body-segments, seven 
 somites generally going to make up the thorax, and an equal 
 number entering into the composition of the abdomen (count- 
 ing the telson as a somite). The Malacostraca are divided 
 into two primary sections, termed respectively Edriophthal-
 
 i;6 ANNULOSA. 
 
 mata and Podophthalmata, according as the eyes are sessile or 
 are supported upon eyestalks. 
 
 DIVISION A. EDRIOPHTHALMATA. The division of the 
 Sessile-eyed Crustaceans comprises those Malacostraca in 
 which the eyes are not supported upon stalks or peduncles, 
 and there is mostly no carapace. The eyes are sometimes 
 compound, sometimes simple, and are placed on the sides of 
 the head. The head is almost always distinct from the body ; 
 and there are typically seven pairs of feet in the adult. 
 (Hence the name of Tetradecapoda applied to this division by 
 Agassiz.) The Edriophthalmata, include the orders Lizmodi- 
 poda, Amphipoda, and Isopoda, of which the two latter are 
 alone known in a fossil condition, whilst the last is the only 
 one of any importance. 
 
 ORDER AMPHIPODA. 
 
 Small Crustaceans in which the respiratory organs have the 
 form of membranous vesicles attached to the bases of the thoracic 
 limbs. Abdomen well developed, and composed of seven segments. 
 Seven pairs of thoracic limbs. 
 
 The most familiar recent forms of the Amphipoda are the 
 "fresh-water Shrimps" (Gammarus), the Sand-hoppers (Tali- 
 trus), and the Shore-hoppers (Orchestid). The oldest repre- 
 sentative of the order is a doubtful form, which has been 
 described by Mr Woodward from the Upper Silurian Rocks 
 under the name of Necrogammarus. The Carboniferous genus 
 Gampsonyx has been referred here, but is more properly placed 
 amongst the Stomapoda. There are no other fossil Amphipods 
 of any importance. 
 
 ORDER ISOPODA. 
 
 Crustaceans in which the head is distinct from the segment 
 bearing tJie first pair of feet. The eyes are compound and sessile. 
 There are usually seven pairs of thoracic appendages, borne upon 
 seven movable segments. The animal sometimes /ins tJie power 
 of rolling into a ball. The abdominal segments are coalescent, 
 and form a broad caudal shield, beneath which the branchice are 
 carried. 
 
 Of the living Isopods, some (Bopyridtz) are parasitic in 
 their adult condition upon other Crustaceans. Others, such as 
 the common Wood-lice (Oniscus), live habitually upon the land. 
 Others, again, are littoral in their habits, or frequent the sea. 
 
 The oldest known Isopod is a large form which has been 
 described by Mr Henry Woodward from the Devonian Rocks
 
 CRUSTACEA. 1/7 
 
 under the name of Prcearcturus. It is believed to resemble 
 
 the living Arcturus Baffinsii. From the Carboniferous Rocks 
 
 an Isopod has been described under 
 
 the name of Acanthotelson. In the 
 
 Permian Rocks we have the genus 
 
 Prosoponiscus, which, however, has 
 
 been referred to the Amphipoda. 
 
 In the Upper Oolites (Purbeck 
 
 beds) occurs the Archceoniscus 
 
 Brodiei (fig. 120), often in large 
 
 numbers. In the Chalk occurs the 
 
 genus Palcega, which ranges to the 
 
 Miocene Tertiary. Lastly, several ^ ol j e s | u Isopod ' from *** Upper 
 
 forms, some of which are of very 
 
 uncertain affinities, have been described from the Tertiary 
 
 Rocks. 
 
 DIVISION B. PODOPHTHALMATA. The members of this 
 division are Malacostracous Crustaceans, in which the eyes 
 are compound, and are supported upon movable stalks or 
 peduncles, and the anterior portion of the body (cephalo- 
 thorax) is protected by a carapace. In this division are in- 
 cluded the two orders of the Stomapoda and Decapoda. 
 
 ORDER STOMAPODA. 
 
 Stalk-eyed Crustaceans in which there are generally from six 
 to eight pairs of legs, and the branchice are not enclosed in a cavity 
 beneath the thorax, but are either suspended beneath the abdomen, 
 or, more rarely, attached to the thoracic legs. 
 
 Of the living Stomapods the best-known forms are the 
 Locust-shrimps (Squilld), the Glass-shrimps (Erichthys\ and 
 the Opossum-shrimps (Mysis). The earliest -known example 
 of the Stomapoda is the Gampsonyx fimbriatus of the Carboni- 
 ferous Rocks ; and the Pygocephalus Couperi of the same 
 formation is also probably to be referred to this order. The 
 genus Squilla itself does not appear to be represented in rocks 
 older than the Eocene Tertiary. 
 
 ORDER DECAPODA. 
 
 Crustaceans -with five pairs of ambulatory legs, of which the 
 first pair is modified to form nipping-claws, some of the other 
 pairs behind this being often chelate as well. There is a large 
 cephalothoradc carapace, and the branchice are contained in cavi- 
 ties at the sides of the thorax.
 
 1/8 ANNULOSA. 
 
 The order Decapoda includes the highest forms of the entire 
 class of the Crustaceans, such as the Lobsters, Hermit-crabs, 
 and Crabs, and it is divided into the following three tribes : 
 
 TRIBE I. MACRURA. The members of this tribe, such as 
 the Lobsters, Shrimps, Prawns, and Cray-fish, have a long and 
 well-developed abdomen, the posterior extremity of which 
 forms a powerful natatory organ or caudal fin. This is con- 
 stituted by a greatly-expanded pair of natatory appendages 
 (" swimmerets ") borne upon the last segment but one of the 
 abdomen, between which is placed the last segment or " tel- 
 son." 
 
 The Macrurous Decapods are unquestionably of a lower 
 type than the Brachyurous Decapods or Crabs ; so that it is 
 no matter of surprise to find that the former, so far as is 
 known, have enjoyed a vastly higher antiquity than the latter. 
 The Brachyura are not known in deposits older than the 
 Oolites. The Macrura, on the other hand, were in existence 
 before the close of the Palaeozoic period. In the Carboni- 
 ferous formation we have several forms of Prawn-like Crusta- 
 ceans belonging to the genus Anthrapal&mon (or Anthracopa- 
 lamon), of which a species is figured below (fig. 121). In 
 
 Fig. M.Antkrafalamon Salteri, Carboniferous. (After Saker.) 
 
 the Permian Rocks no Macrurous Decapods are known to 
 occur. In the Trias, examples of the genera Galatea and 
 Litogaster have been detected, and other forms have been 
 alleged to occur. In the Jurassic and Cretaceous strata 
 "Long-tailed" Decapods are extremely abundant, and are 
 often beautifully preserved. Amongst the more remarkable 
 of the Jurassic genera may be mentioned Eryon (fig. 122),
 
 CRUSTACEA. 
 
 179 
 
 which commences in the Lias, but attains its maximum in the 
 Middle Oolitic strata, being especially abundant in the fine- 
 grained Lithographic Slates of Solenhofen. In this singular 
 genus, the carapace is large and broad, and nearly quadrate in 
 figure, whilst the antennas are very small. Another singular 
 genus from the Solenhofen Slates is Megachirus, in which the 
 first pair of legs is enormously elongated, but not terminated 
 by chelae. In the Cretaceous Rocks are numerous Macrourans, 
 belonging to the genera Meyeria, Enoploclytia, Hoploparia, &c. 
 In many parts of the Tertiary series, especially in the London 
 Clay (Eocene), are numerous remains of Macrura, some of 
 
 Fig. 122. Eryon 
 
 , Middle Oolites [Solenhofen Slates). 
 
 which have been referred, with more or less doubt, to such 
 living genera as Astacus and Palinurus. 
 
 TRIBE II. ANOMURA. The Anomurous Decapods are dis- 
 tinguished by the condition of the abdomen, which is neither 
 so well developed as in the Macrura, nor so rudimentary as in 
 the Brachyura. The abdomen does not take any part in 
 locomotion, and does not terminate posteriorly in a caudal 
 fin. The penultimate segment of the abdomen, however, is 
 mostly furnished with more or less well-developed appendages.
 
 i So 
 
 ANNULOSA. 
 
 The best-known living Anomura are the Hermit-crabs or Sol- 
 dier-crabs (Paguridce}, the Crab-lobsters (Ponel/ancc), and the 
 Sponge-crabs (Dromia). 
 
 The Anomura are of small importance as fossils. They 
 commence in the Secondary period, a few forms having been 
 described from the Oolites, and a greater number from the 
 Cretaceous Rocks. In the Tertiary period Anomurous Crus- 
 taceans are not uncommon ; and the genus Pagurus itself 
 appears to be represented in the Red Crag (Pliocene). The 
 Dromilites of the London Clay is supposed to be related to 
 the living Dromia. 
 
 TRIBE III. BRACHYURA. The "Short-tailed" Decapods 
 or Crabs are distinguished by having a rudimentary abdomen, 
 which is tucked up beneath the cephalothorax. The carapace 
 is usually very large, and the extremity of the abdomen is not 
 provided with any appendages. Most of the Crabs are littoral 
 in their habits, and have legs formed for walking. Others are 
 adapted for swimming, and the Land-crabs habitually live 
 inland. 
 
 As before remarked, the Brachyurous Decapods are much 
 later in their appearance than the Macrura. The oldest 
 
 known Crab, at present, is 
 the Pal&inacfms longipes, de- 
 scribed by Mr Henry Wood- 
 ward from the Forest Marble 
 (Lower Oolites). In the 
 Cretaceous series Crabs are 
 tolerably abundant, one Cre- 
 taceous form belonging to 
 the recent genus Cancer. In 
 the Tertiary Rocks, and es- 
 pecially in the London Clay 
 (Eocene), remains of Crabs 
 occur in profusion. The 
 chief Tertiary genera are 
 Xanthopsis, Xantholites, Cancer^ 123), Grapsus, and Ebalia. 
 
 Fig. 123. Cancel (Carpilius) macrockelus, 
 Tertiary.
 
 ARACHNIDA. l8l 
 
 CHAPTER XVII. 
 
 ARACHNIDA, MYRIAPODA, AND INSECT A. 
 CLASS ARACHNIDA. 
 
 THE Arachnida are Articulate animals, in which the respiratory 
 organs, when present, are in the form of pulmonary chambers or 
 sacs, or of ramified tubes (" tracheae ") formed by an involution 
 of the integument and fitted for breathing air directly; or both 
 these organs are combined. In no case are the breathing-organs in 
 the form of gills. There are four pairs of locomotive limbs, and 
 there are no limbs attached to the segments of the abdomen. There 
 is only one pair of antenna, and these are not present as antenna, 
 but are converted into Jaws or pincers. The head is amalgamated 
 with the thorax to form a cephalothorax, the eyes are sessile, and 
 the integuments are more or less chitinous. 
 
 The Arachnida are mainly distinguished from the Crustacea* 
 by the absence of gills, and the general presence of organs 
 adapted for breathing air directly. They are distinguished 
 from the Insects by the possession of four pairs of legs, by 
 never possessing wings, and by having simple eyes, whilst the 
 head is amalgamated with the thorax. From the Myriapods 
 they are distinguished by the fact that the legs of the latter are 
 
 Fig. 124. A recent Scorpion (reduced). The great nipping-claws of the Scorpion are not 
 legs, but are a development of organs belonging to the mouth. 
 
 never less than nine pairs in number, whilst the segments of 
 the thorax are distinct from one another and from the head, 
 
 * Van Beneden would refer the Trilobites, King-crabs, and Eurypterids 
 to the Arachnida, but such a radical change must be supported by over- 
 whelming evidence before it can be accepted.
 
 182 
 
 ANNULOSA. 
 
 and the segments of the abdomen carry legs. As is the case 
 with all the air-breathing Articulates, the remains of Arachnida, 
 though of considerable theoretical interest, are of very rare 
 occurrence as fossils. They will therefore be very briefly 
 noticed here. Of the groups of the Arachnida, the Mites 
 (Acarida), the Harvest-spiders (P/ta/angida),ihe Rook-scorpions 
 (PseudoscorpionidcR), the Scorpions (Pcdipalpi], and the true 
 Spiders (Araneida), have all been detected in a fossil condition. 
 The three first groups require no consideration here, being 
 almost unknown except as occurring in amber, which is a fossil 
 resin of late Tertiary age. The Scorpions and Spiders both 
 appear to have come into existence in the Carboniferous period, 
 and the forms which then existed do not appear to have been 
 strikingly different from living types. 
 
 ORDER PEDIPALPI. The typical members of this order are 
 the Scorpions (Scorpionidce), in which the abdomen is distinctly 
 
 Fig. 125. Cydophthalmus senior. A fossil Scorpion from the Coal-measures of Bohemia. 
 
 segmented, and not separated front the thorax by any marked con- 
 striction. The respiratory organs are in the form of pulmonary 
 sacs opening on the under surface of the abdomen by distinct 
 apertures or " stigmata." The jaws (maxillae) carry an enor-
 
 MYRIAPODA. 183 
 
 mously-developed pair of nipping-claws (fig. 124), and the 
 antennae are also converted into chelae. The head carries six, 
 eight, or twelve simple eyes, and the last joint of the abdomen 
 (telson), terminates in a hooked claw, perforated for the trans- 
 mission of the duct of a poison-gland. 
 
 As regards their distribution in time, the Scorpions com- 
 mence in the Carboniferous period, where they are represented 
 by the genera Eoscorpius and Cydophthalmus. The most 
 celebrated fossil Scorpion is the Cydophthalmus senior (fig. 125) 
 of the Bohemian Coal-measures. This remarkable form re- 
 sembles the living Androctonus in having twelve eyes, but 
 these are disposed in a circle, whereas in the latter there are 
 six eyes on each side of the head. 
 
 ORDER ARANEIDA. This order includes the true Spiders, 
 which are characterised by the amalgamation of the head and 
 thorax into a single mass, to which the generally soft and unseg- 
 mented abdomen is attached by a constricted portion or peduncle. 
 Respiration is effected by pulmonary sacs in combination with 
 air-tubes (tracheae). The head bears from six to eight simple 
 eyes. 
 
 The oldest-known Spiders occur in the Carboniferous Rocks. 
 In the Coal-measures of Upper Silesia, Romer has described a 
 Spider, which is allied to the living Lycosa, and which he has 
 termed Protolycosa anthracophila. Other fossil Spiders have 
 been described from the Lithographic Slates of Solenhofen 
 (Middle Oolite), and from the Tertiary Rocks, and a good 
 many species occur preserved in amber. 
 
 CLASS MYRIAPODA. 
 
 The Myriapods are Articulate animals in which the head is 
 distinct, and the remainder of the body is divided into nearly 
 similar segments. There is no marked boimdary-line betweeji the 
 thorax and abdomen, and the segments of the latter carry locomotive 
 limbs. There is one pair of jointed antennas, and the number of 
 legs is always more than eight pairs. Respiration is effected by 
 air-tubes (trachea^. 
 
 The living Myriapods are divided into the three orders 
 Chilopoda, Chilognatha, and Pauropoda. In the Chilopoda are 
 the Centipedes, characterised by their masticatory mouth, and 
 carnivorous habits, by the possession of legs in single pairs 
 (usually from fifteen to forty pairs), and by having antennae of 
 from fourteen to forty or more joints. In the Chilognatha are 
 the Millipedes and Gallyworms, characterised by their vege- 
 tarian habits, by having the segments of the body so amal-
 
 1 84 ANNULOSA. 
 
 gamated that the legs appear to be arranged in double pairs, 
 and by having antennae of six or seven joints. In the Pauro- 
 poda is the single genus Pauropus, characterised by having 
 only nine pairs of legs, and the antennas bifid, with three 
 long multi-articulate appendages. 
 
 T^Hf^ 
 
 ^^m^piii^ 
 
 Fig. 126. Millipede (//*). 
 
 The oldest-known Myriapods occur in the Coal-measures, 
 the two best-known genera being Xylobius and Archiulus. 
 These genera belong to the order Chilognatha, and comprise, 
 therefore, vegetable-feeders. In Xylobius (fig. 127) the seg- 
 
 Fig. 127. Xylobius Sigillaria, a Carboniferous Myriapod. (After Dawson.) 
 a, Natural size ; b, Anterior portion, enlarged ; c, Posterior portion, enlarged. 
 
 ments are divided by cross sutures into numerous fragments, in 
 a manner wholly unknown amongst recent forms. Several 
 species of this genus are known, of which the one figured 
 above derives its specific name from the fact that it is found 
 in the hollow trunks of Sigillaria, It must have possessed, 
 like the living Gallyworms, the power of rolling itself up into 
 a ball (Dawson). In the allied genus Archiulus, the segments 
 are not broken up into fragments, as they are in Xylobius. 
 The characters of both these genera are so peculiar that they 
 have been placed in a separate family under the name of 
 Archiulidce. Other Myriapods have been discovered in the 
 Carboniferous Rocks of North America and Britain, and have 
 been referred to the genus Euphobcria. The true place of
 
 INSECT A. 185 
 
 these is uncertain, and they seem to have possessed the 
 anomalous character of a row of dorsal spines. In the Litho- 
 graphic Slates of Solenhofen (Middle Oolites) occur the 
 remains of an animal which is referred to the Myriapoda by 
 Count Miinster, under the name of Geophilus proavus. Other 
 Myriapods have been described from Tertiary strata and from 
 amber. 
 
 CLASS INSECTA. 
 
 The Insects are Articulate Animals, in which the head, thorax, 
 and abdomen are distinct from one another. The thorax consists 
 of three segments, each of which carries a pair of legs. Mostly 
 there are two pairs of wings borne by the two hinder segments of 
 the thorax. The abdomen never carries locomotive limbs, but the 
 last abdominal segments may carry reproductive or sensory appen- 
 dages. A single pair of jointed antenna is present, and the eyes are 
 generally compound. Respiration is effected by air-tubes (trachetR). 
 
 As regards the general distribution of the Insecta in time, 
 the oldest-known forms are from the Devonian Rocks of North 
 America. Here occur the remains of several insects which 
 belong to the order of the Neuropterous Insects (or to the 
 Pseudo-neuroptera). Amongst the most remarkable of these is 
 the Platephemera antiqua of Mr Scudder (fig. 128). This 
 species must have attained a 
 large size five inches in ex- 
 panse of wing and it is re- 
 garded by Mr Scudder as 
 being referable to the Ephe- 
 merida (the May-flies). This 
 eminent authority, however, 
 regards it as a "synthetic 
 type ; " that is to say, as a 
 form combining peculiarities ~ 
 
 . r jr lg . I2 8. Wing of Platephemera antiqua 
 
 Of Structure which are nOW (after Dawson), Devonian, 
 
 only found indifferentgroups. 
 
 Three other genera belonging to the Neuroptera have been 
 described from the Devonian Rocks of North America, under 
 the names Homothetus, Lithentomum, and Xenoneura. 
 
 In the Carboniferous Rocks, the remains of Insects, as might 
 have been expected, are comparatively more abundant, though 
 still far from common. In the rocks of this period we have 
 representatives of the orders Neuroptera, Orthoptera, and Coleop- 
 tera (Beetles). The Neuroptera are represented by a remark- 
 able form, which has been referred to the Ephemerida under 
 the name of Haplophlebium Barnesii (fig. 129). This insect
 
 1 86 
 
 ANNULOSA. 
 
 must have attained a size much larger than that of any recent 
 Ephemerids, measuring fully seven inches in expanse of wing. 
 
 Fig. 129. Haplophlebium Bantesii (after Dawson). From the Carboniferous Rocks 
 of Canada, a Profile of base of wing. 
 
 Another remarkable Carboniferous insect is the Archimulacris 
 Acadicus of Mr Scudder (fig. 130). It belongs to a group of 
 Insects which are tolerably abundant in 
 Carboniferous strata viz. , the Cockroaches ; 
 but it does not agree with any living forms. 
 In the Secondary period, remains of In- 
 sects are much more abundant than in any 
 Palaeozoic deposit. The Jurassic Rocks 
 have yielded the earliest examples of the 
 orders Hymenoptera and Heiniptera, whilst 
 the orders Neuroptera, Orthoptera, and 
 Coleoptera are well represented. In the 
 Tertiary Rocks, again, the remains of In- 
 sects become still more abundant, and in 
 some deposits they are found in the greatest 
 profusion. Whilst all the above-mentioned orders are repre- 
 sented, the Tertiary Rocks have also yielded the first traces 
 (with doubtful exceptions) of the orders Diptera andLepidoptera. 
 Amber, which is, geologically speaking, a very modern pro- 
 duct, has yielded the remains of a vast number of insects, all 
 of which belong to extinct forms. 
 
 The following are the names of the Orders of Insects which 
 are known in a fossil condition, with the date of their first 
 appearance : 
 
 130- 
 
 Acadicus (after 
 Dawson). From the 
 Carboniferous Rocks of
 
 SUB-KINGDOM MOLLUSCA. 187 
 
 1. Neuroptera (Dragon-flies, White Ants, May-flies, &c.) Devonian. 
 
 2. Orthoplera (Cockroaches, Crickets, Locusts, &c.) Carboniferous. 
 
 3. Coleoptera (Beetles). Carboniferous. 
 
 4. Hymenoptera (Bees, Wasps, Saw-flies, Ants). Jurassic. 
 
 5. Hemiptera (Aphides, Field-bugs, Cicadas, &c.) Jurassic. 
 
 6. Lepidoptera (Butterflies and Moths). Tertiary. 
 
 7. Diptera (House-flies, Flesh-flies, Gnats, Crane-flies, &c.) Tertiary. 
 
 8. Tkysanura (Spring-tails). Late Tertiary (in amber). 
 
 CHAPTER XVIII. 
 SUB-KINGDOM MOLLUSCA. 
 
 POLYZOA. 
 
 SUB-KINGDOM MOLLUSCA. The Mollusca comprise the ani- 
 mals ordinarily known as Shell-fish, from their commonly pos- 
 sessing an exoskeleton or shell. The Molluscs are soft-bodied 
 and destitute of any evident segmentation. Commonly the integu- 
 ment secretes a hard calcareous or horny envelope, but this may be 
 absent. The alimentary canal is always present, and never com- 
 municates with the body-cavity. The nervous system consists 
 typically of three pairs of ganglia, disposed in a characteristically 
 scattered manner ; but in the lower forms a single ganglion alone 
 is present. A heart may or may not be present, and there may or 
 may not be distinct respiratory organs. 
 
 As a matter of course, it is only with the shell of the Mol- 
 lusca that the palaeontologist has to deal, and those forms 
 which are destitute of this structure are wholly unknown in the 
 fossil condition. The special characters of the shell will be 
 treated of in speaking of the separate classes. In the mean- 
 while it is sufficient to draw attention to some general consi- 
 derations. In the Sea-mosses and Sea-mats (Polyzoa\ the 
 animal is compound, and the hard structures secreted by the 
 colony would not come under the common designation of 
 " shell." In these cases the investment of the colony would 
 rather be termed a " polypidom," and when of a horny nature, 
 it does indeed show a very close resemblance to the " polypary" 
 of the Sertularian Zoophytes. In the Ascidian Molluscs or 
 Sea-squirts (Tunicata), the animal is simply enclosed in a 
 leathery or cartilaginous case, in which calcareous matter is 
 very rarely developed. Hence we need feel no surprise that 
 the Tunicaries, with one or two very problematical exceptions,
 
 1 88 MOLLUSCA. 
 
 are not known in the fossil state. The Lamp-shells and their 
 allies (Brachiopoda) possess a bivalve shell, consisting of two 
 pieces or " valves," which are more or less highly calcareous. 
 Coming to the higher Mollusca, the true bivalve Shell-fish 
 (Lamellibranchiata), as their common name implies, have also 
 a bivalve shell ; but this is distinguished from the shell of the 
 Brachiopods by sufficiently good characters. No Lamelli- 
 branch is destitute of a shell, and the remains of this class 
 occur more or less abundantly in all deposits except the most 
 ancient. The ordinary univalve Shell-fish (Gasteropoda), as 
 indicated by their common name, have usually a shell com- 
 posed of a single piece or "valve." In many Gasteropods, 
 however, there is either no shell at all, when the animal is said 
 to be " naked " (as in the Sea-slugs), or the shell is quite rudi- 
 mentary, and is concealed within the mantle (as in the ordin- 
 ary slugs). In other Gasteropods again (viz. in the Chitons), the 
 shell is " multivalve," consisting of eight pieces or valves placed 
 one behind the other. Most, however, of the " multivalve " 
 shells of older writers are really referable to the Cirripedia. 
 In the minute Oceanic Molluscs which form the class Ptero- 
 poda, the animal is sometimes naked, but is more usually 
 protected by a symmetrical glassy shell, which is always uni- 
 valve. In the class of the Cephalopoda, finally, great diversity 
 exists in the character of the skeleton. All the ordinary Cut- 
 tle-fishes have an internal skeleton, embedded in the mantle, 
 and not visible externally. This internal skeleton may be 
 calcareous or horny, and it may be of a very complicated 
 nature ; but it merely serves to support the soft parts of the 
 animal, and it does not form an external case in which the 
 animal lives. In one Cuttle-fish only (viz., the Argonaut or 
 Paper Nautilus), is there an external shell, but the nature of 
 this is quite peculiar, and it cannot be compared with the 
 shell of any of the ordinary Molluscs. In another group of 
 the Cephalopoda, represented at the present day by the Pearly 
 Nautilus, there is a well-developed external shell, which is 
 always composed of a single piece, and is always chambered, 
 the animal living in the last and largest chamber of the shell. 
 
 In composition the shell of the higher Mollusca consists of 
 carbonate of lime usually having the atomic arrangement of 
 calcite with a small proportion of animal matter. In the 
 Pholadida, however, the calcareous matter exists in the allo- 
 tropic condition of arragonite, which is very much harder than 
 calcite. As regards their texture, three principal varieties of 
 shells may be distinguished viz., the " porcellanous," the 
 " nacreous," and the " fibrous." In the nacreous or pearly
 
 GENERAL CHARACTERS OF MOLLUSCA. 189 
 
 shells, as seen in " mother-of-pearl," the shell has a peculiar 
 lustre, due to the minute undulations of the edges of alternate 
 layers of carbonate of lime and membrane. The " fibrous " 
 shells are composed of successive layers of prismatic cells. 
 The " porcellanous " shell has a more complicated structure, 
 and is composed of three layers or strata, each of which is 
 made up of very numerous plates, " like cards placed on edge." 
 The direction in which these vertical plates are placed, is 
 sometimes transverse in the central layer, and lengthwise in 
 the two others ; or longitudinal in the middle, and transverse 
 in the outer and inner strata. 
 
 From their so commonly possessing h'ard structures, whether 
 external or internal, no fossils are more abundant or import- 
 ant than Molluscs. As regards the general distribution of the 
 Mollusca in time, the sub-kingdom commences its existence in 
 the Cambrian period, and there is no reason to suppose that 
 this is really its first appearance. In the Cambrian Rocks, 
 the classes of the Polyzoa, Brachiopoda, Pteropoda, Gasteropoda, 
 and Cephalopoda are certainly represented, and the Lamelli- 
 branchiata existed in Lower Silurian times, if not earlier. 
 Speaking generally, the chief representatives of the Mollusca 
 in Palaeozoic time are the chambered Cephalopods (Tetra- 
 branchiata} and the Brachiopoda; in Mesozoic time, the Cuttle- 
 fishes (Dibranchiate Cephalopods), the chambered Cephalo- 
 pods, and the Polyzoa ; in Kainozoic time, the Lamellibranchs 
 and Gasteropods. The Polyzoa are comparatively poorly re- 
 presented in Palasozoic Rocks, and attain their maximum 
 towards the close of the Mesozoic period. The Brachiopods 
 are vastly more abundant in Palaeozoic deposits than in Meso- 
 zoic, and have gradually declined to the present day. The 
 Lamellibranchiata seem to have been gradually increasing in 
 importance since their first appearance in the Lower Silurian 
 seas, and they have attained their maximum at the present 
 day. The Gasteropods, upon the whole, like the Bivalves, 
 seem to have reached their culminating point in recent seas ; 
 whilst the Pteropods seem to have been as abundant in Silurian 
 seas as they are at present. The history of the Cephalopoda is 
 a remarkable one. The Tetrabranchiate forms, with chambered 
 shells, attained their maximum in the earlier portion of the 
 Silurian period, as regards their simpler types ; but the more 
 complex types of the group swarmed in the seas of the 
 Secondary period, and finally disappeared at the close of this 
 epoch. This group at the present day is represented solely 
 by the Pearly Nautilus. The Dibranchiate Cephalopoda, on 
 the other hand, represented at the present day by the Cuttle-
 
 190 MOLLUSCA. 
 
 fishes, did not make their appearance till the commence- 
 ment of the Secondary period, and seem to have reached 
 their maximum in existing seas. 
 
 The sub-kingdom Mollusca is divided into two great divi- 
 sions, termed respectively the Molluscoida and the Mollusca 
 Proper. The division Molluscoida comprises the three classes 
 of the Polyzoa, Tunicata, and Brachiopoda, characterised by 
 having a nervous system consisting of a single ganglion or prin- 
 cipal pair of ganglia, whilst there is either no distinct organ of 
 the circulation or an imperfect heart. In the division of the 
 Mollusca Proper are comprised the classes of the Lamelli- 
 branchiata (Bivalves), Gasteropoda (Univalves), Pteropoda, and 
 Cephalopoda. All these classes are distinguished by having 
 a nervous system composed of three principal pairs of ganglia; 
 whilst there is a well-developed heart, consisting of at least two 
 chambers. 
 
 CLASS POLYZOA OR BRYOZOA. 
 
 Animal composite, forming colonies, all the members of which 
 are produced by budding from a primitive being (zooid). Each 
 member of the colony (zooid) is enclosed in a double-walled sac, 
 the outer coat of which is mostly hardened by horny or calcareous 
 matter. There is no heart, and the mouth is surrounded by a 
 circle or crescent of hollow ciliated tentacles. The colonies are all 
 but invariably fixed to some foreign object, and are in many cases 
 plant-like inform. 
 
 All the Polyzoa live in an associated form in colonies or 
 " polyzoaria," which are sometimes foliaceous, sometimes 
 branched and plant-like, sometimes encrusting, and very 
 rarely are free. Each " polyzoarium " consists of an assem- 
 blage of distinct but similiar zooids arising by continuous 
 gemmation from a single primordial individual. The colonies 
 thus produced are in very many respects closely similar to 
 those of many of the Hydroid Polypes, with which, indeed, 
 the Polyzoa were for a long time classed. The " polyzoarium," 
 however, of a Polyzoon differs from the polypidom of a com- 
 posite Hydroid in the general fact that the separate cells of 
 the former do not communicate with one another otherwise 
 than by the continuity of the external integument ; whereas 
 the zooids of the latter are united by an organic connecting 
 medium, or " ccenosarc," from which they take their origin. 
 On this point Mr Busk observes : 
 
 " It has been before said that the Polyzoa are always asso- 
 ciated into compound growths, made up of a congeries of 
 individuals, which, though distinct, yet retain some degree of
 
 POLYZOA. IQI 
 
 intercommunication, comparable in kind perhaps, though not 
 in degree, to what obtains in many of the compound Ascidi- 
 ans. That this community exists is proved by the otherwise 
 inexplicable circumstance that the polyzoaria in many in- 
 stances present elements common to the whole growth, and 
 not belonging specially to any individual. The chief bond of 
 connection would appear to reside partly in the continuity of 
 the external integument, and partly also, in all probability, in 
 a slow interchange of the vital fluid with which the cavities of 
 the cells are charged." 
 
 In one sub-order of the Polyzoa (Ctenostomata), the polyzo- 
 arium consists of a series of cells arising from a common tube, 
 but this exception does not affect the value of the above 
 general distinction between the Polyzoa and the Hydroida, 
 
 A second point of difference is found in the invariably cor- 
 neous (or chitinous) texture of the polypidoms of the Hydroida, 
 whereas those of the Polyzoa may be corneous or fleshy, but 
 are in the majority of instances more or less highly charged 
 with carbonate of lime. 
 
 As before remarked, the colonies of the Polyzoa are pro- 
 duced by a process of continuous budding from a primitive 
 being or zooid. The budding takes place according to a 
 determinate law, differing in different forms, and the resulting 
 colony varies in shape according to the method of budding in 
 each species. All the zooids of the colony are termed " poly- 
 pides," and the entire colony consists simply of an aggregation 
 of precisely similar polypides, which may be simply united by 
 their external integuments or, more rarely, spring from a com- 
 mon tube. It is only with the outer investment of the colony 
 that the palaeontologist has to deal ; but it may be well briefly 
 to describe the structure of a typical polypide. 
 
 The polypide of a Polyzob'n (fig. 131, 2) consists essentially 
 of a double-walled sac, filled with fluid, and perforated by an 
 aperture where the mouth of the polypide is situated. In the 
 majority of cases the outer wall of the sac (termed the " ecto- 
 cyst ") is of a horny consistence, or may be more or less highly 
 calcareous. It forms a little chamber, which is technically 
 called the " cell." At one point, varying in its position, the 
 cell is furnished with an aperture or "mouth" (fig. 131, i), 
 whence the polypide can protrude its tentaculate head. The 
 inner wall of the sac (termed the " endocyst ") is invariably 
 flexible and membranous, and the space included within it is 
 filled with fluid, in which floats the alimentary canal. The 
 commencement of the alimentary canal is surrounded by a 
 series of hollow ciliated tentacles, which are mostly arranged
 
 IQ2 MOLLUSCA. 
 
 in a circle in the marine Polyzoa, but are disposed in the 
 shape of a horse-shoe in most of the fresh-water forms. The 
 digestive canal passes through the body-cavity, without open- 
 ing into it, and terminates in a distinct anus placed near the 
 mouth. The only other organs possessed by the polypide are 
 a nervous ganglion, and the organs of reproduction, each 
 zooid being hermaphrodite. 
 
 Fig. 131. Morphology of Polyzoa. i. Portion < 
 magnified. 2. Diagram of a PolyzoOn (after Allma 
 by tentacles ; b Alimentary canal ; c Anus ; d Nei 
 cyst) ; f Testis ; f Ovary ; g Retractor muscle. 
 num,"ofaPolyzo5n. 
 
 f the ccenoecium of Flustra tntncata, 
 i): a Region of the mouth surrounded 
 vous ganglion ; e Investing sac (ecto- 
 3. Bird's-head process, or "avicula- 
 
 In order, then, to arrive at a clear conception of the struc- 
 ture of a Polyzbon, we have simply to imagine that such a 
 polypide as above described should have the power of repeat- 
 ing itself by gemmation, " thus producing one or more pre- 
 cisely similar systems, holding a definite position relatively to 
 one another, while all continue organically united." 
 
 The only element of the Polyzoa with which the palaeonto- 
 logist is concerned is the external investment of the colony 
 the " coencecium " or " polyzoarium." This is formed by the 
 combined ectocysts of the various polypides, and it varies 
 greatly both in form and actual composition. In form, it may 
 be plant-like, rooted at one point, and rising into foliaceous 
 expansions or arborescent growths ; or it may spread over 
 some foreign object as a continuous crust. In consistence, it 
 may be fleshy, horny, sub-calcareous, or completely calcareous ;
 
 POLYZOA. 193 
 
 the simply fleshy forms, as a matter of course, never occurring 
 in a fossil condition. 
 
 The form of the " cell," formed by the ectocyst or outer 
 wall of each polypide, varies considerably, and important dis- 
 tinctions may be drawn from this character alone. In one 
 large group of the Polyzoa the Cheilostomata the mouth of 
 the cell is never quite terminal 
 in position, but is always placed 
 upon the front of the cell, gene- 
 rally close to one end (fig. 132) ; 
 whilst the diameter of the mouth 
 is less than the diameter of the 
 cell. In most of these forms, 
 also, the mouth of the cell is 
 provided with a movable lid or 
 shutter, by which it can be closed 
 
 when the animal is retracted Fig. ^-^.Escharina Oceani, show- 
 within it. In another great group 
 the Cyclostomata the cells are 
 
 tubular in form, and the mouth is terminal in position, whilst 
 its diameter usually equals that of the cell. In these forms, 
 also, there is no special apparatus for the closure of the mouth 
 of the cell. 
 
 The surface of the cell may be " either smooth and entire, 
 spinous or granulous ; perforated with minute pores, or cribri- 
 form with larger openings ; reticulate or ribbed, &c., all of 
 which conditions, with certain precautions, afford excellent 
 diagnostic characters " (Busk). The margins of the mouth of 
 the cell, also, may be " simple or thickened, unarmed or beset 
 with erect ' marginal spines,' which again may be either rigid 
 or articulated at the base, simple or branched." 
 
 There still remain three structures which are present in many 
 forms, and especially in the Cheilostomata, which require some 
 notice. The structures in question are known as the "ovicell," 
 the " avicularia," and the " vibracula." 
 
 The " ovicell " is a structure especially characteristic of the 
 Cheilostomatous Polyzoa; but its presence is not universal, and 
 when present it may be inconspicuous. Its general form is that 
 of "a more or less rounded eminence situated above or behind 
 the cell. . . . The cavity of the organ is continuous with 
 the perivisceral space, through a passage situated at the upper 
 and back part of the cell, and through which it would appear 
 the ova are conveyed as into a sort of marsupial pouch. This 
 organ is wanting in the Cyclostomata, in which its functions are
 
 194 MOLLUSCA. 
 
 apparently supplied by a dilatation of the body of the cell 
 itself." (Busk.) 
 
 The " avicularia " and " vibracula " are peculiar appendages 
 of the ectocyst, supposed to be weapons of offence and defence, 
 or to subserve some unknown function in the economy of the 
 colony, and believed by Huxley to be peculiarly modified 
 polypides. The avicularia, or "bird's-head processes," differ 
 a good deal in shape, but consist essentially of a " movable 
 mandible and a cup furnished with a horny beak, with which 
 the point of the mandible is capable of being brought into 
 apposition " (Busk). In shape they are often closely similar 
 to the head of a bird (fig. 131, 3), and they perform a peculiar 
 snapping movement, which is continued long after the apparent 
 death of the colony. In many respects, the avicularia are 
 comparable with the " pedicellariae " of the Sea-urchins and 
 Star-fishes. In the " vibracula," the place of the mandible of 
 the avicularium is taken by a bristle or seta, which is capable of 
 extensive movement. 
 
 The following table exhibits the leading groups of the 
 Polyzoa : 
 
 TABLE OF THE DIVISIONS OF THE POLYZOA. 
 
 ORDER I. PHYLACTOL^EMATA. 
 
 Tentacles arranged in the shape of a horse-shoe or crescent. Mouth 
 furnished with a valve-like organ or "epistome." 
 
 Sub-order I. Lophopea (fresh- water). Arms of the tentacular disc ("lopho- 
 phore") free or obsolete ; consistence, horny or sub -calcareous. 
 
 Sub-order 2. Pedicellinea (marine). Arms of the tentacular disc united 
 at their extremities ; consistence, soft and fleshy. 
 
 Sub-order 3. Rhabdopleurea (marine). Coencecium branched, adherent, 
 membranous, with a chitinous rod on its adherent side. Tentacular disc 
 horse-shoe-shaped. No epistome (?) 
 
 ORDER II. GYMNOL^EMATA. 
 
 Tentacles arranged in the form of a more or less complete circle. No 
 valve-like organ, or "epistome," arching over the mouth. 
 
 Sub-order 4. Paludicellea (fresh-water). Polypide completely retractile ; 
 evagination of tentacular sheath imperfect ; consistence, homy or sub- 
 calcareous. 
 
 Sub-order 5. Cheilostomata (marine). Polypide completely retractile ; 
 evagination perfect ; orifice of cell sub-terminal, of less diameter than the 
 cell, and usually closed with a movable lip or shutter, sometimes by a con- 
 tractile sphincter; cells not tubular ; consistence, calcareous, horny, or fleshy. 
 
 Sub-order 6. Cyclostomala (marine). Cell tubular ; orifice terminal, of 
 the same diameter as the cell, without any movable apparatus for its closure; 
 consistence, calcareous. 
 
 Sub-order 7. Ctenostomata (marine). Orifice of the cell terminal, furnished 
 with a usually setose fringe for its closure ; cells distinct, arising from a 
 common tube ; consistence, horny or carnose.
 
 POLYZOA. 
 
 195 
 
 Of the above sub-orders of the Polyzoa, only the marine 
 groups of the Cheilostomata and Cydostomata are known to 
 occur in the fossil condition ; their preservation being due to 
 their marine habits and their general possession of a calcareous 
 or sub-calcareous coencecium. The general facts as to the dis- 
 tribution of the Polyzoa in past time have been already alluded 
 to. The Oldhamia of the Cambrian Rocks and the Graptolites 
 have been referred to the Polyzoa ; but the former is probably 
 a plant, and the latter almost certainly belong to the Hydrozoa. 
 Leaving these out of account, the Polyzoa seem to commence 
 in the Upper Cambrian, and are well represented in the Silu- 
 rian, Devonian, Carboniferous, and Permian Rocks, but espe- 
 cially in the Carboniferous. None of the Palaeozoic genera 
 extend into the Secondary period. In the Secondary period 
 Polyzoa are very abundant, and they attain their maximum 
 of development in the Cretaceous period, the Chalk having 
 yielded over two hundred species belonging to this class. In 
 the Tertiary period, also, Polyzoa are abundant; the Coralline 
 Crag (Pliocene) deriving its name from the great profusion of 
 its Polyzoan remains. 
 
 Of the Palaeozoic Polyzoa the most important forms belong 
 to the family of the Fenestellidce or " Lace-corals." These 
 commence in the Lower Silurian, and extend to the Permian ; 
 but they are especially characteristic of the Carboniferous 
 Rocks. In Fenestella itself (fig. 133), the ccencecium forms a 
 
 Fig. 133. Fenestella Lyelli. a Natural size ; b Portion enlarged; c Cells and spines 
 in profile. From the Carboniferous Rocks of Canada (after Dawson). 
 
 funnel-shaped or fan-shaped expansion, the base of which is 
 attached to some foreign object. The coencecium is composed 
 of a number of nearly parallel stems, united to one another by 
 numerous cross-bars or dissepiments, enclosing small inter-
 
 196 MOLLUSCA. 
 
 spaces. The outer surface of the branches is minutely porous 
 or longitudinally striated. The inner surface of the branches 
 exhibits a central ridge or keel, separating the mouths of two 
 rows of cells. Sometimes there is an additional row of cells 
 on the mesial keel, and the dissepiments are usually destitute 
 of cells. The entire ccenoecium is calcareous. In the nearly 
 allied genus Retepora, the ccencecium is also a fan-shaped ex- 
 pansion, and is also of a calcareous consistence. In place, 
 however, of transverse dissepiments, the branches of the ccenoe- 
 cium unite with one another in such a manner as to form ovate 
 interspaces or " fenestrules." The outer surface of the ccence- 
 cium is non-celluliferous and minutely striated. The inner 
 surface bears several rows of small cells. 
 
 In the genus Ptilopora (fig. 134) are forms essentially similar 
 
 Fig. 134. Ptilopora pluma; the right hand figure of the natural size, the left-hand 
 figure enlarged. Carboniferous. 
 
 to Fenestella, but having a feather-like arrangement, consisting 
 of a central stem giving off lateral branches, which are con- 
 nected by dissepiments, leaving oval fenestrules. In Glauco- 
 nome (Acanthocladia, King) are forms in which the coenoecium 
 consists of a central axis giving off lateral branches, which bear 
 longitudinally-disposed cellules, but which are not united by 
 transverse dissepiments. Lastly, in Anhimedipora, which is 
 found abundantly in parts of the Carboniferous series of the 
 United States, the ccenoecium is wound in an oblique spiral 
 round a central axis. The only other Palaeozoic genus of any 
 special importance is Ptilodictya, the species of which are 
 especially characteristic of the Silurian Rocks. In this genus, 
 the coencecium is flattened, foliaceous, or more commonly
 
 POLYZOA. 
 
 197 
 
 dichotomously branched. The cellules are placed obliquely 
 on both sides of the coenoecium, and have prominent oval 
 mouths. 
 
 In the Secondary period, the remains of Polyzoa are abund- 
 ant, and some of the genera are still represented in recent 
 
 Fig. 135. Entalophora cellarioides, natural size and enlarged. Oolites. 
 
 seas. Nearly twenty genera are known from the Jurassic 
 Rocks, amongst which may be mentioned Idmonea, Eschara, 
 Defrancia, Diastopora, Bidiastopora, (fig. 136), &&& Entalophora 
 
 Fig. 136. Bidiastopora cervicornis, natural size and enlarged. Oolites. 
 
 (fig. 135). All of these, except Eschara, belong to the group 
 of the Cyclostomata, distinguished by their tubular cells, the 
 mouth of which equals in breadth the diameter of the cell. 
 
 It is in the Cretaceous period that the Polyzoa attain their 
 maximum, nearly two hundred species being known in the 
 Chalk. Most of the Cretaceous forms belong to the Eschar- 
 idce, the genus Eschara being abundantly represented. All 
 the members of this family belong to the group of the Cheilos- 
 tomatous Polyzoa, in which the orifice of the cell is not terminal, 
 and is of less diameter than the cell itself. 
 
 In the Tertiary Rocks Polyzoa are likewise abundant, and 
 many of the genera are represented at the present day by
 
 198 
 
 MOLLUSCA. 
 
 living forms. One of the greatest depots of fossil Polyzoa is 
 the White Crag of Suffolk, which is for this reason very inap- 
 propriately called the " Coralline Crag." Amongst the more 
 important Tertiary genera may be mentioned Eschara, Celle- 
 pora, Flustra, Tubulipora, Idmonea, and Fascicularia (or Mcand- 
 ropora). One of the most singular of these' is the genus Fasci- 
 cularia (fig. 137), in which the coenoecium is more or less 
 
 ' ' W 
 
 Fig. 137. Fascicularia (Meandropora) cerebri/ormis, Miocene Tertiary. 
 
 spherical, composed of vertical laminae arranged somewhat 
 like the convolutions of the brain, and carrying the cell-mouths 
 at their extremities. 
 
 CHAPTER XIX. 
 BRACHIOPODA. 
 
 THE Brachiopoda are defined as Molluscous animals in which 
 the body is protected by a bivalve shell > which is lined by expansions 
 of the integument or " mantle." The mouth is furnished with 
 long, spirally-coiled; cirriferous processes or "arms." The animal 
 is never composite. (Fig. 138). 
 
 Fig. 138. Brachiopoda. Teretratula vitrea. i. Showing the ciliated " arms ; " 
 a. Showing the shell with its loop. (After Woodward.) 
 
 The Brachiopoda are essentially very similar in structure to 
 the Polyzoa, from which they are distinguished by the fact that
 
 BRACHIOPODA. 
 
 I 99 
 
 they are never composite, and by the possession of a bivalve, 
 calcareous, or sub-calcareous shell. They are commonly known 
 as " Lamp-shells," and are all inhabitants of the sea. All the 
 living forms are fixed to some solid object in their adult con- 
 dition ; but there is good reason to believe that many of the 
 fossil forms were unattached and free in their fully-grown con- 
 dition. From the presence of a bivalve shell, the Brachiopods 
 have often been placed near the true bivalve Molluscs (the 
 Lamellibranchiata) ; but their organisation is very much in- 
 ferior, and there are also sufficient differences in the shell to 
 justify their separation. 
 
 The two valves of the shell in any Brachiopod are articulated 
 together by an apparatus of teeth and sockets, or are kept in 
 apposition by muscular action alone. As regards the contained 
 animal, the position of the valves is anterior and posterior, so 
 that they are properly termed the " ventral " and " dorsal " 
 valves. One of the valves is always slightly, sometimes greatly, 
 larger than the other, so that the shell is said to be " inequi- 
 valve" (fig. 139). On the other hand, a line drawn vertically 
 
 Fig. -L^.R 
 
 C, View of the base, a Ventral valve ; b Dorsal valve ; f Base ; c Beak ; k Foramen. 
 Lower Cretaceous. 
 
 from the beak of the shell to its base (in fig. 139 B, from c to/), 
 would divide it into two equal halves, so that the shell is said 
 to be " equilateral." In the true bivalve Shell-fish (Lamelli- 
 branchiata), on the contrary, the valves of the shell are placed 
 upon the sides of the contained animal, so that they are " right " 
 and " left," instead of being dorsal and ventral. Further, the 
 two valves are usually of the same size (" equivalve "), and a 
 line drawn from the beak to the base would almost always 
 divide the shell into unequal halves ; so that the shell is " in- 
 equilateral." 
 
 Ordinarily the ventral valve of the shell of the Brachiopods 
 is the largest of the two, and it is generally furnished with a 
 prominent curved "beak." Very commonly the beak is per-
 
 200 
 
 MOLLUSCA. 
 
 forated by a larger or smaller aperture, which is termed the 
 " foramen " (fig. 139, B), and which serves for the transmission 
 of a muscular peduncle or stem by which the shell is attached 
 to some foreign object. In some cases, however (as in Lingula), 
 the peduncle simply passes between the apices of the valves, 
 and there is no foramen ; whilst in others (as in Crania, fig. 
 161), the shell is merely attached by the substance of the ven- 
 tral valve. The dorsal valve, which is also usually the smallest, 
 is always free, and is never perforated by a foramen. Further, 
 as already remarked, there is reason to believe that many fossil 
 forms were free and unattached in their adult condition. 
 
 In most living Brachiopods the valves are articulated to one 
 another by two teeth which are developed upon the ventral 
 valve, and fit into corresponding sockets in the dorsal valve. 
 Behind the dental sockets of the dorsal valve there is usually a 
 prominent process (" cardinal process "), to which are attached 
 two " cardinal muscles." These are inserted on each side of 
 the centre of the ventral valve, and serve to open the shell. 
 The valves of the shell are closed by proper "adductor muscles" 
 (usually four in number), which also pass between the valves ; 
 and in those in which hinge-teeth are wanting, it is by these 
 muscles that the valves are kept together. These muscles 
 leave " scars " or impressions at their points of insertion and 
 origin : and the number and form of these scars afford impor- 
 tant diagnostic characters to the palaeontologist. 
 
 Very commonly, the beaks of the dorsal and ventral valves 
 are separated from one another by a narrower or wider space, 
 which is termed the "hinge-area" (fig. 140). In some genera, 
 
 'rerebratella. Astieriana, Cretaceous, t Hinge-area; ttt Ueltidium. 
 
 as in Spirifera, the area is very conspicuous ; in other cases it 
 is very narrow, or even does not exist. In front of the foramen 
 of the ventral valve, and very often forming part of its circum- 
 ference, there is commonly a triangular plate, which may be
 
 BRACHIOPODA. 2OI 
 
 composed of one or two pieces, and which is termed the " del- 
 tidium" (fig. 140, m). In other cases this structure is alto- 
 gether wanting. 
 
 In intimate structure, the shell of most of the Brachiopoda 
 (fig. 141) consists " of flattened prisms, of considerable length, 
 arranged parallel to one another with great regularity, and at a 
 very acute angle usually only about 10 
 or 1 2 with the surfaces of the shell." 
 (Carpenter.) In most cases, also, the 
 shell is perforated by a series of minute 
 canals, which pass from one surface of 
 the shell to the other, in a more or less 
 vertical direction, usually widening as 
 they approach the external surface. 
 These canals give the shell a "punc- 
 tated " structure, and in the living ani- 
 mal they contain caeca! tubuli, or pro- showin the flattened risms 
 longations, from the mantle, which are of the shell, and the canals, 
 considered by Huxley as analogous to 
 
 the vascular processes by which in many Ascidians the muscular 
 tunic, or "mantle," is attached to the outer tunic, or "test." 
 In some of the Brachiopoda (as in the Rhynchondlidcz] the shell 
 is " impunctate," or is devoid of this singular canal system. 
 
 The inner surface of the valves of the shell is lined by ex- 
 pansions of the integument which secrete the shell, and are 
 called the " lobes " of the " pallium," or "mantle." The diges- 
 tive organs and muscles occupy a small space near the beak 
 of the shell, which is partitioned off by a membranous septum, 
 which is perforated by the aperture of the mouth. The re- 
 mainder of the cavity of the shell is almost filled by two long 
 oral processes, which are termed the " arms," and from which 
 the name of the class has been derived (fig. 138, i). These 
 organs are lateral prolongations of the margins of the mouth, 
 usually of great length, closely coiled up, and fringed on one 
 side with lateral processes, or " cirri." In many Brachiopods 
 the arms are supported upon a more or less complicated inter- 
 nal calcareous framework or skeleton, which is sometimes called 
 the "carriage-spring apparatus." 
 
 In some forms, as in the typical Terebratulcz (fig. 138, 2), the 
 internal skeleton which supports the arms is a short shelly loop, 
 of a very simple character. In these cases it is only at their 
 bases that the arms are supported, and they are therefore 
 more or less movable. In other cases, as in the SpiriferidcR 
 (fig. 142), the arms must have been immovable, as they are 
 supported by two thin spirally-rolled lamellae, which form two
 
 202 MOLLUSCA. 
 
 calcareous spires in the interior of the dorsal valve. In some 
 cases, the whorls of these spires are in turn furnished with 
 minute calcareous spines, showing that the cirri of the arms 
 
 Fig. n-z.Spirifera hysterica, Carboniferous. The right-hand figure shows the interior 
 
 n-z.Spiriera hysterca, aronerous. e rgt-an gure so 
 of the dorsal valve, with the calcareous spires for the support of the 
 
 anus. 
 
 were also supported by an internal skeleton. The form and 
 development of the calcareous supports of the arms, though 
 liable to vary with age, nevertheless furnish important characters 
 in the discrimination of fossil Brachiopods. 
 
 The Brachiopoda may be divided into two groups, called 
 respectively the Articulata and Inarticulata. In the former 
 the valves of the shell are united along a hinge-line, the lobes 
 of the mantle are not completely free, and the intestine ends 
 csecally. In this group are the recent Terebratulida and Rhyn- 
 dionellidcR. In the Inarticulata the valves of the shell are not 
 united along a hinge-line, the mantle-lobes are completely free, 
 and the intestine terminates in a distinct anus. In this group 
 are the Craniadce, Discintdce, and Lingulidce. 
 
 The Brachiopods are of such importance as fossils that the 
 characters of the more important groups, with their geological 
 range, and leading genera will here be given, along with figures 
 of the commoner types. As regards the general distribution 
 of the class in time, the Brachiopoda are found from the Cam- 
 brian Rocks up to the present day, and present us with an 
 example of a group which appears to be slowly dying out 
 Nearly two thousand extinct species have been described, and 
 the class appears to have attained its maximum in the Silurian 
 epoch, which is, for this reason, sometimes called the " Age 
 of Brachiopods." Numerous genera and species are found also 
 in both the Devonian and Carboniferous formations. In the 
 Secondary Rocks Brachiopoda are still abundant, though less 
 so than in the Palaeozoic period. In the Tertiary epoch a still 
 further diminution takes place, and at the present clay we are 
 not acquainted with a hundred living forms. Of the families 
 of Brachiopoda, the Productida, Strophomcnida, and Spiriferida 
 are the more important extinct types. Of the genera, the most
 
 BRACHIOPODA. 203 
 
 persistent is the genus Lingttla, which commences in the Cam- 
 brian Rocks, and has maintained its place up to the present 
 day, though it appears to be gradually dying out. 
 
 According to Woodward : " The hingeless genera attained 
 their maximum in the Palaeozoic age, and only three now sur- 
 vive (Lingula, Distinct, Crania) the representatives of as many 
 distinct families. Of the genera with articulated valves those 
 provided with spiral arms appeared first, and attained their 
 maximum while the Terebratulidtz were still few in number. 
 The subdivision with calcareous spires disappeared with the 
 Liassic period, whereas the genus Rhynchonella still exists. 
 Lastly, the typical group, Terebratulidce, attained its maximum 
 in the Chalk period, and is scarcely yet on the decline." 
 
 Of the families of the Brachiopoda, the Productidtz and 
 Strophomenidce are exclusively Palaeozoic. The Spiriferida 
 are mainly Palaeozoic, but extend into the Lias, where they 
 finally disappear. The Lingulidce commence in the Cambrian 
 period, and have survived to the present day. The Rhyncho- 
 nellidce, Craniadcz, and Discinidce commence in the Silurian 
 period, and are represented by living forms in existing seas. 
 The Koninckinidcz are exclusively Triassic. The Thecidida ex- 
 tend from the Trias to the present day ; and the Terebratulida 
 appear to commence in the Devonian, and are well represented 
 by living forms. In the following are given the leading char- 
 acters and more important forms of the families of the Brachio- 
 poda : * 
 
 FAM. I. TEREBRATULID^E. Shell minutely punctate: ven- 
 tral valve with a prominent beak, perforated by a foramen for 
 the emission of a muscular ped- 
 uncle, whereby the animal is 
 fixed to some submarine object. 
 Foramen partially surrounded 
 by a deltidium of one or two 
 pieces. Arms entirely or par- 
 tially supported by calcified 
 processes, usually in the form 
 of a loop, and always fixed to Fig ^._ Terebratula sacculus> Car - 
 
 the dorsal Valve (fig. 143.) boniferous. The right-hand figure shows 
 
 In the genus Terebratula it- 
 self, and in Terebratulina, the 
 loop supporting the arms is very short, the former commencing 
 
 * Most of the details of this section are taken from the magnificent 
 Monograph of the Brachiopoda, published by the Palseontographical 
 Society, and written by Thomas Davidson, Esq., F.R.S., the greatest 
 living authority upon the subject of the Brachiopods.
 
 204 
 
 MOLLUSCA. 
 
 in the Devonian period, the latter in the Oolitic, and both 
 being represented by living forms. In the genus Waldheimia 
 there is a very long loop, which is bent backwards, and the 
 same is the case with Terebratella. The former appears to 
 commence in the Trias, the latter in the Cretaceous Rocks, and 
 both have survived to the present day. Forming a section of 
 the Terebratulida, or sometimes regarded 
 as a separate family, are the two or three 
 species which make up the genus Strin- 
 gocephalus. These (fig. 144) are all De- 
 vonian, and are characterised by the pos- 
 session of a long loop, and a widely- 
 punctated shell. The beak of the ventral 
 valve is very prominent, and is pierced by 
 a foramen, which is large in the young, 
 and small in the adult shell ; and the ventral valve has a well- 
 developed mesial septum. 
 
 FAM. II. THECIDID^:. Shell fixed to the sea-bottom by 
 the substance of the beak of the larger or ventral valve; 
 structure punctated. Oral processes (arms) united in the form 
 
 144. Stringoce~ 
 Burtini, Devon- 
 
 Fig. n$.Thecidium papillatmn. e Hinge-area ; n Hinge-teeth of ventral valve ; 
 r r Granulated border of the interior of the dorsal valve. 
 
 of a bridge over the visceral cavity ; cirrated arms folded upon 
 themselves, and supported by a calcareous loop. (Fig. 145.)
 
 BRACHIOPODA. 
 
 205 
 
 The members of this family are all attached to some foreign 
 body by a portion of the beak of the ventral valve, which, in 
 the adult state, has either no foramen, or an exceedingly small 
 one. The ventral valve has a well-marked hinge-area and an 
 indistinct triangular deltidium. All the known species belong 
 to the single genus Theddium, represented at the present day 
 by a single living species. In time, the genus Theddium 
 seems to have commenced in the Upper Trias, and is well re- 
 presented in parts of the Jurassic and Cretaceous Series. 
 
 FAM. III. SPIRIFERID;E. Animal free when adult, or rarely 
 attached by a muscular peduncle. Shell punctated or un- 
 punctated. Arms greatly 
 developed, and entirely 
 supported upon a thin, 
 shelly, spirally-rolled la- 
 mella (fig. 142 and fig. 
 146.) 
 
 The family of the Spir- 
 iferidcs is pre - eminently 
 Palaeozoic, but several 
 forms extend into the older 
 Secondary Rocks. No 
 
 member of the family, however, has yet been found in rocks 
 younger than the Lias. Of the genera of the family, in the gen- 
 us Spirifera, or Spirifer (fig. 148), the valves of the shell are 
 articulated by teeth and sockets, and the shell is not punctated. 
 The hinge-area is divided across in each valve by a triangular 
 fissure, which in the ventral valve is closed more or less corn- 
 
 Fig. 146. Athyris subtilita. Lower Car- 
 boniferous. The right-hand figure shows the 
 interior of the dorsal valve, with the spiral sup- 
 ports for the arms. (After Dawson.) 
 
 Figs. 147 and 148. Spirifera sculptilis, Devonian. Spirifera mucronata, Devonian. 
 
 pletely by a pseudo-deltidium, and in the dorsal valve is 
 occupied by the cardinal process. The true Spirifers are 
 mainly Silurian and Devonian, and the forms of the latter 
 formation often have the shell winged, or drawn out at the 
 lateral angles (fig. 148). The genus Spiriferina differs from 
 Spirifer chiefly in having the shell punctated, and extends 
 from the Devonian to the Lias. In the genus Cyrtia, the 
 shell is impunctate, and the deltidium is perforated by a small
 
 206 
 
 MOLLUSCA. 
 
 foramen. This genus extends from the Upper Silurian to the 
 Trias. In the genus Athyris (fig. 146) there is no hinge-area 
 or deltidium, and the beak of the ventral valve does not appear 
 to be perforated by a foramen in the adult condition. All the 
 species of Athyris appear to be Palaeozoic, and they are es- 
 pecially characteristic of the Devonian period. In the genus 
 Spirigera (including Retzia) there is no true hinge-area, and 
 the beak of the ventral valve is terminated by a round foramen, 
 with a distinct deltidium. The members of this genus extend 
 from the Silurian to the Trias. In the genus Uncites the shell 
 
 Fig. 149. Atrypa(Spirigerina)reticuleiris t Silurian. 
 
 is impunctate, there is no hinge-area, and the ventral valve has 
 a long incurved beak, which is perforated in the young shell 
 by a small foramen. The genus is, so far as known, exclusively 
 Devonian. Lastly, in the genus Atrypa (fig. 149) the shell is 
 impunctate, and the beak of the ventral valve is long and 
 incurved. The beak is perforated 
 by a small foramen, completed by a 
 deltidium. Owing to the curvature 
 of the beak, however, this foramen is 
 often concealed, so that the beak 
 seems to be imperforate ; hence the 
 name of the genus (Gr. a, without ; 
 tnipa, aperture.) It is probable that 
 the shell was unattached in the later 
 portions of its existence. The genus 
 is exclusively Palaeozoic, appearing 
 to be confined to the Silurian and 
 Devonian formations. The best- 
 known species is A. reticttlaris, figured above. 
 
 FAM. IV. KONINCKINID^E. Animal unknown. Shell free ; 
 valves unarticulated (?). Oral arms supported by two lamellae 
 spirally coiled (fig. 150). 
 
 The only genus of this family is Koninckia, represented by 
 
 150. Kounickia Leon- 
 hardi, snowing the spiral sup- 
 ports for the arms. Tnas.
 
 BRACHIOPODA. 2O? 
 
 the single species K. Leonhardi of the Trias of St Cassian. 
 The shell resembles Producta in being eared, and the dorsal 
 valve is concave, and follows the curve of the ventral valve. 
 It differs from Producta in having the arms supported upon 
 spiral processes. 
 
 FAM. V. RHYNCHONELLID^E. Animal free, or attached by a 
 muscular peduncle issuing from an aperture situated under the 
 extremity of the beak of the ventral valve. Arms spirally 
 rolled, flexible, and supported only at their origin by a pair of 
 short, curved, shelly processes. Shell-structure fibrous and 
 impunctate. (Fig. 151.) 
 
 Fig. 151. R hyuchonella capax ; dorsal, profile, and ventral views. 
 Lower Silurian. 
 
 The Rhynchonellida range from the Lower Silurian to the 
 present day, in the person of the genus Rhynchonella itself; but 
 the remaining genera of the family are exclusively Palaeozoic. 
 The genus Rhynchonella (fig. 151) has the valves more or less 
 convex, smooth or plaited, united by teeth and sockets. The 
 shell is trigonal, generally with a mesial fold and sinus (fig. 139), 
 and having the beak of the ventral valve acute, incurved, 
 or prominent. The foramen is situated under the beak, open 
 to view, or concealed, and entirely or partially completed by 
 a deltidium. The species of the genus Rhynchonella are very 
 abundant in both Palaeozoic and Mesozoic deposits, and two 
 species are known at the present day. 
 
 In the genus Pentamerus (fig. 152), the shell is ovate, the 
 valves articulated by teeth and sockets, generally ribbed or 
 striated, but sometimes smooth. 
 
 The beaks are incurved, that of the ventral valve concealing 
 a triangular fissure. Inside the ventral valve " two contiguous 
 vertical septa coalesce into one median plate, extending from 
 the beak to a greater or less distance ; and then diverge and 
 form the dental plates, enclosing a triangular chamber of much 
 smaller dimensions than the lateral ones." (Davidson.) The 
 small central chamber must have been occupied by the diges- 
 tive organs, and the spiral arms must have filled the great
 
 208 
 
 MOLLUSCA. 
 
 lateral spaces. In the interior of the smaller or dorsal valve 
 are two longitudinal septa, which often form a chamber cor- 
 responding to and apposed to the median chamber in the ven- 
 
 Fig. 152. Penta 
 
 V 
 
 nightii. The right-hand figur 
 tal plates of the shell. Upper 
 
 l septa 
 
 tral valve. The Pentameri range from the Lower Silurian to 
 the Carboniferous inclusive ; but they are especially character- 
 istic of that portion of the Silurian series known as the Lland- 
 overy formation. They often occur in the greatest profusion, 
 and the species have in many cases an enormous geographical 
 range. 
 
 The two other genera generally placed in the Rhynchonel- 
 lidce viz., Camarophoria and Porambonites, are of little impor- 
 tance. The former is confined to the Carboniferous and 
 Permian deposits, and the latter occurs exclusively in strata of 
 Lower Silurian age. 
 
 FAM. VI. STROPHOMENIDJE. Animal unknown ; some pro- 
 bably free others attached, during the whole or a portion of 
 their existence, by a muscular peduncle. No calcified supports 
 for the arms. Shell with a straight hinge-line and a low trian- 
 gular area in each valve. Shell-structure fibrous or punctated. 
 The Strophomenida are exclusively Palaeozoic, and include the 
 
 Fig. iS3-OrtAis Davitt- 
 toni; dorsal and side view. 
 Silurian. 
 
 ponata; dorsal and 
 Silurian. 
 
 genera Ort/u's, Orthisina, Strophomena, Lcfttana, and David- 
 sonia, of which the first four only are sufficiently abundant to 
 need notice here.
 
 BRACHIOPODA. 
 
 209 
 
 In the genus Orthis the valves are articulated by teeth and 
 sockets, and usually are more or less transversely oblong (fig. 
 153). There is a straight hinge-line, generally 
 shorter than the width of the shell. Each valve 
 has a hinge-area, notched in its centre by a 
 triangular fissure through which the fibres of 
 the peduncle were transmitted. The shell is 
 often more or less flattened or depressed, and 
 the surface may be smooth, but is more com- 
 monly ornamented with striae, or furnished with 
 well-marked longitudinal ribs. The species of 
 the genus Orthis abound in the Silurian, Devonian, and Car- 
 boniferous periods, especially in the first of these ; but the 
 genus is not known to have survived the Carboniferous period. 
 
 In the genus Orthisina (fig. 156) the shell nearly resembles 
 that of Orthis; but there is a double hinge-area, largest in 
 the ventral valve, the central fissures of 
 which are always covered by a convex delti- 
 dium ; whereas in the latter genus they are 
 open. In some species (as in O. Verneuilt) 
 the deltidium is perforated by a foramen 
 under the beak of the ventral valve. The 
 typical species of Orthisina are Silurian; 
 but the genus is stated by Mr Davidson to 
 range through the Devonian and Carbon- 
 iferous into the Permian. 
 
 In Strophomena (fig. 157) the shell is 
 depressed, generally semicircular, the hinge-line as long as 
 the width of the shell, or longer. The surface may be smooth, 
 but is most commonly striated or ribbed. There is a double 
 
 157. Strophomena antiguata, Silurian. 
 
 hinge-area, which is largest in the ventral valve. Each hinge- 
 
 area has a median notch, which, in the ventral valve, is par- 
 
 tially covered by a deltidium. The ventral valve may be 
 
 o
 
 
 210 MOLLUSCA. 
 
 convex or concave, and the dorsal valve follows the curvature 
 of the ventral valve. The species of the genus Strophomena 
 are very abundant in the Silurian, Devonian, and Carbonifer- 
 ous formations, often attaining a large size ; but they do not 
 seem to have survived the close of the last-named period. 
 
 In the genus Lepttzna are forms smaller than the Stropho- 
 mence, but resembling them in many respects. The shell is 
 more or less completely semicircular (fig. 158), with a double 
 hinge-area, notched in the centre, the 
 fissure in the ventral valve being partly 
 covered by a deltidium. The valves 
 articulate by teeth and sockets, and the 
 surface is generally striated. The Lep- 
 tcBticB extend from the Silurian Rocks 
 to the summit of the Lias, but are not 
 ^.. known in any younger deposits. 
 ; b FAM. VII. PRODUCTID^E. Animal un- 
 of known. Shell entirely free, or attached 
 to submarine objects by the substance 
 of the beak; valves either regularly articulated, or kept in 
 place by muscular action alone. No calcified supports for 
 the oral processes. The Productida are exclusively Palaeozoic, 
 and are especially characteristic of the Devonian, Carbonifer- 
 ous, and Permian deposits. 
 
 The two most important genera of the Productida are 
 Chonetes and Producta. In the genus Chonetes (fig. 159) the 
 shell is concavo-convex, transversely oblong, with a straight 
 
 Fig. 159. Chonetes Dalmaniana, Carboniferous. 
 
 hinge-line. The hinge-line is as wide as the shell, or the shell 
 is eared. The ventral valve is convex, the dorsal concave, 
 and both have a distinct hinge-area, with a central fissure, 
 closed in the ventral valve by a pseudo -deltidium. The 
 upper edge of the hinge-area of the ventral valve is furnished 
 with a row of delicate, tubular spines. The species of
 
 BRACHIOPODA. 
 
 211 
 
 Chonetes are distributed in the Silurian, Devonian, and Car- 
 boniferous periods, but they are most abundant in the last 
 of these. 
 
 In the genus Producta (fig. 1 60) the valves are not articu- 
 lated by any apparatus of teeth and sockets, and the shell 
 
 Fig. 160. Producta cora, Carboniferous, a Dorsal valve ; b Ventral valve. 
 (After Dawson.) 
 
 would appear to have been free in the adult condition. The 
 shell is generally transversely elongated, and is auriculate, or 
 furnished with ear-like expansions. There is a straight hinge- 
 line, usually shorter than the width of the shell. The hinge- 
 area is rudimentary or wanting. The ventral valve is convex, 
 the dorsal concave, following the curve of the former. The 
 surface is ribbed or striated, and the ribs carry a greater or 
 less number of longer or snorter tubular spines, which are 
 especially abundant upon the auricular expansions. The 
 species of Producta range from the Devonian to the Permian, 
 but the genus is essentially and especially characteristic of the 
 Carboniferous period. 
 
 FAM. VIII. CRANIAD^E. Animal fixed to submarine ob- 
 jects by the substance of the ventral valve. Arms fleshy and 
 
 Fig. 16 
 
 nia Ignabergensis, Cretaceous. 
 
 spirally coiled. No hinge or articulating processes ; upper or 
 dorsal valve limpet-shaped (fig. 161). The family includes the
 
 212 MOLLUSCA. 
 
 single genus Crania, which commenced in the Silurian period, 
 and has continued to exist without interruption to the present 
 day. The shell may be smooth, or striated with radiating 
 ribs, sometimes with spines or foliaceous expansions. The 
 ventral valve is the shallowest, and the shell is usually attached 
 by a portion of its substance. The dorsal valve is more or 
 less conical, and the valves are simply kept in apposition by 
 muscular action. 
 
 FAM. IX. DISCINIDJE. Animal attached by means of a 
 muscular peduncle passing through the ventral or lower valve, 
 by means of a slit in its hinder portion or a circular foramen 
 excavated in its substance. Arms fleshy. Valves unarticulated. 
 The Discinida range from the Silurian period to the present 
 day. The three most important genera are Discina, Trematis, 
 and Siphonotreta. 
 
 In Discina (fig. 162) the shell is generally circular or orbicu- 
 lar in shape. The upper valve is limpet-shaped, smooth or 
 
 Fig. 162. Discina Circe, Silurian. Fig. 163. Discina Pelopea, Silurian. 
 
 concentrically striated ; the ventral valve is flat or partly con- 
 vex, perforated by a longitudinal slit, which is placed in the 
 middle of an oval depressed disc. The valves are not articu- 
 lated to one another, but are kept together by muscular action 
 alone. The species of the genus Discina range from the 
 Silurian Rocks to the present day, seven species being now 
 living. 
 
 In the genus Trematis both valves are more or less convex, 
 and the general shape of the shell is more or less oval or sub- 
 orbicular. The ventral valve is furnished 
 with a slit for the passage of a peduncle 
 of attachment. This genus seems to be 
 exclusively Silurian. 
 
 In the genus Siphonotrcta (fig. 164) 
 the shell is oval, inequivalve, with un- 
 articulated valves. The beak of the 
 ventral valve is perforated by a foramen 
 which opens on its back, and communicates with the interior 
 by a cylindrical tube. The surface of the shell is covered with
 
 BRACHIOPODA. 
 
 213 
 
 concentric lines of growth, and furnished with numerous deli- 
 cate tubular spines, which, however, are rarely preserved. All 
 the Siphonotreta at present known belong to the Silurian period. 
 
 FAM. X. LINGULID^E. Animal fixed by a muscular peduncle 
 passing out between the beaks of the valves. Arms fleshy, not 
 supported by calcified processes. Shell unarticulated, sub-equi- 
 valve, of a horny texture. The Lingulidce range, in the person 
 of Lingula itself, from the Cambrian period to the present day. 
 
 In the genus Lingula, (fig. 165) the shell is oblong, com- 
 pressed, the dorsal valve little smaller than the ventral. The 
 
 Fig. 165. Lingula Eva, Lower Silurian. Dorsal and ventral valves. 
 (After Billings.) 
 
 shell is oval, rounded, or satchel-shaped, tapering more or less 
 towards the beaks. The surface is concentrically striated with 
 lines of growth. The genus commences to be represented in 
 the Cambrian Rocks, and has continued without interruption, 
 and with no perceptible change, to the present day. 
 
 In Ob0lus the valves are orbicular, sub-equal, smooth, the 
 ventral valve having a longitudinal furrow for the passage of 
 
 Fig. -L^.Obolella cingulata, Billings. Upper Cambrian. 
 
 fibres of attachment. The valves are unarticulated, and are 
 maintained in apposition by muscular action. All the known 
 species of Obolus are confined to the Silurian period, and are 
 especially characteristic of the Lower Silurian period. The
 
 2 14 MOLLUSCA. 
 
 genus Oboldla (fig. 166) of Mr Billings is only separated from 
 Obolus by certain internal characters. The little shells belong- 
 ing to this genus sometimes occur in myriads in the Potsdam 
 Group (Upper Cambrian) of North America. 
 
 CHAPTER XX. 
 LAMELLIBRANCHIA TA. 
 
 THE Lamellibranchiata or Bivalve Shell-fish are distinguished 
 by the fact that the head is not distinct, and the mouth is destitute 
 of any apparatus of teeth. The body is more or less completely 
 protected in a bivalve shell, composed of two, usually symmetrical, 
 pieces or valves. There are generally two leaf -like lamellar gills 
 upon each side of the body. 
 
 The Lamellibranchs include all the ordinary Bivalve Shell- 
 fish, such as Oysters, Cockles, Mussels, and the like, and they 
 are all either marine or inhabitants of fresh water. 
 
 Though they agree with the Brachiopoda in possessing a 
 shell which is composed of two pieces or valves, there are, 
 nevertheless, many points in which the shell of a Lamelli- 
 branch is distinguishable from that of a Brachiopod, irrespec- 
 tive of the great difference in the structure of the animal in 
 each. The shell in the Brachiopoda, as we have seen, is rarely 
 or never quite equivalve, and always has its two sides equally 
 developed (equilateral) ; whilst the valves are placed antero- 
 posteriorly as regards {he animal, one in front and one behind, 
 so that they are " dorsal " and " ventral." In the Lamellibran- 
 chiata, on the other hand, the two valves are usually of nearly 
 equal size (equivalve), and are more developed on one side 
 than on the other (inequilateral) ; whilst their position as re- 
 gards the animal is always lateral, so that they are properly 
 termed " right " and " left " valves, instead of " ventral " and 
 " dorsal." 
 
 It is to be remembered, however, that many of the Bivalves, 
 such as the Oysters, habitually lie on one side, in which case 
 the valves, though really right and left, are called " upper" and 
 "lower." It is to be borne in mind also that the two valves, 
 especially in the attached Bivalves, may be very unsymmetri- 
 cal, one valve being much larger or deeper than the other. 
 Lastly, there are some cases in which the shell becomes very
 
 LAMELLIBRANCHIATA. 2 1 5 
 
 nearly equilateral, the line drawn from the beaks to the base 
 dividing the shell into two almost equal halves. 
 
 i 
 
 Fig. 167. Left valve of Cytherea chione (after Woodward). A, Anterior margin : 
 B, Posterior margin ; C, Ventral margin or base ; ti Umbo ; h Ligament ; / Lunule ; 
 c Cardinal tooth ; tt Lateral teeth ; a Anterior adductor ; a Posterior adductor; / Pal- 
 lial line ; j Pallial sinus, caused by the retractor muscles of the siphons. 
 
 The following are the chief points to be noticed in connec- 
 tion with the shell of any Lamellibranch : Each valve of the 
 shell may be regarded as essentially a hollow cone, the apex 
 of which is turned more or less to one side ; so that more of 
 the shell is situated on one side of the apex than on the other. 
 The apex of the valve is called the " umbo," or " beak " (fig. 
 167, u], and is always turned towards the mouth of the animal. 
 Consequently the side of the shell towards which the umbones 
 are turned is the " anterior" side, and it is usually the shortest 
 half of the shell. The longer half of the shell, from which the 
 umbones turn away, is called the " posterior" side, but in some 
 cases this is equal to, or even shorter than, the anterior side. 
 The side of the shell where the beaks are situated, and where 
 the valves are united to one another, is called the " dorsal " 
 side ; and the opposite margin, along which the shell opens, is 
 called the " ventral " side, or " base." The length of the shell 
 is measured from its anterior to its posterior margin, and its 
 breadth from the dorsal margin to the base. 
 
 At the dorsal margin the valves are united to one another 
 for a shorter or longer distance, along a line which is called the 
 " hinge-line." The union is effected in most shells by means 
 of a series of parts which interlock with one another (the 
 " teeth "), but these are sometimes absent, when the shell is
 
 2l6 MOLLUSCA. 
 
 said to be " edentulous." Posterior to the umbones, in most 
 bivalves, is another structure passing between the valves, which 
 is called the " ligament," and which is usually composed of two 
 parts, either distinct or combined with one another. These 
 two parts are known as the " external ligament " (or the liga- 
 ment proper), and the "cartilage," and they constitute the 
 agency whereby the shell is opened ; but one or other of them 
 may be absent. The ligament proper is outside the shell, and 
 consists of a band of horny fibres, passing from one valve to 
 the other just behind the beak, in such a manner that it is put 
 upon the stretch when the shell is closed. The cartilage, or 
 internal ligament, is lodged between the hinge-lines of the two 
 valves, generally in one or more " pits," or in special processes 
 of the shell. It consists of elastic fibres placed perpendicularly 
 between the surfaces by which it is contained, so that they are 
 necessarily shortened and compressed when the valves are 
 shut. To open the shell, therefore, it is simply necessary for 
 the animal to relax the muscles which are provided for the 
 closure of the valves, whereupon the elastic force of the liga- 
 ment and cartilage is sufficient of itself to open the shell. 
 
 The hinge-line is mostly curved, but it may be quite straight. 
 Generally the beaks are more or less contiguous, but they may 
 be removed from one another to a greater or less distance, and 
 in some anomalous forms they are not near one another at all. 
 In the Arcada the two beaks are separated from one another 
 by an oval or lozenge-shaped flat space or area. When teeth 
 are present, they differ much in their form and arrangement. 
 In some forms (fig. 167) the teeth are divisible into three sets 
 one group, of one or more teeth, placed immediately beneath 
 the umbo, and known as the " cardinal teeth ; " and two 
 groups on either side of the preceding, termed the " lateral 
 teeth." Sometimes there may be lateral teeth only ; some- 
 times the cardinal teeth alone are present ; and in some cases 
 (Arcadce) there is a row of similar and equal teeth. 
 
 In the interior of the shell of the Bivalves are found certain 
 markings which are often of great importance to the palaeon- 
 tologist. The body is enclosed in an expansion of the dorsal 
 integument, which constitutes the "mantle" or "pallium," 
 whereby the shell is secreted. Towards its circumference the 
 mantle is more or less completely united to the shell, leaving 
 in its interior, when the soft parts are removed, a more or less 
 distinctly impressed line, which is called the " pallial line " or 
 " pallial impression " (fig. 168, a). In some of the Bivalves the 
 two halves or " lobes " of the mantle are united at their mar- 
 gins, so that the animal is enveloped in an almost closed sac.
 
 LAMELLIBRANCHIATA. 2 1/ 
 
 In these cases it is necessary that there should be orifices in 
 the mantle-sac by which water can be admitted to the gills, and 
 can be expelled again from the body. The margins or lips of 
 these orifices are usually drawn out or extended into longer or 
 shorter muscular tubes, which are termed the " siphons," and 
 which may be either separate, or may be united to one another 
 along one side. The Bivalves which possess these siphons 
 are said to be " siphonate," and there are two leading modi- 
 fications in the arrangement of these tubes. In the Siphonate 
 Bivalves which spend their existence buried in sand or mud, 
 as well as in many other cases, the siphons are long, and can 
 be partially or entirely retracted within the shell by means of 
 special muscles, called the " retractor-muscles of the siphons." 
 In these cases, the pallial line does not run in an unbroken 
 curve, but is deflected inwards posteriorly, so as to form an 
 indentation or bay, which is termed the " pallial sinus " (fig. 
 168, 2). The presence, therefore, of an indented pallial line 
 shows that the animal possessed retractile siphons. In other 
 
 Fig. 168. Shells of Lamellibranchiata. i. Cyclas antnica, a dimyary shell with an 
 entire pallial line. 2. Tapes pullastra, a dimyary shell with an indented pallial line. 
 3. Perna epkippinm, a monomyary shell. (After Woodward.) a Pallial line; b 
 Muscular impressions left by the adductors ; c Siphonal impression. 
 
 Bivalves the respiratory siphons are of small size, and are des- 
 titute of retractor muscles, so that they cannot be withdrawn 
 within the shell. In these cases the " pallial line," or the im- 
 pression caused by the attachment of the muscular border of 
 the mantle, is unbroken in its curvature, and presents no 
 indentation (fig. 168, i). In another group of the Bivalves 
 there are no respiratory siphons at all, and the mantle-lobes 
 are free, and are not united to one another at their edges. In 
 these cases also, the pallial line is unbroken or " simple." 
 When, therefore, we find a Bivalve shell in which the pallial 
 line is not indented by a sinus, we know that the animal which 
 inhabited the shell either possessed no siphons, or that if siphons 
 were present, they were small and not retractile.
 
 2l8 MOLLUSCA. 
 
 In accordance with these considerations, the Lamellibranchi- 
 ata are divided into two sections, according as respiratory 
 siphons are present or absent, and according to their nature 
 when they exist. 
 
 SECTION A. ASIPHONIDA. Animal without respiratory si- 
 phons ; mantle-lobes free ; the pallial line simple and not in- 
 dented (Integro-pallialia). 
 
 This section comprises the families Ostreidcs, Aviculida, My- 
 tilidce, Arcada, Trigoniada, and Unionidce. 
 
 SECTION B. SIPHONIDA. Animal with respiratory siphons ; 
 mantle-lobes more or less united. 
 
 Two subdivisions are comprised in this section. In the 
 first the siphons are short, and the pallial line is simple (Integro- 
 pallialia} ; as is seen in the families Chamida, Hippuritida, 
 Tridacnida, Cardiadce, Lucinida, Cycladida, and Cyprinidcz. 
 
 The second subdivision (Sinu-pallialia) is distinguished 
 by the possession of long respiratory siphons, and a sinnated 
 pallial line, and it comprises the families Venerida, Mactridce, 
 TellinidcK, Solenida, Myacida, Anatinida, Gastrochanidce, and 
 Pholadidce. 
 
 Besides the impressions left by the muscular border of the 
 mantle, and by the retractor muscles of the siphons, when 
 these are present, there are other impressions caused by the 
 insertion into the shell of the muscles by which the valves are 
 brought together the " adductor muscles." The number of 
 adductor muscles never exceeds two, but there may be only 
 one ; and in accordance with this distinction the Bivalves have 
 been divided into the two groups of the Dimyaria and Mono- 
 myaria. These divisions, however, are of small actual value. 
 In most Bivalves there are two adductor muscles passing be- 
 tween the inner surfaces of the valves, one being placed 
 anteriorly, in front of the mouth, whilst the other is situated 
 posteriorly, in the neighbourhood of the vent. In the Mono- 
 myary Bivalves it is the posterior adductor which remains, 
 and the anterior adductor is absent. The adductors leave 
 distinct " muscular impressions," or scars, in the interior of the 
 shell, so that it is easy in any given specimen to determine 
 where there was only one adductor, or whether two were pre- 
 sent (see fig. 1 68). 
 
 The habits of the Lamellibranchiata are very various. Some, 
 such as the Oyster ( Ostred), and the Scallop (Pecteii), habit- 
 ually lie on one side, the lower valve being the deepest, and 
 the foot being wanting, or rudimentary. Others, such as the 
 Mussel (Mytilus), and the Pinna, are attached to some foreign 
 object by an apparatus of threads, which is called the " byssus,"
 
 LAMELLIBRANCHIATA. 2 1 9 
 
 and is secreted by a special gland. Others are fixed to some 
 solid body by the substance of one of the valves. Many, such 
 as the Myas, spend their existence sunk in the sand of the sea- 
 shore or in the mud of estuaries. Others, as the PJwlades 
 and Lithodomi, bore holes in rock or wood, in which they live. 
 Finally, many are permanently free and locomotive. 
 
 As regards the general distribution in time of the Lamelli- 
 branchiata, the class seems to have commenced in the Lower 
 Silurian Rocks, and to have steadily increased up to the pre- 
 sent day, when it seems to have attained its maximum, both 
 as regards numbers and as regards variety of type. The recent 
 Bivalves are also superior in organisation to those which have 
 preceded them. In the Palaeozoic and earlier Secondary de- 
 posits the Bivalves belong mainly to the group of the Asiph- 
 onida, in which there are no respiratory siphons. In the later 
 Secondary and Tertiary Rocks, on the other hand, there is a 
 predominance of Siphonate Bivalves, in which the mantle-lobes 
 are united and there are respiratory siphons. Upon the whole, 
 the Lamellibranchiata are sparingly represented in the Lower 
 Silurian, more abundant in the Upper Silurian, reduced in 
 numbers in the Devonian, very plentiful in the Carboniferous, 
 scanty in the Permian and Trias, profusely represented in the 
 Jurassic Rocks, and very abundant in the Cretaceous and Ter- 
 tiary periods (Lobley). In the Carboniferous Rocks the family 
 of the Aviculidcz is especially abundant. One very singular 
 and aberrant family viz., the Hippuritida is exclusively con- 
 fined to the Secondary period, and is not known to occur out 
 of the limits of the Cretaceous formation. The Veneridce, 
 which are perhaps the most highly organised of the Lamelli- 
 branchiata, appear for the first time in the Oolitic Rocks, and, 
 increasing in the Tertiary period, have culminated in the 
 Recent period. The remains of Lamellibranchiata are very 
 abundant in many formations, and are of great palaeontological 
 importance. It will therefore be well to review the families* 
 of the class briefly, giving the leading characters, more impor- 
 tant genera, and geological distribution of each. 
 
 SECTION A. ASIPHONIDA. 
 
 FAM. i. OSTREID^:. Shell inequivalve, slightly inequilateral, 
 free or attached ; hinge usually edentulous. Ligament internal. 
 
 * In the following synoptical view of the Lamellibranchiata, the classi- 
 fication adopted in Woodward's admirable Manual of the Mollusca has 
 been mainly followed.
 
 220 
 
 MOLLUSCA. 
 
 Lobes of the mantle entirely separated ; the foot small and 
 byssiferous, or wanting. A single adductor muscle. 
 
 In the typical Oysters, forming the genus Ostrea (figs. 169, 
 
 Couloni, Lower Greensand. ' 
 
 170), the shell is irregular, and is attached by the left valve, 
 which is also convex, and has a well-marked beak. The upper 
 valve is generally flat or concave, and is the smallest of the 
 
 Fig. 170. Ostrea aquila, Lower Greensand. 
 
 two valves. The hinge is toothless. Both valves may be 
 more or less completely plain, and the upper one especially 
 often is so. The lower valve, however, is commonly plaited, 
 and both valves are sometimes thus ornamented, as in Ostrea 
 Marshii of the Oolites (fig. 171). 
 
 In the sub-genus Gryphaa are included Oysters which were 
 either quite free or very slightly attached. The left or lower 
 valve (fig. 172) is much the largest, and has a very pronounced 
 incurved beak, whilst the right valve is small and concave. In 
 the sub-genus Exogyra, again, the beaks are " reversed" that 
 is to say, turned towards the posterior side of the shell. True 
 Oysters commence to be represented in the Carboniferous
 
 LAMELLIBRANCHIATA. 
 
 221 
 
 seas, abound in the Secondary and Tertiary periods, and are 
 very plentiful at the present day. The sub-genera Gryphaa 
 and Exogyra are exclusively Mesozoic, the former abounding 
 
 Fig. I7i. Ostrea Marshii, Oxford 
 Clay (Middle Oolites). 
 
 ryptuea incurva, Lias. 
 
 especially in the lower portion of the Oolitic series, whilst the 
 latter is chiefly characteristic of the later Oolitic and Cretace- 
 ous deposits. 
 
 In the AnomicR the shell is thin and translucent, and is fixed 
 to some solid body by a plug which passes through a hole or 
 
 Fig. 173. Pecten Islandicus, left valve. Post-Tertiary and Recent 
 
 notch in the right valve. The typical fossil species are dis- 
 tributed from the Oolites upwards. The Oolitic genus Placu- 
 nopsis is also related to Anomia. 
 
 The genus Pecten includes the Scallops (fig. 173), in which
 
 222 MOLLUSCA. 
 
 the shell rests upon the right valve, and the beaks are furnished 
 with ears. The anterior ears are usually the largest and most 
 prominent, and the shell is generally furnished with ribs radiat- 
 ing from the umbos. The right valve is the deepest, and is 
 notched below the anterior ear. Counting in its sub-genera, 
 nearly five hundred species of the genus Pecten are known in 
 the fossil state, commencing in the Devonian Rocks, and ex- 
 tending to the present day. The Palaeozoic Pectens are dis- 
 tinguished from their successors in more modern rocks by 
 having the posterior ears larger than the anterior; and they 
 are therefore placed by M'Coy in a new genus, under the 
 name of Aviculopecten. They are, however, usually regarded as 
 belonging to the Aviculida. 
 
 In the genus Lima (or Plagiostoma) the shell is equivalve and 
 free, whilst the beaks are separated from one another and are 
 eared. The genus is represented by numerous species in the 
 rocks of the Secondary period, and has survived to the present 
 day. 
 
 In Spondylus (fig. 174) the shell is inequivalve, and is fixed by 
 the right valve to some foreign body. The beaks are apart and 
 
 Fig. ^^.Spoiidylus spinosus, Chalk. 
 
 eared, and the shell is covered with spines, foliaceous expan- 
 sions, or ribs radiating from the beak. The lower valve has a 
 triangular hinge-area, and there are two teeth in each valve. 
 The Spondyli seem to have commenced in the Cretaceous 
 period, in which they are very abundant, and they have con- 
 tinued through the Tertiary period to the present day. 
 
 Lastly, the Plicatula (fig. 175) approach the Spondyli nearly, 
 by having an inequivalve shell, which is attached by the right 
 valve, and by having two hinge-teeth in each valve. The shell, 
 however, is rarely eared, the hinge-area is obscure, and the 
 valves are not spiny, though they may be plaited. The Plica- 
 tula extend from the Trias to the present day, and they abound 
 to such an extent in parts of the Lower Greensand (Cretaceous),
 
 LAMELLIBRANCHIATA. 
 
 223 
 
 as to have given rise to the name of " Argile a Plicatules " ap- 
 plied to the beds in question. 
 
 Fig. 175. Plicatula placunea, Lower Greensand. 
 
 FAM. 2. AVICULID^E. Shell inequivalve, very oblique, at- 
 tached by a byssus ; hinge nearly or quite edentulous. Mantle- 
 lobes free; anterior adductor small, leaving its impression 
 within the umbo; posterior adductor large and sub-central. 
 Foot small. 
 
 Leaving out of consideration the genus Aviculopecten, which 
 holds a dubious position, and has been already spoken of, the 
 chief fossil genera of the Aviculidce are Avicula, Posidonomya, 
 
 Fig. 176. A vicula demissa, 
 Lower Silurian. 
 
 Fig. 177. A mbonychia. radiata, 
 Lower Silurian. 
 
 Gervillia, Perna, Inoceramus, and Pinna. In the genus Avicula 
 (fig. 176) the shell is oblique and very inequivalve. The right
 
 224 MOLLUSCA. 
 
 valve has a notch under the anterior ear; and the hinge has 
 one or two cardinal teeth, sometimes with an elongated pos- 
 terior tooth. The true Aviculcs are represented by very numer- 
 ous fossil species, extending from the Lower Silurian Rocks to 
 the present day. Of the sub-genera of Avicula, the three most 
 important fossil forms are Ambonychia, Pteritiea, and Cardiola, 
 the place of the last in this family being somewhat doubtful. 
 In the Ambonychia (fig. 177) the valves are gibbous, nearly 
 equal, and the anterior ear is almost obsolete. They extend 
 from the Lower Silurian to the Carboniferous. The Pterineas 
 (fig. 178) are very abundant in the Silurian Rocks, especially 
 in the upper division of the series, and they extend to the Car- 
 
 Fig. 178. A, Pterineasub-falcata; B, Cardiola interrupta; C, Cardiolafibrosa. 
 (After M'Coy and Salter.) Silurian. 
 
 boniferous Rocks. They have a shell with large ears and very 
 oblique, the hinge-area being long and straight. The Cardiolce 
 have an oblique, equivalve shell (fig. 178, B), radiately ribbed, 
 with prominent beaks and a short hinge-area. They are mainly 
 characteristic of the Upper Silurian Rocks, but they have been 
 stated to occur in the Lower Silurian, and they are found in 
 the Devonian. 
 
 The shells of the genus Posidonomya are very thin, con- 
 centrically striated, equivalve and earless. They extend from 
 the Silurian to the Trias, but are especially characteristic of 
 the Carboniferous Rocks. Many of the smaller shells referred 
 to Posidonomya are undoubtedly referable to the Crustacean 
 genus Estheria, 
 
 The genus Gcn>illia comprises a number of fossil shells, 
 which range from the Carboniferous Rocks to the Chalk, and 
 which are very like the true Avicula. The shell is elongated, 
 the anterior ear small, and the posterior ear broad and wing- 
 like. Nearly allied to Gervillia is the genus Perna, which 
 commenced in the Trias, and is represented in recent seas. 
 
 Nearly related to both Gervillia and Perna is the genus 
 Inoceramus (figs. 179, 180), which is entirely confined to the 
 Secondary period, and is mainly characteristic of the Creta-
 
 LAMELLIBRANCHIATA. 
 
 225 
 
 ceous series. The shells of this genus are inequivalve, with 
 radiating ribs or concentric furrows, and with prominent 
 beaks. The hinge-line is long and straight, with numerous 
 
 Fig. \ig.Inoceramus sukatus. Gault (Cretaceous). 
 
 Fig. 180. Inoceramus probl 
 
 caitilage-pits. Some of the Inocerami attain a length of two 
 or three feet, and fragments of them are often found perfor- 
 ated by boring sponges. 
 
 The last genus of the Aviculida is Pinna, in which the shell 
 is equivalve and wedge-shaped, and the beaks are placed 
 quite on the anterior side of the shell. The Pinnce seem to 
 have commenced in the Devonian, but their existence prior 
 to the Carboniferous period is a matter of some uncertainty. 
 Many species are known in the Secondary and Tertiary 
 Rocks, and the genus is well represented by living forms. 
 The sub-genus Trichites is exclusively Oolitic, and the shells 
 referred here sometimes attained an enormous size. 
 
 FAM. 3. MYTILID^E. Shell equivalve ; umbones anterior; 
 hinge edentulous ; anterior muscular impression small, pos- 
 terior large. Shell attached by a byssus. Mantle-lobes united 
 between the siphonal apertures. Foot cylindrical, grooved, and 
 byssiferous. The chief fossil genera of the Mytilidtz are 
 MytihtS) Modiola, Lithodomus, Modiolopsis, and Orthonota. 
 
 In the genus Mytilus are the true Mussels, in which the 
 shell is wedge-shaped, and the beaks terminal. Numerous 
 fossil forms are known, commencing in the Permian. The 
 Modiolce, or " Horse-mussels," have the beaks anterior, blunt, 
 not pointed, the hinge edentulous, and the shell oblong,
 
 226 
 
 MOLLUSCA. 
 
 More than one hundred fossil species have been described, 
 commencing in the Lias, and extending to the present day. 
 The Palaeozoic Modiola are probably referable to different gen- 
 era. The Date-shells (Lithodonms) form a sub-genus QiModiola, 
 and are distinguished by their habit of forming perforations 
 in rocks, in which they live. They appear to date from the 
 Lower Oolitic Rocks, and are known to palaeontologists by 
 both their shells and their burrows. 
 
 The genus Modiolopsis (fig. 181), includes a number of 
 Silurian shells, the true place of which is somewhat uncertain. 
 
 Fig. 181. Modiolopsis modioU 
 
 Lower Silurian. 
 
 -^ ^ 
 
 The shell is equivalve, very inequilateral, the beaks anterior, 
 and the surface smooth, or marked by fine concentric lines of 
 growth. The shell is thin, and its posterior end is consider- 
 ably broader than the anterior. 
 
 The genus Orthonota likewise comprises a number of Silu- 
 rian Bivalves, and is also in a somewhat doubtful position. 
 The shell (fig. 182) is elongated, 
 equivalve, very inequilateral, 
 having the beaks placed close 
 to its anterior end. The shell 
 is thin, and its margins are 
 parallel. 
 
 FAM. 4. ARCADE. Shell 
 equivalve ; hinge long, with 
 many comb-like teeth ; muscu- 
 lar impressions nearly equal ; 
 mantle -lobes separated; foot 
 large, bent, and deeply grooved. The most important fossil 
 genera of this family are Area, Cucu/faa, Pectunculus, Nucula, 
 Ctenodonta, Cyrtodonta, and Ltda. 
 
 The Arks (Area] have a straight hinge-line, with remote 
 beaks, separated from one another by an oval or lozenge- 
 
 Fig. i&2.Vrt/ioHota parallel*. 
 Lower Silurian.
 
 LAMELLIBRANCHIATA. 
 
 227 
 
 shaped ligamental area (fig. 183). The teeth are numerous 
 
 and transverse, and the surface is generally strongly ribbed. 
 
 Species of Area have been 
 
 described from the Lower 
 
 Silurian Rocks upwards. It 
 
 is probable, however, that 
 
 the older Palaeozoic forms 
 
 referred here really belong 
 
 to other genera, especially 
 
 Ctenodonta and Cyrtodonta. 
 
 In Cucullcea the shell is 
 ventricose, and the hinge- 
 teeth are few and oblique, 
 and at each end of the hinge 
 become parallel with the 
 hinge-line. Species of this genus have been described from 
 the Lower Silurian upwards. 
 
 The Pectunculi have a nearly round and equilateral shell, the 
 beaks separated by a striated ligamental area, the hinge-line 
 curved, and the hinge-teeth forming a semicircular row. Pect- 
 wiculus is a comparatively modern genus, and does not seem 
 to have come into existence before the Cretaceous period. 
 Numerous species are known in the Tertiary Rocks. 
 
 The NucultK (fig. 184) have a trigonal shell, the beaks of 
 which are reversed, and turned towards the posterior side of 
 the shell, which is also the shortest side. The hinge has 
 
 Fig. 183. Area antiqua. 
 
 Fig. IBS. Ctenodonta contracta. 
 Lower Silurian, a Interior of right 
 Fig. 184. unciila bimrgata. Gault. valve; b Exterior of the same. 
 
 numerous teeth on each side of a central internal cartilage-pit. 
 The Palaeozoic shells referred to Nucula probably belong to 
 other genera. Many species, however, are known from the 
 Secondary and Tertiary Rocks. 
 
 The genera Ctenodonta and Cucullella are both nearly re- 
 lated to one another and to Nucula, and both are exclusively 
 Palasozoic, and are mainly, if not entirely, Silurian. The 
 Ctenodonta (fig. 185) are extremely like Nucula, but are dis-
 
 228 
 
 MOLLUSCA. 
 
 tinguished by having an external ligament. The posterior side 
 of the shell is generally the shortest, but the reverse is some- 
 times the case. 
 
 The shells of the genus Cyrtodonta (Palaarca of Hall) are 
 very inequilateral, the umbones being anterior (fig. 186). The 
 
 Fig. 186. Cyrtodonta Hindi (Billings). Lower Silurian, a Dorsal view ; b Side view. 
 
 hinge-area is undefined, and the surface generally smooth. 
 There are a few (three) anterior cardinal teeth, and " two or 
 three remote oblique posterior teeth parallel to the hinge- 
 margin " (Salter). The species of Cyrtodonta appear to be 
 exclusively confined to the Silurian and Devonian Rocks. 
 
 In the genus Leda the shell resembles that of Nucitla, especi- 
 ally in having numerous teeth on either side of a central 
 cartilage-pit. The shell, however, is oblong, rounded in front, 
 and pointed behind. The occurrence of Leda in the Palaeozoic 
 period is dubious ; but numerous species are known from the 
 Secondary and Tertiary Rocks. 
 
 FAM. 5. TRIGONIAD^. Shell equivalve, trigonal ; hinge-teeth 
 few, diverging ; umbones directed posteriorly. Mantle open ; 
 foot long and bent. The most important genera of this family 
 are Trigonia, Myophoria, and Axinus.
 
 LAMELLIBRANCHIATA. 
 
 22 9 
 
 In Trigonia (fig. 187) the shell is trigonal, with tubercles, 
 radiating ribs, or concentric ridges. The hinge-teeth are 
 two in one valve and three in the other. The Trigonice are 
 
 Fig. 187. Trigonia scabra. Chalk. 
 
 essentially Mesozoic, being only known, in the fossil con- 
 dition, as extending from the Trias to the Chalk. They are 
 not known with certainty to be represented in the Tertiary 
 Rocks at all; but the Australian seas have yielded some 
 living forms. 
 
 The shells of the genus Myophoria have the umbones direct- 
 ed anteriorly, and are in most respects closely similar to Tri- 
 gonia, They belong exclusively to the Triassic period. 
 
 The genus Axinus (Schizodtis) is also nearly related to Tri- 
 gonia, but the shell is thinner, and is smooth, and the posterior 
 side is not so distinctly angular, but is marked by an oblique 
 ridge. The shells of this genus extend from the Upper 
 Silurian to the Trias, but are especially characteristic of the 
 Permian Rocks. 
 
 FAM. 6. UNIONID.E. Shell usually equivalve, with a large 
 external ligament. Anterior hinge-teeth thick and striated ; 
 posterior laminar or want- 
 ing. Mantle-lobes united 
 between the siphonal ap- 
 ertures. Foot very large, 
 compressed, byssiferous in 
 the fry. All the members 
 of the Unionida are in- 
 habitants of fresh water, 
 and they are, therefore, not 
 known as fossils except in 
 fluviatile and lacustrine de- 
 posits. The only two fossil 
 genera of the family are 
 Unio and Anodon. Fig " l88 " WeaWe 
 
 In the genus Unio (fig. 
 1 88) the shell is oval or elongated, somewhat resembling that 
 of a mussel (hence the name of River-mussels commonly
 
 230 MOLLUSCA. 
 
 given to the Unios). The species of this genus appear to 
 commence in the Lower Cretaceous Rocks, and they are 
 very abundant at the present day. The beaks of fossil speci- 
 mens are often deeply eroded, as are those of living forms. 
 
 The Anodons or Swan-mussels closely resemble the Unios, 
 but the shell is edentulous. The earliest fossil forms occur in 
 the Lower Tertiaries (Eocene). 
 
 SECTION B. SIPHONIDA. 
 
 Sub-division I. Integropallialia. Siphons short, pallial line 
 simple. 
 
 FAM. 7. CHAMIDJE. Shell inequivalve, attached. Hinge- 
 teeth 2-1 (two in one valve and one in the other). Impres- 
 sions of the adductors large. Mantle closed ; pedal and 
 siphonal orifices small and nearly equal. Foot very small. 
 The most important fossil forms of this family belong to the 
 genera C/iatna, Diceras, an.d Requieiiia. 
 
 In the genus Chama the shell is attached usually by the 
 beak of the left valve, but sometimes by that of the right The 
 upper valve is the smallest, and both bear foliaceous expan- 
 sions. The free valve carries one tooth which articulates with 
 two teeth in the attached valve. The Chamas do not appear 
 as fossils till we reach the Cretaceous Rocks, and they have 
 continued to exist up to the present day. 
 
 In the remarkable genus Diceras (fig. 189), the shell is 
 "sub-equivalve, attached by 
 either umbo; beaks very promi- 
 nent, spiral, furrowed externally 
 by ligamental grooves ; hinge 
 very thick, teeth 2-1, promi- 
 nent ; muscular impressions 
 bounded by long spiral ridges, 
 sometimes obsolete " (Wood- 
 ward). The species of Diceras 
 are exclusively confined to the 
 Middle Oolites. In this for- 
 mation in the Alps they occur 
 ^ such abundance as to give 
 rise to the name of " Calcaire 
 
 a Dicerates," applied to beds of the same age as the Coral 
 Rag of Britain. 
 
 The genus Requienia is exclusively confined to the Cre- 
 taceous period, and differs from Diceras chiefly in having a
 
 LAMELLIBRANCH1ATA. 
 
 231 
 
 very inequivalve shell, always attached by its left valve. The 
 attached valve is the largest, and is spiral, whilst the free valve 
 is small and sub-spiral. 
 
 FAM. 8. HIPPURITID^E (Rudistes of Lamarck). "Shell in- 
 equivalve, unsymmetrical, thick, attached by the right umbo ; 
 umbones frequently camerated ; structure and sculpturing of 
 the valves dissimilar ; ligament internal ; hinge-teeth 1-2 ; 
 adductor impressions two, large, those of the left valve on 
 prominent apophyses ; pallial line simple, sub-marginal." 
 (Woodward). 
 
 The Hippuritidcz are not only entirely extinct, but are ex- 
 clusively confined to the Cretaceous Rocks, whence more than 
 one hundred species have been described. All the members 
 of this family were attached, and lived in beds like oysters. 
 The two valves of the shell are always altogether unlike in 
 sculpturing, appearance, shape, and size ; and the cast of the 
 interior of the shell is often extremely different to the form of 
 the shell itself. About a hundred 
 species of the family are known, 
 all of which are Cretaceous, oc- 
 curring in Britain, Southern 
 Europe, the West Indies, North 
 America, Algeria, and Egypt. 
 Species of this family occur in 
 such numbers in certain compact 
 marbles in the south of Europe, 
 of the age of the Lower Chalk, 
 as to have given origin to the 
 name of " Hippurite Limestones " 
 applied to these strata. 
 
 The Hippiiritid<z have been 
 especially studied by Dr S. P. 
 Woodward, who makes the fol- 
 lowing remarks upon their struc- 
 ture and affinities : " They are 
 the most problematical of all fos- 
 sils ; there are no recent shells 
 which can be supposed to Belong 
 to the same family ; and the con- 
 dition in which they usually occur Fig . ^._H ippurites Totlcasiana . 
 
 has involved them in greater Ob- A lar S e individual, with two smaller 
 
 scurity. The characters which nes attached to * 
 
 determine their position amongst the ordinary Bivalves are 
 
 the following : 
 
 " i. The shell is composed of two distinct layers.
 
 232 MOLLUSCA. 
 
 " 2. They are essentially unsymmetrical and right-and-left 
 valved. 
 
 " 3. The sculpturing of the valves is dissimilar. 
 
 " 4. There is evidence of a large internal ligament. 
 
 " 5. The hinge-teeth are developed from the free valve. 
 
 " 6. The muscular impressions are two only. 
 
 " 7. There is a distinct pallial line. 
 
 " The outer layer of shell in the Hippurite and Radiolite 
 consists of prismatic cellular structure ; the prisms are perpen- 
 dicular to the shell-laminae, and subdivided often minutely. 
 The cells appear to have been empty, like those of Ostrea. 
 The inner layer which forms the hinge and lines the umbones, 
 
 is sub-nacreous, and very rarely preserved The 
 
 inner shell-layer is seldom compact, its laminae are extremely 
 thin, and separated by intervals like the water-chambers of 
 
 Spondylus The chief peculiarity of the Hippuri- 
 
 tidce is the dissimilarity in the structure of the valves, but even 
 this is deprived of much significance by its inconstancy. The 
 free valve of Hippurites is perforated by radiating canals, 
 which open round its inner margin, and communicate with the 
 upper surface by numerous pores, as if to supply the interior 
 
 with filtered water In the closely allied genus 
 
 Radiolites there is no trace of such canals, nor in Caprotina" 
 
 The shell of Hippurites (fig. 190) is inversely conical or 
 cylindrical, and sometimes attains a length of a foot or more. 
 
 Fig. lai.Cafrina Agnilloni. The right-hand figure shows the interior of 
 the left valve. 
 
 The shell is attached by the larger conical valve, and is closed 
 by a small depressed free valve, with a central umbo. In
 
 LAMELLIBRANCHIATA. 233 
 
 Radiolites the shell is inversely conical, bi-conical, or cylin- 
 drical, with dissimilar valves. The upper valve is sometimes 
 flat, sometimes conical, and has a central umbo. In Caprina 
 (fig. 191) the valves of the shell are dissimilar, the fixed valve 
 being conical, whilst the free valve is oblique, or is spirally 
 rolled. The free valve is thick, and is " perforated by one or 
 more rows of flattened canals, radiating from the umbo, and 
 opening all round the margin" (Woodward). The cavity of 
 the free valve is sometimes chambered. 
 
 FAM. 9. TRIDACNIDJE. Shell equivalve ; ligament external ; 
 muscular impressions blended, sub-central. Animal attached 
 by a byssus, or free. Mantle-lobes extensively united ; pedal . 
 aperture large; siphonal orifices surrounded by a thickened 
 pallia! border. Foot finger-like and byssiferous. The shell is 
 truncated in front, the surface ribbed, and the margins toothed. 
 The family contains the single genus Tridacna, which is not 
 known to have come into existence before the period of the 
 Miocene Tertiary. 
 
 FAM. 10. CARDIAD^:. Shell equivalve, heart-shaped, with 
 radiating ribs ; cardinal teeth 2 ; lateral teeth i-i in each 
 valve. Mantle open in front ; siphons usually very short ; foot 
 large and sickle-shaped. The only two genera of this family 
 are Cardium and Conocardium, 
 
 In Cardium are comprised the true Cockles, in which the 
 shell is ventricose, the beaks pronounced, and placed nearly in 
 the centre of the dorsal margin (fig. 192), the margins crenated, 
 
 Fig. 192. Cardium Hillanum. Upper Greeusand. 
 
 and the pallial line more or less indented. It is doubtful it 
 any true Cardium has been detected in the Silurian Rocks. 
 With the Devonian, however, the genus begins to be well re- 
 presented, and it has continued up to the present day, attaining 
 its maximum in existing seas. The species figured above is 
 separated from the true Cockles by having the posterior slope 
 of the shell radiately striated, whilst the sides are concentri- 
 cally furrowed.
 
 234 MOLLUSCA. 
 
 The genus Conocardium comprises a number of Palaeozoic 
 shells, in which the anterior side is conical and gaping ; whilst 
 the posterior margin is truncated, and there is a longer or 
 shorter siphonal tube placed near the beaks. 
 
 FAM. ii. LUCINID^E. Shell orbicular, free ; cardinal teeth i 
 or 2; lateral teeth i-i, or obsolete. Mantle -lobes open 
 below, with one or two siphonal orifices behind; foot elon- 
 gated, cylindrical, or strap-shaped. The most important fossil 
 genera of the Lucinida are Lutina and Corbis. Nearly two 
 hundred species of the former have been described, commenc- 
 ing with the Devonian ; and about eighty species of the former 
 are known, commencing with the Lias. 
 
 FAM. 12. CYCLADID*:. Shell sub-orbicular, closed; hinge 
 with cardinal and lateral teeth; ligament external. Mantle 
 open in front ; a single siphon, or two more or less united. 
 Foot large, tongue-shaped. The genera Cydas and Cyrena 
 compose this family, and both are inhabitants of fresh water ; 
 though the latter not uncommonly frequents brackish water, 
 and one species of the former has been described as marine. 
 
 In the Cydades the shell is thin, and there are two hinge- 
 teeth in one valve and one in 
 
 ^fe\ df^~<\ the otnen In Cydas itself 
 
 / /jji \\ the shell is nearly equilateral, 
 
 {. /fU \ but in the sub-genus Pisi- 
 
 mm /dfig | dium, it is inequilateral, with 
 
 I ^&^ : \3w J-J the anterior side the longest 
 
 ^^^D[^/ In Cyrena (fig. 193) the shell 
 
 Fig. ^.-Cyrena antigua. tocene. js thick, and there are three 
 
 hinge -teeth in each valve. 
 
 Both Cydas and Cyrena seem to have come into existence at 
 the commencement of the Cretaceous period (Wealden), and 
 they are abundantly distributed through the Tertiary Rocks. 
 
 FAM. 13. CYPRINID^E. Shell equivalve, closed; ligament 
 external ; cardinal teeth 1-3 in each valve, and usually a 
 posterior tooth. Mantle-lobes united behind by a curtain 
 pierced with two siphonal orifices. Foot thick and tongue- 
 shaped. Of the genera of the Cyprinidte, the more important 
 fossil forms belong to Cyprina, Astarte, Crassatella, Isocardia, 
 Cardita, and the extinct Megalodon, Anthracosia, Hippopodium, 
 and Pachyrisma. Taken as a whole, the Cyprinidte have passed 
 their acme, and have begun to decline in numbers and im- 
 portance. 
 
 Cyprina has a large, strong, oval shell, covered with a thick 
 epidermis. Numerous fossil species are known, commencing 
 in the Trias.
 
 LAMELLIBRANCHIATA. 
 
 235 
 
 Astarte includes thick, generally concentrically - furrowed 
 shells. Two hundred fossil species are known, commencing 
 in the Lias. 
 
 Crassaiella (fig. 194) comprises thick, solid, ventricose 
 shells, attenuated posteriorly, and generally having a concen- 
 
 Fig. 194. Crassatella ponderosa. Eocene Tertiary. 
 
 trically-furrowed surface. Unlike the two preceding genera, 
 Crassatella has the ligament internal. The genus commences 
 in the Cretaceous Rocks, is abundant in the Tertiaries, and is 
 well represented at the present day. 
 
 In the Heart-cockles (Isocardia) the beaks are remote and 
 sub-spiral, and the shell is heart-shaped. The Isocardia do 
 not appear to have existed in the Palaeozoic period, but com- 
 mence in the Trias, are tolerably abundant in the Oolites and 
 Cretaceous Rocks, decline in numbers in the Tertiaries, and 
 are represented by a few forms in existing seas. 
 
 Cardita (fig. 195) includes Cockle-shaped shells, which 
 have radiating ribs, an external ligament, and a toothed 
 
 rdita planicosta. Eocene Tertiary. 
 
 margin. The genus commences in the Trias, but attains its 
 maximum in the Tertiary period, about a hundred species 
 having been enumerated from rocks of this age.
 
 236 MOLLUSCA. 
 
 Allied to Cardita is the extinct genus Hippopodium, well 
 known by the thick and solid H. ponderosum of the Lias. 
 
 Pachyrisma is another extinct genus, in which the shell is 
 also very thick and ponderous in its structure. It has large 
 sub-spiral umbones, and is peculiar to the Great Oolite. 
 
 Megalodon is likewise extinct, and includes massive shells, 
 with sub-spiral beaks and an external ligament. The genus 
 is doubtfully represented in the Silurian and Carboniferous 
 Rocks, and is characteristically Devonian. 
 
 Lastly may be mentioned the shells which are known as 
 Anthracosia, which abound in parts of the Carboniferous 
 series. These are nearly allied to the extinct genus Cardinia, 
 if they do not actually belong to it. They are exclusively 
 Palaeozoic, and extend from the Upper Silurian to the 
 Carboniferous ; whereas Cardinia is very doubtfully repre- 
 sented in rocks older than the Lias. 
 
 Sub-division II. Sinupallialia. Respiratory siphons large; 
 pallial line indented. 
 
 FAM. 14. VENERID^E. Shell regular, sub-orbicular or oblong; 
 ligament external ; hinge with usually three diverging teeth in 
 each valve. Animal usually free and locomotive ; mantle with 
 a rather large anterior opening ; siphons unequal, more or less 
 united. Foot tongue-shaped, compressed, sometimes grooved 
 and byssiferous. The Vaieridce are the most highly organised 
 of the Bivalves, and comprise some of the most beautiful 
 examples of the class. They commence in the Oolitic Rocks, 
 are abundant in the Tertiaries, and have attained their maxi- 
 mum at the present day. All the more important fossil forms 
 belong to the nearly-allied genera Venus and Cytherca. Both 
 of these commenced their existence in the Oolites, the former 
 being represented by about one hundred and fifty, the latter 
 by nearly a hundred extinct forms. 
 
 FAM. 15. MACTRID^E. Shell equivalve, trigonal; hinge with 
 two diverging cardinal teeth, and usually with anterior and pos- 
 terior lateral teeth. Mantle more or less open in front ; siphons 
 united, with fringed orifices ; foot compressed. The only two 
 genera of any importance as fossils are Mactra and Littraria, 
 both of which live buried in sand or mud. The Mactra have 
 a nearly equilateral shell, with a short pallial sinus, and an 
 internal ligament contained in a triangular pit. They appear to 
 have commenced in the Lias, and have attained their maximum 
 at the present day. In Lutraria the shell is oblong and gaping 
 at both ends, the pallial sinus is deep, and the internal ligament 
 is supported by a prominent cartilage-plate. The genus is not 
 known in rocks earlier than the Miocene Tertiary.
 
 LAMELLIBRANCHIATA. 
 
 237 
 
 FAM. 1 6. TELLINIDJE. Shell free, usually equivalve and 
 closed; cardinal teeth two at most, laterals i-i, sometimes 
 wanting. Ligament on the shortest side of the shell, some- 
 times internal. Mantle widely open in front. Siphons long 
 and slender; foot tongue-shaped, compressed. Pallial sinus 
 very large. The chief fossil genera are Tellina, Psammobia, 
 and Donax. In Tellina the shell is very slightly inequivalve 
 (fig. 196) with a prominent external ligament. More than 
 a hundred fossil species 
 are known, dating from 
 the Oolitic period; but 
 the genus has attained its 
 maximum at the present 
 day. In Psammobia the 
 shell is oblong, compres- 
 sed, and slightly gaping at 
 both ends ; whilst in Donax 
 the shell is wedge-shaped, the front rounded and produced, 
 the posterior side short. Both genera commence in the 
 Eocene Tertiary, and are represented by numerous species at 
 the present day. 
 
 FAM. 17. SOLENID^E. Shell elongated, gaping at both 
 ends ; ligament external ; hinge-teeth usually 2-3. Siphons 
 short and united (in the long-shelled genera), or longer and 
 
 Fig. 196. Tellina proximo., right valve. 
 Post-Pliocene. 
 
 Fig. 197. Mya. truncata, Post-Pliocene Fig. 198. Portion of the hinge of 
 
 and Recent. Mya arenaria, showing the cartilage- 
 
 process. 
 
 partly separate (in the genera with shorter shells). Foot 
 very large and powerful. Gills prolonged into the bran- 
 chial siphon. This family is of small geological importance. 
 The Razor-shells (Solen) are represented by a few Tertiary 
 forms, commencing in the Eocene ; and the genera Cul- 
 tellus and Solecurtus commence their existence in the Creta- 
 ceous Rocks. 
 
 FAM. 1 8. MYACIM:. Shell gaping posteriorly. Mantle 
 almost entirely closed ; siphons united, partly or wholly retrac-
 
 238 
 
 MOLLUSCA. 
 
 tile. Foot very small. The more important genera of this 
 family are Mya, Corbula, Thetis, Panopcea, and Saxicava. 
 
 In the Gapers (Mya}, the shell is oblong, inequivalve, and 
 gaping at both ends. The left valve is the smallest, and 
 it carries an internal ligament supported upon a prominent 
 cartilage-process (fig. 198). The Myas live buried verti- 
 cally in sand or mud. They are not known to have existed 
 before the period of the Middle Tertiary (Miocene), and 
 almost all the fossil species are in existence at the present 
 day. 
 
 In Corbula the shell is inequivalve, the left valve the 
 smallest, and with a prominent cartilage-process ; but the shell 
 is gibbous, and does not gape at its ends, whilst the pallial 
 sinus is small. Numerous fossil species are known, commenc- 
 ing in the Lower Oolites. 
 
 The genus Thetis is a small one, including thin, translucent, 
 sub-orbicular shells, with an ex- 
 ternal ligament. A few species 
 of the genus are known, com- 
 mencing with the Lower Cre- 
 taceous Rocks. 
 
 Panopcea resembles Mya in 
 having a thick oblong shell, 
 gaping at each end; but the 
 shell is equivalve, and the liga- 
 ment is external. Very numerous fossil species of this genus 
 are known, commencing in the Lower Oolites. 
 
 Saxicava, as its name implies, 
 includes shells which form bur- 
 rows in rocks. The adult shell 
 (fig. 199) is edentulous, equi- 
 valve, and oblong, gaping at the 
 ends, and furnished with an ex- 
 ternal ligament. The genus seems 
 to commence in the Eocene 
 Tertiary, and has continued to 
 the present day. 
 
 FAM. 19. ANATINID.E. Shell 
 often inequivalve, with an external 
 ligament. Mantle-lobes more or 
 less united. Siphons long, more 
 or less united. Foot small. The 
 more abundant and important 
 fossil genera of this family are 
 Anatina, Pholadomya, and Myacites. 
 
 Fig. 199. Saxicava rugosa, 1 
 valve. Post-Pliocene and Recent. 
 
 Fig. 200. Anatina sfxitulata. 
 Kimmeridge Clay (Upper Oolites*
 
 LAMELLIBRANCHIATA. 239 
 
 In the Lantern-shells (Anatina) the shell is oblong, gaping 
 posteriorly, and having the beaks directed towards the posterior 
 side (fig. 200). The hinge of each valve carries a spoon- 
 shaped cartilage-process. The 
 Anatince are doubtfully repre- 
 sented in the Devonian, and 
 still more dubiously in the 
 Silurian Rocks. They occur, 
 however, abundantly in the 
 Secondary Rocks, and are 
 present in smaller numbers in 
 
 the Tei'tiarieS. F'g- zo 1 - Pholadomya (equivalvis. 
 
 The genus Pholadomya in- 
 cludes a large number of shells, which are equivalve, ob- 
 long, and gaping posteriorly (fig. 201). The shell is thin, 
 ventricose, and adorned with radiating ribs on the sides. 
 The ligament is external, and there is a large pallial sinus. 
 The species of Pholadomya are very numerous in the Secondary 
 Rocks, where they attain their maximum. They are much 
 reduced in number in the Tertiaries, and are barely repre- 
 sented at the present day. 
 
 The genus Myacites has a gaping ventricose shell, with the 
 umbones directed anteriorly, and the ligament external. They 
 are known in the Palaeozoic period, commencing in the Silu- 
 rian ; and they are represented in the earlier portion of the 
 Secondary period; but they seem to have died out in the 
 Chalk. 
 
 FAM. 20. GASTROCH^NID^E. Shell equivalve, gaping, with 
 thin edentulous valves, sometimes cemented to a calcareous 
 tube. Mantle-margins thick in front, united, with a small 
 pedal aperture. Siphons very long, united. Foot finger- 
 shaped. The members of the Gastrochcenidce burrow in mud 
 or stone, and the only two fossil genera are Gastrochczna and 
 Clavagella, the existence of Aspergillum in a fossil state being 
 doubtful. 
 
 In Gastroch&na the shell is wedge-shaped, gaping in front 
 and closed behind. The fossil species commence in the In- 
 ferior Oolite, and the genus is represented at the present day. 
 In Clavagella (fig. 202) the shell is oblong, one of the valves 
 being free, whilst the other forms part of a more or less elon- 
 gated calcareous tube, which is often divided by a longitudinal 
 partition and terminates in tubular openings. The fossil 
 Clavagelltz commence in the Upper Greensand, and the genus 
 is represented by several living species. 
 
 FAM. 21. PHOLADIDJE. Shell gaping at both ends, without
 
 240 
 
 MOLLUSCA. 
 
 Fig. *<yi.Clavagella cretacea. Chalk. 
 
 hinge or ligament, often with accessory valves. Animal club- 
 shaped or worm-like, with a 
 short tnmcated foot. Mantle 
 closed in front ; siphons long, 
 united to near their extremi- 
 ties. 
 
 In the genus Pholas the 
 shell is cylindrical or oval, 
 the valves are edentulous, and 
 there is no ligament or a rudi- 
 mentary one. The pallial 
 sinus is very deep, and the 
 dorsal margin of the shell is 
 protected by accessory valves. 
 The Pholadcs inhabit burrows 
 which they form for themselves in clay, peat, or rock. Many 
 fossil species of the genus are known, commencing in the 
 Jurassic Rocks. 
 
 In the genus Teredo the shell is " globular, open in front 
 and behind, lodged at the inner extremity of a burrow partly 
 or entirely lined by shell ; valves three-lobed, concentrically 
 striated, and with one transverse furrow ; hinge-margins re- 
 flected in front, marked by the anterior muscular impressions : 
 umbonal cavity with a long curved muscular process." (Wood- 
 ward.) Species of Teredo occasionally reach a very large size, 
 and they are known in the fossil state both by their shells and 
 by their burrows in wood. The genus seems to have com- 
 menced in the Lias, and is well represented at the present 
 day. 
 
 CHAPTER XXI. 
 GASTEROPODA. 
 
 THE Gasteropods are Molluscs in which the body is furnished 
 with a distinct head, and the mouth is provided with a mastica- 
 tory apparatus or " lingual ribbon" Locomotion is effected by 
 means of a broad, horizontally-flattened, ventral disc the "foot" 
 or by a vertically-flattened, fin-like modification of the same. 
 The body is never included in a bivalve shell ; and may be naked. 
 Usually, h(ni<ever, tJiere is a " univalve " shell, or in some cases a 
 " multivalve " shell. 
 
 This class includes all those Molluscous animals which are
 
 GASTEROPODA. 241 
 
 commonly known as " Univalves," such as Land-snails, Sea- 
 snails, Whelks, Limpets, &c. In the Chitons, however, the 
 shell is composed of eight pieces (" multivalve ") ; and in the 
 Slugs, the shell is minute and is completely concealed in the 
 mantle ; whilst in the Sea-slugs and Sea-lemons the animal is 
 " naked," and is destitute of a shell. 
 
 In their habits the Gasteropods show great differences, 
 most of them being free and locomotive, though some are 
 sedentary. The typical forms move about more or less 
 actively by the successive contractions and expansions of a 
 muscular organ developed upon the ventral surface of the body 
 and known as the " foot." In many cases the posterior por- 
 tion of the foot secretes a calcareous, horny, or fibrous plate, 
 
 Fig. 203. A mpullaria canaliculata, one of the Apple-shells, o Operculum ; 
 j Respiratory siphon. 
 
 which is called the " operculum " (fig. 203, o), and which serves 
 to close the aperture of the shell when the animal is retracted 
 within it. Lastly, in one aberrant group of the Gasteropods 
 (Heteropoda) the animal is fitted for swimming in the open 
 ocean, by the conversion of the " foot " into a vertically- 
 flattened fin. 
 
 The respiratory process in the Gasteropods differs consider- 
 ably in different cases ; and the class may be divided into two 
 principal sections, according as the animal is fitted for breath- 
 ing air directly or through the medium of water. The air- 
 breathing Gasteropods are known as the Pulmonata or Pul- 
 monifera, and comprise forms which either live on land (Snails, 
 Slugs, &c.), or which inhabit fresh water (Pond-snails, &c.) 
 The water-breathing Gasteropods are mostly provided with 
 distinct gills or " branchiae," and they form the section of the 
 Branchifera. They are mostly inhabitants of the sea; but 
 some of them inhabit fresh water.
 
 242 MOLLUSCA. 
 
 Shell of the Gasteropoda. The shell of the Gasteropoda is 
 composed either of a single piece (univalve), or of a number 
 of plates succeeding one another from before backwards (mul- 
 tivalve). The univalve shell is to be regarded as essentially a 
 cone, the apex of which is more or less oblique. In the 
 simplest form of the shell the conical shape is retained without 
 any alteration, as is seen in the common Limpet (Patella}. In 
 the great majority of cases, however, the cone is considerably 
 elongated, so as to form a tube, which may retain this shape 
 (as in Dentaliuni), but is usually coiled up into a spiral. The 
 " spiral univalve " (fig. 205) may, in fact, be looked upon as the 
 typical form of the shell in the Gasteropoda. In some cases 
 the coils of the shell termed technically the " whorls " are 
 hardly in contact with one another (as in Vermetus). More 
 commonly the whorls are in contact, and are so amalgamated 
 that the inner side of each convolution is formed by the pre- 
 existing whorl. In some cases the whorls of the shell are 
 coiled round a central axis in the same plane, when the shell 
 is said to be " discoidal " (as in the common fresh-water shell 
 Planorbis). In most cases, however, the whorls are wound 
 round an axis in an oblique manner, a true spiral being formed, 
 and the shell becoming " turreted," " trochoid," " turbinated," 
 &c. This last form (fig. 204) is the one which may be looked 
 
 Fig. 204. Cassis cancellata, a Spiral Gasteropod. \a " Spire," placed at the posterior 
 end of the shell ; 6 " Mouth," placed at the anterior end of the shell ; c Inner or colu- 
 mellar lip ; d Outer lip ; e Notch for the passage of a respiratory siphon. 
 
 upon as most characteristic of the Gasteropods, the shell being 
 composed of a number of whorls passing obliquely round a 
 central axis or " columella," having the embryonic shell or 
 " nucleus " at its apex, and having the mouth or " aperture " 
 of the shell placed at the extremity of the last and largest of 
 the whorls, termed the " body-whorl." The lines or grooves 
 formed by the junction of the whorls are termed the " sutures,"
 
 GASTEROPODA. 
 
 243 
 
 and the whorls above the body-whorl constitute the " spire " 
 of the shell. The axis of the shell (columella) round which 
 the whorls are coiled is usually solid, when the shell is said to 
 be "imperforate;" but it is sometimes hollow, when the shell is 
 said to be " perforated," and the aperture of the axis near the 
 mouth of the shell is called the " umbilicus." The margin of 
 the "aperture" of the shell is termed the " peristome," and is 
 composed of an outer and inner lip (fig. 204), of which the 
 former is often expanded or fringed with spines. When these 
 expansions or fringes are periodically formed, the place of the 
 mouth of the shell at different stages of its growth is marked 
 by ridges or rows of spines, which cross the whorls, and are 
 called " varices." The animal withdraws into its shell by a 
 retractor muscle, which passes into the foot, or is attached to 
 the operculum ; its scar or impression being placed, in the 
 spiral univalves, upon the columella. 
 
 205. Scalaria 
 Grcenlandicci) a Ho- 
 lostoraatous Univalve. 
 Post-Pliocene. 
 
 Fig. 2o6.Fusus tpmatus, a Si- 
 phonostomatous Univalve. Post- 
 Pliocene. 
 
 In the multivalve Gasteropods, the shell is composed of 
 eight transverse imbricated plates, which succeed one another 
 from before backwards, and are embedded in the leathery or 
 fibrous border of the mantle, which may be plain, or may be 
 beset with bristles, spines, or scales. 
 
 In the marine Univalves two important variations exist in 
 the form of the mouth of the shell. In one group (fig. 205)
 
 244 MOLLUSCA. 
 
 the mouth of the shell is unbroken or " entire," not having 
 any notch or indentation of its margin. The shells in which 
 the mouth has this form are termed " holostomatous ; " and 
 for the most part they belong to Gasteropods which are phyto- 
 phagous, or live upon vegetable food. The possession, how- 
 ever, of a holostomatous shell in reality simply proves that the 
 animal had no respiratory " siphons," or tubes formed by the 
 folding of the mantle. In a second group the aperture of the 
 shell (fig. 206) is notched in front ; and the shell is said to be 
 " siphonostomatous." There may be a posterior notch as 
 well as the anterior one, and one or both of these notches may 
 be produced into longer or shorter canals. The Siphonosto- 
 matous Univalves are mainly carnivorous in their habits ; but 
 the notched mouth does not necessarily indicate the nature of 
 the food. The possession of a Siphonostomatous shell, on the 
 contrary, merely indicates that the animal possessed tubular 
 inflections of the mantle, or " respiratory siphons," by which 
 the water is conveyed to and from the gills. 
 
 Divisions of the Gasteropoda. The following table shows 
 the chief divisions of the Gasteropoda : 
 
 TABLE OF THE GASTEROPODA. 
 
 SECTION A. BRANCHIFERA. Respiration aquatic, by the walls of the 
 mantle-cavity or by gills. 
 
 ORDER I. PROSOBRANCHIATA. The branchiae situated (proson) 
 in advance of the heart. 
 
 Division a. Siphonostomata. Margin of the shell-aperture 
 notched or produced into a canal. This division comprises the 
 families of the Strombidtz (Wing-shells), Muricidte, Buccinida 
 (Whelks), Conida (Cones), Volutidie (Volutes), and Cyprcrida 
 (Cowries). 
 
 Division b. Holostomata. Margin of the shell-aperture "en- 
 tire" rarely notched or produced into a canal. This division 
 includes the families of the Naticida, Pyramidellida, Cerithiad<e, 
 Afelaniadtf, Turritellida:, Littorinida: (Periwinkles), Paludinidte 
 (River-snails), Neritida, Turbinidtz (Top-shells), Haliotidte, Fis- 
 surellidtz (Keyhole-limpets), Calyptrtrida (Bonnet-limpets), Palel- 
 lida (Limpets), Dentalida (Tooth-shells), and Chitonidcc. 
 ORDER II. OPISTHOBRANCHIATA. Branchiae placed towards the 
 rear (opistheit) of the body. 
 
 Division a. Tectibranchiata. Brdnchitt covered by the shell or 
 mantle. A shell in most. Sexes united. The division includes the 
 families of the Tornatellidif, Bullida; (Bubble-shells), Aplysiada 
 (Sea-hares), Pleurobranehia<Le> and Phyllidiada;. 
 
 Division b. Nudibranchiata. Animal destitute of a shell in the 
 adult condition. Bronchia external, on the back or sides of the 
 body. This division includes the various naked Gasteropods 
 commonly known as Sea-lemons and Sea-slugs. 
 ORDER III. NUCLEOBRANCHIATA, or HETEROPODA. Shell pre- 
 sent or absent. Animal free-swimming and oceanic, with a fin-like
 
 GASTEROPODA. 245 
 
 tail or flattened ventral fin. This order includes the two families of 
 the Firolidce and Atlantida. 
 
 SECTION B. PULMONIFERA. Respiration aerial, by means of a pul- 
 monary chamber. 
 
 ORDER IV. INOPERCULATA. Shell not provided with an oper- 
 culum. This order comprises the families of the Helicida (Land- 
 snails), Limacidte (Slugs), Oncidiadtz, Limnceida (Pond-snails), and 
 Avriculidtz. 
 
 ORDER V. OPERCULATA. Shell provided with an operculum. In 
 this order are the families Cyclostomidce and Aciculidee. 
 
 Distribution of the Gasteropoda in time. As regards the 
 general distribution of the Gasteropods in past time, all the 
 families of the Prosobranchiata are known by fossil representa- 
 tives. Of the Opisthobranchiata the Tectibranchiate section 
 is tolerably well represented in past time ; but the section of 
 the Nudibranchiata, from the total absence of the shell, is not 
 known at all in the fossil condition. Both families of the 
 Heteropoda are represented by fossil forms. The Pulmonate 
 Gasteropods, from the fact that they either live on land or 
 inhabit fresh water, are necessarily hot so fully represented in 
 past time as are the Branchiate Gasteropods. Still, nearly 
 all the families of the air-breathing Univalves have fossil 
 representatives. 
 
 Taken as a whole, the Gasteropoda are represented in past 
 time from the Upper Cambrian Rocks upwards. Of the 
 Branchifera, the Holostomata are more abundant in the Palaeo- 
 zoic period ; and the Siphonostomata predominate more in the 
 Secondary and Tertiary periods, attaining their maximum at 
 the present day. The place of the carnivorous Siphonostomata 
 in the Palaeozoic seas appears to have been filled by the 
 Tetrabranchiate Cephalopods. The Branchiate Gasteropods 
 of fresh water are chiefly represented as fossils by the genera 
 Paludina, Valvata, and Ampullaria. 
 
 The Heteropoda are likewise of very ancient origin, having 
 commenced their existence in the Upper Cambrian deposits. 
 The genera Bellerophon, Porcellia, Cyrtolites, and Maclurea, 
 are exclusively Palaeozoic ; Bellerophina is found in the 
 Gault (Secondary), and Carinaria has been detected in the 
 Tertiaries. 
 
 The Pulmonate Gasteropoda, as was to be anticipated, are 
 not found abundantly as fossils, occurring chiefly in lacustrine 
 and estuarine deposits, in which the genera Limnaa, Physa, 
 Ancyius, &c., are amongst those most commonly represented. 
 These, however, are entirely Mesozoic and Kainozoic. In 
 the Palaeozoic period the sole known representatives of the
 
 246 
 
 MOLLUSCA. 
 
 Pulmonifera are the Pupa vetusta and Zonites priscus of the 
 Carboniferous Rocks. 
 
 In the following* are given the characters of those families 
 of the Gasteropoda which occur in the fossil state, with the 
 leading genera of each family and their range in time. 
 
 SECTION A. BRANCHIFERA. Respiration aquatic, generally 
 by gills. 
 
 ORDER I. PROSOBRANCHIATA. Gills situated in advance of 
 the heart. 
 
 Division a. Siphonostomata. Mouth of the shell notched, or 
 produced into a canal. 
 
 FAM. i. STROMBID^E. Shell with an expanded lip, deeply 
 notched near the canal. Operculum claw-shaped. Foot nar- 
 row, adapted for leaping. All the existing genera of the 
 StrombidcR are represented in the fossil state, but the family 
 does not seem to have come into existence before the Jurassic 
 period, and it attained its maximum in the Tertiary period. 
 
 Fig. 307. Pteroceras octant. Neocomian. 
 
 The genus Strombus has a shell with a short spire, a long 
 aperture, and an expanded outer lip, there being a posterior as 
 well as an anterior notch. The Strombs are represented in 
 
 * Tn the characters of the families of the Gasteropoda, as in those of the 
 Lamellibranchiata, Woodward's 'Manual of the Mollusca' has been mainly 
 followed.
 
 GASTEROPODA. 247 
 
 the Cretaceous and Tertiary Rocks; but they attain their 
 maximum in existing seas. 
 
 The Scorpion-shells form the genus Pteroceras (fig. 207), in 
 which the shell of the adult has its outer lip furnished with 
 long claws, one of which forms a posterior canal close to the 
 spire. Many fossil species are known, commencing in the 
 Lias. 
 
 In the genus Rostellaria, the spire is long, and has the 
 posterior canal running up it. Many fossil species are known, 
 commencing in the Cretaceous Rocks. The outer lip is 
 always expanded, and in some forms is enormously so. 
 Lastly, the genus Seraphs comprises smooth shells, with a 
 short or obsolete spire, a thin outer lip, and a long narrow 
 mouth. The fossil species date from the Eocene Tertiary. 
 
 FAM. 2. MURICID^E. Shell with a straight anterior canal, 
 the aperture entire posteriorly. Foot broad. The MuricidcB 
 are essentially characteristic of the Tertiary and Recent 
 periods. They commence, however, in the Jurassic Rocks, in 
 some doubtful examples, and they are certainly represented 
 in the Cretaceous Rocks by not a few forms. 
 
 In the genus Murex the canal is often very long, and may 
 be partially closed ; the shell is ornamented with longitudinal 
 ridges or rows of spines (varices), and the aperture is rounded. 
 
 In the nearly-related Typhis (fig. 208) there are tubular 
 spines between the varices, and the last of these lodges the 
 posterior siphon. Both 
 Mnrex and Typhis com- 
 mence in the Eocene Ter- 
 tiary, and have attained 
 their maximum in existing 
 seas. 
 
 Pisania commences to 
 be represented in the 
 Eocene, as do the genera 
 Ranella, Triton, and Can- 
 cellaria. Fasdolaria and 
 Pyrula commence their 
 
 existence in the Cre- F ' g ' 2 8 - / >'^ *<^ ^enele-ary. 
 
 taceous Rocks ; and Turbinella and Trichotropis do not make 
 their appearance till the Miocene. Lastly, the great genus 
 Fusus, distinguished by the spindle-shaped, many-whorled 
 shell, and long straight canal (fig. 209), appears to have its 
 commencement in the Oolites. Fusi become very numerous 
 towards the close of the Cretaceous period, and they are 
 very plentiful in the Tertiaries. One of the common fossils
 
 248 MOLLUSCA. 
 
 of the Red Crag (Newer Pliocene) is the reversed shell, 
 Fusus contrarius, which is now known to exist in the living 
 state as well. 
 
 Fig. 209. fusus Necomiensis. Fig. 210. Buccinum undatum (var.) 
 
 Lower Greensand. Post-Pliocene and Recent 
 
 FAM. 3. BucciNiD^E. Shell notched anteriorly, or with the 
 canal reflected, producing a kind of varix on the front of the 
 shell. With the exception of the extinct genus Piirpurina of 
 the Lower Oolites, and some species of Buccinum in the Cre- 
 taceous Rocks, the family of the Bucdnidce. is exclusively con- 
 fined to the Tertiary and Recent periods. The two great 
 families, therefore, of the Muricidoe and Bucdnidce are essen- 
 tially characteristic of the later periods of the earth's history. 
 The most important fossil genera of the Buccinida are Buc- 
 cinum, Terebra, JVassa, Purpura, Cassis, and Oliva. 
 
 The Whelks form the genus Buccinum (fig. 210), dis- 
 tinguished by the ventricose body-whorl, large aperture, and 
 short reflected canal. Some few species of Buccinum are 
 found in the Upper Cretaceous Rocks ; but the genus is 
 essentially Tertiary and Recent. 
 
 Terebra comprises the Auger-shells, distinguished from the 
 Whelks by their long, pointed shells, consisting of many whorls, 
 and having a small mouth. They commence in the Eocene 
 Tertiary. The Dog-whelks (Nassa) also commence in the 
 Eocene, and are distinguished from the Whelks chiefly by 
 having the columellar lip expanded and callous, with a tooth 
 near the anterior canal. The shells of the genus Purpura
 
 GASTEROPODA. 
 
 249 
 
 have a short spire and wide aperture, with an expanded and 
 flattened inner lip. They commence in the Miocene Tertiary. 
 The Helmet-shells (Cassis) begin in the Eocene, and are dis- 
 tinguished by their short spire, large body-whorl, long aperture, 
 recurved canal, and expanded inner lip. Lastly, the Olives 
 (Oliva) and Rice-shells (Olivella) are characterised by their 
 cylindrical polished shell, with a short spire, a long narrow 
 aperture, notched in front, and obliquely-striated columella. 
 The living Olives are tropical and sub-tropical in their dis- 
 tribution, and the fossil species commence in the Eocene 
 Tertiary. 
 
 FAM. 4. CONID.E. Shell inversely conical, with a long nar- 
 row aperture, the outer lip notched at or near the suture. The 
 Conidce. commence in the Cretaceous Rocks, abound in the 
 Tertiaries, and attain their maximum at the present day. 
 
 The true Cones form the genus C0nus, and are distinguished 
 by their short spire and regularly conical 
 shell, of which the outer lip is notched 
 near the suture. The Cones are repre- 
 sented in the Chalk, but are mainly Ter- 
 tiary and Recent. The genus Pleurotoma 
 is distinguished by a spindle-shaped shell, 
 with a long spire, the outer lip having 
 a deep slit near the suture. The genus 
 commences in the Chalk, and has an 
 enormous development in the Tertiaries, 
 from which nearly three hundred species 
 are known. The maximum, however, is 
 attained in existing seas, in which there 
 are very numerous species. 
 
 FAM. 5. VOLUTION. Shell turreted or 
 convolute, the aperture notched in front ; 
 the Qolumella obliquely plaited. No 
 operculum. Foot very large ; mantle 
 often reflected over the shell. The living 
 members of the Volutida are chiefly in- 
 habitants of warm seas, and are often 
 remarkable for their brilliant colours. 
 The family does not appear to have ex- 
 isted till towards the later portion of the 
 Cretaceous period ; but it is abundantly 
 represented in the Tertiaries, and attains 
 its maximum in existing seas. The most 
 important genera are Voluta and Mitra. 
 
 The true Volutes form the genus Voluta (fig. 211), charac- 
 
 Fig. an. Valuta elongata. 
 Chalk.
 
 2$0 MOLLUSCA. 
 
 tensed by the short spire, large, deeply-notched aperture, and 
 columella with several plaits. Species of Valuta occur in the 
 Cretaceous period, but the genus is mainly Tertiary and Recent. 
 In the genus Mitra the shell is spindle- 
 shaped, with a long spire, and small 
 mouth. The Mitra commence in the 
 Cretaceous period, but the fossil species 
 are mainly distributed through the Ter- 
 tiary formations. 
 
 FAM. 6. CVPRJEIDM. Shell convo- 
 lute, enamelled ; spire concealed ; aper- 
 ture narrow, channelled at each end. 
 Outer lip thin in the young shell, but 
 thickened and inflected in the adult. 
 Foot broad ; mantle forming lobes which 
 Fig. an. Gyp-** eiegans. meet over the back of the shell. The 
 only important genus of this family is 
 that of Cypraa (fig. 212), comprising the numerous and well- 
 known living shells which are commonly called Cowries. The 
 Cypraa. are mainly, but not exclusively, inhabitants of warm 
 seas, and they attain their highest development between the 
 tropics. The fossil species date from the Cretaceous period, 
 and abound in the Tertiaries. 
 
 The shell of the Cowries in the young state is furnished 
 with a prominent spire, and has a thin outer lip. In the 
 adult state (fig. 212) the spire is completely concealed within 
 the shell, the entire surface is generally covered with shining 
 enamel, the inner lip is crenulated, and the outer lip is thick- 
 ened, inflected, and crenulated. The small Cowries of which 
 Cyprcea Europcea is the type, are not known as occurring in the 
 fossil condition. 
 
 Division b.Holostomata. Margin of the shell-aperture "entire" 
 rarely notched or produced into a canal. 
 
 FAM. 7. NATICID.*. Shell globular, of few whorls, with a 
 small spire ; outer lip acute ; inner lip (pillar) often callous. 
 Foot very large ; mantle-lobes hiding more or less of the shell. 
 This family is stated to commence in the Upper Silurian 
 Rocks ; but there is more or less uncertainty as to the true 
 affinities of the Palaeozoic fossils which are referred here. 
 The most important fossil genus is Natica itself. 
 
 The shell in Natica (fig. 213) is thick, smooth, and polished, 
 often with coloured markings. The inner lip is callous, and 
 the shell is umbilicated. Fossil Natica have been described 
 from the Upper Silurian, Devonian, Carboniferous, and Per- 
 mian Rocks; and they are very abundant in all the Secondary
 
 GASTEROPODA. 25 I 
 
 and Tertiary formations. The sub-genus Naticopsis is Carbo- 
 niferous, Naticella is Triassic, and Globulus is found in the 
 Eocene. 
 
 FAM. 8. PYRAMIDELLID^:. Shell turreted, with a small 
 aperture ; sometimes with one or more prominent plaits on the 
 columella. Operculum horny and imbricated. The Pyrami- 
 dellidce commence in the Lower Silurian Rocks, and appear to 
 be on the decline at the present day. The chief fossil forms 
 belong to the genera Chemnitzia, Eulima, Loxonema, an/i 
 Macrocheilus. 
 
 Chemnitzia includes a number of slender, turreted, many- 
 whorled shells, with plaited whorls, and a simple aperture. The 
 genus appears to commence in the Permian Rocks, and whilst 
 more than one hundred and fifty fossil species are known, the 
 number of living forms is very small. Many of the shells, how- 
 ever, included under this head, are of very doubtful affinities. 
 
 Fig. 213. Natica clausa. Fig. 214. Macrocheilus sub- 
 
 Post-Pliocene. \ costatrts. Devonian. 
 
 Eulima includes small, polished, elongated shells, with level 
 whorls and a reflected inner lip. Eulimtz are of doubtful oc- 
 currence in the Carboniferous Rocks, are sparingly represented 
 in the Secondary Rocks, but are tolerably abundant in the 
 Tertiaries. 
 
 The genera Loxonema and Macrocheilus (fig. 214), lastly, 
 include Palaeozoic shells, whose true place is in many cases 
 uncertain. The former extends from the Lower Silurian to 
 the Trias, but the latter is mainly, if not exclusively, confined 
 to the Devonian and Carboniferous Rocks.
 
 252 
 
 MOLLUSCA. 
 
 FAM. 9. CERITHIAD^E. Shell spiral, turreted ; aperture 
 channelled in front, with a less distinct posterior canal. Lip 
 generally expanded in the adult. Operculum horny and 
 spiral. The Cerithiadce are exclusively confined to the Second- 
 ary, Tertiary, and Recent periods, and are represented in the 
 Tertiary Rocks by a vast number of forms. The most import- 
 ant fossil forms belong to the genera Cerithium, Potamides, 
 Nerincea, and Aporrhais, of which Nerincea is extinct, and is 
 exclusively confined to the Secondary period. 
 
 For all practical purposes Cerithium and Potamides may be 
 considered together, as no 
 strict line of demarcation 
 can be drawn between the 
 fossil forms. In both, the 
 shell is turreted and many- 
 whorled (fig. 215), with or 
 without varices. 
 
 The aperture of the shell 
 is small, with a tortuous an- 
 terior canal, and an ex- 
 panded outer lip. Most of 
 the living forms are inhabi- 
 tants of fresh or brackish 
 waters, and they are chiefly 
 found in hot climates. The 
 fossil forms, to the number 
 of nearly five hundred, 
 commence in the Trias, but they attain their maximum of 
 development in the Eocene Tertiary. 
 
 In the genus Nerincea (fig. 216), the shell is turreted, many- 
 whorled, and nearly cylindrical. The columella carries con- 
 tinuous ridges, and similar ridges exist on the interior of the 
 whorls, so that casts of the interior of the shell are often very 
 unlike the form of the exterior. The aperture of the shell is 
 channelled in front. The species of Nerincea are exclusively 
 Jurassic and Cretaceous, and are very numerous. One of the 
 limestones of the Jura, believed to be of the age of the Coral 
 Rag (Middle Oolite) of Britain, abounds to such an extent 
 in these shells as to have gained the name of " Calcaire i. 
 Ne'rine'es." 
 
 In the genus Aporrhais, lastly, the shell is turreted, and the 
 outer lip of the adult is greatly expanded and lobed. The 
 species of this genus are marine in their habits. A great many 
 Jurassic and Cretaceous shells, generally referred at present to 
 Rostellaria, probably belong really to Aporrhais ; but the de- 
 
 Fig. 216. Nerincea 
 bisulcata. Chalk.
 
 GASTEROPODA. 253 
 
 termination of these fossils by the shells alone is attended with 
 great difficulties. 
 
 FAM. 10. MELANIAD^E. Shell spiral, turreted; aperture 
 often channelled or notched in front ; outer lip acute. Oper- 
 culum horny and spiral. Many fossil shells have been referred 
 to the Melaniadc&i but it is probable that most of these belong 
 to the Palaeozoic genus Loxonema and the Mesozoic Chem- 
 nitzia. The true Melanice do not appear to have commenced 
 their existence till the Eocene Tertiary. All the living species 
 inhabit fresh water, generally in the warmer parts of the world ; 
 and it is probable that all the fossil species occur only in fluvia- 
 tile and lacustrine deposits. 
 
 FAM. ii. TURRITELLID^E. Shell tubular or spiral, often 
 turreted; upper part partitioned off; aperture simple. Oper- 
 culum horny, many-whorled. Foot very short. Branchial 
 plume single. The Turritellidce are not known to have existed 
 in the Palaeozoic period ; but they appear to commence about 
 the middle of the Jurassic period, abounding in the Tertiaries, 
 and attaining their maximum in existing seas. The chief 
 fossil genera are Turritella, Vermetus, and Scalaria, 
 
 In Turritella (fig. 217) the shell is turreted. many-whorled, 
 and spirally striated; the aperture is 
 small and rounded, and the peristome 
 thin. Species of Turritella have been 
 described from the Palaeozoic and older 
 Mesozoic formations, but almost cer- 
 tainly belong to the genera Murchisonia 
 and Loxonema. The genus is for the 
 first time represented with certainty in 
 the Lower Cretaceous Rocks (Neo- 
 comian), and many fossil species are 
 found in the Tertiaries. 
 
 The genus Vermetus comprises tubu- 
 lar shells, the chief interest of which 
 is the strong resemblance which they 
 show to the Annelidous genus Serpula. 
 The shell is attached, and though regularly spiral when young, 
 is always irregular in its growth when adult. The fossil species 
 are best distinguished from Serpula by the fact that the tube 
 is repeatedly partitioned off by calcareous septa, as the animal 
 grows. It is, however, often a matter of extreme difficulty to 
 determine whether a given specimen be a Vermetus or a Ser- 
 pula. Fossil Vermeti are known from the Lower Cretaceous 
 upwards. 
 
 The genus Scalaria comprises the Wentle-traps, in which
 
 254 
 
 MOLLUSCA. 
 
 the shell is very like that of Turritella, but the whorls are 
 ornamented with transverse ribs, and the peristome is continu- 
 ous round the circular aperture (fig. 205). The Scalaria com- 
 mence in the Middle Oolites (Coral Rag), and attain their 
 maximum in existing seas. 
 
 FAM. 12. LITTORINIDJE. Shell spiral, top-shaped, or de- 
 pressed ; aperture rounded and entire, operculum horny 
 and pauci-spiral. The exact range of the Littorinida in 
 time is uncertain, owing to the difficulty of determining the 
 true affinities of many fossil Univalves. Several Paleozoic 
 and Mesozoic shells have been referred to Littorina, and 
 the genus Rissoa commences in the Permian. The family, 
 however, is mainly characteristic of the Tertiary and Recent 
 periods. 
 
 In the genus Littorina are the true Periwinkles, distinguished 
 by their thick, generally top-shaped and pointed shells, of few 
 whorls, and with an imperforate columella. The undoubted 
 fossil species range from the Middle Tertiaries to the present 
 day. 
 
 In the genus Solarium (fig. 218) the shell is much depressed; 
 there is a large and deep umbilicus, 
 running from the base to the apex 
 ^ tne sne H> an d the aperture of the 
 shell ' s rhombic. Doubtful Second- 
 ar y f rms f this 8 enus are known ; 
 t> ut the undoubted species com- 
 mence in the Eocene Tertiary. The 
 genus Phorus also comprises shells, 
 the true range of which is very un- 
 certain. Undoubted species, how- 
 ever, date from the Cretaceous 
 period. Lastly, in the genus Rissoa 
 the shell is very small, pointed, and 
 many-whorled, with a small round 
 aperture surrounded by a continuous 
 peristome. Many fossil species are 
 known, commencing in the Permian 
 Rocks, abounding in the Oolites, and being very abundant in 
 the later Tertiaries. 
 
 FAM. 13. PALUDINIDJE. Shell conical or globular; aper- 
 ture rounded and entire; operculum horny or shelly. The 
 Paludinidce are essentially inhabitants of fresh water ; though 
 they sometimes live in brackish, or even in salt water. As a 
 matter of course, therefore, they are chiefly, if not exclusively, 
 found as fossils in deposits which are believed to be fluviatile
 
 GASTEROPODA. 
 
 255 
 
 or lacustrine in their origin. The three chief or only living 
 genera are, Pallid ina, Valvata, and Ampullaria. The two 
 former date from the Cretaceous period, the first possibly 
 from the Jurassic, and both abound in the Wealden and in 
 many Tertiary deposits. The existence of Ampullaria in a 
 fossil state is attended with considerable uncertainty, chiefly 
 from the great difficulty, or impossibility, of separating them 
 from species of the marine genus Natica. 
 
 FAM. 14. NERITID^E. Shell thick, globular, with a very 
 small spire ; aperture semi-lunate, its columellar side expanded ; 
 outer lip acute. Operculum shelly, sub-spiral. The Neritida 
 are not known as occurring in the Palaeozoic Rocks, but are 
 found from the Jurassic period onwards, attaining their maxi- 
 mum at the present day. 
 
 In the genus Nerita (fig. 219) the shell is thick, with a broad 
 columella, the inner edge of which is straight and toothed. 
 
 Fig. 219. Nerita Schemidelliana, Eocene Tertiary. 
 
 The outer lip is thickened and often denticulated internally. 
 The true Nerites are inhabitants of warm seas ; and they date 
 in past time from the Lias. The nearly-allied genus Neritina 
 includes the so-called " fresh- water Nerites," which agree in 
 most characters with Nerita, but inhabit fresh or brackish 
 waters. The fossil species commence in the Eocene Tertiary. 
 Lastly, the genus Pileolus comprises small limpet-shaped shells, 
 with a semi-lunar aperture below. The only fossil species are 
 from the Lower Oolites (Great Oolite). 
 
 FAM. 15. TURBINID.*. Shell turbinated (top-shaped) or 
 pyramidal, nacreous (i.e. pearly) inside. Operculum horny and 
 multi-spiral, or calcareous and pauci-spiral. The family of the 
 TurbinidcB has a very high antiquity, dating from the Lower 
 Silurian ; but many of the older shells referred to this family 
 are of more or less doubtful affinities. The most important 
 fossil genera are Turbo, Trochus, and Euomphalus. 
 
 In the genus Turbo (hg. 220) the shell is turbinated, with a
 
 2 S 6 
 
 MOLLUSCA. 
 
 round base. The whorls are convex ; the aperture is large and 
 
 rounded ; and the operculum is calcareous. A great number 
 of fossil species of this genus have been 
 described, commencing in the Lower 
 Silurian ; but there is considerable 
 doubt *a.s to the true position of many 
 of the older forms. 
 
 In the genus Troehus the shell is 
 pyramidal, with a nearly flat base ; the 
 aperture is oblique and rhombic in 
 shape, and the operculum is horny. A 
 great number of species of this genus, 
 also, have been described, commenc- 
 ing in the Silurian Rocks. As in the 
 case of Turbo, however, the affinities 
 
 of many of the older forms are very problematical. 
 
 The genus Euomphalus (fig. 221) is entirely extinct, and is 
 
 essentially Palaeozoic, ranging from the Silurian to the Trias, 
 
 Fig. 220. Turbo subcostatus. 
 Devonian. 
 
 Fig. 221. Euom/>halus De Cewi (Billings), a Front view ; 6 View of the umbilicus. 
 Devonian. 
 
 but being most abundant in the Carboniferous Rocks. The 
 shell in this genus is depressed or discoidal, the whorls lying 
 nearly or quite in the same plane. The whorls are angulated 
 or coronated, the aperture is polygonal, the umbilicus is very 
 large, and there is a shelly operculum. The genus Ophileta is 
 closely allied to Euomphalus, if not identical with it. 
 
 FAM. 16. HALIOTID^E. Shell spiral, ear-shaped, or trochoid; 
 aperture large, nacreous. Outer lip notched or perforated. 
 No operculum. Mantle-margin with a posterior fold or siphon, 
 occupying the slit or perforation in the shell. 
 
 The living genera Haliotis and Sdssurclla are not known in
 
 GASTEROPODA. 
 
 257 
 
 rocks older than the Miocene Tertiary. The extinct genera 
 Pleurotomaria and Murchisonia are, on the other hand, of great 
 antiquity, the latter being exclusively Palaeozoic, and the 
 former mainly so. 
 
 The genus Haliotis comprises the so-called " ear-shells," 
 distinguished by their ear-shaped shell, with a minute spire, 
 an enormous aperture, and a series of round perforations in 
 the outer angle of the shell. A few fossil species are known, 
 commencing in the Miocene. 
 
 In the genus Scissurella, which also commences in the 
 Miocene, the shell is thin, with a large and greatly expanded 
 body-whorl, and the place of the perforations of Haliotis is 
 taken by a simple slit in the margin of the outer lip. 
 
 The genus Pleurotomaria comprises a great number of 
 Palaeozoic univalves, which occur in the Silurian, Devonian, 
 and Carboniferous formations. In sediments later than the 
 Carboniferous the genus is largely represented, extending even 
 to the close of the Mesozoic period. In the Jurassic period 
 especially the genus has a great development, most of the 
 forms being more ornate than those from the older rocks. 
 In the Cretaceous Rocks the genus finally dies out, with 
 the sole exception of a single living species. The form of 
 the shell in Pleurotomaria (fig. 222) differs considerably in 
 different cases. Very 
 commonly the shell is 
 very similar to that of 
 Trochus. In other cases 
 it more nearlyresembles 
 Turbo ; and sometimes 
 it is very much flatten- 
 ed out and depressed. 
 The shell consists of 
 few whorls, of which 
 the last may be discon- 
 nected from the others, 
 and is essentially dis- 
 tinguished by its sub- 
 quadrate aperture, with 
 a deeper or shallower 
 slit in the outer lip. As 
 the shell grows, this slit 
 becomes progressively filled up, forming a well-marked band on 
 the whorls. By this character Pleurotomaria may generally be 
 distinguished readily from such shells as Trochus and Turbo. 
 
 Murchisonia (fig. 224) is another genus of great importance 
 
 Fig. 222. Pleurotomaria Agave. Lower 
 Silurian (Billings). 
 
 Fig. 223. Pleurotomaria Dryope. Lower 
 Silurian (Billings).
 
 2$8 MOLLUSCA. 
 
 to the student of the older rocks, as it is exclusively confined 
 to the Palaeozoic period, ranging from the Lower Silurian to 
 the Permian. The shell in Murchisonia closely resembles 
 that of Pleurotomaria, but is usually more elongated and com- 
 posed of a greater number of whorls. The outer lip is deeply 
 notched, and the whorls have the same band on their exterior 
 as is present in Plcnrotomaria. The aperture of the shell is 
 slightly channelled in front, and the surface is often variously 
 sculptured and adorned. 
 
 We may place here, provisionally, the Palaeozoic genus 
 Holopea (fig. 225), the exact affinities of which are doubtful. 
 
 The shell in this genus is 
 spiral, the aperture oval, 
 and the outer lip sinuated 
 near the base. The genus 
 has been compared to the 
 violet-snail (lanthina) of 
 the Atlantic, in which 
 case its place should be 
 here ; but its true posi- 
 tion is altogether uncer- 
 tain. It is exclusively 
 Silurian in its range ; and 
 it is probable that the 
 genus Platyceras should 
 be united with it, in which 
 case the vertical range 
 will be extended at any 
 rate to the Carboniferous. 
 FAM. 17. FISSURELLID^E : Shell conical, patelliform, with a 
 notch in the anterior margin, or a perforation at the apex, 
 which is occupied by the anal siphon. Muscular impression 
 horse-shoe shaped, open in front. The existence of the Fis- 
 surdlidce in the Palaeozoic period is open to considerable 
 doubt ; but a good many fossil forms are known from the 
 Secondary and Tertiary Rocks. 
 
 The genus Fissurella comprises the so-called " Keyhole 
 Limpets," distinguished by having the apex of the shell per- 
 forated by a larger or smaller, generally oval aperture. Doubt- 
 ful examples of the genus have been indicated as occurring in 
 the Devonian and Carboniferous ; but there are a good many 
 unequivocal species in the Secondary and Tertiary Rocks. In 
 the Oolitic genus Rimnla the perforation, instead of being at 
 the apex of the shell, is placed a little above the anterior 
 margin. Lastly, in Emargimila the anterior margin is fur- 
 
 Fig. i2t,.Mnrchi 
 o>iia S racilis( 
 Lower Silurian. 
 
 Fig. 225. 
 Gnelphensis (Billings). 
 Middle Silurian.
 
 GASTEROPODA. 259 
 
 nished with a longitudinal notch or slit. The species of this 
 genus date from the Trias. 
 
 FAM. 1 8. CALYPTR^ID^E : Shell limpet-shaped, with a more 
 or less spiral apex ; interior simple, or divided by a shelly 
 process to which the adductor muscles are attached. Exclud- 
 ing shells whose true position is uncertain, it would appear 
 very questionable if any of the Calyptraida are found in the 
 Palaeozoic Rocks. They are by no means abundant in the 
 Secondary formations ; and though more plentiful in the Ter- 
 tiaries, they attain their maximum in existing seas. 
 
 The genus Calyptrcza includes the so-called " Cup-and- 
 saucer limpets," in which the interior has a half-cup-shaped 
 process attached to the apex of the shell, and open in front. 
 With doubtful exceptions, the fossil species of Calyptrcea are 
 all of Tertiary age. In the genus Crepidula there is a shelly 
 partition covering the posterior half of the interior of the shell. 
 The fossil species date from the Eocene Tertiary. In the 
 genus Pileopsis (or Capuhis) are included the " Bonnet-lim- 
 pets," in which the apex of the shell is spirally recurved. If 
 Platyceras be excluded from this genus, the species of Pileopsis 
 date from the Lias ; but the former is Palaeozoic. 
 
 FAM. 19. PATELLID^:: Shell conical, with the apex turned 
 forwards ; muscular impression horse-shoe shaped, open in 
 front. Foot as large as the margin of the mantle. Respira- 
 tory organ in the form of one or two branchial plumes, 
 lodged in a cervical cavity, or of a series of lamellae sur- 
 rounding the animal between the body and the mantle. . The 
 Patellidce commence to be represented in the Lower Silurian 
 Rocks, and have continued to the present day. 
 
 
 Fig. 226. MetoptoiiM nycteis. a Side view ; b View of the upper side. 
 Lower Silurian (Billings). 
 
 The genera Patella (including the common Limpets), Ac- 
 mcea, and Metoptoma can hardly be separated in practice 
 from one another. Patella and Acmcea, at any rate, are 
 palaeontologically indivisible, since the only distinctions be- 
 tween them are in the nature of the respiratory organs. In-
 
 260 MOLLUSCA. 
 
 eluding these genera, therefore, in one, the range of the 
 Limpets is from the Silurian upwards. 
 
 The genus Metoptoma (fig. 226) very closely resembles 
 Patella, but the muscular scar consists of a number of dis- 
 connected cavities. In the typical species, also, the anterior 
 side, under the apex of the shell, is truncated or nearly straight. 
 Species of Metoptoma are particularly abundant in the Lower 
 Silurian series ; but they range as far as the Carboniferous. 
 
 FAM. 20. DENTALID^E : Shell tubular, symmetrical, curved, 
 open at both ends. Aperture circular. Foot pointed, with 
 symmetrical side-lobes. The " Tooth-shells " are generally 
 placed here, in the vicinity of the Limpets ; but they are re- 
 ferred by Huxley to the class of the Pteropoda. The family 
 comprises the single genus Dentalium, well known by the 
 tubular, smooth, or longitudinally striated shell, open at both 
 ends. The fossil species are liable to be confounded with the 
 tubes of Tubicolar Annelides, or a reverse mistake to this may 
 be made. Several species have been described from the 
 Devonian, and more especially from the Carboniferous Rocks, 
 some of them of large size ; but more or less doubt obtains as 
 to the true nature of these. The Secondary Rocks have 
 yielded a considerable number of species, and they become 
 still more numerous in the Tertiaries. 
 
 FAM. 21. CHITONID^E: Shell multivalve, composed of eight 
 transverse plates, disposed one behind the other in an imbricat- 
 ed manner. Animal with a broad creeping foot; branchiae 
 forming a series of lamellae between the foot and the mantle, 
 round the posterior part of the body. The Chitonida com- 
 prise only the single genus Chiton, with several 
 more or less distinct sub-genera. The species of 
 the family commence in the Lower Silurian, and are 
 rare as fossils, attaining their maximum at the pre- 
 sent day. 
 
 The distinctive peculiarities of the shell of the 
 Chitons (fig. 227), by which they may always be 
 separated from the Cirripedes, are the following : 
 i. The shell never consists of more or fewer than 
 eight pieces. 2. The valves of the shell are al- 
 ways placed one behind the other in a unilinear 
 series. 3. The six middle plates of the shell are 
 divided, each, by lines of sculpturing into three dis- 
 tinct areas a dorsal and two lateral areas. 4. Each plate 
 is imbedded in the mantle of the animal by forward extensions 
 of its front edge, which are termed the "apophyses." 
 
 The Chitons are represented by fossil species in the Silurian,
 
 GASTEROPODA. 
 
 26l 
 
 228. Cinulia Avella. 
 D'Orbigny). Chalk. 
 
 : (Avellana 
 
 Devonian, Carboniferous, and Permian Rocks, and are not so 
 excessively rare in the Carboniferous Limestone. They are 
 very poorly represented in the Secondary Rocks, and are by 
 no means abundant in the Tertiaries. 
 
 ORDER II. OPISTHOBRANCHIATA : Gills placed towards the 
 rear of the body. 
 
 FAM. 22. TORNATELLID^E : Shell external, spiral or con- 
 voluted ; aperture long and narrow ; columella plaited. The 
 Tornatellidcz are mainly Mesozoic, ranging from the Trias or 
 from the base of the Jurassic series to the Chalk inclusive, 
 and attaining their maximum in the Cretaceous series. 
 Several genera are entirely 
 extinct, of which the most im- 
 portant is Cinulia (fig. 228). 
 In this genus the shell is 
 globular, with a small spire, 
 the outer lip reflected and 
 crenulated interiorly, and the 
 columella with tooth - like 
 folds. All the species are 
 Cretaceous. In the genus 
 Tornatella, the shell is ovate, 
 with a well-marked spire, the outer lip thin, and the colu- 
 mella with a strong fold. The fossil species range from the 
 Trias upwards, and the genus, though on the decline, is re- 
 presented by several living species. Many of the Secondary 
 species belong to more or less distinct sub-genera ( Cylindrites, 
 Acteonella, and Acteonina). 
 
 FAM. 23. BULLID^E : Shell convoluted, thin ; spire small or 
 concealed ; lip sharp. Animal often more 
 or less completely investing the shell. 
 The Bullidtz commence their existence in 
 the Jurassic period, and have continued 
 to the present day. The only important 
 genus is Sulla, comprising tlv: so-called 
 "Bubble-shells" (fig. 229). The species 
 of this genus are not uncommon in the fossil condition, com- 
 mencing in the Oolites. 
 
 FAM. 24. APLYSIAD^ : Shell absent or rudimentary, con- 
 cealed by the mantle when present. Animal slug-like ; sides 
 extensively lobed and reflected over the back and shell. One 
 or two shells from the younger Tertiary rocks have been re- 
 ferred, with great doubt, to the genus Aplysia. 
 
 FAM. 25. PLEUROBRANCHID./E : Shell limpet-like or con- 
 cealed, rarely wanting. Mantle or shell covering the back of 
 
 Fig. 229. Bulla supra- 
 jurensis. Middle Oolites.
 
 262 MOLLUSCA. 
 
 the animal. Two doubtful species belonging to the genus 
 Umbrella have been described from the Tertiaries ; but the 
 family is otherwise unknown in the fossil condition. 
 
 CHAPTER XXII. 
 
 GASTEROPODA Continued. 
 
 HETEROPODA AND PULMONIFERA. 
 
 ORDER III. HETEROPODA OR NUCLEOBRANCHIATA : The 
 Gasteropods of this order differ from the typical members of 
 the class in being organised to lead an existence in t/ie open 
 ocean, locomotion being effected by a fin-like tail, or by a fan- 
 shaped vertically-flattened ventral fin. They are found swim- 
 ming at or near the surface of the ocean ; and the body may be 
 completely protected by a shell, within which the animal can 
 retire, and which can be closed by an operculum. In other 
 cases, as in Carinaria (fig. 230), the body is large, and there is 
 
 Fig. 230. Heteropoda. Cariftarla cymbium. f Proboscis ; / Tentacles ; b Branchiae ; 
 s Shell ; / Foot ; d Disc. (After Woodward.) 
 
 only a small shell protecting the gills and heart. In other 
 cases, again, the shell is completely wanting. The order is 
 divided into the two families of the Firolidie and Atlantida. 
 The former of these is represented by a single species only, 
 from the Miocene Tertiary. The latter had a great develop- 
 ment in Palaeozoic seas, and is represented in the formations 
 of this period by several remarkable genera. 
 
 FAM. i. FIROLID^E : Body large, never completely pro- 
 tected by a shell, often shell-less. Sometimes a small delicate
 
 GASTEROPODA. 263 
 
 hyaline shell, placed on the back, protecting the gills. The 
 only genus of this family which is represented in a fossil state 
 is Carinaria (fig. 230), a single species of which has been found 
 in deposits of Tertiary age (Miocene). 
 
 FAM. 2. ATLANTID^E : Animal furnished with a well-de- 
 veloped shell, into which it can retire. Shell symmetrical, 
 discoidal, destitute of septa, often provided with an operculum. 
 This family is represented by the genera Bellerophon, Madurea, 
 Cyrtolites, Ecculiomphalus, and Porcellia, most of which are 
 exclusively Palaeozoic, whilst the others are mainly so. 
 
 In the genus Bellerophon (fig. 231) the shell is symmetrical, 
 convoluted, the coils of the shell usually lying in one plane. 
 
 Fig. 231. Belleroplwn Argo (Billings), a Front view ; i> side view. Lower Silurian. 
 
 The whorls are few, smooth or sculptured, and there is a 
 dorsal keel along the convex margin of the shell. The aper- 
 ture is often more or less expanded, and is in most instances 
 emarginate or deeply notched on the dorsal side. The genus 
 ranges from the Lower Silurian to the Carboniferous. The 
 Bellerophina of the Gault (Upper Cretaceous) is doubtfully 
 allied to Bellerophon, and may belong to the Pteropoda. 
 
 The genus Madurea is very remarkable in its structure, and 
 all the known species are entirely confined to the Lower 
 Silurian Rocks. The shell (fig. 232) in this singular genus is 
 " discoidal, few-whorled, longitudinally grooved at the back, 
 and slightly rugose with lines of growth ; dextral side convex, 
 deeply and narrowly perforated ; left side flat, exposing the 
 inner whorls ; operculum sinistrally sub-spiral, solid, with two 
 internal projections, one of them beneath the nucleus, very 
 thick and rugose" (Woodward). Madurea has been variously 
 regarded as " dextral " or " sinistral ; " but the probabilities are 
 in favour of the view that it is truly dextral. In this case, the 
 flat side of the shell is the umbilicus, and the spire must be 
 regarded as sunk below the general surface of the shell. (On 
 this view the specimen figured at b, fig. 232, is represented up- 
 side down.) The species of Madurea occur chiefly at the base
 
 264 
 
 MOLLUSCA. 
 
 of the Lower Silurian series both in North America and in 
 Scotland, occurring in some localities in the greatest profusion. 
 
 ;- 
 
 Fig. 232. Mad-urea crenulata. a Spire ; fi front , c base. Lower Silurian. 
 
 The genus Ophileta (fig. 233) of the Silurian Rocks may be 
 mentioned here, though its true affinities are extremely doubt- 
 
 Fig. 233. Ophileta bella (Billings). Different views of a nearly perfect specimen. 
 Quebec Group (Upper Cambrian ?) 
 
 ful. The shell in this genus is discoidal, and very closely 
 resembles that of Euomphalus. The aperture, however, is 
 stated by Mr Billings to have a sinus in the 
 lower lip and a notch in the upper lip 
 characters which are not present in Mac- 
 lurea. It is a matter of question whether 
 Ophileta should be regarded as comprising 
 species of Maclurea with slender whorls, 
 or whether it should be placed in the Tur- 
 binidce, in or near Enomphalus, or whether 
 it should not be placed in the Haliotidx and 
 be regarded as a discoidal Pleurotomaria. 
 
 In the genus Cyrtolites (fig. 234) the shell 
 is thin, symmetrical, discoidal, or coiled into 
 the shape of a horn, the whorls more or less disconnected, 
 furnished with a keel, and sculptured. The species of this 
 
 Fig. VM.Cyrtolite 
 anuitus. Lower Silu
 
 GASTEROPODA. 265 
 
 genus range from the Lower Silurian to the Carboniferous 
 Rocks, and are, therefore, exclusively Palaeozoic. 
 
 In Ecculiomphalus (fig. 235) the shell is very like that of 
 Cyrtolites, but the whorls are few in number, and are widely 
 separated from one another. The shell is thin, and the coils 
 
 Fig. 235. Ecculiomphalus distant. Quebec Group (Upper Cambrian?) 
 
 lie in the same plane. The species of this genus range from 
 the Lower Silurian to the Carboniferous, and have been com- 
 pared to Euomphali imperfectly rolled up ; but the true affini- 
 ties of the genus are doubtful. 
 
 Lastly, the genus Porcellia includes shells which are com- 
 posed of many whorls coiled into a flat spiral. The whorls are 
 keeled, and the aperture has a dorsal slit. The species of this 
 genus are mainly Palagozoic, but range into the Trias. 
 
 SECTION B. PULMONIFERA : Respiration aerial, by means 
 of a pulmonary chamber. The Pulmonifera include the ordin- 
 ary Land-snails, Slugs, Pond-snails, &c., and are usually provided 
 with a well-developed shell ; though this may be rudimentary 
 (as in the Slugs), or even wanting. In the Land-snails and 
 Pond-snails there is a well-developed shell into which the 
 animal can retire completely. The Slugs, again, have a merely 
 rudimentary shell which is completely concealed within the 
 mantle. The completely shell-less forms are necessarily wholly 
 unknown as fossils. The Slugs, with a rudimentary shell, are 
 only doubtfully represented in a fossil state, and that only in 
 the Tertiary Rocks. The abundance of the shell-bearing forms 
 as fossils depends mainly on the habits of the animal. The 
 Land-snails, being terrestrial in their habits, are, necessarily, 
 but sparingly represented as fossils, and they do not date back
 
 266 
 
 MOLLUSCA. 
 
 to a time anterior to the Carboniferous. The Pond-snails, be- 
 ing exclusively confined to fresh water, are only known as fossils 
 in fluviatile and lacustrine deposits, and they are exclusively 
 Secondary and Tertiary, not being known in the Palaeozoic 
 period. The Pulmonifera are divided into the two orders of 
 the Inoperculata and Operculata, according as the shell is des- 
 titute of an operculum, or is provided with this apparatus. 
 
 ORDER IV. INOPERCULATA:^/^// not provided with an 
 operculum. 
 
 FAM. i. HELICID^: : Shell well developed, capable of con- 
 taining the entire animal. With the exception of Pupa and 
 Zonites (the last a sub-genus of Helix), all the Helicida belong to 
 the Tertiary and Recent periods. As they are all terrestrial in 
 their habits, they are necessarily of rare occurrence as fossils, 
 occurring chiefly in fluviatile and lacustrine deposits. The two 
 genera above mentioned have been found in the Coal-Measures, 
 and are the oldest forms of the group. The chief fossil genera 
 are Helix, Bulimus, Achatina, Pupa, and Clausilia. 
 
 In the genus Helix are the ordinary Land-snails (fig. 236), 
 in which the shell is conical, sometimes depressed, or some- 
 times discoidal ; the aperture transverse, crescentic or rounded, 
 and the columella perforated or imperforate. The Land-snails, 
 with one exception, are all confined to the Tertiary and Recent 
 periods. The exception to this statement is \he Zonitcs priscus 
 (fig. 236), discovered by Dr Dawson in the Coal-Measures of 
 
 
 I 
 
 Fig. 236. Zonites (Contilus) priscus (after Dawson). a Specimen enlarged twelve 
 diameters; b Sculpture, magnified. Coal-Measures, Nova Scotia. 
 
 Nova Scotia. This is a true Land-snail referred to Zonites or 
 Conn/us, a sub-genus of Helix itself. 
 
 In Bulimus the shell is turreted or oblong, the columella 
 generally simple, and the outer lip usually expanded and 
 thickened. In the nearly allied genus Achatina the columella
 
 GASTEROPODA. 
 
 267 
 
 is twisted, and the lips of the shell- aperture are thin. Both 
 genera date their existence from the Eocene Tertiary. 
 
 In the genus Pupa the shell is cylindrical or oblong, with a 
 round, often toothed, aperture. The oldest member of this 
 genus is the Pupa vetusta (fig. 237), discovered by Dr Dawson 
 in the Coal-Measures of Nova 
 Scotia, in the hollow trunk of an 
 erect Sigillaria. This ancient 
 form is remarkably like some 
 living " Chrysalis-shells," and 
 there appears to be no reason 
 for framing a new genus (Den- 
 dropupa} for its reception. With 
 the exception of this little shell, 
 all the fossil species of Pupa are 
 confined to the Tertiary period, 
 commencing in the Eocene. 
 
 In the genus Clausilia the 
 shell is spindle-shaped, coiled 
 into a left-handed spiral (" sin- 
 istral"), with an elliptical aper- 
 ture, partially contracted by 
 shelly processes. The Clausi- 
 lice, so far as known, date their 
 existence from the Eocene 
 Tertiary. 
 
 FAM. 2. LIMACID.E : Shell rudimentary, usually internal or 
 concealed by the mantle. The " Slugs " are included in this 
 family, and they are only known in the fossil state by doubtful 
 remains in the Miocene and Pliocene Tertiary. A species of 
 Testacdla has also been indicated as occurring in the Miocene. 
 
 FAM. 3. LIMN^EID^E : Shell well developed, thin and horn- 
 coloured. Aperture simple ; lip sharp. The 
 Limnaidcs are all inhabitants of fresh water, 
 and they are found in fluviatile \and lacus- 
 trine deposits. They are believed to com- 
 mence in the Jurassic period, members of 
 this family having been described from the 
 Lias and from the Purbeck beds (Upper 
 Oolites). It is not, however, until we reach 
 the base of the Cretaceous system (Weald 
 Clay) that these forms appear in any abun- 
 dance. 
 
 The genus Limtuea (fig. 238) includes the 
 so-called " Pond-snails," characterised by their thin, spiral, 
 
 Fig. *y].Puj>a (_Dendropupa) vetusta. 
 (After Dawson.) a Natural size; En- 
 larged ; c Apex enlarged ; d Sculpture, 
 magnified. Coal-Measures.
 
 268 MOLLUSCA. 
 
 elongated shells, with a large body-whorl and an obliquely- 
 twisted columella. The species of this genus commence in 
 the Wealden (Lower Cretaceous) perhaps in the Upper 
 Oolites and are abundantly represented throughout the Ter- 
 tiary series. 
 
 In the genus Physa (fig. 239) the shell is left-handed (" sinis- 
 tral "), ovate, thin, and polished, with the aperture rounded in 
 front. Species of this genus have been indi- 
 cated as occurring in the Purbeck beds (Up- 
 per Oolites) and Wealden (Cretaceous). 
 Most of the fossil species, however, belong to 
 the Tertiary period, and the genus attains its 
 maximum at the present day. 
 
 The genus Ancylus comprises the so-called 
 " River-Limpets," at once distinguished by 
 their thin, conical, limpet-shaped shells. A few 
 fossil species are known, chiefly, if not exclu- 
 Fi g . 2 39; rhysa. sively, confined to the Tertiary period. 
 
 The genus Planorbis comprises a number 
 of well-known fresh-water shells, in which the shell is discoidal 
 and many-whorled, the aperture crescentic, and the lip thin. 
 The fossil species of this genus date from the Lias (?), but are 
 not plentiful except in the Tertiary deposits, whence a large 
 number of forms has been obtained. 
 
 FAM. 4. AURICULID^E : Shell spiral, with a horny epidermis ; 
 aperture elongated and denticulated. The species of this 
 family inhabit salt marshes and places overflowed by the sea. 
 They are of little importance as fossils, dating from the Eocene 
 Tertiary. 
 
 ORDER V. OPERCULATA : Shell furnished with an oper- 
 culum. 
 
 FAM. 5. CYCLOSTOMID^ : Shell spiral, rarely elongated, 
 often depressed. Aperture nearly circular. 
 Operculum spiral. The genus Cydostoma 
 (fig. 240) includes almost all the fossil 
 species of this family, and dates from the 
 Eocene Tertiary. All the members of this 
 family are terrestrial in their habits, and 
 they are of small importance as fossils. 
 FAM. 6. ACICULID^ : Shell elongated, 
 
 Fig. *4p.Cyciosto>na. cylindrical ; operculum thin and sub- 
 ArnoudU. Eocene Ter- S pi ra l. A species of Aciciila has been in- 
 dicated as occurring in the Pliocene Terti- 
 ary ; but the family is otherwise unrepresented by fossil forms.
 
 PTEROPODA. 
 
 269 
 
 CHAPTER XXIII. 
 
 CLASS PTEROPODA. 
 
 THE Pteropoda are defined by being free and pelagic, swimming 
 by means of two wing-like appendages (epipodia), developed 
 from each side of the anterior extremity of the body. The 
 flexure of the intestine is neural. 
 
 As to the position of the Pteropoda in the Molluscan scale, 
 they must be looked upon as inferior in organisation to any of 
 the Gasteropoda, of which class they are often regarded as the 
 lowest division. They permanently represent, in fact, the tran- 
 sient, larval stage of the Sea-snails. 
 
 The living Pteropods are all of small size, and are found 
 swimming at the surface of the open ocean, often in enormous 
 numbers. Locomotion 
 is effected by two wing- 
 like fins (fig. 241) devel- 
 oped from the sides of 
 the head. In some cases 
 the body is naked and 
 unprotected ; but there 
 is commonly a symmetri- 
 cal glassy shell, either 
 consisting of a dorsal and 
 ventral plate united, or 
 forming a spiral. 
 
 The Pteropoda are divided into two orders, termed Thecoso- 
 mata and Gymnosomata; the former characterised by possess- 
 ing an external shell and an indistinct head ; the latter by 
 being devoid of a shell, and by having a distinct head, with 
 fins attached to the neck. 
 
 The Gymnosomatous Pteropods, in which there is no shell, 
 as a matter of course, are wholly unknown in the fossil con- 
 dition. The Thecosomatous Pteropods, in which there is a 
 shell, are divided into two families the Hyaleida and Lima- 
 cinidce. The latter comprises forms in which there is a small 
 spiral shell, which is sometimes provided with an operculum ; 
 but it is unrepresented in a fossil state. The former family 
 comprises forms in which the shell is symmetrical, straight or 
 curved, globular or needle-shaped, and it is represented by a 
 considerable number of fossil forms, most of which are ex- 
 tremely unlike any known living examples of the class, being 
 often of comparatively colossal dimensions. The fossil forms 
 
 241. Pteropoda. a Cleodora pyramidata ; 
 "uvieria columnella. (After Woodward.)
 
 2/0 MOLLUSCA. 
 
 mostly belong to the genera Hyalea, Cuvieria, Cleodora, T/ieca, 
 Pterotheca, Tentaculites, and Conularia; but other less import- 
 ant types are known to have existed in past time. Of the 
 above-mentioned generic forms, the first three are well repre- 
 sented at the present day by living forms. The remaining 
 four are almost exclusively Palaeozoic, Conularia alone surviv- 
 ing into the earlier portion of the Mesozoic period. Not only 
 is this the case, but the forms in question all commence their 
 existence in the Lower Silurian or Upper Cambrian, and none 
 of them except Conularia transgresses the upper limit of the 
 Devonian Rocks. Lastly, almost all these forms are of com- 
 paratively gigantic size, and they differ in many respects from 
 living forms. 
 
 In the genus Hyalea (fig. 242) the shell is globular, trans- 
 lucent, the dorsal plate ex- 
 ejfflk tended into a hood ; the aper- 
 ^/ \ Rtf/B ture is contracted, with a late- 
 X^5^ \*& ral slit on each si(1 e- The 
 fossil species are only known 
 
 Fig. ^.-HyahaOrbignyana. Miocene J n t he Miocene and PllOCCne 
 
 Tertiary, and the genus at- 
 tains its maximum in existing seas. Cleodora has a pyramidal 
 shell, and dates from the Miocene ; and Cuvieria (fig. 241) 
 has a cylindrical shell, and dates from the Pliocene. Both 
 these genera attain their maximum at the present day. 
 
 The genus Theca (the Hyolithcs of Continental and American 
 palaeontologists) comprises a number of singular forms in 
 which the shell is straight, sheath- 
 shaped, tapering to a point, triangular, 
 and destitute of lateral appendages 
 (fig. 243). The mouth of the shell 
 is trigonal, sometimes closed by an 
 operculum, sometimes furnished with 
 curved lateral appendages. The length 
 of the shell is commonly about an inch 
 or an inch and a half. Nearly ninety 
 species of this genus are enumerated 
 b 7 M - Barrande, distributed in the 
 and us opercuium. (After Sal- Upper Cambrian, Silurian, and Devon- 
 
 ter.) From the Tremadoc Slates r . , , 
 
 (Upper Cambrian ?> ian formations, but not extending into 
 
 the Carboniferous period. 
 
 The genus Pterotheca of Salter is exclusively Silurian, and is 
 characterised by having the " shell transversely oval, bilobed, 
 with wavy sides and a strong median keel ; ventral plate short, 
 narrow, and flat."
 
 PTEROPODA. 271 
 
 The genus Conularia is one of the most extraordinary of the 
 extinct genera of the Pteropods, if only for the enormous size 
 attained by many examples. The shape 
 of the shell is very like that of some 
 living Pteropods, but specimens occa- 
 sionally reach the length of nearly a foot, 
 with a breadth of more than an inch. 
 The shell in Conularia (fig. 244) is 
 straight, tapering towards one end, and 
 having a sub-quadrate or rhomboidal 
 aperture at the other. The form of the 
 shell is generally distinctly four-sided, 
 the sides being finely striated with trans- 
 verse lines. The shell is generally of 
 extreme tenuity ; but the internal cavity 
 is sometimes restricted by concentric 
 lamellae, and the apex may be partitioned 
 off. M. Barrande enumerates eighty-three ^iiata. ^Devonian? 1 "' 
 species of Conularia, most of which are 
 
 Palaeozoic, commencing in the lowest Silurian deposits. The 
 genus, however, extends into the Mesozoic Rocks, the last 
 species, so far as at present known, appearing in the Lias. 
 
 Lastly, the genus Tentaculites comprises a number of singular 
 Palaeozoic fossils, the true position of which cannot be said 
 to be absolutely free from doubt. Most authorities now place 
 Tentaculites, with apparently good reason, in the Pteropoda ; 
 but others would still refer this genus to 
 the Tubicolar Annelides. It must be ad- 
 mitted, also, that in some respects Ten- 
 taculites approximates pretty closely to the 
 Annelidous genera Conchicolites and Cor- 
 nulites. Upon the whole, however, the 
 mode of occurrence of Tentaculites and 
 its undoubted free habit of existence leave 
 little doubt as to its true place being 
 amongst the Pteropods. The sn^ll of 
 Tentaculites (fig. 245) has the form of a 
 straight conical tube, tapering towards one 
 extremity to a pointed closed apex, and 
 expanding towards the other to a circular 
 aperture. The walls of the shell are thin, and are surrounded 
 with numerous thickened rings or annulations, sometimes with 
 intermediate striae, over a whole or part of the length of the tube. 
 The size of Tentaculites varies much in different cases, being 
 sometimes less than a couple of lines in length, and sometimes
 
 2/2 MOLLUSCA. 
 
 attaining a length of an inch or more. Fifty-two species of 
 Tentaculites are enumerated by M. Barrande, commencing in 
 the Lower Silurian and ranging into the Devonian. The genus 
 is essentially Silurian, and examples of some species often 
 occur in myriads through a considerable thickness of strata. 
 
 CHAPTER XXIV. 
 CLASS CEPHALOPODA. 
 
 CLASS IV. CEPHALOPODA. The members of the Cephalo- 
 poda are denned by the possession of eight or more arms placed 
 in a circle round the mouth ; the body is enclosed in a muscular 
 mantle-sac, and there are two or four plume-like gills within the 
 mantle. There is an anterior tubular orifice (the ' ' infundibulum " 
 or "funnel"}, through which the effete water of respiration is 
 expelled. 
 
 The Cephalopoda, comprising the Cuttle-fishes, Squids, Pearly 
 Nautilus, &c., constitute the most highly organised of the 
 classes of the Mollusca. They are all marine and carnivorous, 
 and are possessed of considerable locomotive powers. At the 
 bottom of the sea they can walk about, head downwards, by 
 means of the arms which surround the mouth, and which are 
 usually provided with numerous suckers or " acetabula." They 
 are also enabled to swim, partly by means of lateral expansions 
 of the integument or fins (not always present), and partly by 
 means of the forcible expulsion of water through the tubular 
 " funnel," the reaction of which causes the animal to move in 
 the opposite direction. 
 
 The majority of the living Cephalopods are naked, possess- 
 ing only an internal skeleton, and this often a rudimentary 
 one ; but the Argonaut (Paper Nautilus) and the Pearly Nau- 
 tilus are protected with an external shell, though the nature of 
 this is extremely different in the two forms. 
 
 The body in the Cephalopoda is symmetrical, and is enclosed 
 in an integument which may be regarded as a modification of 
 the mantle of the other Mollusca. Ordinarily there is a toler- 
 ably distinct separation of the body into an anterior cephalic 
 portion (prosonta), and a posterior portion, enveloped in the 
 mantle, and containing the viscera (metasoma). The head is 
 very distinct, bearing a pair of large globular eyes, and having 
 the mouth in its centre. The mouth is surrounded by a circle
 
 CEPHALOPODA. 
 
 273 
 
 of eight, ten, or more, long muscular processes, or "arms " 
 
 (fig. 246), which are generally provided with rows of suckers. 
 
 In the Octopod Cuttle-fishes there are only eight arms, and 
 
 these are all nearly alike. In the 
 
 Decapod Cuttle-fishes there are 
 
 ten arms, but two of these called 
 
 " tentacles " are much longer 
 
 than the others, and bear suckers 
 
 only at their extremities, which 
 
 are enlarged and club-shaped. 
 
 In the Pearly Nautilus the arms 
 
 are numerous, and are devoid of 
 
 suckers. 
 
 The parts of the Cephalopoda 
 which may be preserved in a fossil 
 condition, and which thus inte- 
 rest the paleontologist, are the 
 mandibles, the ink-bag, and the 
 skeleton, whether this be internal 
 or external. 
 
 The mandibles are contained 
 within the mouth or " buccal 
 cavity " of the animal, and have 
 the form of powerful jaws, work- 
 ing vertically like the beak of a 
 bird. They are horny or calcare- 
 ous, and in shape closely resem- 
 ble the beak of a parrot, with this difference, that the largest 
 of the two mandibles is placed inferiorly. Mandibles of this 
 nature are present in both the Cuttle-fishes and the Pearly 
 Nautilus, and they doubtless existed in all the extinct forms. 
 They not uncommonly occur as fossils, but they do not appear 
 to have been observed out of the Jurassic and Cretaceous 
 Rocks. They are commonly called "Rhyncholites," and genera 
 such as Rhynchoteuthis have been founded upon them (fig. 
 247). 
 
 The ink-bag is a special gland possessed by the Cuttle-fishes, 
 for the purpose of secreting an inky fluid, which the animal can 
 discharge into the water, so as to enable it to escape when 
 menaced or pursued. The secretion of the ink-bag consists of 
 finely-divided particles of carbon suspended in fluid, and it is 
 extremely indestructible. The ink-bag, with its contained se- 
 cretion, is not uncommonly found in the fossil condition ; but 
 it has only been observed in strata of Secondary age.. In the 
 Tetrabranchiate Cephalopods, in which there is an 'external 
 s 
 
 Fig. 246. Cephalopoda. Sepiola 
 Atlantica, one of the Cuttle-fishes 
 (after Woodward).
 
 2/4 MOLLUSCA. 
 
 shell, and this means of defence is not needed, there is no ink- 
 bag. 
 
 The shell of the Cephalopoda is sometimes external, some- 
 times internal. The internal skeleton is known as the " cuttle- 
 
 Lower Greensand (Cretaceous). 
 
 bone," " sepiostaire," or " pen " (gladhis), and may be either 
 corneous or calcareous. In some cases it is rendered complex 
 by the addition of a chambered portion or " phragmacone," 
 which is to be regarded as a visceral skeleton or " splanchno- 
 skeleton." In Spirula the phragmacone is the sole internal 
 skeleton, and is coiled into a spiral, the coils of which lie in 
 one plane, and are near one another, but not in contact. It 
 thus resembles the shell of the Pearly Nautilus, but it is inter- 
 nal, and differs, therefore, entirely from the external shell of the 
 latter. The only living Cephalopods which are provided with 
 an external shell are the Paper Nautilus (Argonauta), and the 
 Pearly Nautilus (Nautilus pompilius) ; but not only is the struc- 
 ture of the animal different in each of these, but the nature of 
 the shell itself is entirely different. The shell of the Argonaut is 
 involuted, but is not divided into chambers, and it is secreted 
 by the webbed extremities of two of the dorsal arms of the 
 female. The arms are bent backwards, so as to allow the 
 animal to live in the shell, but there is in reality no organic 
 connection between the shell and the body of the animal. In 
 fact, the shell of the Argonaut, being confined to the female, 
 and serving by its empty apex as a receptacle for the ova, may 
 be looked upon as a " nidamental shell," or, as it is secreted by 
 a modified portion of the foot, it may more properly be re- 
 garded as a " pedal shell." The shell of the Pearly Nautilus 
 (fig. 248), on the other hand, is a true pallial shell, and is se- 
 creted by the body of the animal, to which it is organically 
 connected. It is involuted, but it differs from the shell of the 
 Argonaut in being divided into a series of chambers by shelly
 
 CEPHALOPODA. 275 
 
 partitions or septa, which are pierced by a tube or " siphuncle," 
 the animal itself living in the last chamber only of the shell. 
 
 The Cephalopoda are divided into two extremely distinct and 
 well-marked orders, termed the Dibranchiata and Tetrabran- 
 chiala. The former is characterised by the possession of two 
 gills only, and by the fact that the shell, if external (as it very 
 rarely is), is never chambered. In this order are comprised 
 the living Cuttle-fishes, Squids, and Paper Nautilus, with the 
 extinct family of the Belemnitidcz, The latter is distinguished 
 by the presence of four gills, and by the possession of an exter- 
 nal many-chambered shell This order is abundantly repre- 
 sented in past time, but has no other living representative than 
 the Pearly Nautilus alone. The following table gives the char- 
 acters and leading genera of the families of Cephalopoda : 
 
 SYNOPSIS OF THE FAMILIES OF THE CEPHALOPODA. 
 CLASS CEPHALOPODA. 
 
 ORDER I. DIBRANCHIATA. 
 
 Animal with two branchiae ; not more than eight or ten arms, 
 provided with suckers ; an ink-bag Shell commonly internal and 
 rudimentary ; rarely external, but not chambered. 
 SECTION A. OCTOPODA. 
 
 Arms eight, suckers sessile. 
 Fam. I. Argonautidce. 
 
 Female provided with a calcareous, external, monothalamous 
 shell, secreted by the webbed extremities of two of the dorsal 
 arms. Gen. Argonauta. 
 Fam. 2. Octopodidce. 
 
 Shell internal, rudimentary, uncalcified. No pallial fins in 
 most. 111. Gen. Octopus, Tremoctopus, Eledone, Pinnoctopus. 
 SECTION B. DECAPODA. 
 
 Arms eight, ivith two clavate " tentacles ;" suckers pedunculated. 
 Fam. 3. Teuthida. 
 
 Shell an internal horny "pen" or "gladius." Fins mostly 
 terminal. 111. Gen. Loligo, Onychoteuthis, Ommastrephes. 
 Fam. 4. Belemnitidte. 
 
 Shell internal, composed of a conical chambered portion 
 ( " phragmacone ") with a marginvj siphuncle, produced into a 
 horny plate or "pen," and lodged in a cylindrical fibrous 
 "guard." 111. Gen. Belemnites, Belemnitella, Belemnoteuthis. 
 Fam. 5. Sepiadtz. 
 
 Shell calcareous, consisting of a broad, laminar plate, termi- 
 nating in an imperfectly-chambered apex (" phragmacone"). 111. 
 Gen. Sepia, Beloptera, Spirulirostra. 
 Fam. 6. Spirulida. 
 
 Shell internal, nacreous, chambered, discoidal ; the whorls 
 separate ; a ventral siphuncle. Gen. Spirula. 
 ORDER II. TETRABRANCHIATA. 
 
 Animal with four gills ; arms more than ten, without suckers ; 
 no ink-bag ; shell external, chambered, and siphuncled.
 
 276 MOLLUSCA. 
 
 Fam, I. Nautilidee. 
 
 Sutures of the shell simple ; the siphuncle central, sub-central, 
 or near the concavity of the curved shells, simple. 
 Sub-family Nautilidtz pi'oper. 
 
 Body-chamber capacious ; aperture simple ; siphuncle 
 central or internal. 111. Gen. Nautilus, Lituites, Trocho- 
 ceras. 
 
 Sub-family Orthoteratida. 
 
 Shell 
 
 Shell straight, curved, or discoidal ; body-chamber 
 small ; aperture contracted ; siphuncle complicated. I1L 
 Gen. Orthoteras, Phragmoceras, Cyrtoceras. 
 Fam. 2. Ammonitida. 
 
 Shell discoidal, curved, spiral, or straight ; body-chamber 
 elongated ; aperture guarded by processes, or closed by an oper- 
 culum ; sutures angulated, lobed, or foliaceous ; siphuncle external 
 or dorsal (on the convex side of the curved shells). 111. Gen. 
 Ammonites, Ceratites, faculties, Turrilites, Scaphites, Ancyloceras. 
 
 As regards their general distribution in time, the Cephalo- 
 pods are largely represented in all the primary groups of strati- 
 fied rocks from the Lower Silurian up to the present day. Of 
 the two orders of Cephalopoda, the Tdrabranchiata is the oldest, 
 attaining its maximum in the Palaeozoic period, decreasing in 
 the Mesozoic and Kainozoic epochs, and being represented at 
 the present day by the single form, Nautilus pompilius. Of the 
 sections of this order, the Nautilidee proper and the Orthocer- 
 atidcs are pre-eminently Palaeozoic, and the Ammonitida are 
 not only pre-eminently but are almost exclusively Secondary. 
 Of the abundance of the two former families in the Silurian 
 seas some idea may be obtained when it is mentioned that over 
 a thousand species have been described by M. Barrande from 
 the Silurian basin of Bohemia alone. IhzNautilidce proper have 
 gradually decreased in numbers from the Palaeozoic, through 
 the Secondary and Tertiary periods, to the present day. The 
 Orthoccratida died out much sooner, being exclusively Palaeo- 
 zoic, with the exception of the genera Orthoceras itself and 
 Cyrtoceras, which survived into the commencement of the Se- 
 condary period, finally dying out in the Trias. 
 
 The second family of the Tetrabranchiata viz., the Ammo- 
 nitida is almost exclusively Secondary, being very largely re- 
 presented by numerous species of the genera Ammonites, Cera- 
 tites, Baailites, Turrilites, &c. The only Palaeozoic genera are 
 Goniatites an&Bactrites, of which the former is found from the 
 Upper Silurian to the Trias, whilst the latter is a Silurian 
 and Devonian form. The genus Ceratites is characteristically 
 Triassic, but it is said to occur in the Devonian Rocks, and 
 some species are Cretaceous. All the remaining genera are 
 exclusively Secondary, the genera Baailites, Turrilites, Hamites 
 and Ptychoceras being confined to the Cretaceous period.
 
 TETRABRANCHIATE CEPHALOPODS. 2// 
 
 Of the Dibranchiate Cephalopods the record is less perfect, 
 as they have few structures which are capable of preservation. 
 They attain their maximum, as fossils, shortly after their first 
 appearance in the Secondary Rocks, where they are represented 
 by the large and important family of the Belemnitidce. Some 
 of the Teuthida and Sepiadce are found both in the Secondary 
 and in the Tertiary Rocks, and two species of Argonaut have 
 been discovered in the later Tertiaries. No example of a Di- 
 branchiate Cephalopod is known from the Palaeozoic deposits, 
 and the order attains its maximum at the present day. 
 
 CHAPTER XXV. 
 TETRABRANCHIA TE CEPHALOPODS. 
 
 THE Tetrabranchiate Cephalopods are characterised by being 
 creeping animals, protected by an external, many-chambered shell, 
 the septa between the chambers of which are perforated by a mem- 
 branous or calcareous tube, termed the " siphuncle" The arms 
 are numerous, and are devoid of suckers ; the. branchia are four 
 in number, two on each side of the body ; the funnel does not form 
 a complete tube ; and there is no ink-bag. 
 
 The Tetrabranchiate Cephalopods have an enormous de- 
 velopment in past time, several thousand species, mostly 
 belonging to extinct types, being known from the Palaeozoic 
 Rocks alone. In the Mesozoic Rocks the members of this 
 order were almost equally abundant. In the Tertiary Rocks 
 the order is reduced to the single genus Nautilus, represented 
 at the present day by the single species Naiitihis pompilius 
 (the Pearly Nautilus). The palseontological importance of this 
 order being so great, it may be as well to preface the account 
 of the extinct forms by a short description of the structure of 
 the living Nautilus pompilius, as described by Professor Owen, 
 from the only perfect specimen which has as yet been obtained. 
 
 The soft structures in the Pearly Nautilus may be divided 
 into a posterior, soft, membranous mass (metasomd), containing 
 the viscera, and an anterior muscular division, comprising the 
 head (prosoma) ; the whole being contained in the outermost, 
 capacious chamber (the body-chamber) of the shell, from which 
 the head can be protruded at will. The shell itself (fig. 248) 
 is involuted and many-chambered, the animal being contained 
 successively in each chamber, and retiring from it as its size
 
 278 MOLLUSCA. 
 
 becomes sufficiently great to necessitate the acquisition of more 
 room. Each chamber, as the animal retires from it, is walled 
 off by a curved, nacreous septum ; the communication between 
 the chambers being still kept up by a membranous tube or 
 siphuncle, which opens at one extremity into the pericardium, 
 
 Fig. 248. Pearly Nautilus (Xauiilus fiontpilitts). a Mantle ; b Its dorsal fo 
 c Hood ; o Eye ; / Tentacles ; /Funnel. 
 
 and is continued through the entire length of the shell. The 
 position of the siphuncle is in the centre of each septum. 
 
 Posteriorly the mantle of the Nautilus is very thin, but it is 
 much thicker in front, and forms a thick fold or collar sur- 
 rounding the head and its appendages. From the sides of the 
 head spring a great number of muscular prehensile processes 
 or " arms," which are annulated, but are not provided with cups 
 or suckers. In the centre of the head is the mouth, surrounded 
 by a circular fleshy lip, external to which is a series of labial 
 processes. The mouth opens into a buccal cavity, armed with 
 two horny mandibles, partially calcified towards their extremi- 
 ties, and shaped like the beak of a parrot, except that the under 
 mandible is the longest. There is also a " tongue," which is 
 fleshy and sentient in front, but is armed with recurved teeth 
 behind. The gullet opens into a large crop, which in turn 
 conducts to a gizzard, and the intestine terminates at the base 
 of the funnel. On each side of the crop is a well-developed 
 liver. 
 
 The heart is contained in a large cavity, divided into several
 
 TETRABRANCHIATE CEPHALOPODS. 279 
 
 chambers, and termed the " pericardium " (Owen). The re- 
 spiratory organs are in the form of four pyramidal branchiae, 
 two on each side. 
 
 The chief masses of the nervous system are the cerebral and 
 infra-cesophageal ganglia, which are partially protected by a 
 cartilaginous plate, which is to be regarded as a rudimentary 
 cranium, and which sends out processes for the attachment of 
 muscles. The organs of sense are two large eyes, attached by 
 short stalks to the sides of the head, and two hollow plicated 
 sub-ocular processes, believed to be olfactory in their function. 
 
 The reproductive organs of the female consist of an ovary, 
 oviduct, and accessory nidamental gland. 
 
 There is no ink-bag, and the funnel does not form a com- 
 plete tube, but consists of two muscular lobes, which are simply 
 in apposition. It is the organ by which swimming is effected, 
 the animal being propelled through the water by means of the 
 reaction produced by the successive jets emitted from the 
 funnel. The function of the chambers of the shell appears to 
 be that of reducing the specific gravity of the animal to near 
 that of the surrounding water, since they are probably filled 
 with some gas secreted by the animal, or with water itself. The 
 function of the siphuncle is unknown, except in so far as it 
 doubtless serves to maintain the vitality of the shell. 
 
 SHELL OF THE TETRABRANCHIATA. The shells of all the 
 Tetrabranchiata agree in the following points : 
 
 1. The shell is external. 
 
 2. The shell is divided into a series of chambers by plates 
 or " septa," the edges of which, where they appear on the shell, 
 are termed the "sutures." 
 
 3. The outermost chamber of the shell is the largest, and is 
 the one inhabited by the animal. 
 
 4. The various chambers of the shell are united by a tube, 
 termed the " siphuncle." 
 
 Agreeing in all these fundamental points of structure, two 
 very distinct types of shell may be distinguished as charac- 
 teristic of the two families NautUictek*$&& Ammonitidce, into 
 which the order Tetrabranchiata is divided. 
 
 In the family Nautilidce (fig. 249), the " septa " of the shell 
 are simple, curved, or slightly lobed ; the " sutures " are more 
 or less completely plain ; and the " siphuncle " is central, sub- 
 central, or internal (i.e., on the concave side of the curved shells). 
 
 In the family Ammonitidtz (fig. 249), on the other hand, the 
 septa are folded and complex ; the sutures are angulated, zig- 
 zag, lobed, or foliaceous ; and the siphuncle is external (i.e., 
 on the convex side of the curved shells).
 
 280 
 
 MOLLUSCA. 
 
 In both these great types of shell, a series of representative 
 forms exists, resembling each other in the manner in which the 
 shell is folded or coiled, but differing in their fundamental 
 structure. All these different forms may be looked upon as 
 produced by the modification of a greatly-elongated cone, the 
 structure of which may be in conformity with the type either of 
 the Nautilida or of the Ammonitidce, The following table 
 (after Woodward) exhibits some of the representative forms in 
 the two families : 
 
 Shell straight . . 
 
 bent on itself 
 
 curved . . 
 
 spiral . . . 
 
 , discoidal . 
 
 Nautilida. 
 Orthoceras . 
 Ascoceras . 
 Cyrtoceras . 
 Trochoceras 
 Gyroceras . 
 
 discoidal and produced Lituites . 
 involute . Nautilus . 
 
 Ammonitidtt. 
 Baculites. 
 Ptychoceras. 
 Toxoceras. 
 Turrilites. 
 Crioceras. 
 Ancyloceras. 
 Ammonites. 
 
 .0 .0 - Q ,0 
 
 .-jaw 
 
 Fig. 249. Diagram to illustrate the position of the siphuncle and the form of the septa 
 in various Tetrabranchiate Cephalopoda. The upper row of figures represents transverse 
 sections of the shells, the lower row represents the edges of the septa, a a Ammonite or 
 Baculite ; b b Ceratite ; c c Goniatite ; ddClymenia; ee Nautilus or Orthoceras. 
 
 DISTRIBUTION OF TETRABRANCHIATA IN TIME. Regarded 
 as a whole, the Tetrabranchiate Cephalopods form a group 
 which early attained its maximum, and which is now almost 
 extinct. The greatest development, in point of numbers, took 
 place in the Palaeozoic period ; and the forms then existing 
 belonged to decidedly simpler types than those which followed 
 them. The greatest number of types existed during the Meso- 
 zoic period ; and here the order still maintained a great abun- 
 dance of individuals. With the close of the Secondary epoch 
 a large number of complex types disappeared wholly, and the 
 order was left without any representative in the Tertiary Rocks 
 except the simple and ancient genus Nautilus.
 
 NAUTILID.-E. 
 
 28l 
 
 As regards the two great sections of the order, the Nauti- 
 lidcB are the most ancient, dating their existence from the 
 Lower Silurian, if not from the Upper Cambrian. Not only 
 is this the case, but they are pre-eminently Palaeozoic, very few 
 forms surviving into the Secondary period, and only one into 
 the Tertiary. The Ammonitidce, on the other hand, are pre- 
 eminently Mesozoic, and no member of this group is known 
 to have survived into the Kainozoic period. This group, 
 however, is represented by two comparatively simple types in 
 the Palaeozoic period, commencing their existence from the 
 Silurian. 
 
 In the following are given the characters and distribution in 
 time of the leading forms of the Tetrabranchiate Cephalo- 
 pods : 
 
 NAUTILID^E. 
 
 FAM. I. NAUTILIDJE. Sutures of the shell simple ; thesiphuncle 
 simple, central, sub-central, or near the concavity of the curred 
 shells. 
 
 SUB-FAMILY i. NAUTILID^E PROPER. Body-chamber capa- 
 cious ; aperture of the shell simple ; siphuncle central or in- 
 ternal. The genera of this sub-family are Nautilus, Lituites, 
 Trochoceras, and Clymenia ; of which the last three are ex- 
 clusively Palaeozoic, whilst the first ranges through all the 
 great formations from the Silurian upwards, and is represented 
 at the present day by the Pearly Nautilus. 
 
 In the genus Nautilus (fig. 250) the shell is involute .or dis- 
 coidal, consisting of a few whorls coiled into a flat spiral. The 
 
 Fig. 250. Nautilus Danicus. Upper Cretaceous (" Danien " of D'Orbigny). 
 
 body-chamber is of large size, and the siphuncle is central, or 
 nearly so. The genus Nautilus ranges from the Upper Silu-
 
 282 
 
 MOLLUSCA. 
 
 rian to the present day, having its maximum of development 
 in the Carboniferous period. The Palaeozoic forms are mostly 
 discoidal, having the whorls more 
 or less completely exposed. The 
 7vdw////oflaterdepositsare mostly 
 like the living species in having 
 each whorl overlapping the pre- 
 ceding, so that merely an " um- 
 bilicus " is visible. Many of the 
 extinct forms, belonging to all 
 ages, agree with the living Naut- 
 ilus in having the surface quite 
 smooth ( Lcevigati ). Others, 
 which are especially character- 
 istic of the Jurassic Rocks, have 
 the surface striated (Striati). 
 Others, chiefly of Cretaceous 
 age, have the surface marked by distinct ribs (JRtuKati). 
 
 In the Upper Silurian and Devonian Rocks Nautili are few; 
 in the Carboniferous, many species are known; in the Permian 
 
 Rocks and Trias are 
 but few species; but the 
 Jurassic and Cretaceous 
 Rocks have yielded a 
 considerable number. 
 Lastly, several Tertiary 
 species are known, all 
 of which agree with the 
 
 Fig. 251. Lituites coniu-arietis. 
 Lower Silurian. 
 
 in having their surface 
 completely smooth. 
 
 In the genus Lituites 
 (fig. 251) the shell is at 
 first coiled discoidally 
 with close or discon- 
 nected whorls ; but the 
 last chamber is pro- 
 duced into a straight 
 or slightly-curved line. 
 The siphuncle is placed 
 in the centreof the septa 
 of the shell. All the 
 known species of Lituites are confined to the Silurian forma- 
 tion ; but some occur in deposits the age of which is pro- 
 bably Upper Cambrian. 
 
 Fig. isv.Ciymenia Sedgvvickii. Devonian. The 
 lower figure shows the form of the suture.
 
 NAUTILID^i. 
 
 283 
 
 The genus Trochocems is one which was founded by M. 
 Barrande to include certain singular Silurian Cephalopods in 
 which the shell is doubly curved. In the typical forms 
 corresponding with Turrilites amongst the Ammonitidcz the 
 coils of the shell are in contact and pass obliquely round a 
 central axis, so that the shell becomes turreted. In other 
 cases, however, the shells are simply bent, and we have an 
 approach to the genus Cyrtoceras, 
 
 In the genus Clymenia (fig. 252) the shell is discoidal, coiled 
 into a flat spiral, and closely resembling some of the older 
 forms of Nautilus. The inner side of each whorl is deeply 
 excavated for the reception of the convexity of the internal 
 whorl. The septa are simple, like those of Nautilus, or are 
 slightly lobed, and the siphuncle is internal, placed on the 
 concave side of the whorls. Numerous species of Clymenia are 
 known, all belonging to the Devonian period ; and some of 
 the Upper Devonian limestones of 
 Germany are so profusely charged 
 with fossils of this genus as to have 
 received the name of " Clymenien- 
 kalk." 
 
 SUB - FAMILY 2. ORTHOCERAT- 
 IDTE. Shell straight, curved, or 
 discoidal ; body - chamber small ; 
 aperture of the shell small, some- 
 times extremely contracted; siph- 
 uncle complicated. The Ortho- 
 ceratidcz commence in the lowest 
 Silurian deposits, and attain their 
 maximum of development in the 
 Silurian Rocks. The family is well 
 represented in the Devonian and 
 Carboniferous Rocks, but is much 
 reduced in numbers in the Per- 
 mians. The last appearance of the 
 family is in the Triassic Rocks, 
 where it is represented by the 
 genera Orthoceras and Cyrtoceras. 
 The chief genera of this sub- 
 family are Orthoceras, Gompho- 
 ceras, Phragmoceras, Cyrtoceras, 
 Gyroceras, and Ascoceras. 
 
 In the genus Orthoceras (fig. 253) the shell is straight, the 
 siphuncle central or excentric, often of a very complex struc- 
 ture, and the aperture of the shell sometimes contracted. The 
 
 253. Urtliocen 
 septum. Lower Silurian. The lower 
 figure is a section, showing the form 
 and position of the siphuncle.
 
 28 4 
 
 MOLLUSCA. 
 
 Orthocerata are pre-eminently fossils of the Silurian, Devonian, 
 and Carboniferous Rocks. They are, however, found in the 
 Permians, and, passing into the Mesozoic series, they make 
 their last appearance near the summit of the Triassic Rocks. 
 They sometimes attained an enormous size, occasionally ex- 
 ceeding six feet in length, with a diameter of more than a foot. 
 Some idea of the vast numbers of these Cephalopods in the 
 Palaeozoic seas may be obtained from the statement that M. 
 Barrande enumerates more than five hundred species as occur- 
 ring in the small Silurian basin of Bohemia alone. The 
 numerous species of Orthoceras are divided by the above- 
 named distinguished palaeontologist into two principal sections 
 the Short-coned Orthoceratites, and the Long-coned Ortho- 
 ceratites according as the shell has the form of a short cone 
 with a large apical angle, or of a prolonged cone with a small 
 apical angle. The first of these groups is a very small one, and 
 almost all the more common forms come into the second group. 
 The nature of the siphuncle is very different in different 
 Orthocerata, and more or less well marked sub-genera have 
 been founded upon the characters of this structure. In the 
 sub-genus Huronia the siphuncle is of very large size, each 
 joint being cylindrical below but inflated above, the outer 
 walls of the siphuncle being connected with an internal central 
 
 __ tube by radiating plates. In the forms 
 
 termed Cochleati the siphuncle consists 
 of a succession of spheroidal bead-like 
 joints. In the sub-genus Endoceras the 
 siphuncle is very large, marginal, ex- 
 centric, or central, and it is partitioned 
 off by funnel-shaped diaphragms. There 
 is, however, considerable difference of 
 opinion as to the true nature of the 
 siphuncle in this sub-genus. Lastly, in 
 the sub-genus Gonioceras the transverse 
 section of the shell is flattened, and the 
 sutures are undulated. 
 
 The genus Cyrtoceras (fig. 254) very 
 closely resembles Orthoceras, but the 
 shell is curved instead of being straight, 
 and the siphuncle is either sub-central, 
 or is more commonly internal i.e., on 
 the concave side of the shell. Cyrtoceras has about the same 
 vertical range as Orthoceras, ranging from the Silurian through 
 all the Palaeozoic formations, and disappearing in the Trias. 
 The genus is characteristically Silurian, and M. Barrande has 
 
 Fig. 254 -^rtoceraf ito- 
 dorus (Billings). Lower 
 Silurian.
 
 285 
 
 described nearly two hundred and fifty species from rocks of 
 this age in Bohemia. 
 
 Fig. 255. Pkragmoceras(Campulites)ventricosns. Upper Silurian. The right- 
 hand figure shows the form of the aperture. 
 
 In the genus Phragmoceras 
 (fig. 255) the shell is curved, 
 
 and its aperture is contracted 
 in the most extraordinary 
 manner in the middle, so as 
 to assume somewhat of the 
 shape of a keyhole. The 
 siphuncle in the majority of 
 cases is placed upon the con- 
 cave side of the shell. In 
 other cases, the ventral side 
 of the Mollusc corresponds 
 with the convex side of the 
 shell. Th e species of Phrag- 
 moceras are Silurian and De- 
 vonian, mainly the former ; 
 and M. Barrande enumerates 
 thirty-eight species as occur- 
 ring in the Silurian basin of 
 Bohemia. 
 
 In the genus Gomphoceras, 
 the shell is spindle-shaped, or 
 globular, tapering towards its 
 apex. The aperture is con- 
 tracted in the middle, like that of Phragmoceras, and the 
 siphuncle is generally sub-central. In most cases the ventral 
 
 Fig. 256. Asc 
 lings), showing t 
 Lower Silurian. 
 
 -as Canadensis (Bil- 
 he form of the septa.
 
 286 MOLLUSCA. 
 
 side of the shell is relatively the most convex, but the reverse 
 of this sometimes occurs. The species of Gomphoceras range 
 from the Silurian to the Carboniferous, but belong mainly to 
 the former. M. Barrande enumerates no less than seventy- 
 three species as occurring in the Silurian Rocks of Bohemia. 
 
 The genus Ascoceras (fig. 256) comprises some singular forms 
 in which the shell is globular or flask-shaped, and the septa do 
 not run at right angles to the axis of the shell, but nearly 
 parallel with it, being at the same time curved in an extra- 
 ordinary manner. The air-chambers also are restricted to a 
 portion only of the shell. In Aphragmites the air-chambers are 
 not persistent. Both these genera are exclusively confined to 
 the Silurian Rocks, abounding chiefly in the upper division of 
 the series. 
 
 Lastly, in the genus Gyroccras the shell is coiled into a flat 
 spiral, the volutions of which are not contiguous. The siphuncle 
 is excentric. This genus is, perhaps, hardly separated from 
 Lituites by any sufficiently good characters. The species of 
 the genus are mainly Upper Silurian and Devonian. 
 
 AMMONITID.S. 
 
 FAM. II. AMMONITID^E. Shell discoidal, curved, spiral, or 
 straight ; body-chamber elongated ; aperture guarded by processes, 
 or closed by an operculum; sutures angulated, lobed, or foliaceous ; 
 siphuncle external or dorsal, on the convex side of the curved shells. 
 
 The chief point by which the Ammonitida are distinguished 
 from the Nautilidce is the nature of the septa between the air- 
 chambers. The latter have septa which are simply curved, 
 and which consequently exhibit plain or very slightly lobed 
 edges or sutures. In the Ammonitida, on the other hand, the 
 septa are " nearly flat in the middle, and folded round the 
 edge (like a shirt-frill), where they abut against the outer shell- 
 wall " (Woodward). The result of this is that the " sutures " 
 or edges of the septa appear on the surface of the shell in the 
 form of angulated, lobed, or foliaceous lines (fig. 257). 
 
 The angulated or digitated portions of the suture, which are 
 directed inwards, away from the mouth of the shell, are called 
 the " lobes" The elevations between the " lobes," which 
 point towards the mouth of the shell, are called the " saddles" 
 These parts have the following arrangement (fig. 257) : In 
 the middle of the back or convex surface of the shell, tra- 
 versed by the siphuncle, is a single unpaired lobe which is 
 termed the "dorsal lobe" (D). The lobe on each side of this 
 is the "lateral-superior" lobe (L). The lobe next to this
 
 AMMONITID^:. 287 
 
 again is the "lateral-inferior" lobe; and the lobes which 
 follow this (of a variable number) are the " auxiliary " lobes 
 (A 1 , A 2 , A 3 , A 4 ). Lastly, there is a second unpaired lobe im- 
 mediately opposite to the dorsal lobe, placed upon the con- 
 cave side of the shell, and termed the " ventral " lobe. The 
 " saddles " are similarly subdivided. Between the dorsal and 
 lateral-superior lobes comes the " dorsal saddle " (SD). Next 
 to this, between the superior-lateral and inferior-lateral lobes 
 is placed the " lateral saddle " (SL) on each side ; and this 
 is followed by a variable number of " auxiliary saddles " 
 (S 1 , S 2 , S 3 , S 4 ). 
 
 Fig. 257. One-half of the suture of Ammonites Truellii. D, Dorsal lobe, traversed 
 by the siphuncle ; L, Lateral-superior lobe ; E, Lateral-inferior lobe ; Al, A, A 3 , A4, Aux- 
 iliary lobes; SD, Dorsal saddle ; SL, Lateral saddle ; SI, S 2 , S3, S-, Auxiliary saddles. 
 
 The aperture of the shell in the Ammonitida is commonly 
 furnished with lateral processes of greater or less length ; and 
 in some, if not in all cases, it was further protected by a horny 
 or shelly operculum. Sometimes the operculum consists of a 
 single piece : but in other cases it is divided into two sym- 
 metrical halves by a straight median suture. The opercula of 
 this latter kind were originally described as separate fossils, 
 under the name of Trigonellites. 
 
 As regards the general distribution in time of the Ammon- 
 itidce, the earliest-known forms of the -g^oup appear in the 
 Silurian Rocks; the genus Bactrites in the Lower Silurian, 
 and Goniatites in the Upper Silurian. No other Palaeozoic 
 types of the group are known ; but with the commencement 
 of the Mesozoic period begins an era in which an enormous 
 development of the Ammonitidtz took place. The genus 
 Ceratites is characteristically Triassic. The Jurassic Rocks 
 are chiefly distinguished by species of the genus Ammonites 
 itself, though other generic types are not wanting. Lastly, in 
 the Cretaceous Rocks we find, along with Ammonites proper,
 
 288 
 
 MOLLUSCA. 
 
 several remarkable forms, such as Turrilites, Baciilites, Hamites, 
 Scaphites, and Ptychoceras. With the close of the Cretaceous 
 period the Ammonitida disappeared altogether, and no ex- 
 ample of this large and varied family has as yet been detected 
 in the Tertiaries, or is known to exist in Recent seas. 
 
 GENERA OF AMMONITID^E. 
 
 The genus Goniatites (fig. 258) comprises ancient forms of 
 the Ammonitidae, in which the shell is discoidal ; the sutures 
 are simply lobed or angulated ; and 
 the siphuncle is dorsal. The earliest- 
 known forms of this genus are found 
 in the Upper Silurian Rocks, the last 
 in the Trias, and the most in the Car- 
 boniferous. 
 
 The genus Bactrites comprises forms 
 quite similar to Goniatites, except that 
 the shell, instead of being rolled up, is 
 straight. The genus represents Ortho- 
 ceras. from which it differs in the 
 
 possession of lobed septa, and in the position of the siph- 
 uncle. The known species range from the Lower Silurian to 
 the Devonian. 
 
 The genus Ceratites (fig. 259) comprises forms which re-
 
 AMMONITID^E. 
 
 289 
 
 semble Goniatites in having a discoidal shell, the coils of which 
 lie in one plane and are contiguous. It is distinguished, how- 
 ever, from Goniatites on the one hand and Ammonites on the 
 other, by having the 
 ''lobes "of the suture 
 denticulated or cren- 
 ulated, whilst the 
 " saddles " are simply 
 rounded. The species 
 of Ceratites are typi- 
 cally Triassic, the best- 
 known form being the 
 C. nodosus of the 
 Muschelkalk. Some 
 species, however, oc- 
 cur in the Cretaceous 
 Rocks, though no 
 member of the genus 
 has as yet been de- 
 tected in the intervening Jurassic deposits. 
 
 The genus Ammonites comprises by far the greater number 
 of the Ammonitidce, over five hundred species being already 
 known. The shell in Ammonites is spirally rolled up into a 
 flat spiral, all the volutions of which are contiguous (figs. 
 
 *vz t ites n o do sits. 
 (Middle Trias). 
 
 Muschelkalk 
 
 Fig. 260. Ammonites Hitmphresianus. Inferior Oolite. 
 
 260, 261). The innermost whorls of the shell are more or less 
 concealed; the septa are undulated; the sutures are lobed, 
 foliaceous, or ramified; and the siphuncle is dorsal. The 
 species of the genus Ammonites range from the Trias to the
 
 290 MOLLUSCA. 
 
 Chalk, and are thus exclusively confined to the Secondary period. 
 Within these limits, each rock-group is characterised by par- 
 ticular species, the number of individuals being often very great, 
 and the size which is sometimes attained being nothing short of 
 
 Fig. 261. Ammonites bifrons. Lias. 
 
 gigantic. In the Lias particular species of Ammonites succeed 
 one another regularly, each having its own definite horizon, 
 which it does not transgress. It is thus possible to distinguish 
 a certain number of zones, each characterised by a particular 
 Ammonite. Some of these zones are very persistent and ex- 
 tend over very wide areas, thus affording valuable aid to the 
 geologist in his determination of rocks. It is to be remem- 
 bered, however, that there are other species which are not thus 
 restricted in their vertical range, even in the same formations 
 in which definite zones occur. 
 
 The numerous species of Ammonites are divided into groups 
 as follows (Pictet) : 
 
 SECTION A. Back with an entire keel. 
 
 1. Arietes . . . Lower Oolites. Ex, A. bisulcatus. 
 
 2. Falciferi . . Lower Oolites. Ex. A. serpentinus. 
 
 3. Cristati . . . Cretaceous. Ex, A. inflatus. 
 
 SECTION B. Both crenated or tubtrculated. 
 
 4. Amalthei . . Oolites. Ex, A. cordatus. 
 
 5. Pukhelli (or Rhotomagenscs} . . Cretaceous. Ex. A. crenatus. 
 
 SECTION C. Back compressed and sharp. 
 
 6. Clypeiformi (or Disci) . . . Oolites. Ex. A. discus.
 
 AMMONITID-ffi. 
 
 291 
 
 SECTION D. Back channelled. 
 
 7. Dentati . . . Oolitic and Cretaceous. Ex. A. Jason. 
 
 8. Gemmati . . . Trias. Ex. A. Aon. 
 
 SECTION E. Back squared. 
 
 9. Flexuosi . . . Cretaceous. Ex. A. radiatus. 
 
 10. Compressi . . Cretaceous. Ex. A. Beaumontianus. 
 
 11. Armati . . . Oolitic. Ex. A. perarmatus. 
 
 12. Angulicostati . Oolitic and Cretaceous Ex. A. Milletianus. 
 
 SECTION F. Back round. 
 
 13. Capricorni . . Lias. Ex. A. planicostatus. 
 
 14. Heterophylli . . Oolitic. Ex. A. heterophyllus. 
 
 15. Ligati .... Cretaceous. Ex. A. Mayorianus. 
 
 16. Planulati . . . Oolitic. Ex. A. annulatus. 
 \1~jCoronati . . . Oolitic. Ex. A. Humphresianus. 
 
 \%~ Macrocephali . . Oolitic and Cretaceous. Ex. A. microstoma. 
 
 19. Globosi . . . Trias. Ex. A. globus. 
 
 20. Fimbriati . . Jurassic and Cretaceous. Ex. A. sub-fimbriatus. 
 
 In the genus Crioceras are included forms which resemble 
 the Ammonites in all essential characters, but in which the 
 volutions of the shell are not contiguous. The shell, there- 
 fore, is discoidal, with separate whorls, thus corresponding 
 with Gyroceras amongst the series of the Nautilida. All the 
 known species of Crioceras belong to the Cretaceous period, 
 ranging from the Lower Greensand to the Gault. 
 
 In the genus Toxoceras the shell is simply arcuate, or bent 
 like a horn, and is never spirally rolled up ; so that this genus 
 represents Cyrtoceras in the series of the Nautilidee. The 
 species of Toxoceras range from the lower Oolites to the Gault, 
 but the genus is characteristically Cretaceous. 
 
 In the genus Ancyloceras (fig. 262) the shell at first re- 
 
 Fig. 262. Ancyloceras Mathe, 
 
 sembles that of Crioceras, consisting of several volutions which 
 are coiled into a flat spiral, but which are not in contact with 
 one another. The shell differs from Crioceras, however, in the 
 fact that the last volution is produced at a tangent, and is ulti-
 
 2 9 2 
 
 MOLLUSCA. 
 
 mately bent back in the form of a crosier. The species of 
 Ancyloceras are Jurassic and Cretaceous, ranging from the In- 
 ferior Oolite to the Chalk. 
 
 In the genus Scaphites, the shell resembles that of Ancylo- 
 ceras in consisting of a series of volutions coiled into a flat 
 spiral, and having the last volution de- 
 tached from the others, produced, and 
 ultimately bent back in the form of a 
 crosier. Scaphites differs from Ancylo- 
 ceras in the fact that the volutions of 
 the enrolled part of the shell are in con- 
 tact, instead of being separate as they 
 are in the latter. The produced whorl, 
 also, is rarely of any great length, but 
 is speedily bent back upon itself. All 
 the species of Scaphites are Cretaceous, 
 ranging from the Lower Greensand to 
 the Chalk. 
 
 In the genus Helicoceras the shell is 
 coiled into a turreted spiral, the volu- 
 tions of which are not contiguous. The 
 shell is, also, left-handed or " sinistral." 
 With the exception of a single species 
 from the Inferior Oolite, all the species 
 of Helicoceras belong to the Cretaceous 
 period. 
 
 In the genus Turrilites the shell 
 agrees with that of the preceding in 
 being composed of volutions which 
 pass obliquely round a central axis 
 (fig. 263), so as to form a turreted 
 spiral. The shell is, also, left-handed 
 or " sinistral." In Turrilites, however, 
 the whorls of the shell are in contact, 
 instead of being disconnected as they 
 are in Helicoceras. The genus corre- 
 sponds with Trochoceras in the series of 
 the Nautilida. All the species of Tur- 
 rilites are Cretaceous, ranging from the 
 Gault to the Chalk. 
 
 In the genus Hamites the shell is an 
 extremely-elongated cone, which is bent upon itself more than 
 once, in a hook-like manner, all the volutions being separate. 
 Numerous species of Hamites are known, all of them being Cre- 
 taceous, and ranging from the Lower Greensand to the Chalk. 
 
 Fig. &$. Turrilites 
 catenattu. Gault.
 
 DIBRANCHIATE CEPHALOPODS. 293 
 
 In the genus Ptychoceras the shell is, also, a much elongated 
 cone, which is simply bent upon itself once, the two straight 
 portions of the shell being in contact. The range of this genus 
 is the same as that of Hamites, extending from the Lower 
 Greensand to the Chalk. 
 
 Lastly, in the genus Baculites the shell is simply a straight 
 elongated cone, not bent in any way. Baculites corresponds, 
 therefore, with Orthoceras in the series of the Nautilidce. The 
 range of Baculites is the same as that of the preceding from 
 the Lower Greensand to the Chalk ; but the genus is most 
 abundant in the Chalk itself. 
 
 CHAPTER XXVI. 
 DIBRANCHIATE CEPHALOPODS. 
 
 THE Dibranchiate Cephalopods or Cuttle-fishes are character- 
 ised as being swimming animals, almost invariably naked, with 
 never more than eight or ten arms, which are always provided 
 with suckers. There are two branchia, which are ftirnished 
 with branchial hearts ; an ink-sac is always present ; the funnel 
 is a complete tube, and the shell is internal, or, if external, is not 
 chambered. 
 
 The Cuttle-fishes are rapacious and active animals, swim- 
 ming freely by means of the jet of water expelled from the 
 funnel. The arms constitute powerful offensive weapons, 
 being excessively tenacious in their hold, and being sometimes 
 provided with a sharp claw in the centre of each sucker. They 
 are mostly nocturnal or crepuscular animals, and they some- 
 times attain to a great size. They may be divided into two sec- 
 tions, Octopoda and Decapoda, according as they have simply 
 eight arms, or eight arms and two additional " tentacles." 
 
 The parts of a Dibranchiate Cephaloporr which may be pre- 
 served in a fossil condition are the mandibles, the ink-sac, the 
 shell (if such be present), and the internal skeleton. The occur- 
 rence of the mandibles and ink-sacs of Dibranchiate Cephalo- 
 pods in a fossil state has been already spoken of (p. 273), and 
 need not be further noticed here. An external shell is pre- 
 sent only in the Argonaut amongst living Cuttle-fishes, and 
 similar structures are of rare occurrence as fossils in some of 
 the youngest portions of the earth's crust. The internal 
 skeleton of the Cuttle-fishes differs very much in its characters
 
 294 MOLLUSCA. 
 
 in different cases. In the Calamaries the skeleton is in the 
 form of a horny " pen," consisting of a median shaft and of 
 two lateral expansions or wings. In the Sepiadce the skeleton 
 has the form of a broad, laminated, calcareous plate, having a 
 more or less perfectly chambered apex or " mucro." In the 
 singular Spirula the skeleton has the form of a chambered 
 tube coiled into a spiral, the coils of which are separate from 
 one another. Lastly, in the extinct family of the Belemnitida, 
 there was a complicated internal support It is, then, chiefly 
 from the preservation of their internal skeletons that the 
 Dibranchiate Cephalopods are known to have existed in past 
 periods of the earth's history. In addition, however, to the 
 skeleton, mandibles, and ink-bag, cases are not altogether un- 
 known in which the hooks of the suckers, and even the out- 
 lines of the arms and body, have been preserved in a fossil 
 condition. 
 
 As regards their general distribution in time, the record of 
 the Dibranchiate Cephalopods is much less complete than that 
 of the Tetrabranchiata. _ In the vast series of the Palaeozoic 
 formations no trace has ever been discovered of the existence 
 of any member of this order. Shortly after the commence- 
 ment of the Mesozoic period appear the first Belemnites ; and 
 all the Secondary formations after the oldest teem with the 
 remains of this family of the Dibranchiata. Remains of the 
 living families of the Tettthidce and Sepiada are also not un- 
 known in the Mesozoic Rocks, but no trace of the great group 
 of the Belemnitida has hitherto been detected in Tertiary de- 
 posits. Upon the whole, the order must be regarded as having 
 attained its maximum at the present day. In the following 
 are given the characters, chief genera, and distribution in time 
 of the families of the Dibranchiate Cephalopods. 
 
 SECTION A. OCTOPODA. The Cephalopods comprised in 
 this section are distinguished by the possession of eight arms, 
 which are provided with sessile suckers. The body is short 
 and bursiform, ordinarily without fins. The shell is internal 
 and rudimentary ; in one instance only (Argonaut) external. 
 
 FAM. i. ARGONAUTIDJE. Female provided with a delicate, 
 symmetrical, involuted shell, which is secreted by the webbed 
 extremities of the two dorsal arms, and is not attached in any 
 way to the body of the animal. Male much smaller than the 
 female, shell-less. This family includes only the single genus 
 Argonauta (the Paper Nautilus). One or two species of 
 Argonaut have been discovered in the Pliocene Tertiary. 
 
 FAM. 2. OCTOPODID^E. Shell internal, rudimentary, repre- 
 sented by two short styles encysted in the substance of the
 
 DIBRANCHIATE CEPHALOPODS. 
 
 295 
 
 mantle. This family includes the living Poulpes and their 
 allies, but has no fossil representatives. 
 
 SECTION B. DECAPODA. The Cuttle-fishes of this section 
 have eight " arms " and two additional "tentacles," which are 
 much longer than the true arms, and carry suckers on their 
 extremities only, which are expanded and club-shaped. The 
 suckers are pedunculated, the body is furnished with lateral 
 fins, and the shell is always internal. 
 
 FAM. 3. TEUTHID^E. Shell consisting of an internal horny 
 " pen " or " gladius," composed of a central shaft and two 
 lateral wings. Several of such pens may exist in a single 
 individual, packed one behind the other. Fins mostly ter- 
 minal and angular. This family comprises the living Cala- 
 maries and Squids, and the following fossil genera have been 
 founded upon " pens " which have been discovered in various 
 Secondary deposits. 
 
 a. Teudopsis. Pen lanceolate, produced in front, dilated and 
 spatulate behind. Five species of this genus have been de- 
 scribed from the Lias. 
 
 b. Beloteuthis. Pen lanceolate, pointed in front, with two 
 small wing-like expansions behind (fig. 264). Six species have 
 been described by Count Miinster from 
 
 the Upper Lias of Wiirtemberg. 
 
 c. Leptoteuthis. Pen horny, hastate, 
 broad in front, pointed behind. A single 
 species is known from the Oxford Clay 
 (Jurassic). 
 
 d. Besides the above, remains found 
 in the Jurassic Rocks have been referred 
 to the living genera Enoploteuthis and 
 Ommastrephes ; and the extinct genus 
 Acanthoteuthis has also been placed in 
 this family. 
 
 FAM. 4. SEPIAD^E. Internal skeleton 
 in the form of a broad, laminated, calcare- 
 ous plate, with an imperfectly-chambered- 
 apex (or " mucro "). The chambered 
 portion of the skeleton corresponds with 
 the " phragmacone " of the Belemnites. 
 The fossil species of this family range from the Middle Oolites 
 upwards, and belong to the following three genera : 
 
 a. Sepia. Shell broad and thick in front, laminated, and 
 terminating in a prominent mucro. The fossil forms belong 
 to the Oxford Clay (Jurassic) and Eocene Tertiary, and the 
 genus attains its maximum at the present day. 
 
 Fig. 264. Beloteuthis sub- 
 costata. Jurassic (Lias).
 
 2 9 6 
 
 MOLLUSCA. 
 
 b. Spirulirostra. The shell (fig. 265) in this singular genus 
 consists of a chambered portion or phragmacone coiled into a 
 spiral, the volutions of which are separated. This is lodged in 
 a pointed calcareous portion or " rostrum." The only known 
 species of this genus is found in the Miocene Tertiary. 
 
 Fig. ?(>$. SJ>iriih 
 
 Billardii. Miocene Tertiary. 
 
 c. Beloptera. Shell consisting of a nearly straight chambered 
 portion or "phragmacone," perforated by a siphuncle, and 
 lodged in a pointed calcareous rostrum which is furnished with 
 lateral wings. Two species only of this genus are known, both 
 from the Eocene Tertiary. 
 
 d. Belemnosis. This genus has been founded for the recep- 
 tion of an Eocene fossil closely resembling Beloptera, but differ- 
 ing in not possessing any lateral expansions. 
 
 FAM. 5. SPIRULID^E. Shell nacreous, discoidal, composed 
 of volutions which are not in contact with one another. The 
 shell is divided into a series of air-chambers by curved shelly 
 partitions, pierced by a ventral tube or " siphuncle." The 
 entire shell corresponds with the " phragmacone " of the skele- 
 ton of the Belemnites. Spintlirostra and Beloptera are often 
 referred to this family ; but if these be placed in the Sepiadce, 
 the family of the Spirulidce is then without any known fossil 
 representative. 
 
 FAM. 6. BELEMNITIDJE. Shell internal, composed of a 
 conical chambered portion (" phragmacone "), with a marginal 
 or ventral siphuncle, lodged in a cylindrical fibrous " guard," 
 and produced in front into a thin horny or shelly plate or 
 " pen " (the " pro-ostracum "). The Beleitmitida are exclusively 
 confined to the Secondary Rocks, ranging from the top of the
 
 DIBRANCHIATE CEPHALOPODS. 
 
 297 
 
 Trias to the Chalk. The following are the more important 
 genera belonging to this family : 
 
 a. Belemnites. The skeleton of the Belemnite consists of a 
 sub - cylindrical, longer or shorter, 
 fibrous body (fig. 266), which is 
 termed the ''rostrum" or "guard." 
 The length of the guard varies very 
 much in different cases, and it is the 
 part of the Belemnite which is most 
 commonly found in a fossil condi- 
 tion. At the front or broad end, the 
 guard is hollowed out into a conical 
 excavation, which is termed the 
 " alveolus." Within the alveolus, 
 in perfect specimens, is contained 
 the " phragmacone." This consists 
 of a conical series of chambers, se- 
 parated from one another by curved 
 shelly partitions or septa, which 
 are perforated by apertures for the 
 passage of the " siphuncle." The 
 siphuncle traverses the middle of 
 the ventral wall of the phragmacone, 
 and the whole series of chambers is 
 enclosed in a thin shell-wall (the 
 "conotheca" of Huxley). Anteri- 
 orly the conotheca or investment of 
 the phragmacone is prolonged for- 
 wards into a horny or shelly plate, 
 which corresponds with part of the 
 " pen" of the Calamaries, and which 
 is termed the " pro-ostracum " (fig. 
 266, r). The form of the "pro- 
 ostracum " varies greatly in different 
 cases, and it affords important char- 
 acters in the discrimination of spe- 
 cific and generic forms in the Belem- 
 nitid(Z. Owing, however, to its ex- 
 treme tenuity, it is very rarely found 
 preserved in a fossil condition, and 
 its value to the working palaeonto- 
 logist is thus greatly reduced. 
 
 Not only is the internal skeleton 
 of the Belemnite known, but various specimens have been dis- 
 covered, from which much has been learnt as to other points 
 
 Fig. 266. Diagram of Belem- 
 nite (after Professor Phillips), r 
 
 pro- 
 
 Horny or shelly pen or 
 ostracum; "^Chambered "phrag- 
 macone" in its cavity (a) or "al- 
 veolus ; " g " Guard.
 
 298 MOLLUSCA. 
 
 of its anatomy. Thus we know that the body was furnished 
 with lateral fins, that there were eight arms and two longer 
 " tentacles," that the suckers were provided with horny hooks, 
 that there was a large ink-sac, and that the mouth was armed 
 with horny mandibles. 
 
 The following table of the sections and sub-sections of the 
 species of the genus Belemnites is the one given by Dr S. P. 
 Woodward : 
 Section I. Acceli. 
 
 Without dorsal or ventral grooves. 
 Sub-section I. Acuarii. 
 
 Without lateral furrows, but often channelled at the extreme 
 
 point. (Ex. B. acuarius. Lias.) 
 Sub-section 2. Clavati, 
 
 With lateral furrows. (Ex. B. clavatus. Lias.) 
 Section II. Gastrocoeli. 
 
 Ventral groove distinct. 
 Sub- section I. Canaliculati. 
 
 No lateral furrows. (Ex. B. canaliculatus. Inf. Oolite.) 
 Sub-section 2. Hastati. 
 
 Lateral furrows distinct. (Ex. B. hastatus. Oolite.) 
 Section III. NotoccelL 
 
 With a dorsal groove, and furrowed on each side. (Ex. 
 B. dilatatus. Neocomian. ) 
 
 The species of the genus Belemnites range from the top of 
 the Trias, where the earliest forms appear, to the 
 Upper Greensand, in which the genus finally dis- 
 appears. The species are most numerous in the 
 Jurassic Rocks, and often occur in the greatest 
 abundance in particular beds or particular localities. 
 It would seem not improbable that the genus Belop- 
 tera, before noticed, should be referred to the Belem- 
 nitidte, and the genus Bekmnosepia (or Geoteuthis), 
 formerly referred to the Tcuthidce, appears to be al- 
 most certainly referable here. 
 
 b. Belemnitella. In this genus (fig. 267) the skele- 
 ton is very similar in its general arrangement to that 
 of Belemnites ; but there is a straight fissure in the 
 guard, at its upper end, on the ventral side of the 
 wall of the alveolus. The species of this genus are 
 _ exclusively Cretaceous, and are only found in the 
 
 per portion of this formation, ranging from the 
 
 c. Belemnoteiithis. " Shell consisting of a phrag- 
 maeonc, like that of the Belemnite ; a horny dorsal pen with 
 obscure lateral bands ; and a thin fibrous guard, with two 
 diverging ridges on the dorsal side. Animal provided with
 
 VERTEBRATA. 299 
 
 arms and tentacles of nearly equal length, furnished with a 
 double alternating series of horny hooks, from 20 to 40 pairs 
 on each arm ; mantle free all round ; fins large, medio-dorsal." 
 (Woodward.) Only one species is known, from the Oxford 
 Clay (Middle Oolites). High authorities, such as Owen and 
 D'Orbigny, question the validity of this genus, and regard it 
 as being founded upon specimens of Belemnites. 
 
 d. Xiphoteuthis. Guard narrow and cylindrical, containing 
 a very long, deep-chambered, narrow phragmacone. Pro- 
 ostracum greatly developed (nearly a foot in length), very 
 narrow at its base, widening out anteriorly, and finally ter- 
 minating in a pointed apex. Only a single species is known, 
 from the Lias. 
 
 CHAPTER XXVII. 
 SUB-KINGDOM VERTEBRATA. 
 
 THE sub-kingdom Vertebrata may be shortly defined as includ- 
 ing animals in which the body is composed of a succession of 
 definite segments, arranged along a longitudinal axis ; the main 
 masses of the nervous system (brain and spinal cord} are situated 
 along the dorsal surface of the body, and are completely shut off 
 from the general body-cavity. The limbs are never more than 
 fottr in number, and are always turned away from that aspect of 
 the body upon which the main masses of the nervous system are 
 situated. In all, the nervous axis is primitively supported by a 
 cellular rod, which is termed the " notochord ;" but in most the 
 notochord is replaced in the adult by the bony axis known as the 
 " spine" or " vertebral column" 
 
 The past existence of Vertebrate animals is chiefly recognised 
 by the preservation of their hard structures. These hard struc- 
 tures are of two kinds some belonging to the internal or true 
 skeleton (endoskeleton), others being of the nature of horny 
 or bony plates, scales, or appendages of various kinds, de- 
 veloped in the integument (exoskeleton). The nature of the 
 exoskeleton in the Vertebrates differs very much in different 
 cases, and it will be considered when treating of the separate 
 groups. It will be well, however, to give an extremely 
 general and brief view of the structure of the endoskeleton, 
 taking for this purpose a Mammal as a typical form. In this 
 way the student will be enabled readily to trace the modifica- 
 tions of the skeleton in the lower forms, and will without
 
 300 VERTEBRATA. 
 
 difficulty comprehend the terms which are necessarily em- 
 ployed in the definitions of the various groups. It may be 
 added here, before proceeding further, that it does not seem 
 requisite to treat the Vertebrata with the same fulness as the 
 Invertebrata. The fossil remains of Vertebrates are in many 
 cases of the highest theoretical interest, but they come much 
 less frequently under the notice of the ordinary student than 
 do the remains of the Invertebrates. No practical study, also, 
 of the fossil Vertebrates can be carried out without a consider- 
 able acquaintance with Comparative Osteology. Lastly, the 
 remains of Vertebrate animals generally occur in such a frag- 
 mentary condition that a sufficient series of specimens for pro- 
 fitable study can rarely be obtained, except under peculiarly 
 favourable circumstances, in special cases, or where access can 
 be had to a first-rate museum. For these and other reasons it 
 is thought enough, in a treatise intended for the working palae- 
 ontologist, to give a general account of each class of the Verte- 
 brata, with definitions of the orders, and a brief notice of the 
 leading forms of each. Only in cases of special interest will any 
 details of a more minute character than the above be given. 
 
 The skeleton of the Vertebrata may be regarded as consisting 
 essentially of the bones which go to form the head and trunk 
 on the one hand (sometimes called the " axial " skeleton), and 
 of those which form the supports for the limbs ("appendicular" 
 skeleton) on the other hand. The bones of the head and 
 trunk may be looked upon as essentially composed of a series 
 of bony rings or segments, arranged longitudinally, one behind 
 the other. Anteriorly these segments are much expanded, and 
 likewise much modified, to form the bony case which encloses 
 the brain, and which is termed the cranium or skull. Behind 
 the head the segments enclose a much smaller cavity, which is 
 called the " neural " or spinal canal, as it encloses the spinal 
 cord ; and they are arranged one behind the other, forming 
 the vertebral column. The segments which form the verte- 
 bral column are called " vertebras," and they have the follow- 
 ing general structure : Each vertebra (fig. 268, A) consists of 
 a central piece, which is the fundamental and essential element 
 of the vertebra, and is known as the " body " or " centrum" (c). 
 From the upper or posterior surface of the centrum spring two 
 bony arches (n ), which are called the " neural arches " or 
 " neurapophyses," because they form with the body a canal the 
 " neural canal " which encloses the spinal cord. From the 
 point where the neural arches meet behind, there is usually 
 developed a longer or shorter spine, which is termed the " spi- 
 nous process " or " neural spine " (s). From the neural arches
 
 GENERAL CHARACTERS OF VERTEBRATA. 30! 
 
 there are also developed in the typical vertebra two processes 
 (a a), which are known as the "articular" processes, or "zyga- 
 pophyses." The vertebrae are united to one another partly 
 by these, but to a greater extent by the bodies or " centra." 
 From the sides of the vertebral body, at the point of junction 
 with the neural arches, there proceed two lateral processes 
 (d-d), which are known as the "transverse processes." 
 
 Fig. 268. A, Lumbar vertebra of a Whale : c Body or centrum ; n n Neural arches ; 
 j Neural spine ; a a Articular processes ; d d Transverse processes. B, Diagram of a 
 thoracic vertebra : c Centrum ; n n Neural arches enclosing the neural canal ; J Neural 
 spine; r r Ribs, assisting in the formation of the haemal arch; p p Costal cartilages; 
 b Sternum, with haemal spine. (After Owen.) 
 
 These elements form the vertebra of the human anatomist, 
 but the "vertebra" of the transcendental anatomist is com- 
 pleted by a second arch which is placed beneath the body of 
 the vertebra, and which is called the " haemal " arch, as it 
 includes and protects the main organs of the circulation. 
 This second arch is often only recognisable with great diffi- 
 culty, as its parts are generally much modified, but a good 
 example may be obtained in the human chest, or in the caudal 
 vertebra of a bony fish. 
 
 As a general rule, the vertebral column is divisible into a 
 number of distinct regions, of which the following are recog- 
 nisable in man and in the higher Vertebrata : i. A series of 
 vertebrae which compose the neck, and constitute the " cer- 
 vical region " of the spine (fig. 269, c\ 2. A number of vertebrae 
 which usually carry well-developed ribs, and form the " dorsal 
 region " (d). 3. A series of vertebrae which form the region 
 of the loins, or " lumbar region " (fr). 4. A greater or less 
 number of vertebrae which constitute the " sacral region," and
 
 302 
 
 VERTEBRATA. 
 
 are usually amalgamated or " anchylosed " together to form a 
 single bone, the " sacrum " (j). 5. The spinal column is com- 
 pleted by a variable number of vertebrae which constitute the 
 "caudal" region, or tail (/). 
 
 Fig. 269. Skeleton of the Beaver (Castor fiber), showing the different regions of the 
 vertebral column, c Cervical region ; d Dorsal region ; b Lumbar region ; s Sacrum ; 
 / Caudal region. 
 
 As regards the skull of the Vertebrates, the most important 
 points to be noticed are the manner in which the cranium 
 articulates with the vertebral column, and the structure of the 
 lower jaw or " mandible." In Birds and Reptiles the skull 
 articulates with the first vertebra of the neck by means of a 
 single articulating surface or " condyle," carried upon the 
 occipital bone. In the Amphibians, again, and in the Mam- 
 mals, there are two " occipital condyles," by which the skull 
 is jointed to the neck. The lower' jaw is sometimes want- 
 ing, but, when present, it consists in all Vertebrata of two 
 halves or " rami," which are united to one another in front, 
 and articulate separately with the skull behind. In many 
 cases, each half, or " ramus," of the lower jaw consists of 
 several pieces united to one another by sutures ; but in the 
 Mammalia each ramus consists of no more than a single 
 piece. The two rami are very variously connected with one 
 another, being sometimes only joined by ligaments and mus-
 
 GENERAL CHARACTERS OF VERTEBRATA. 303 
 
 cles, sometimes united by cartilage or by bony suture, and 
 sometimes fused or anchylosed with one another, so as to 
 leave no evidence of their true composition. The mode by 
 which each ramus of the lower jaw articulates with the skull 
 also varies. In the Mammalia the lower jaw articulates with 
 a cavity formed on what is known to human anatomists as the 
 temporal bone ; but in Birds and Eeptiles, the lower jaw articu- 
 lates with the skull, not directly, but by the intervention of a 
 special bone, known as the "quadrate bone" or "0s quadratum." 
 
 As regards the limbs of Vertebrates, whilst many differences 
 exist, which will be afterwards noticed, there is a general 
 agreement in the parts of which they are composed. As a 
 rule, each pair of limbs is joined to the trunk by means of a 
 series of bones which also correspond to one another in general 
 structure. The fore-limbs, often called the " pectoral " limbs, 
 are united with the trunk by means of a bony arch, which is 
 called the " pectoral " or " scapular " arch ; whilst the hind- 
 limbs are similarly connected with the trunk by means of the 
 " pelvic arch." In giving a general description of the parts 
 which compose the limbs and their supporting arches, it will 
 be best to take the case of a Mammal, and the departures 
 from this type will then be readily recognised. 
 
 The pectoral or scapular arch consists usually of three bones, 
 the "scapula" or shoulder-blade, the "coracoid," and the 
 "clavicle" or collar-bone; but in the great majority of the 
 Mammals, the coracoid is anchylosed with the scapula, of 
 which it forms a mere process. The scapula or shoulder- 
 blade (fig. 270, s) is usually placed outside the ribs, and it 
 forms, either alone or in conjunction with the other bones of 
 the shoulder-girdle, the cavity with which the upper arm is 
 articulated. The coracoid, though rarely existing as a distinct 
 bone in the Mammals, plays a very important part in other 
 Vertebrates. The clavicles are often wanting, or rudimentary, 
 and they are the least essential elements of the scapular arch. 
 The fore-limb proper consists, firstly, of a single bone which 
 forms the upper arm, and which is known as the humerus (Ji). 
 This articulates above with the shoulder-girdle, and is followed 
 below by the fore-arm, which consists of two bones, called the 
 radius and ulna. Of these the radius is chiefly concerned 
 with carrying the hand. The radius and ulna are followed by 
 the bones of the wrist, which are usually composed of several 
 bones, and constitute what is called the carpus (d). These 
 support the bones of the root of the hand, which vary in 
 number, but are always more or less cylindrical in shape. 
 They constitute what is called the metacarpus. The bones of
 
 304 
 
 VERTEBRATA. 
 
 the metacarpus carry the digits, which also vary in number, 
 but are composed each of from two to three cylindrical bones, 
 which are known as the phalanges (/). 
 
 Homologous parts are, as a rule, readily recognisable in the 
 hind-limb. The pelvic arch, by which the hind-limb is united 
 with the trunk, consists of three pieces the ilium, iscnium, 
 and pubes which are usually anchylosed together, and form 
 conjointly what is known as the innominate bone (fig. 27 1, /). In 
 
 Fig. 270. Pectoral limb 
 farm) of Chimpanzee. (After 
 Owen), c Clavicle ; s Scapula 
 or shoulder-blade; h Humerus; 
 r Radius ; Ulna ; d Bones of 
 the wrist, or carpus; tn Meta- 
 carpus ; / Phalanges of the 
 fingers. 
 
 Fig. 271. Hind-limb of the 
 Chimpanzee. Innominate 
 bone : /"Thigh-bone or femur ; 
 t Tibia ; s Fibula ; r Bones of 
 the ankle, or tarsus ; m Meta- 
 tarsus ; / Phalanges. 
 
 most Mammals, the two innominate bones unite in front by a 
 ligamentous or cartilaginous union, and they constitute, with 
 the sacrum, what is known as the pelvis. The hind-limb pro- 
 per consists of the following parts : i. The thigh-bone or 
 femur, corresponding with the humerus in the fore-limb. 2.
 
 VERTEBRATA. 305 
 
 The bones of the shank, corresponding with the radius and 
 ulna of the fore-limb, and known as the tibia and fibula. Of 
 these, the tibia is mainly, or altogether, concerned in carrying 
 the foot, and it is thus shown to correspond to the radius, 
 whilst the fibula corresponds to the ulna. 3. The small bones 
 of the ankle, known as the tarsus, and varying in number in 
 different cases. 4. A variable number of cylindrical bones 
 (normally five), which are called the metatarsus, and which 
 correspond to the metacarpus. 5. Lastly, the metatarsus car- 
 ries the digits, which consist, each, of from two to three small 
 bones we phalanges, as in the fore-limb. 
 
 The sub-kingdom Vertebrata is divided into the following 
 five classes : 
 
 1. PISCES (Fishes). Respiration by means of gills ; heart 
 usually two-chambered ; an exoskeleton, in the form of horny 
 scales or bony plates, generally present; blood cold. Limbs, 
 when present, in the form of fins, or expansions of the integu- 
 ment supported by bony or cartilaginous spines or " rays." 
 
 2. AMPHIBIA (Amphibians). Respiration at first exclusively 
 by gills, afterwards by lungs, either alone or associated with 
 gills. Heart of the adult three-chambered ; blood cold. The 
 skull connected with the vertebral column by two occipital 
 condyles. The limbs, when present, never converted into fins, 
 and composed of the same parts as in the higher Vertebrates. 
 
 3. REPTILIA (Reptiles). Respiration aerial, by lungs, and 
 never by gills. Pulmonary and systemic circulations connected 
 together either within the heart or in its immediate neighbour- 
 hood. Heart of the adult three-chambered in most; rarely 
 four-chambered. Blood cold. Skull united to the vertebral 
 column by one occipital condyle. Exoskeleton in the form 
 of horny scales or bony plates, or both combined. 
 
 4. AVES (Birds). Respiration aerial, by lungs, and never 
 by gills. Bronchial tubes opening on the surface of the lungs 
 into air-sacs. A greater or less number of the bones almost 
 always hollow and filled with air. The skull connected with the 
 vertebral column by a single occipital condyle. Heart four- 
 chambered ; the pulmonary and systemic circulations distinct, 
 and the blood warm. Epidermic appendages in the form of fea- 
 thers. Pectoral limbs in the form of wings. Animal oviparous. 
 
 5. MAMMALIA (Quadrupeds). Respiration aerial, by lungs, 
 and never by gills. The terminations of the air-passages (bron- 
 chi) never connected with air-sacs. Heart four- chambered ; 
 the pulmonary and systemic circulations distinct ; the blood 
 warm. Skull connected with the vertebral column by two arti- 
 culating surfaces or condyles. Some part or other of the integu-
 
 306 VERTEBRATA. 
 
 ment provided at some time or other with epidermic append- 
 ages in the form of hairs. The young nourished for a shorter 
 or longer time by means of a special fluid the milk secreted 
 by special glands the mammary glands. Animal viviparous. 
 As regards the general distribution in time of the Vcrtebrata, 
 the earliest known traces of the existence of this sub-kingdom 
 are found in the Upper Silurian Rocks. Here are the remains of 
 Ganoid and Plagiostomous fishes ; and we may fairly anticipate 
 that further research will ultimately result in putting back the 
 first appearance of Fishes at any rate to the Lower Silurian. 
 The class of the Amphibians is not known to have come into 
 existence prior to the commencement of the Carboniferous 
 period, but it had attained a great development before the 
 close of this epoch. The class of the true Reptiles is repre- 
 sented, by more or less doubtful examples only, in the newer 
 Palaeozoic deposits. In the Mesozoic Rocks, however, the 
 development of this class was so great that the Secondary 
 period has been termed the " Age of Reptiles." The class 
 Aves is doubtfully represented by foot-prints in strata of the 
 age of the Trias ; but no Palaeozoic remains of this class have 
 been as yet detected. The earliest undoubted remains of 
 Birds occur in the Jurassic series, and the class has continued 
 to be represented more or less abundantly to the present day. 
 Lastly, the class of the Mammalia, so far as at present known, 
 finds its earliest fossil representative in strata of the age of the 
 Trias (New Red Sandstone). The" Mammals, however, can- 
 not be said to be in any way abundant as fossils, till we reach 
 the Eocene Tertiary. From this point onward the remains of 
 Mammals are as abundant as, in the nature of the case, they 
 could reasonably be expected to be. 
 
 CHAPTER XXVIII. 
 FISHES. 
 
 THE first class of the Vertebrata is that of the Fishes (Pisces), 
 which may be broadly defined as including Vertebrate animals 
 ii'hich are provided with gills throughout the whole of life ; the 
 heart, when present, consists (with one exception] of a single auricle 
 and a single ventricle; the blood is cold ; the limbs, when present, 
 are in the form of fins, or expansions of the integument. 
 
 In form, Fishes are adapted for rapid locomotion in water, 
 the shape of the body being such as to give rise to the least
 
 FISHES. 307 
 
 possible friction in swimming. To this end also, as well as 
 for purposes of defence, the body is usually enveloped with a 
 coating of scales developed in the inferior or dermal layer of 
 the skin. The more important modifications in the form of 
 these dermal scales are as follows : I. Cycloid scales (fig. 272), 
 consisting of thin, flexible, horny scales, circular or elliptical 
 in shape, and having a more or less completely smooth outline. 
 These are the scales which are characteristic of most of the 
 ordinary bony fishes. II. Ctenoid scales (fig. 273), also con- 
 sisting of thin horny plates, but having their posterior margins 
 
 Fig. 272. Cycloid scale. Fig. 273. Ctenoid scale. Fig. 274. Ganoid scale. 
 
 fringed with spines, or cut into comb-like projections. III. 
 Ganoid scales, composed of an inferior layer consisting of bone, 
 covered by a superficial layer of hard polished enamel (the so- 
 called "ganoine"). These scales (fig. 274) are usually much 
 larger and thicker than the ordinary scales, and though they 
 are often articulated to one another by special processes, they 
 only rarely overlap. IV. Placoid scales, consisting of detached 
 bony grains, tubercles, or plates, of which the latter are not 
 uncommonly armed with spines. 
 
 It is very important for the geologist to recognise the charac- 
 ters of these different scales, as he may have to decide upon 
 the characters of a fossil fish merely from detached scales. 
 Such decisions, however, are always more or less hazardous, 
 since the scales of the different orders of the living fishes are 
 not invariably of the same kind in all the forms of the order. 
 Thus, ganoid scales are not peculiar to the order of the Ganoid 
 fishes, but occur also in some of the Bony Fishes (Teleostei). 
 The scales, also, form at best but one' character, and they can 
 hardly be said to constitute the most important character of 
 any fish. A classification, therefore, which is based primarily 
 upon the nature of the scales, necessarily is more or less "artifi- 
 cial," and is liable to bring into juxtaposition forms which have 
 no real affinity to one another. For these reasons, most 
 zoologists do not accept the classification of the Fishes into the 
 four orders of the Cycloidei, Ctenoidei, Ganoidei, and Placoidei, 
 since this classification, though sanctioned by such an eminent
 
 308 VERTEBRATA. 
 
 authority as Professor Agassiz, is founded solely upon the 
 nature of the integumentary covering. The palaeontologist, 
 however, whose materials often consist of nothing more than 
 detached scales, is not rarely driven, by the necessity of the 
 case, to provisionally classify his specimens in accordance with 
 the nature of these appendages. 
 
 As regards their true osseous system or endoskeleton, Fishes 
 vary very widely. In the Lancelet there can hardly be said 
 to be any skeleton, the spinal cord being simply supported by 
 the gelatinous notochord, which remains throughout life. In 
 others the skeleton remains permanently cartilaginous ; in 
 others it is partially cartilaginous and partially ossified ; and, 
 lastly, in most modern fishes it is entirely ossified, or converted 
 into bone. Taking a bony fish (fig. 275) as in this respect a 
 typical example of the class, the following are the chief points 
 in the osteology of a fish which require notice : 
 
 The vertebral column in a bony fish consists of vertebrae 
 which are hollow at both ends, or biconcave, and are techni- 
 cally said to be " amphicoelous." The cup-like margins of the 
 vertebral bodies are united by ligaments, and the cavities 
 formed between contiguous vertebra? are filled with the gela- 
 tinous remains of the notochord. This elastic gelatinous sub- 
 stance acts as a kind of ball-and-socket joint between the 
 bodies of the vertebrae, thus giving the whole spine the extreme 
 mobility which is requisite for animals living in a watery 
 medium. The ossification of the vertebrae is often much more 
 imperfect than the above, but in no case except that of the 
 Bony Pike (Lepidosteus) is ossification carried to a greater 
 extent than this. In this fish, however, the vertebral column 
 is composed of " opisthocoelous " vertebrae that is, of vertebrae 
 the bodies of which are concave behind and convex in front. 
 The entire spinal column is divisible into not more than two 
 distinct regions, an abdominal and a caudal region. The ab- 
 dominal vertebrae possess a superior or neural^ arch (through 
 which passes the spinal cord), a superior spinous process 
 (neural spine), and two transverse processes to which the ribs 
 are usually attached. The caudal vertebrae (fig. 275) have no 
 marked transverse processes ; but in addition to the neural 
 arches and spines, they give off an inferior or h&mal arch 
 below the body of the vertebrae, and the haemal arches carry 
 inferior spinous processes (haemal spines). 
 
 The ribs of a bony fish are attached to the transverse pro- 
 cesses, or to the bodies, of the abdominal vertebrae, in the form 
 of slender curved bones which articulate with no more than 
 one vertebra each, and that only at a single point. Unlike the
 
 FISHES. 
 
 309 
 
 ribs of the higher Vertebrates, the ribs do not enclose a thoracic 
 cavity, but are simply imbedded in the muscles which bound 
 the abdomen. Usually each rib gives off a spine-like bone, 
 which is directed backwards amongst the muscles. Inferiorly 
 the extremities of the ribs are free, or are rarely united to der- 
 mal ossifications in the middle line of the abdomen but there 
 is never any breast-bone or sternum properly so called. 
 
 Fig. 275. Skeleton of the common Perch (Perca JJiiviatilis). p Pectoral fin ; v One 
 of the ventral fins ; a Anal fin, supported upon interspinous bones (z*) ; c Caudal fin ; 
 d First dorsal fin ; d' Second dorsal fin, both supported upon interspinous bones ; *'* 
 Interspinous bones ; r Ribs ; j Spinous processes of vertebra ; h Haemal processes of 
 vertebras. 
 
 The only remaining bones connected with the skeleton of 
 the trunk are the so-called interspinous bones (fig. 275, i t). 
 These form a series of dagger-shaped bones plunged in the 
 middle line of the body between the great lateral muscles 
 which make up the greater part of the body of a fish. The 
 internal ends or points of the interspinous bones are attached 
 by ligament to the spinous processes of the vertebrae ; whilst 
 to their outer ends are articulated the " rays " of the so-called 
 " median " fins, which will be hereafter described. As a rule, 
 there is only one interspinous bone to each spinous process, 
 but in the Flat-fishes (Sole, Turbot, &c.) there are two. 
 
 Beside the fins which represent the limbs (pectoral and 
 ventral fins), fishes possess other fins placed in the middle line 
 of the body, and all of these alike are supported by bony spines 
 or "rays," which are of two kinds, termed respectively "spi- 
 nous rays " and " soft rays." The " spinous rays " are simple 
 bony spines, apparently composed of a single piece each, but 
 really consisting of two halves firmly united along the middle 
 line. The " soft rays " are composed of several slender spines
 
 3io 
 
 VERTEBRATA. 
 
 proceeding from a common base, and all divided transversely 
 into numerous short pieces. The soft rays occur in many fishes 
 in different fins, but they are invariably found in the caudal 
 fin or tail (fig. 275, c). The rays of the median fins, whatever 
 their character may be, always articulate by a hinge-joint with 
 the heads of the interspinous bones. 
 
 The skull of the bony fishes is an extremely complicated 
 structure, and it is impossible to enter into its composition 
 here. The only portions of the skull which require special 
 mention are the bones which form the gill-cover or operculum. 
 For reasons connected with the respiratory process in fishes, 
 there generally exists between the head and the scapular arch 
 a great cavity or gap on each side, within which are contained 
 the branchiae. The cavity thus formed opens externally on 
 each side of the neck by a single vertical fissure or " gill-slit," 
 closed by a broad flap, called the "gill-cover" or " operculum," 
 and by a membrane termed the " branchiostegal membrane." 
 
 The gill-cover (fig. 276, /, o, s, /') is composed of a chain of 
 broad flat bones, termed the opercular bones. Of these, the 
 
 Fig. 276. Skull of Cod (Morrhua vulgaris) Cuvicr. a Urohyal; b Basihyal; f 
 Ceratohyal ; d Branchiostegal rays ; / Prae-opcrculum ; a Operculum proper ; s Sub-oper- 
 culum; /' Inter-operculum ; m Mandible; " Intermaxillary bone. 
 
 innermost articulates with the skull (tympano-mandibular arch), 
 and is called the " pne-operculum ; " the next is a large bone
 
 FISHES. 3 1 1 
 
 called the " operculum " proper ; and the remaining two bones, 
 called respectively the " sub-operculum " and " inter-opercu- 
 lum," form, with the operculum proper, the edge of the gill- 
 cover. These various bones are united together by membrane, 
 and they form collectively a kind of movable door, by means of 
 which the branchial chamber can be alternately opened and 
 shut. Besides the gill-cover, however, the branchial chamber 
 is closed by a membrane called the " branchiostegal mem- 
 brane," which is attached to the os hyoides. The membrane 
 is supported and spread out by a number of slender curved 
 spines, which are attached to the lateral branches of the hyoid 
 bone, act very much as the ribs of an umbrella, and known as 
 the " branchiostegal rays " (fig. 276, d). 
 
 The limSs of fishes depart considerably from the typical form 
 exhibited in the higher Vertebrates. One or both pairs of 
 limbs may be wanting, but when present the limbs are always 
 in the form of fins that is, of expansions of the integument 
 strengthened by bony or cartilaginous fin-rays. The anterior 
 limbs are known as the pectoral fins, and the posterior as the 
 ventral fins ; and they are at once distinguished from the 
 so-called "median" fins by being always disposed in pairs, 
 usually symmetrically. Hence they are often spoken of as the 
 paired fins. 
 
 The fore-limbs or pectoral fins possess in a modified form 
 most of the bones which are present in the anterior extremities 
 of the higher Vertebrata. They vary much in size and in other 
 characters. Sometimes they are enormously expanded, as in 
 the Flying-fish (Exoccetus) ; and at other times they form merely 
 a pair of paddles, as in the extinct Pterichthys. The hind- 
 limbs or ventral fins are wanting in many fishes, and they are 
 less developed and less fixed in position than are the pectorals. 
 In some cases the ventral fins are " abdominal " in position, 
 and are placed more or less towards the hinder part of the 
 body (as in the Sharks, Ganoids, and Mud-fishes). In other 
 cases, they are "thoracic," that is, they are placed beneath the 
 pectorals ; and in some cases they are situated on the sides of 
 the neck in advance of the pectorals, when they are said to be 
 "jugular." In these cases, the pelvic arch is attached to the 
 pectoral arch, and is therefore wholly re\noved from its normal 
 position. 
 
 In addition to the pectoral and ventral fins the homologues 
 of the limbs which may be wanting, fishes are furnished 
 with certain other expansions of the integument, which are 
 " median " in position, and must on no account be confounded 
 with the true " paired " fins. These median fins are variable
 
 312 VERTEBRATA. 
 
 in number, and in some cases there is but a single fringe 
 running round the posterior extremity of the body. In all 
 cases, however, the median fins are " azygous " that is- to 
 say, they occupy the middle line of the body, and are not 
 symmetrically disposed in pairs. Most commonly, the median 
 fins consist of one or two expansions of the dorsal integument, 
 called the "dorsal fins" (fig. 277, d d 1 ) ; one or two on the 
 ventral surface near the anus the "anal fins" (fig. 277, a); 
 and a broad fin at the extremity of the vertebral column, called 
 the " caudal fin " or tail (c). In all cases, the rays which sup- 
 port the median fins are articulated with the so-called inter- 
 spinous bones, which have been previously described. Though 
 called " median," from their position in the middle line of the 
 body, and from their being unpaired, the median fins of Fishes, 
 as shown by Goodsir and Humphrey, are truly to be regarded 
 as formed by the coalescence of two lateral elements in the 
 mesial plane of the body. 
 
 Fig. 277. Outline of a fish (Perca rramtlata), showing the paired and unpaired fins. 
 / One of the pectoral fins ; v One of the ventral fins ; d First dorsal fin ; d' Second dor- 
 sal fin ; a Anal fin ; c Caudal fin. 
 
 The caudal fin or tail of fishes is always set vertically at the 
 extremity of the spine, so as to work from side to side, and it 
 is the chief organ of progression in the fishes. In its vertical 
 position and in the possession of fin-rays, it differs altogether 
 from the horizontal integumentary expansion which constitutes 
 the tail of the Whales, Dolphins, and Sirenia (Dugong and 
 Manatee). In the form of the tail, fishes exhibit two very dis- 
 tinct types of structure, termed respectively the "homocercal " 
 and " heterocercal " type of tail (fig. 278). The homocercal 
 tail is the one which most commonly occurs in our modern 
 fishes, and it is characterised by the fact that the two lobes of
 
 FISHES. 
 
 313 
 
 Fig. 278. Tails of different fishes. 
 a Homocercal tail (Sword-fish) ; b Het- 
 erocercal tail (Sturgeon.) 
 
 the tail are equal, and the vertebral column, instead of being 
 prolonged into the upper lobe of the tail, stops short at its 
 base. In the heterocercal tail, on the other hand, the vertebral 
 column is prolonged into the up- 
 per lobe of the tail, so that the 
 tail becomes unequally lobed, its 
 greater portion being placed be- 
 low the spine. Even where the 
 vertebral column is not pro- 
 longed into the upper lobe, the 
 tail may nevertheless become 
 heterocercal, in consequence of 
 a great development of the 
 haemal spines as compared with 
 the neural spines of the vertebrae. 
 As regards their general dis- 
 tribution in time, the geological 
 history of fishes presents some 
 points of peculiar interest. Of 
 all the classes of the great sub- 
 kingdom Vertebrata, the fishes 
 are the lowest in point of or- 
 ganisation. It might therefore 
 have been reasonably expected that they would present us 
 with the first indications of vertebrate life upon the globe ; 
 and such is indeed the case. After passing through the enor- 
 mous group of deposits known as the Laurentian, Huronian, 
 Cambrian, and Lower Silurian formations representing an 
 immense lapse of time during which, so far as we yet know, 
 no vertebrate animal had been created we find in the Upper 
 Silurian Rocks the first traces of fish. The earliest of these, in 
 Britain, is found in the base of the Ludlow Rocks (Lower Lud- 
 low Shale), and belongs to the placoganoid genus Pteraspis. 
 Also in the Ludlow Rocks, but at the summit of their upper 
 division, are found fin-spines and shagreen, probably belonging 
 to Cestraciont fishes that is to say, to fishes of as high a 
 grade of organisation as the Elasmobranchii. So abundant 
 are the remains of fishes in the next great geological epoch 
 namely, the Devonian or Old Red" Sandstone that this period 
 has frequently been designated the " Age of Fishes." Most of 
 the fishes of the Old Red Sandstone belong to the order Gan- 
 oidei. In the Carboniferous and Permian Rocks, which close 
 the Palaeozoic period, most of the fishes are still Ganoid, but 
 the former contain the remains of many Plagiostomous fishes. 
 At the close of the Palaeozoic and the commencement of the
 
 3H VERTEBRATA. 
 
 Mesozoic epoch, the Ganoid fishes begin to lose that predomi- 
 nant position which they before occupied, though they continue 
 to be represented through the whole of the Mesozoic and Kain- 
 ozoic periods up to the present day. The Ganoids, therefore, 
 are an instance of a family which has endured through the 
 greater part of geological time, but which early attained its 
 maximum, and has been slowly dying out ever since. Towards 
 the close of the Mesozoic period (in the Cretaceous period) the 
 great order of the Teleostean or Bony fishes is for the first time 
 known certainly to have made its appearance. The orders 
 of the Marsipobranchii, Pharyngobranchii, and Dipnoi have 
 not left, so far as is known, any traces of their existence in 
 past time. Judging from analogy, however, it is highly pro- 
 bable that the two former of these must have had a vast anti- 
 quity, and it is not impossible that trie so-called "Conodonts" 
 from the Lower Silurian Rocks of Russia may yet be shown to 
 be the horny teeth of fishes allied to the Lampreys. At pre- 
 sent, however, the weight of evidence is in favour of looking 
 upon these problematical little bodies as probably referable to 
 some of the Invertebrata. 
 
 These so-called " Conodonts " are microscopic in their 
 dimensions, and have the form of " minute, glistening, slender, 
 conical bodies, hollow at the base, pointed at the end, more or 
 less bent, with sharp opposite margins" (Owen). They show 
 no trace of dental structure, and Professor Owen concludes 
 that they " have most analogy with the spines, or hooklets, or 
 denticles of Naked Molluscs and Annelides." 
 
 It is also to be borne in mind that, though it has not yet 
 been possible to definitely refer any fossil fishes to the order 
 of the Dipnoi, recent discoveries have rendered it extremely 
 probable that some well-known extinct types really belong to 
 this order. Thus, the great " Barramunda " ( Ceratodus Fosteri) 
 of the rivers of Queensland would seem to be truly referable to 
 the Triassic genus Ceratodus, in which case this latter must be 
 removed to the DipnoL This remarkable fish also presents 
 some striking points of resemblance with certain extinct 
 Ganoids, such as Dipterus. Upon the whole, therefore, there 
 are good grounds for accepting Dr. Giinther's suggestion that 
 the Dipnoi should be regarded as a mere sub-order of the 
 Ganoids. 
 
 In the following chapter are given the orders of the Fishes, 
 with the leading characters and geological distribution of each. 
 The order, however, of the Pharyngobranchii (comprising only 
 the living Lancelet), and that of the Marsipobranchii (compris- 
 ing the Lampreys and Hag-fishes), may be here dismissed, as
 
 TELEOSTEI. 315 
 
 they are not known to be represented by any fossil forms. 
 There remain, therefore, for consideration the orders of the 
 Teleostei (Bony Fishes), Ganoidei (Ganoids), Elasmobranchii 
 (Sharks and Rays), and Dipnoi (Mud-fishes). 
 
 CHAPTER XXIX. 
 
 ORDERS OF FISHES. 
 
 ORDER I. TELEOSTEI. This order includes the great majority 
 of fishes in which there is a well-ossified endoskeleton, and it 
 corresponds very nearly with Cuvier's division of the "osse- 
 ous " fishes. The Teleostei are defined as follows : The skele- 
 ton is usually well ossified ; the cranium is provided with cranial 
 bones, and a mandible is present; whilst the -vertebral column 
 almost always consists of more or less completely ossified vertebrce. 
 The pectoral arch has a clavicle; and the two pairs of limbs, when 
 present, are in the form of fins supported by rays. The gills are 
 free, pectinated or tufted in shape, a bony gill-cover and branchio- 
 stegal rays being always developed. The branchial artery has its 
 base developed into a bulbus arteriosus ; but this is never rhythmi- 
 cally contractile, and is separated from the ventricle by no more 
 than a single row of valves. 
 
 The scales in the Teleostean fishes are generally thin, horny, 
 flexible plates, which overlap one another, and have the " cy- 
 cloid " or " ctenoid " characters. The order, therefore, corres- 
 ponds, in a general way, with the orders Ctenoidei and Cycloidei 
 of Agassiz. Some of the Teleostean fishes, however, are pro- 
 vided with ganoid scales. 
 
 Excluding the Leptolepidce, which are sometimes referred to 
 this order, the Teleostei do not seem to have any representatives 
 in times anterior to the Cretaceous period that is, towards the 
 close of the Mesozoic period. From this time on, however, Bony 
 Fishes with cycloid or ctenoid scales are the chief fossil repre- 
 sentatives of the whole class of the fishes, and the order 
 appears to have attained its maximum at the present day. 
 
 The order Teleostei is divided 'into the following sub-orders : 
 
 SUB-ORDER A. MALACOPTERI, Owen (= Physostomata, Mul- 
 ler). This sub-order is defined by usually possessing a com- 
 plete set of fins, supported by rays, all of which are " soft " or 
 many-jointed, with the occasional exception of the first rays in 
 the dorsal and pectoral fins. A swim-bladder is always present,
 
 316 ORDERS OF FISHES. 
 
 and always communicates with the oesophagus by means of a 
 duct, which is the homologue of the windpipe. The skin is 
 rarely naked, and is mostly furnished with cycloid scales ; but 
 in some cases ganoid plates are present. 
 
 The more important families comprised in this sub-order are 
 the Mnrcenida (Eels), the Clupeida (Herrings), the Pikes 
 (Esocida>), the Cyprinida (Carp, Chub, Barbel, &c.), and the 
 Salmonidoe (Salmon and Trout). Few of these families ap- 
 peared in rocks older than the Eocene Tertiary. The Salmon- 
 ides are only sparsely represented in deposits older than those 
 of the Post-Tertiary epoch. The Cyprinida and Esoddce are 
 both represented in the fresh-water deposits of the Tertiary 
 period, and the Murcenidce appear for the first time in the 
 Eocene. The genus Osmeroides (fig. 279) has been referred 
 
 Fig. 279. i. Bery.v (Osmeroides) Lewftiensfs, a Percoid fish from the Chalk ; 
 2. OtmeroieUs Mantelli, a Salmonoid fish from the Chalk. 
 
 to a position in the neighbourhood of the Salmonidce, and 
 dates from the Cretaceous period. The Clupeoicls, also, 
 make their first appearance in the Cretaceous period. Also 
 in this group are the Sheat-fishes (Siluridce), which are chiefly 
 noticeable because they are amongst the small number of 
 living fishes possessed of structures of the same nature as
 
 TELEOSTEI. 317 
 
 the fossil spines known as " ichthyodorulites." The structure 
 in question consists of the first ray of the pectoral fins, which 
 is largely developed and constitutes a formidable spine, which 
 the animal can erect and depress at pleasure. Unlike the old 
 " ichthyodorulites," however, the spines of the Siluridce have 
 their bases modified for articulation with another bone, and 
 they are not simply hollow and implanted in the flesh. The 
 " Siluroids " are also remarkable for their resemblance to cer- 
 tain of the extinct Ganoid fishes (e.g., Pterichthys, Coccosteus, 
 &c.), caused by the fact that the head is protected with an exo- 
 skeleton of dermal bones. The Siluroid fishes, however, are 
 hardly represented at all in the fossil state, being only known 
 by two or three doubtful Tertiary examples. 
 
 SUB-ORDER B. ANACANTHINI. This sub-order is distin- 
 guished by the fact that the fins are entirely supported by 
 " soft" rays, and never possess " spiny" rays ; whilst the ven- 
 tral fins are either wanting, or, if present, are placed under the 
 throat, beneath or in advance of the pectorals, and supported 
 by the pectoral arch. The swim-bladder may be wanting, but 
 when present it does not communicate with the oesophagus by 
 a duct. 
 
 The only important families in this sub-order are the Gadidce 
 (Cod-family) and the Pleuronectida (Flat Fishes). The Gadidce 
 
 o. Rhombus minimus. A small fossil Turbot from the Eocene Tertiary of 
 Monte Bolca. 
 
 comprise the living Cod, Haddock, Whiting, &c., and appear 
 to date their existence from the Eocene Tertiary. The Pleuro- 
 nectida comprise the living Sole, Flounder, Plaice, and the 
 like, in which the body is very much compressed from side to
 
 318 ORDERS OF FISHES. 
 
 side, and is bordered by long dorsal and anal fins. The bones 
 of the head are twisted in such a manner that both eyes are 
 brought to one side of the body. The fish keeps this side up- 
 permost, and is dark-coloured on this aspect ; whilst the oppo- 
 site side, on which it rests, is white. The mouth has the two 
 sides unequal, the pectorals are rarely of the same size, the 
 ventrals look like a continuation of the anal fin, and the bran- 
 chiostegal rays are six in number. The Pleuronectidce are only 
 known by two or three fossils, of which the oldest is the little 
 Rhombus minimus (fig. 280) of the Eocene deposits of Monte 
 Bolca, 
 
 SUB-ORDER C. ACANTHOPTERI. This sub-order is character- 
 ised by the fact that one or more of the first rays in the fins are 
 in the form of true, unjointed, inflexible, " spiny " rays. The 
 exoskeleton consists, as a rule, of ctenoid scales. The ventral 
 fins are generally beneath or in advance of the pectorals, and 
 the duct of the swim-bladder is invariably obliterated. 
 
 The chief living families of this sub-order are the Perch 
 family (Percidce), the Mullets (Mugilidce), the Mackerel family 
 (Scomberida), the Gurnards (Sclerogenida), the Blennies (Blen- 
 niidte), the Gobies (Gobiidce), and the Chaetodons (Chatodon- 
 tidce). The fossil representatives of this sub-order are mainly 
 Tertiary; but the genus Beryx (fig. 279) dates from the Cre- 
 taceous period. In the Eocene Tertiary of Monte Bolca occur 
 several remarkable forms, of which one of the most singular is 
 the Chaetodont genus Platax (fig. 281). 
 
 SUB-ORDER D. PLECTOGNATHI. This sub-order is charac- 
 terised by the fact that the maxillary and premaxillary bones 
 are immovably connected on each side of the jaw. The endo- 
 skeleton is only partially ossified, and the vertebral column 
 often remains permanently cartilaginous. The exoskeleton is 
 in the form of ganoid plates, scales, or spines. The ventral 
 fins are generally wanting, and the air-bladder is destitute of 
 a duct. 
 
 This sub-order includes the living Trunk-fishes (Oslracion- 
 tida), File-fishes (Balistida), and Globe-fishes (Gymnodontida), 
 The fossil forms are few in number, and the earliest date from 
 the Eocene Tertiary. They are chiefly noticeable for the re- 
 semblance to the true Ganoid fishes, produced by their parti- 
 ally ossified endoskeleton and by their possession of ganoid 
 scales. 
 
 SUB-ORDER E. LOPHOBRANCHII. This is a small and unim- 
 portant group, mainly characterised by the peculiar structure 
 of the gills, which are arranged in little tufts upon the branchial 
 arches, instead of the comb-like plates of the typical bony
 
 GANOIDEI. 
 
 319 
 
 fishes. The endoskeleton is only partially converted into bone, 
 and the exoskeleton, by way of compensation, consists of 
 ganoid plates. The swim-bladder is destitute of an air-duct. 
 
 This sub-order comprises the living Pipe-fishes (Syngna- 
 thidtz) and Sea-horses (Hippocampida). A few fossil forms are 
 known, dating from the Eocene Tertiary. 
 
 Fig. ^-i.Platax altissimus, a Chzetodont from the Eocene Tertiary of Monte Bolca. 
 
 ORDER II. GANOIDEI. The order of the true Ganoid 
 Fishes may be defined by the following characters. The endo-
 
 32O ORDERS OF FISHES. 
 
 skeleton is only partially ossified, the vertebral column mostly re- 
 maining cartilaginous throughout life, especially amongst the extinct 
 forms of the Paleeozoic period, in which the notochord is persistent. 
 The skull is furnished with distinct cranial bones, and the lower 
 jaw is present. The exoskeleton is in the form of ganoid scales, 
 plates, or spines. There are usually two pairs of limbs, in the 
 form of fins, each supported by fin-rays. The first rays of the fins 
 are mostly in the form of strong spines. The pectoral arch has a 
 clavicle, and the posterior limbs (ventral fins) are placed close to the 
 anus. The caudal fin is mostly unsymmetrical or " heterocercal" 
 The swim-bladder is always present, is often cellular, and is pro- 
 vided with an air-duct. The intestine is often furnished with a 
 spiral valve. T/ie gills and opercular apparatus are essentially 
 the same as in the Bony fishes. The heart has one auricle and a 
 ventricle, and the base of the branchial artery is dilated into a 
 bulbus -arteriosus, which is rhythmically contractile, is furnished 
 with a distinct coat of striated muscular fibres, and is provided 
 with several transverse rows of valves. 
 
 Of these characters, those which it is most important to 
 remember are the following : 
 
 I. The endoskeleton is rarely thoroughly ossified, but varies a 
 good deal as to the extent to which ossification is carried. In 
 some forms, including most of the older members of the order, 
 the chorda dorsalis is persistent, no vertebral centra are de- 
 veloped, and the skull is cartilaginous, and is protected by 
 ganoid plates. Even in these forms, however, the peripheral 
 elements of the vertebrae are ossified. In others, the bodies of 
 the vertebrae are marked out by osseous or semi-cartilaginous 
 rings, enclosing the primitive matter of the notochord. In 
 others, the vertebrae are like those of the Bony fishes that is 
 to say, deeply biconcave or " amphicoelous." In one Ganoid, 
 however the Bony Pike (Lepidosteus) the vertebral column 
 consists of a series of " opisthoccelous " vertebrae that is to 
 say, vertebrae which are convex in front and concave behind. 
 This is the highest point of development reached in the spinal 
 column of any fish, and its structure is more Reptilian than 
 Piscine. 
 
 II. The exoskeleton consists, in all Ganoid fishes, of scales, 
 plates, or spines, which are said to possess ganoid characters. 
 The peculiarities of these scales are that they are composed of 
 two distinct layers an inferior layer of bone and a superficial 
 covering of a kind of enamel, somewhat similar to the enamel 
 of the teeth, called " ganoine." In form the ganoid scales 
 most generally exhibit themselves as rhomboidal plates, placed 
 edge to edge, without overlapping, in oblique rows, the plates
 
 GANOIDEL 
 
 321 
 
 of each row being often articulated to those of the next by 
 distinct processes. In other cases the ganoid structures are 
 simply in the form of detached plates, tubercles, or spines; and 
 in some cases their shape is even undistinguishable from the 
 horny scales of the typical Teleostean fishes. In all cases, 
 however, whatever their form may be, they have the distinctive 
 ganoid structure, being composed of an inferior layer of true 
 bone and a superior layer of enamel. It is to be remembered, 
 however, that these ganoid plates and scales are not confined 
 to the fishes of the order Ganoidei, but that they occur in two 
 sub-orders of the Bony Fishes namely, the Plectognathi and 
 Lophobranehii and in some others of the Teleostei as well. 
 
 III. As to the fins, both pectorals and ventrals are usually 
 present, and the. ventrals are always placed far back, in the 
 neighbourhood of the anus, and are never situated in the im- 
 mediate vicinity of the pectorals. In some living and many 
 extinct forms the fin-rays of the paired fins are arranged so as 
 to form a fringe round a central lobe (fig. 282). This struc- 
 
 Fig. 282. Ganoid Fishes. A, Polypterus (recent) ; B, Osteolepis (extinct), a One 
 of the pectoral fins, showing the fin-rays arranged round a central lobe ; b One of the 
 ventral fins ; c Anal fin ; d Dorsal fin ; ct Second dorsal fin. 
 
 ture characterises a division of Ganoids called by Huxley, for 
 this reason, Crossopterygidce, or "fringe-fmned." The form of 
 the caudal fin varies, the Ganoids being in this respect inter- 
 mediate between the Bony fishes, in which the tail is " homo- 
 cereal," and the Sharks and Rays, in which there is a " hetero- 
 cercal" caudal fin. In the majority of Ganoids, then, the tail 
 is unsymmetrical or " heterocercal," but it is sometimes equi- 
 lobed or " homocercal."
 
 322 ORDERS OF FISHES. 
 
 As regards the general distribution in time of the Ganoittci, 
 the oldest representatives of the fishes belong, so far as is yet 
 known with certainty, to this order. The order, namely, is 
 represented in the Upper Silurian Rocks of Bohemia and 
 Britain by several Ganoid fishes, which have been referred to 
 five distinct genera. In the Devonian Rocks, or Old Red 
 Sandstone, the Ganoids attain their maximum. The singular 
 family of the Cephalaspidce appears to die out finally at the 
 close of this period, and the great group of the Crossopterygidce 
 attained here its highest development, being represented at the 
 present day by the single genus Polypterus. The Carboniferous 
 and Permian Rocks contain an abundance of Lepidoganoids. 
 In the Mesozoic period, the Lepidoganoids are very largely 
 represented by various extinct types, many of which belong to 
 the family of the Lcpidosteida represented at the present day 
 by the Bony Pike or Gar-pike of North America. Here, also, 
 we have for the first time representatives of the family of the 
 Sturionidtz, to which the living Sturgeons belong. Lastly, in 
 the Oolitic Rocks appear for the first time Lepidoganoids with 
 homocercal tails, and they continue to be represented up to 
 the present day. In the Tertiary Rocks true Sturgeons (Ati- 
 penser) make their appearance ; but the Ganoids are now con- 
 siderably outnumbered by the Teleostean fishes ; and the latter 
 have a still more marked predominance at the present day. 
 
 The classification of the Ganoid Fishes has hitherto proved a 
 matter of extreme difficulty ; and probably no arrangement 
 that has been as yet proposed can be regarded as being, in all 
 its details, more than provisional. A convenient primary- 
 division is that into Lepidoganoids, in which the body is 
 furnished with scales of moderate size, and the endoskeleton 
 is generally more or less perfectly ossified ; and Placogattoids, 
 in which the skeleton is imperfectly ossified, and the head and 
 more or less of the body are protected by large ganoid plates, 
 which in many cases are united together by sutures. Accept- 
 ing this division, the order Ganoidei may be divided into the 
 following sub-orders : 
 
 SECTION i. LEPIDOGANOIDEI. 
 Sub-order A. Amiada:. 
 
 B. Lepidosteida. 
 
 C. Lepidopleurida. 
 
 D. Crossopterygida. 
 
 E. AcanthodidijE, 
 
 SECTION 2. PLACOGANOIDEI. 
 Sub-order F. Ostracostti. 
 G. Sturionida,
 
 GANOIDEI. 323 
 
 The position of at least two of these sub-orders (viz., Acan- 
 thodidce and Ostracostei) in the order of the Ganoids is question- 
 able ; whilst the Sturionidce have been referred elsewhere. In 
 any case, the number of forms included in these sub-orders is 
 so large that nothing more can be done here than simply to 
 draw attention to some of the more striking examples of each. 
 
 SUB-ORDER A. AMIABLE. In this sub-order are included 
 Ganoids in which the scales are rounded and overlap one an- 
 other, and the tail is homocercal. The vertebral column is 
 ossified, and the external appearance approaches closely to 
 that of an ordinary Teleostean fish. A few fossil forms from 
 the Tertiary Rocks have been more or less doubtfully referred 
 to this group ; and the sub-order is represented at the present 
 day by various American fishes, all belonging to the genus 
 Amia. 
 
 SUB -ORDER B. LEPIDOSTEID^E. Scales rhomboidal, not 
 overlapping ; tail heterocercal, sometimes homocercal ; paired 
 fins not lobate ; fin-borders generally with fulcral scales ; true 
 branchiostegal rays. This sub-order is represented at the 
 present day by the Gar-pike (Lepidosteus) of the North Ameri- 
 can continent, and it attained its greatest development in the 
 Mesozoic period. The exact range of the sub-order in time is 
 uncertain, as it has not yet been determined what forms should 
 be included in it. If Cheirolepis be excluded, the sub-order is 
 not represented at all in the Devonian Rocks. In the Car- 
 boniferous and Permian Rocks the sub-order is mainly repre- 
 sented by the genera Palaoniscus and Amblypterus (fig. 283), in 
 which the tail is heterocercal, and the jaws are furnished with 
 
 Fig. y&^Amblypter 
 
 numerous minute teeth. Numerous species of these genera are 
 known in the above-mentioned formations, and both appear for 
 the last time in the Trias. In the Secondary Rocks Lepido- 
 steids are extremely abundant, the chief forms belonging to the
 
 324 
 
 ORDERS OF FISHES. 
 
 families Dapedida, Lepidotida, and Leptolepida. In the Dapedi- 
 dcs (fig. 284, i), the tail-fin is only slightly heterocercal, and the 
 
 Fig. 284 i. Dapedius tetragonolepis. 2. Leptolepis sprattiforntis. 
 3. Lepidotus Valdtnsis. 
 
 back teeth are obtuse. Dapedius itself is compressed and deep- 
 bodied, and is exclusively confined to the Lias. The front-teeth 
 in this genus are notched or bifurcate. sEehmodus is also 
 
 
 Fig. 285. Tetragonolepis (restored). Lias. 
 
 exclusively Liassic ; but Semionotus and Phohdophorus range 
 upwards to the Chalk or to the highest Oolitic strata. The 
 Oolitic genus Tetragonokpis (fig. 285) is closely similar to Da-
 
 GANOIDEI. 
 
 325 
 
 pedius, but the front teeth are not notched. The body is 
 greatly compressed, and there is a single long dorsal fin. 
 The place of this genus is disputed, and it is often referred 
 to the Pycnodonts. The Lepidotidce have a homocercal tail 
 (fig. 283, 3), and possess obtuse teeth. The type -genus, 
 Lepidotus, ranges from the Lias to the Eocene Tertiary. 
 The Leptolepida (fig. 283, 2) have also a homocercal tail, and 
 possess small rounded scales. The species of this family are 
 all Secondary in their distribution. 
 
 SUB-ORDER C. LEPIDOPLEURID^;. "Ganoids with hetero- 
 cercal equilobate tails. Body rhomboidal, covered with 
 rhombic scales, articulated by strong ribs traversing their 
 anterior margins internally. Dorsal fin equal to half the 
 length of the trunk. Anal fin also with an elongate base. 
 Ventrals, when present, small. Paired fins non - lobate. 
 Branchiostegal rays not taking the form of broad plates. 
 Notochord persistent. Arches well ossified." (Young.) The 
 two most important families of this sub-order are the Platy- 
 somidce and Pycnodontida ; of which the former is mainly 
 Carboniferous and Permian, whilst the latter is almost ex- 
 clusively Mesozoic. In the genus Platysomus (fig. 286) the 
 
 Fig. 286. Platysomus gibbosus. Middle Permian. 
 
 tail is heterocercal, the dorsal and anal fins are long, the 
 pectorals are small, and the ventrals appear to be wanting. 
 The teeth are conical and uniserial, and the body is deep 
 and compressed from side to side. The Platysomi are mainly 
 found in the Permian Rocks. In the true Pycnodonts the 
 teeth are multiserial, and are adapted for crushing ; consisting 
 of " a circular or transversely oval crown, flattened above, 
 and sessile on the bone to which it is attached ; or of an
 
 326 ORDERS OF FISHES. 
 
 obtusely conical crown, which is broader than its peduncle of 
 support" (Young). The Pycnodonts are mainly Oolitic, but 
 a few Cretaceous species are known, and one form has been 
 described from the Eocene Tertiary. The Triassic Placodus, 
 formerly referred to this family, is now known to be truly 
 Reptilian. 
 
 SUB-ORDER D. CROSSOPTERYGIDJE. "Dorsal fins two, or, 
 if single, multifid or very long; the pectoral, and usually the 
 ventral, fins lobate ; no branchiostegal rays, but two principal, 
 with sometimes lateral and median, jugular plates, situated 
 between the rami of the mandible ; caudal fin diphycercal, or 
 heterocercal ; scales cycloid or rhomboid, smooth or sculp- 
 tured. " (Huxley. ) 
 
 All the Ganoids of this sub-order are pre-eminently dis- 
 tinguished by the structure of the paired fins, the pectorals 
 always, and the ventrals usually, consisting of a central lobe 
 or stem, which is covered by scales, and to the sides of which 
 the fin -rays are attached. The nearest approach to this 
 structure amongst living fishes is found in the paired fins of 
 the Barramunda (Ceratodus Fosteri} of the rivers of Queens- 
 land. In this singular fish, which is at present referred to the 
 order of the Dipnoi, the pectoral and ventral fins are supported 
 by a median, many-jointed, cartilaginous rod, to which nume- 
 rous lateral branches are attached. The scales in this sub- 
 order are sometimes rhomboidal, not overlapping one another; 
 at other times they are cycloidal in shape, and are arranged 
 in an imbricate manner. 
 
 Professor Huxley divides the Crossopterygidce into the fol- 
 lowing families. (See ' Memoirs of the Geological Survey of 
 Great Britain. Decade X.') : 
 
 Fam. I. POLYPTERII. 
 
 Dorsal fin very long, multifid ; scales rhomboidal. 
 Polypttrus (fig. 282). 
 
 Fam. 2. SAURODIPTERINI. 
 
 Dorsal fins two ; scales rhomboidal, smooth ; fins sub -acutely 
 lobate. 
 Diploptcrus, Osteolfpis (fig. 282), Megalichthys. 
 
 Fam. 3. GI.YPTODIPTERINI. 
 
 Dorsal fins two ; scales rhomboidal or cycloidal, sculptured ; 
 
 pectoral fins acutely lobate ; dentition dendrodont. 
 Sub-fam. A. with rhomboidal scales. 
 
 GlyptoliEtnus (fig. 287), Glyptopomus, Gyroptychitts. 
 Sub-fam. B. with cycloidal scales. 
 
 Holoptychius (fig. 288), Glyfitdefiis, Platygnathus [R/tizodus, 
 Dendrodus, Cricodus, Lamnodus],
 
 GANOIDEI. . 327 
 
 Fam. 4. CTENODIPTERINI. 
 
 Dorsal fins two ; scales cycloidal ; pectorals and ventrals acutely 
 lobate ; dentition ctenodont. 
 
 Dipterus [Ceratodus? Tristichopterus ?] 
 
 Fam. 5. PHANEROPLEURINI. 
 
 Dorsal fin single, very long, not subdivided, supported by many 
 interspinous bones ; scales thin, cycloidal ; teeth conical ; ven- 
 tral fins very long, acutely lobate. 
 
 Phaneropleuron (fig. 290). 
 Fam. 6. CCELACANTHINI. 
 
 Dorsal fins two, each supported by a single interspinous bone ; 
 scales cycloidal ; paired fins obtusely lobate ; air-bladder ossi- 
 fied. Calacanthus, Undina, Macropoma. 
 
 As regards the distribution of the Crossopterygida in time, 
 Professor Huxley remarks: " Of the six families which com- 
 pose it, four are not only Palaeozoic, but are, some exclusively, 
 and all chiefly, confined to rocks of Devonian age an epoch 
 in which, so far as our present knowledge goes, no fish belong- 
 ing to the sub-orders of the Amiadce and Lepidosteida (un- 
 less Cheirolepis be one of the latter) makes its appearance. 
 Rapidly diminishing in number, the Crossopterygidae seem to 
 have had several representatives in the Carboniferous epoch ; 
 but after this period (unless Ceratodus be a Ctenodipterine) 
 they are continued through the Mesozoic age only by a thin, 
 though continuous, line of Ccelacanthini, and terminate, at the 
 present day, in the two or three known species of the single 
 genus Polypterus" 
 
 Of the extinct types of this sub-order, some are sufficiently 
 important to merit especial mention. In the family of the 
 Saurodipterini, the genus Osteolcpis (fig. 282) has a very hetero- 
 cercal tail and smooth scales. The first dorsal is placed near 
 the centre of the back, and the mouth is furnished with sharp 
 teeth. All the species of this genus are Devonian. The Car- 
 boniferous genus Megalichthys appears also to belong here. 
 In this singular genus are large " sauroid " fishes with hetero- 
 cercal tails, rhomboidal scales, and great conical incurved teeth, 
 which are mostly smooth, but are sometimes finely ridged. 
 
 Of the Glyptodipterini with rhomboidal scales, Glyptolcemus 
 (fig. 287) may be taken as the type. In this singular fish, the 
 body is elongated and the head depressed. There are two 
 dorsal fins which are placed very far back, and the ventrals 
 have a similar posterior position. The tail is " divided into 
 two equal lobes by the prolonged conical termination of the 
 body," becoming thus " diphycercal." Glyptolamus is exclu- 
 sively confined to the Devonian period.
 
 328 
 
 ORDERS OF FISHES. 
 
 Of the Glyptodipterines with cycloidal scales, the most 
 important form is Holoptychius (fig. 288). In this genus 
 there are two dorsal fins placed very far back, and the 
 
 . rtj.Glyptolcemus Kiitnairiii. Restored. A. Scale of the same. Devoniar 
 
 Fig. 288. Holoptychius nobilissimus. Restored. A, Scale of the same. Devonian. 
 
 ventrals are similarly approximated to the tail, as in Glypto- 
 /cemus. The body, however, is covered with large scales of a 
 cycloidal form, which overlap one another, and have wrinkled 
 surfaces ; and the tail is inequilobed. The teeth are of two 
 sizes, and the larger ones are longitudinally striated at their 
 bases. The true Holoptychii are Devonian in their distribu- 
 tion. In the Carboniferous Rocks, however, occurs the nearly 
 allied genus Rhizodus (fig. 289), in which the teeth agree with 
 those of Holoptychius in being of two sizes, but they differ in 
 being trenchant on both sides. Rhizodus must have attained 
 a large size, and must have been highly predaceous in its 
 habits. 
 
 The type-genus of the Ctenodipterini is Diptcrus, in which 
 the position and form of the fins are very much the same as 
 in Holoptychius. The body is also covered with cycloidal 
 overlapping scales ; but these scales are smooth. The head 
 is protected by a kind of helmet formed of the anchylosed
 
 GANOIDEI. 
 
 329 
 
 cranial bones, and the teeth are conical in form and nearly 
 equal in size. The species of Dipterus are all Devonian. 
 
 
 Fig. 289. Jaw of Rhizodus Hibberti. Carboniferous. 
 
 The family Phanopleurini comprises only the single genus 
 Phaneropleuron (fig. 290), which is probably exclusively De- 
 vonian. In this singular genus the scales are very thin, 
 cycloidal, and overlapping one another. The dorsal fin is 
 extremely long, and is confluent with the tail-fin, and the pec- 
 torals and ventrals are acutely lobate. The jaws are armed 
 with a single series of short conical teeth, and the notochord 
 was persistent. 
 
 90. Plianeroplertron Atidersoni and scale. Devor 
 
 Lastly, the family of the Ccelacanthi comprises forms which 
 range from the Devonian to the Cretaceous period, and which 
 are distinguished, in the typical genera, by having hollow fin- 
 spines, by having two dorsal fins, each supported by a single 
 interspinous bone, by having cycloidal overlapping scales, and 
 by the remarkable peculiarity that the swim-bladder was ossi- 
 fied. The type-genus Ccelacanthus seems to range from the 
 Carboniferous to the Trias.
 
 330 
 
 ORDERS OF FISHES. 
 
 SUB-ORDER E. ACANTHODID^E. Scales exceedingly small, 
 shagreen-like ; the front of each fin provided with a strong 
 spine, simply implanted in the flesh; no distinctly ossified 
 cranial bones ; no operculum ; tail heterocercal. In their fin- 
 spines, and in some other points, the Acanthodid& approximate 
 closely to the Elasmobranchii ; but they are generally regarded 
 as an order of the Ganoidei. The Acanthodidcs are mainly 
 Devonian, but some forms occur in the Carboniferous Rocks, 
 and a species from the Permian Rocks has been doubtfully 
 referred here. Acanthodes (fig. 291) has a single dorsal fin, and 
 
 Fig. 291. i. Acanthodes Mitchelli. 2. Clitnatius scutigtr. 
 3. Diplacantkus gracilis. Devonian. 
 
 is represented in both Devonian and Carboniferous deposits. 
 Diplacanthus (fig. 291, 3) has two dorsal fins, and is exclusively 
 confined to the Devonian Rocks. 
 
 SUB-ORDER F. OSTRACOSTEI. The Ganoids of this sub- 
 order are characterised by having the head, and generally the 
 anterior portion of the trunk as well, encased in a strong ar- 
 mour composed of numerous large ganoid plates, immovably 
 united to one another. The posterior extremity of the body 
 is more or less completely unprotected ; and whilst the noto- 
 chord is persistent, the peripheral elements of the vertebrae 
 are ossified. The fishes belonging to this section are the 
 most ancient of their class, commencing in the Upper Silurian 
 Rocks. They extend through the Devonian series, but are 
 not known to have survived into the Carboniferous period.
 
 GANOIDEI. 331 
 
 They have generally been placed amongst the Ganoids ; but 
 Professor Huxley has pointed out that they present, many of 
 them, features by which they approximate closely to the Silu- 
 roids amongst the Teleosteans. The more important genera 
 included in this sub-order are Cephalaspis, Pteraspis, Coccosteus, 
 and Pterichthys. 
 
 Cephalaspis (fig. 292) is the type of the family of the Cephal- 
 aspida, and is readily recognised by the fact that the cephalic 
 shield has its posterior angles produced into long " cornua," 
 
 Fig. 292. Cephalaspis Lyetlii. (After Page.) Old Red Sandstone. 
 
 giving it the shape of a " saddler's knife." Besides these la- 
 teral cornua, there is a " posterior cornu " or spine, formed by 
 a prolongation backwards of the hinder margin of the shield in 
 the middle line. The orbits are approximated, and are placed 
 nearly in the centre of the cephalic shield. No jaws or teeth 
 are known, and the mouth was probably soft, and adapted for 
 suction. The head-shield exhibits vascular canals, and shows 
 very distinct bone-cells when examined in thin sections under 
 the microscope. The body is covered with ganoid scales, and 
 there is a well-marked dorsal fin. Pectoral fins have also been 
 described, and the tail is clothed with a heterocercal fin. In 
 the nearly allied Auchenaspis, the structure is very similar to 
 the above, but there is no spine or " posterior cornu/' and 
 there is instead a neck-plate formed by an extension backwards 
 from the cephalic shield. The Cephalaspidce are mainly found 
 in the Old Red Sandstone, the commonest species being C. 
 Lyellii. Other species are found in the " passage-beds " 
 between the Silurian and Old Red, and the genus is not 
 wholly unrepresented in the Upper Silurian deposits. 
 
 In the genus Pteraspis (fig. 293) the head is defended, as in 
 Cephalaspis, by a shield or buckler, which is composed of seve- 
 ral pieces firmly anchylosed. The shield consists of a central 
 disc, the lateral angles of which are produced into short cornua,
 
 332 ORDERS OF FISHES. 
 
 whilst it is extended into a rostrum in front. The posterior 
 spine is very small, and is attached to the disc as a separate 
 piece. The orbits are situated laterally. 
 The minute structure of the shield is very 
 complex, consisting of three layers. The 
 innermost layer is laminated, and is tra- 
 versed by vascular canals. The middle 
 layer is made up of polygonal cavities ; 
 and the outer layer is structureless or 
 fibrous, and is finely striated or grooved. 
 The body was covered with scales ; but 
 nothing is known of the nature of the fins. 
 The genera Cyathaspis and Scaphaspis 
 have been founded upon forms which have 
 
 e usuall 7 been P laced under Pteraspis, and 
 
 of Ludiow. (After Mur- which differ in more or less essential 
 points from the typical species of this 
 genus. The genus Pteraspis, so far as yet known, comprises 
 the most ancient of the fishes, commencing as it does in the 
 earlier portion of the Ludiow formation (Upper Silurian). 
 Other species are known in the Old Red Sandstone ; but the 
 genus appears to have entirely disappeared before the close of 
 the Devonian period. 
 
 In the genus Coccosteus the head was protected by a great 
 shield, the plates of which are covered with small hemispheri- 
 cal tubercles. There is also a ventral or " sternal " shield, 
 which, according to Huxley, seems to have had no direct con- 
 nection with the cephalic buckler. The mouth was furnished 
 with a distinct lower jaw or "mandible," composed of two 
 rami, carrying small teeth. The notochord was persistent, but 
 the neural and haemal spines of the vertebrae, and the rays of 
 the dorsal and anal fins, are well ossified. A heterocercal tail- 
 fin was doubtless present as well. The genus Coccosteus is 
 essentially Devonian ; but a species has been discovered by 
 M. Barrande in the Upper Silurian of Bohemia. 
 
 In the genus Pterichthys (fig. 294) are some very remarkable 
 fishes, first discovered in the Old Red Sandstone by the late 
 Hugh Miller, and nearly related in most respects to Coccosteus. 
 The whole of the head and the anterior part of the trunk were 
 defended by a buckler of large ganoid plates suturally united, 
 those covering the trunk forming a back-plate and a breast- 
 plate articulated together at the sides. The rest of the body 
 was covered with small ganoid scales. A small dorsal fin, a 
 pair of ventrals, a pair of pectorals, and a heterocercal tail-fin 
 were present The form of the pectoral fins is the peculiar
 
 GANOIDEI. 333 
 
 characteristic of the genus. These were in the form of two 
 long curved spines, somewhat like wings, covered by finely- 
 tuberculated ganoid plates. From their form they cannot 
 have been of much use in swimming ; but they probably, as 
 suggested by Owen, enabled the animal to shuffle along the 
 sandy bottom of the sea, if stranded at low water. All the 
 species of Pterichthys are exclusively confined to the Old Red 
 Sandstone. 
 
 Fig. 294. Pterichthys cornutus. Old Red Sandstone. 
 
 SUB-ORDER G. STURIONID^E. In this sub-order the skeleton 
 is almost altogether cartilaginous, and the notochord is per- 
 sistent. The exoskeleton is usually in the form of large gan- 
 oid plates, which are united into a shield over the head, but 
 are detached over the body. Sometimes the exoskeleton is 
 almost absent, and in no case is the mouth furnished with 
 teeth. The tail is heterocercal. 
 
 This sub-order comprises the living Sturgeons, and is not 
 known with certainty to have corne into existence before the 
 Eocene Tertiary, where it is represented by the Acipenser toli- 
 apicus of the London Clay. In the Lias, however, occur two 
 species of the singular genus Chondrosteus, which have usually 
 been referred here, and have been regarded as being most 
 nearly allied to the Paddle-fishes (Spatularid) of North America. 
 The skull, however, is more completely ossified than is the case 
 with any living members of \hzSturionidcR; and the true place 
 of Chondrosteus must be regarded as uncertain.
 
 334 ORDERS OF FISHES. 
 
 CHAPTER XXX. 
 ORDERS OF FISHES Continued. 
 
 ORDER III. ELASMOBRANCHII ( = Sdachia, Muller; Placoidei, 
 Agassiz ; Holocephali and Plagiostomi, Owen). This order in- 
 cludes the Sharks, Rays, and Chimaeroe, and corresponds with 
 the greater and most typical portion of the Chondropterygidce or 
 Cartilaginous Fishes of Cuvier. The order is distinguished by 
 the following characters : The skull and lower jaw are well 
 developed, but there are no cranial bones, and the skull consists of 
 a single cartilaginous box, without any indication of sutures. 
 The vertebral column is sometimes composed of distinct vertebra, 
 sometimes cartilaginous or sub-notochordal. The exoskeleton is in 
 the form of placoid granules, tubercles, or spines. There are two 
 pairs of fins, representing the limbs, and supported by cartilaginous 
 fin-rays ; and the ventral fins are placed far back near the anus. 
 The pectoral arch has no clavicle. The heart consists of a single 
 auricle and ventricle, and the bulbus arteriosus is rhythmically 
 contractile, is provided with a special coat of striated muscular 
 fibres, and is furnished with several transverse rows of valves. 
 The gills are pouch-like. 
 
 In most of the above characters it will be seen at once that 
 the Elasmobranchii agree with the Ganoid fishes, especially as 
 regards the structure of the heart. The following points of 
 difference, however, require more special notice : 
 
 I. The exoskeleton is what is called by Agassiz "placoid." 
 It consists, namely, of no continuous covering of scales or 
 ganoid plates, but of more or less numerous detached grains, 
 tubercles, or spines, composed of bony matter, and scattered 
 here and there in the integument In the case of the Rays, 
 these placoid ossifications often take a very singular shape, 
 consisting of an osseous or cartilaginous disc, from the upper 
 surface of which springs a sharp recurved spine, composed of 
 dentine. 
 
 II. The ///$ are fixed and pouch-like, and differ very mate- 
 rially from those of the Bony and Ganoid fishes. In the case 
 of the Sharks and Rays, the gill-pouches open upon the sur- 
 face by a series of separate apertures, which are placed on the 
 sides of the neck in the former, and on the under surface of 
 the body in the latter. In neither is there any gill-cover or 
 operculum, nor are there any branchiostegal rays. In one 
 section of the order, however viz., the Holocephali though 
 the internal structure of the gills is essentially the same as in
 
 ELASMOBRANCHII. 335 
 
 the Sharks, there is only a single branchial aperture or gill-slit 
 externally, and this is protected by a rudimentary operculum 
 and branchiostegal rays. 
 
 The order Elasmobranchii is divided into the two sub-orders 
 of the Holocephali and Plagiostomi. The former comprises the 
 living Chimcerce, characterised by the mouth being terminal, 
 and there being only a single gill-slit. The latter comprises 
 the living Port Jackson Shark, the true Sharks and Dog-fishes, 
 and the Rays, characterised by having the mouth transverse 
 and placed on the under surface of the head, whilst there are 
 several apertures to the gills. 
 
 As regards their general distribution in time, the Elasmo- 
 branchii are nearly as ancient as the Ganoids. At the top of 
 the Upper Ludlow Eocks, or at the close of the Upper Silurian 
 epoch, there have been discovered the remains of undoubted 
 Plagiostomous fishes, most nearly allied to the existing Port 
 Jackson Shark (Cestration Philippi). These remains consist 
 chiefly of defensive spines, which formed the first rays in the 
 dorsal fins, and upon these the genus Onchus (fig. 295) has been 
 founded. Besides these there have been found portions of skin 
 or " shagreen," with little placoid tubercles, like the skin of a 
 living shark. These have been referred to the genera Sphago- 
 dus and Thelodus. They are the earliest known remains of 
 Plagiostomous fishes, and with the exception of the few re- 
 mains from the Lower Ludlow Rocks, they are the earliest 
 known remains of fishes in the stratified series. The discovery 
 of these remains, at that time the earliest known traces of 
 Vertebrate life, is due to the genius of Sir Eoderick Murchi- 
 son, the author of ' Siluria.' 
 
 Most of the fossil Elasmobranchii belong to the division 
 Cestraphori of Owen, so called because they are provided with 
 the large fin-spines which are known to geologists as " ichthyo- 
 dorulites." The two families of this division the Cestracionts 
 and Hybodonts are largely represented in past time, the 
 former chiefly in the Palaeozoic period, the latter chiefly in the 
 Mesozoic Rocks. Subjoined is an illustration of the "ichthyo- 
 dorulites " and teeth of some of the Palaeozoic Cestraphori. 
 
 The true Sharks are represented in the Mesozoic deposits 
 (e.g., by teeth of Notidanns in the Oolites) ; but they are chiefly 
 Cretaceous and Tertiary. The teeth of Odontaspis, Galeocerdo, 
 and Carcharodon, are good examples from the Eocene of the 
 Isle of Sheppey. The true Rays are older than the true 
 Sharks, the Carboniferous fossil Pleuracanthus being probably 
 the spine of a Ray (fig. 296). Numerous remains of Rays, 
 chiefly in the form of the pavement-like teeth, are known,
 
 336 ORDERS OF FISHES. 
 
 both from the Secondary and Tertiary Rocks. The last divi- 
 sion of the Elasmobranchii viz., that of the Holocephali is 
 poorly represented in past time by the Mesozoic and Kaino- 
 zoic IscktoduS) Elasmodus, Ganodus, and Edaphodus. 
 
 In the following a more detailed account is given of the 
 characters of the various groups of the Elasmobranchii, with 
 the leading characters and more important fossil forms of 
 each : 
 
 SUB-ORDER A. HOLOCEPHALI. This sub-order includes cer- 
 tain curious fishes, of which the only living forms are the 
 Chim&ridce. The notochord is persistent, but the neural 
 arches and transverse processes are cartilaginous. The jaws 
 are bony, and are covered by broad plates representing the 
 teeth. The exoskeleton consists of placoid granules. The 
 first ray of the anterior dorsal fin is in the form of a powerful 
 defensive spine, like the " ichthyodorulites " of many fossil 
 fishes. The ventral fins are abdominal, and the tail is hetero- 
 cercal. There is only a single external gill-aperture, covered 
 with a gill-cover and branchiostegal membrane ; but only a 
 small portion of the borders of the branchial laminae is free. 
 The mouth is placed at the extremity of the head. 
 
 The Chimaeroid fishes are not known to have existed at all 
 during the Palaeozoic period ; but they are not uncommon in 
 the Secondary period and in the Tertiaries. They are exclu- 
 sively known by means of their jaws and teeth and their fin- 
 spines or " ichthyodorulites." The dental plates are united to 
 the beak-shaped jaws; and the dorsal fin-spines are always 
 movable and jointed instead of being supported on a cartilage 
 imbedded in the muscular tissue of the back (as in the Spina- 
 cidcz and Cestrationtida). Of the fossil Chimaeroids, the genera 
 Ischiodus and Ganodus are exclusively Mesozoic ; Edaphodus 
 ranges from the Cretaceous series to the Eocene Tertiary; and 
 Elasmodus is only known from the Eocene. 
 
 SUB-ORDER B. PLAGIOSTOMI. This sub-order is of consider- 
 ably greater importance, as it includes the well-known Sharks 
 and Rays. The vertebral centra are usually more or less ossi- 
 fied, and even when quite cartilaginous, the centra are marked 
 out by distinct rings. The skull is in the form of a cartila- 
 ginous capsule, without distinct cranial bones. The mouth is 
 transverse, and is placed on the under surface of the head. 
 The exoskeleton consists of placoid granules, tubercles, or 
 spines. The branchial sacs open externally by as many dis- 
 tinct apertures as there are sacs, and there is no operculum. 
 A pair of tubes proceed from the pharynx to open on the upper 
 surface of the head by two apertures, which are termed
 
 ELASMOBRANCHII. 337 
 
 " spiracles." By means of these water can be admitted to the 
 pharynx, and thence to the gills. 
 
 By Professor Owen the Plagiostomi are divided into three 
 sections, termed respectively the Cestraphori, the Selachii, and 
 the Batides. 
 
 a. Ccstraphori. In this division there is a strong spine in 
 front of each dorsal fin, and the back teeth are obtuse. The 
 only living representative of this group is the Port Jackson 
 Shark (Cestradon Philippi), characterised by its pavement of 
 plate-like crushing teeth, adapted for comminuting small Mol- 
 luscs and Crustaceans. It is exclusively an inhabitant of the 
 Australian and Chinese seas, and is remarkable for its close re- 
 semblance to a large group of extinct forms, of which the best 
 known are the genera Hybodus and Acrodus from the Second- 
 ary Rocks. 
 
 The Cestraphori are known in a fossil state mainly by their 
 fin-spines, or " ichthyodorulites," and their teeth. It is obvious, 
 however, that it must be often very difficult or altogether impos- 
 sible to determine absolutely whether a spine or a piece of shag- 
 reen belongs to a Cestraciont or to a true Shark. Some of the 
 forms, therefore, to be immediately mentioned, must be regarded 
 as being only provisionally placed amongst the Cestraciontida. 
 
 With this proviso, the earliest known traces of Cestraciont 
 fishes appear to be in the Upper Ludlow Rocks, at the sum- 
 mit of the Silurian series. Here, within the limits of a single 
 stratum, well known as the " bone-bed," occur remains which 
 have been with more or less probability referred to Cestra- 
 cionts. Some of these (fig. 295) are in the form of compressed, 
 
 Fig. 295. A, Spine of Onchus tenuistriatus. B, Shagreen-scales of Thelodus. 
 Both from the bone-bed of the Upper Ludlow Rocks. 
 
 slightly curved spines, the sides of which are grooved longi- 
 tudinally. These have been referred to a provisional genus, 
 under the name of Onchus, and there appears to be little doubt 
 as to their truly belonging to fishes of some kind. It is, how- 
 ever, quite possible that they really belong to Pteraspis, in 
 which case they must be removed from their present place. 
 
 Along with the spines of Onchus arb found fragments of 
 
 prickly skin or shagreen, which have been referred to the 
 
 temporary genus Sphagodus, along with minute cushion-shaped 
 
 bodies, which are doubtless placoid scales, and which have 
 
 Y
 
 338 
 
 ORDERS OF FISHES. 
 
 been referred to another genus under the name of Thelodns 
 (fig. 295, B). In the same bed are found jaw-like bodies, with 
 tooth-like processes of different sizes, which have been named 
 Plectrodus, and have been supposed to be the jaws of fishes. 
 The true nature of these, however, is doubtful, and they cer- 
 tainly do not belong to Plagiostomous fishes. Possibly they 
 are the prickly margins of the cephalic bucklers of Cephalas- 
 pidean fishes. 
 
 It should be mentioned, also, that M. Barrande enumerates 
 Ctenacanthus amongst the fishes found in the Upper Silurian 
 rocks of Bohemia, this genus being otherwise only known in 
 the Devonian and Carboniferous formations. 
 
 In the Devonian Rocks the remains of Cestraphori are not 
 uncommon. The more important fossil spines of the deposits 
 of this period have been referred to the genera O/ic/ius, Ctena- 
 canthus, Homacanthus, and Cosmacanthus. The fossil teeth 
 belong chiefly to the genera Ctenodus, Ctenoptychius, Cladodus, 
 and Conchodus. 
 
 In the Carboniferous period the remains of Cestraphori are 
 comparatively very abundant, though confined generally to 
 
 "^^^ 
 
 Fig. 296. i. Fin-spine of Pleiiracanthus (one of the Rays); a. Gyracanthus; 3. 
 Cttnacanthus ; 4. Tooth of Petalodus; 5. Psammodtis; 6. Cttnoftyckius. All from the 
 
 Carboniferous Rocks. 
 
 particular localities. The spines of the Carboniferous strata 
 have been referred to many genera, of which the most import- 
 ant are Cteiiacanthus (fig. 296, 3), Gyracanthus (fig. 296, 2), Ho-
 
 ELASMOBRANCHII. 
 
 339 
 
 macanthus, Oracanthus, Onchus, Leptacanthus, and Edestes. The 
 fossil teeth of the Carboniferous Rocks have also been referred 
 to many genera, of which the more important are Cochliodus 
 (fig. 297), Psamtnodus, Orodus, Petalodus (fig. 296, 4), Ctenop- 
 tychius (fig. 296, 6), Cladodus, 
 Centrodits, Glossodus, and Petro- 
 dus. Two types may be distin- 
 guished in these teeth. In one 
 type, as in Cochliodus (fig. 297) 
 or Psammodus, the teeth have 
 the form of broad crushing 
 plates, adapted for the com- 
 minution of Molluscs or Crus- 
 taceans. In fact, in these forms 
 the teeth very closely resemble 
 those of the living Port Jackson 
 Shark (Cestracion}. In the other type, as in Cladodus, Orodtts, 
 and Glossodus, the teeth are of what is called the " Hybodont " 
 form, having a general conical shape, and consisting of a cen- 
 tral principal cone, flanked by smaller secondary cones. 
 
 In the Permian series the remains of Cestraphori are scanty, 
 but they are very numerous in all the great formations of the 
 Secondary period. The four most important Mesozoic genera 
 are Hybodus, Acrodus, Strophodus, and Ptychodus. The almost 
 exclusively Triassic genus Ceratodus has generally been referred 
 here also, but its true affinities are with the Dipnoi. 
 
 In the genus Hybodtis (fig. 298) the teeth are shark-like, but 
 are not so trenchant as they are in the true Sharks. They 
 
 Fig. 297. Dental plates of Cochliodus 
 ntortus. Mountain Limestone (Carbon- 
 
 Fig. 299. Fin-spine of Hybodus. Cretaceous 
 
 consist of a central " principal " cone, with smaller " second- 
 ary" cones on each side. The fin-spines (fig. 299) in this 
 genus are longitudinally grooved, and cairy a series of small 
 teeth on their hinder or concave margin. Species of Hybodus 
 abound in the Triassic and Jurassic formations, and occur, 
 though less abundantly, in the Cretaceous Rocks. 
 
 In the genus Acrodus (fig. 300) the teeth are more like those 
 of the Port Jackson Shark. The front teeth are pointed, and
 
 340 ORDERS OF FISHES. 
 
 resemble those of the Hybodonts,but the back teeth are adapted 
 for crushing shell-fish. Each of these crushing teeth has an elon- 
 gated form, with a rounded 
 surface, which is covered 
 with fine transverse striae 
 proceeding from a central 
 longitudinal line. From their 
 general form, colour, and 
 Fig. 300. Tooth of Acrodus nobiiis. Lias. striation, they are common- 
 ly called "fossil leeches" by 
 
 the quarrymen. As in the case ofHybodus, the species of Acrodus 
 are exclusively Mesozoic, ranging from the Trias to the Chalk. 
 The teeth of Strophodus are elongated, very similar to those 
 of Acrodus in their general form, but truncated at both ends, 
 and having their surface reticulated. Like the preceding, the 
 species of Strophodus range from the Trias to the Chalk. 
 
 In the genus Ptychodtts, lastly, the teeth are more or less 
 quadrate in form, and the summit of the crown of the tooth is 
 thrown into parallel transverse folds, ridges, or plications, 
 surrounded by a granulated area. All the species of this genus 
 are Cretaceous. 
 
 A few Tertiary forms of the Cestraphori have been described; 
 but the affinities of most of these are doubtful. At the present 
 day the family is represented by the single living species, the 
 Port Jackson Shark (Cestracion Philippi). 
 
 b. Selachii. This group comprises the Dog-fishes and Sharks, 
 characterised by the elongated, not rhomboidal, form of the 
 body, and by the lateral position of the gill-slits on the sides 
 of the neck. The teeth are sharp and conical, and are arranged 
 in several rows, of which the outermost alone is employed, the 
 inner ones serving to replace the former when worn out 
 
 This family attains its maximum at the present day, and its 
 earliest authentic representatives appear in the Jurassic period. 
 Some Palaeozoic fossils, however, have been, with more or less 
 probability, referred to Sharks, or placed in the neighbourhood 
 of the living Monk-fishes (Squatina). With the exception of 
 occasional vertebrae, all the known remains of Selachians con- 
 sist of teeth. 
 
 In the Jurassic series are found teeth of Notidanus and 
 Sphcnodus. In the Cretaceous Rocks are numerous teeth, 
 referred to the genera Corax, Galcoccrdo, Otodus, Larntia, 
 Oxyrhina, and Odontaspis, all of which continue to be repre- 
 sented in the Tertiary deposits. The teeth of Carcharodon 
 (fig. 303) also occur in the Cretaceous series, but the genus is 
 mainly Tertiary. The teeth of Carcharodon are triangular,
 
 ELASMOBRANCHII. 
 
 341 
 
 serrated on both sides, and sometimes of immense size (five or 
 six inches in length). In Otodus (fig. 302) the teeth are not 
 denticulated at their edges, and they have a secondary tooth 
 
 Fig. 301. Oxyrhinaxiphc 
 don. Miocene. 
 
 Fig 302. Otodus obliguus. 
 Eocene. 
 
 Fig. 303. Carcharodon pro- 
 ductus. Miocene. 
 
 at each side of the base. The teeth of Oxyrhina (fig. 301), 
 lastly, are large and compressed, differing from those of Otodus 
 chiefly in wanting the lateral projections at the base. Upon 
 the whole, the deposits which have yielded the greatest abund- 
 ance of the teeth of these extinct Sharks, are the Upper Green- 
 sand (Cretaceous) and the London Clay (Eocene Tertiary). 
 
 c. Batides. This group 
 includes the Rays and 
 Skates, and is distinguished 
 by the fact that the bran- 
 chial apertures are placed 
 on the under surface of 
 the body, forming two 
 rows of openings a little 
 behind the mouth. In 
 the typical members of 
 the group, the body is 
 flattened out so as to form 
 a kind of disc (fig. 304), 
 the greater part of which 
 is made up of the enor- 
 mously developed pectoral 
 fins. Upon the upper sur- 
 face of the disc are the 
 eyes and spiracles ; upon 
 the lower surface are the 
 nostrils, mouth, and bran- 
 chial apertures. The flat- 
 tened bodies of the Rays, however, must be carefully dis- 
 tinguished from those of the Flat-fishes (Pleuronectida). In 
 
 Fig. 304. Baides. Raia marginaia, one 
 of the Skates. Reduced one-sixth. (After 
 Gosse.)
 
 342 ORDERS OF FISHES. 
 
 the former, the flat surfaces of the body are truly the dorsal 
 and ventral surfaces. In the latter, as before remarked, the 
 body is flattened, not from above downwards, but from side 
 to side, and the head is so twisted that both eyes are brought 
 to one side of the body. 
 
 The tail in the Rays is long and slender, usually armed with 
 spines, and generally with two or three fins (the homologues 
 of the dorsal fins). The mouth is paved with flat teeth of a 
 more or less rhomboidal shape. The integument is often 
 furnished with placoid structures of a peculiar shape, consist- 
 ing of oval or rounded osseous discs, from the centre of each 
 of which springs a curved spine of dentine. The tail also is 
 sometimes armed with a doubly-serrated defensive spine. 
 
 The Rays are known in the fossil condition by their flat 
 crushing teeth mainly, but also by their fin-rays, bony discs, 
 and defensive spines. The earliest trace of the Rays is found 
 in the Carboniferous Rocks, where occurs the doubly-serrated 
 spine which is referred to the genus Platracanthus (fig. 296, i). 
 In this singular form, however, the spine seems to have been 
 inserted at the back of the head, instead of in the tail, as in the 
 living Sting-rays. In the Jurassic Rocks occur the remains of 
 Rays, which have been referred to the genera Squaloraia, 
 Spathobatis, Arthropterus, &c. In the Tertiary Rocks the re- 
 mains of Rays are tolerably 
 abundant, and consist almost 
 exclusively of the dental plates. 
 These consist (fig. 305) of gene- 
 rally flat plates, usually some- 
 what rhomboidal in shape, 
 often placed close together and 
 sometimes united laterally by 
 sutures, so as to " form a kind 
 of mosaic pavement on both 
 the upper and lower jaws " 
 (Owen). Most of the fossil forms belong to the genus Mylio- 
 batis, which comprises the living Eagle-rays. All the fossil 
 species of this family belong to the Tertiary period. 
 
 ORDER IV. DIPNOI ( = Protopteri, Owen). This order is 
 a very small one, and includes only the singular Mud-fishes 
 (Leptdosiren and Ceratodus) \ but it is nevertheless of great im- 
 portance as exhibiting a distinct transition between the Fishes 
 and the Amphibia. So many, in fact, and so striking, are the 
 points of resemblance between the two, that until recently the 
 Lepidosiren (fig. 306) was always made to constitute the lowest 
 class of the Amphibia. The highest authorities, however, now
 
 DIPNOI. 343 
 
 concur in placing it amongst the fishes, of which it constitutes 
 the highest order. The order Dipnoi is defined by the follow- 
 ing characters : The body is fish-like in shape. There is a skull 
 with distinct cranial bones and a lower jaw, but the notochord is 
 persistent, and there are no vertebral centra, nor an occipital con- 
 dyle. The exoskeleton consists of horny, overlapping scales, having 
 the " cycloid" character. The pectoral and ventral limbs are both 
 present, but have (in Lepidosiren) the form of awl-shaped, filiform, 
 many-jointed organs, of which the former only have a membranous 
 fringe infer iorly. The ventral limbs are attached close to the anus, 
 and the pectoral arch has a clavicle ; but the scapular arch is at- 
 tached to the occiput. The hinder extremity of the body is fringed 
 by a vertical median fin. The heart has two auricles and one ventri- 
 cle. The respiratory organs are twofold, consisting on the one hand 
 of free filamentous gills contained in a branchial chamber, which 
 opens externally by a single vertical gill-slit ; and on the other 
 hand of true lungs in the form of a double cellular air-bladder, 
 communicating with the oesophagus by means of an air-duct or 
 trachea. The branchicz are supported upon branchial arches, but 
 these are not connected with the hyoid bone ; and in some cases, at 
 any rate, rudimentary external branching exist as well. The 
 nasal sacs open posteriorly into the throat. 
 
 P 
 
 Fig. 306. Dipnoi. Lepidosiren annectens. 
 
 Until lately the only known members of the order Dipnoi 
 were the Lepidosiren paradoxa of South America and the Lepi- 
 dosiren (Protopterus] annectens of Africa. No fossil also could be 
 referred with any certainty to this order. Recently, however, 
 there has been discovered a most remarkable fish in the rivers 
 of Queensland (Australia), which is almost certainly referable to 
 this order, and which throws great light upon several fossil 
 forms. The organisation of this fish is so extraordinary, and 
 its affinities with some of the extinct Ganoids are so numerous 
 and important, that it will be well to quete at some length the 
 description of it given by Dr. Albert Giinther, one of the most 
 eminent of living ichthyologists. The fish in question has 
 been named the Ceratodus Fosteri, and it is known locally as 
 the " Barramunda." It is said to attain a length of about six
 
 344 ORDERS OF FISHES. 
 
 feet, but its average length is about three feet. The Barra- 
 munda " is eel-shaped, but considerably shorter and thicker 
 than a common eel, and covered with very large scales. The 
 head is flattened and broad, the eye lateral and rather small, 
 the mouth in front of the broad snout and moderately wide. 
 The gill openings are a rather narrow slit on each side of the 
 head. There are no external nostrils. The tail, which is of 
 about the same length as the body without the head, is com- 
 pressed, and tapers to a point, but it is surrounded by a very 
 broad fringe, supported by innumerable fine and long fin-rays. 
 There are two fore and two hind paddles', similar to each other 
 in shape and size, and very different from the fins of ordinary 
 fishes ; their central portion being covered with a scaly skin, 
 and the entire paddle surrounded by a rayed fringe. If we 
 were to cut off the hind part of the tail of a fish, the piece 
 would bear a strong resemblance to one of the paired paddles. 
 The vent is situated in the median line of the abdomen be- 
 tween the paddles. 
 
 " In order to obtain a view of the inside of the mouth, it is 
 necessary to slit it open, at least on one side. We then notice 
 that there are a pair of nasal openings within and on each side 
 of the cavity of the mouth. The palate is armed with a pair 
 of large, long, dental plates, with a flattish undulated and 
 punctated surface, and with five or six sharp prongs on the 
 outer side, entirely similar to the fossil teeth described under 
 the name of Ceratodus. Two similar dental plates of the lower 
 jaw correspond to the upper, their undulated surface fitting 
 exactly to that of the opposite teeth. Beside these molars, 
 the front part of the upper jaw (vomer) is armed with two 
 obliquely placed incisor-like dental lamellae, which have no 
 corresponding teeth in the lower jaw. As we know the kind 
 of food taken by the Barramunda, the use of these teeth is 
 apparent. The incisors will assist in taking up or even tear- 
 ing off leaves, which are then partially crushed between the 
 undulated surfaces of the molars. 
 
 " The skeleton consists of a cartilaginous basis, in the form 
 of a long tapering chord for the body and tail, and in that of a 
 capsule for the head. No segmentation into separate vertebras 
 is visible in any part of the notochord ; but it supports a con- 
 siderable number of apophyses, the abdominal of which bear 
 well-developed ribs, all being solid cartilaginous rods, with a 
 thin sheath of bone. In the same manner no part of the brain- 
 capsule is ossified, but it is nearly entirely enclosed in thin 
 bony lamellae. This is also the structure of the appendages of 
 the skull, as the mandible and the hyoid and scapulary arches.
 
 ELASMOBRANCHII. 345 
 
 From a study of the skull, it becomes apparent at once why 
 in fossil teeth of Ceratodus nothing or very little of the bone 
 attached to them has been preserved. These teeth rest on 
 cartilage as well as on bone, the latter being a very thin and 
 porous layer which could not be preserved, unless the pro- 
 gress of stratification had been going on with as little disturb- 
 ance as in the Solenhofen Schiefer ; but the matrix in which 
 fossil Ceratodont teeth are found shows that it was formed 
 under very different conditions, and it is certainly not of a 
 nature to permit the supposition that thin porous lamellae of 
 bone would have been preserved entire. 
 
 " The structure of the skeleton reminds us much of that of the 
 sturgeons, Chimsera, and especially of Lepidosiren ; and of all 
 the modifications by which it differs from these types, perhaps 
 none is of greater interest than that observed in the paddles. 
 The central part of the paddle, which we have found externally 
 to be covered with scales, is supported by a jointed axis of 
 cartilage extending from the root to the extremity of the pad- 
 dle ; each joint bears a pair of three- or two- or one-jointed 
 branches. This is the case in the hind as well as fore paddles, 
 and we are justified in supposing that those extinct Ganoids of 
 which impressions of paddles with scaly centres have been 
 preserved, were provided with a similar internal skeleton." 
 
 Upon the whole, Dr. Giinther concludes : i. That the Bar- 
 ramunda is not generically separable from the almost exclusively 
 Triassic genus Ceratodus, which was founded simply upon de- 
 tached teeth ; 2. That the Barramunda is very closely allied to 
 certain of the Crossopterygious Ganoids, such as the Dipterus 
 of the Old Red Sandstone, the chief difference being, that the 
 tail of the latter is heterocercal ; 3. That the order Dipnoi 
 should be considered merely as forming a sub-order of the 
 Ganoidei; 4. That the Ganoidei may be united with the Elas- 
 mobranchii into a single group, which may be termed Palceich- 
 thyes, and which is characterised by having a " heart with a 
 contractile bulbus arteriosus, intestine with a spiral valve, and 
 optic nerves non-decussating ; " 5. That the Ganoidei are the 
 Fresh-water Palceichthyes, and the Elasmobranchii are the 
 Marine Palczichthyes. 
 
 If the views of this high authority be ultimately adopted, it 
 will have to be admitted that the Dipnoi, /Instead of being un- 
 known in a fossil state, have enjoyed a- vast antiquity, dating 
 their existence from the Lower Old Red Sandstone.
 
 346 AMPHIBIA. 
 
 CHAPTER XXXI. 
 A M P H I B I A. 
 
 THE class Amphibia comprises the Frogs and Toads, the Sala- 
 mandroids, the C&cili<z, and the extinct Labyrinthodonts, and 
 may be briefly defined as follows : As is the case with the 
 Fishes, branchia, or filaments adapted for breathing air dissolved 
 in water, are always developed upon the visceral arches for a longer 
 or shorter time. On the other hand, the Amphibians differ from 
 the Fishes in the fact that true lungs are always present in the 
 adult; the limbs are never converted into fins ; and when median 
 fins are present, as is sometimes the case, these are never furnished 
 with fin-rays. The limbs, when present, exhibit in their skeleton 
 the same parts as do the limbs of the higher Vertebrates. The 
 skull always articulates with the vertebral column by means of two 
 occipital condyles. The heart consists of two auricles and a single 
 ventricle. The nasal sacs communicate posteriorly with the 
 pharynx; and the rectum, ureters, and ducts of the reproductive 
 organs open into a common chamber or " cloaca" 
 
 The great and distinguishing character of the Amphibia is 
 the fact that they undergo a metamorphosis after their exclusion 
 from the egg. They commence life as water-breathing larvae, 
 provided with gills or branchiae ; but in their adult state they 
 invariably possess lungs ; the branchiae in the higher forms dis- 
 appearing when the lungs are developed, but being in other 
 cases permanently retained throughout life. 
 
 In the earliest embryonic condition the branchiae are exter- 
 nal, placed on the side of the neck, and not situated in an 
 internal chamber as in Fishes. In some cases the external 
 branchiae only are present, and they are, in any case, the gills 
 which are retained in those forms in which the branchiae are 
 permanent (Perennibranchiata). In the tailed Amphibians 
 ( Urodela) and in the Frogs and Toads (Anoura) two sets of 
 gills are developed an external set, which is very soon lost, 
 and an internal set, which is retained for a longer or shorter 
 period. As maturity is approached, true lungs adapted for 
 breathing air are developed. The development, however, of 
 the lungs varies with the completeness with which aerial respi- 
 ration has to be accomplished ; being highest in those forms 
 which lose their gills when grown up (Caducibranchiata), and 
 lowest in those in which the branchiae are retained throughout 
 life (Perennibranchiata). 
 
 The class Amphibia is divided into the four orders of the
 
 URODELA. 347 
 
 Ophiomorpha, Urodela, Anoura,d.ndiLabyrinthodontia. The first 
 of these includes only the serpentiform animals known as 
 Ccealia, and not having any certain fossil representatives, may 
 be altogether passed over here. The order Urodela comprises 
 the so-called " tailed " Amphibians of the present day, such as 
 the Newts and Salamanders. The earliest traces of this order 
 in past time occur in the Tertiary deposits. The order Anoura 
 includes the so-called " tail-less" Amphibians, such as the Frogs 
 and Toads, and is likewise not known to have existed in periods 
 anterior to the Tertiary. Lastly, the order Labyrinthodontia 
 is entirely extinct, and is known to have existed only during 
 the Carboniferous, Permian, and Triassic periods. 
 
 ORDER I. URODELA (= Ichthyomorpha, Owen ; Saurobatra- 
 chia]. This order is commonly spoken of collectively as that 
 of the " Tailed " Amphibians, from the fact that the larval tail 
 is always retained in the adult. The Urodela are characterised 
 by having the skin naked, and almost invariably destitute of 
 any exoskeleton. The body is elongated posteriorly to form a 
 compressed or cylindrical tail, which is permanently retained 
 throughout life. The dorsal vertebrae are biconcave (amphi- 
 cczlous], or concave behind and convex in front (ppisthocalous), 
 and they have short ribs attached to the transverse processes. 
 The bones of the fore-arm (radius and ulna) on the one hand, 
 and those of the shank (tibia and fibula] on the other, are 
 not anchylosed to form single bones. 
 
 The best known of the existing Urodela are the Newts 
 (Triton], the Salamanders (Salamandra], the Mud-eels (Siren], 
 the Axolotl (Siredon], and the Giant-Salamanders (Menopomd). 
 Some of these are " perennibranchiate," retaining the bran- 
 chiae throughout life ; others lose the branchiae, becoming thus 
 " caducibranchiate," but retain the branchial apertures behind 
 the head ; others, lastly, lose both the branchiae and the bran- 
 chial apertures. Most of the Urodela have the four limbs 
 well developed, but some possess only the anterior limbs. 
 
 The geological history of the Urodela is short and of little 
 importance. No trace of the order has hitherto been discovered 
 in any deposits older than the Tertiary. The only exception 
 to this statement is constituted by the fossil described from the 
 Lower Permian Rocks by Geinitz under the name of Palceo- 
 siren, and regarded by him as being m^st nearly allied to the 
 Siren lacertina. It is probable, however, that Palczosiren is 
 really referable to the Labyrinthodontia. In strata of Tertiary 
 age have been discovered the remains of Newts and Sala- 
 manders. The most remarkable fossil referable to this order 
 is the Andrias Scheuchzeri (fig. 307) of the Miocene beds of
 
 AMPHIBIA. 
 
 ffiifflifiiiiifi'ifif >^^ 
 
 " :'*'' " i_J^iii*!^r^fcBS^tei !l '' h ' ''Ik 1 ' ^"^ 
 
 Fig. 307. Andrias Scheuchzeri. Miocene Tertiary.
 
 ANOURA. 
 
 349 
 
 Oeningen. This singular fossil was described by its original 
 discoverer as human, under the name of Homo diluvii testis ; 
 but it is really the skeleton of a Salamandroid of large size. 
 It is very closely allied to the Giant Salamander (Menopoma, 
 or Sieboldia, maxima] of Java. 
 
 ORDER II. ANOURA (= Batrachia, Huxley; Tlieriomorpha, 
 Owen ; Chelonobatrachia, &c.) This order includes the Frogs 
 and Toads, and is perhaps best designated by the name of 
 Anoura, or "Tail-less" Amphibians. The name Batrachia, 
 employed by Huxley, is inexpedient, partly because it is used 
 by Owen to designate the entire class Amphibia, and partly 
 because, in common language, it is usual to understand by a 
 "Batrachian" any of the higher Amphibians; such, for instance, 
 as a Labyrinthodont. 
 
 The Anoura, or Tail-less Amphibians, are characterised by 
 the following points : The adult is destitute of both gills and 
 tail, both of which structures exist in the larva, whilst the two 
 pairs of limbs are always present. The skin is soft, and there 
 are rarely any traces of an exoskeleton. The dorsal vertebras 
 are "proccelous " or concave in front, and are furnished with 
 
 Fig. 308. Skeleton of the common Frog (Rana tempomria). d Dorsal vertebrae, 
 with long transverse process.-s. 
 
 long transverse processes, which take the place of ribs, which 
 are only present in a rudimentary form. The radius and ulna 
 in the fore-limb, and the tibia and fibula in the hind-limb, are
 
 350 AMPHIBIA. 
 
 anchylosed to form single bones (fig. 308). The mouth is 
 sometimes edentulous, but the upper jaw has usually small 
 teeth, and the lower jaw sometimes. The hind-limbs usually 
 have the digits webbed for swimming, and are generally much 
 larger and longer than the fore-limbs. 
 
 The geological history of the Anoura, as in the case of the 
 Urodeta, is of small importance. The two chief groups of the 
 living Anoura namely, the Frogs and the Toads are both 
 represented in past time ; but they do not appear to have come 
 into existence till after the commencement of the Tertiary 
 period. Most of the fossil forms have been detected in de- 
 posits of Miocene age. 
 
 ORDER IV. LABYRINTHODONTIA. The members of this, 
 the last order of the Amphibia, are entirely extinct. They 
 were Batrachians, probably most nearly allied to the Urodela, 
 but all of large size, and some of gigantic dimensions, the skull 
 of one species (Labyrinthodon Jcegeri} being upwards of three 
 feet in length and two feet in breadth. The Labyrinthodonts 
 were first known to science simply by their footprints, which 
 were found in certain sandstones of the age of the Trias. 
 These footprints consisted of a series of alternate pairs of 
 hand-shaped impressions, the hinder print of each pair being 
 much larger than the one in front (fig. 309). So like were 
 these impressions to the shape of the human hand that the 
 unknown animal which produced them was at once christened 
 Cheirotherium, or " Hand-beast." Further discoveries, how- 
 ever, soon showed that the footprints of Cheirotherium had 
 been produced by different species of Batrachians, to which the 
 name of Labyrinthodonts was applied in consequence of the 
 complex microscopic structure of the teeth. 
 
 The order Labyrinthodontia is thus defined by Professor 
 Huxley : " The body is salamandriform, with relatively weak 
 limbs and a long tail. The dorsal vertebrae, when completely 
 ossified, are biconcave, with double transverse processes. The 
 ribs have distinct capitula and tubercula. 
 
 " In the thoracic region, three superficially sculptured exo- 
 skeletal plates, one median and two lateral, occupy the place 
 of the interclavicle and clavicles. Between these and the pelvis 
 is a peculiar armour, formed of rows of oval dermal plates, 
 which lie on each side of the middle line of the abdomen, and 
 are directed obliquely forwards and inwards, to meet in that line. 
 
 " The skull has distinctly ossified epiotic bones, in the same 
 position and of the same form as those of fishes. The cranial 
 bones are sculptured, and many exhibit peculiar smooth sym- 
 metrical grooves the so-called ' mucous canals.'
 
 LABYRINTIIODONTIA. 
 
 351 
 
 " The parietes of the teeth are deeply plaited and folded, so 
 as to give rise to a complicated 
 ' labyrinthine ' pattern in the 
 transverse section of the tooth." 
 
 The points in which the Laby- 
 rinthodonts differ from the mo- 
 dern Urodela are chiefly to be 
 found in the fact that the head 
 is defended by an external cov- 
 ering or helmet of hard and 
 polished osseous plates, in the 
 possession of ventral integument- 
 ary scutes, in the existence of 
 exoskeletal plates occupying the 
 place of the interclavicle and cla- 
 vicles, in the amphiccelous form 
 
 Fig. 309. Foot-prints of a Labyrinthodont (Cfairotfieriutit), from the Trias. The 
 upper figure shows a single foot-print enlarged ; the lower figure shows a slab, with 
 several prints, and traversed by reticulated desiccation-cracks.
 
 352 
 
 AMPHIBIA. 
 
 of the dorsal vertebrae, and in the complicated structure of the 
 teeth. These last-mentioned organs are not only often very 
 numerous, but are of large size. The subjoined illustration 
 (fig. 310) shows the beautiful and complex structure of the 
 teeth, from which the name of the order is derived. 
 
 
 Fig. 310. Section of the tooth of Labyrinthodon (Mastodonsaunts) Jtrgeri. 
 
 The Labyrinthodonts range from the Carboniferous Rocks 
 to the Trias ; but some of the forms commonly included in 
 this order may perhaps belong elsewhere. One type of the 
 Labyrinthodonts is constituted by the singular genus Archcgo- 
 saurus, and the less known Apateon both from the Carboni- 
 ferous Rocks. Archegosaurus is remarkable in having the 
 notochord persistent, and in the possession of permanent bran- 
 chial arches. It has been made by Professor Owen the type 
 of a separate group, the Ganocephala ; but it is probably an 
 immature and larval form. The occipital condyles, also, do 
 not seem to have been ossified in the Archegosauria. 
 
 Of the Carboniferous Labyrinthodonts the most important 
 genera are Anthracosaurus, Pholidogaster, Ophidcrpeton, Ich- 
 thyerpeton, Urocondylus, Lepterpeton, Baphctcs, Raniceps, Den- 
 drcrpeton, Hylcrpeton, and Hylonomns ; though the affinities of 
 some of these are more or less doubtful. Most of the Car- 
 boniferous Labyrinthodonts were of comparatively small size ; 
 but some, such as Baphetcs (fig. 311) and Anthracosaurus ', must 
 have attained gigantic dimensions. All the above-mentioned 
 genera seem to have possessed well-ossified vertebras, with well- 
 developed limbs, the form of the body being mostly salaman- 
 driform, but sometimes fish-like, or serpentiform.
 
 LABYRINTHODONTIA. 
 
 353 
 
 In the Permian Rocks, a few remains of Labyrinthodonts 
 have been discovered, the genus Zygosaurus being peculiar to 
 this period. 
 
 Fig. 311. Baphetes planiceps, from the Carboniferous Rocks of Nova Scotia. (After 
 Dawson.) a Anterior part of the skull, viewed from beneath, and much reduced ; b One 
 of the largest teeth, natural size. 
 
 In the Triassic Rocks the remains of Labyrinthodonts 
 are abundant, the most important genus being Labyrinthodon 
 or Mastodonsaurus. This genus is known mainly by foot- 
 prints and by crania ; and the size attained by some species 
 must have been colossal. No remains of this order have 
 hitherto been discovered in rocks younger than the Trias. 
 
 CHAPTER XXXII. 
 REPTILIA. 
 
 THE true Reptiles and the Birds, unlike as they are in external 
 appearance, are nevertheless related to one another by various 
 points of affinity ; so that they may well be included in a 
 single division, which has been termed Sauropsida by Huxley. 
 The Sauropsida are denned by the possession of the following 
 characters : At no period of existence are branchice, or water- 
 breathing respiratory organs, developed upon the visceral arches ; 
 the red corpuscles of the blood are nucleated : the skull articulates 
 with the vertebral column by means of a single articulating surface 
 or condyle ; and each half or " ramus " of the lower jaw is com- 
 posed of several pieces, and articulates with the skull, not directly, 
 but by the intervention of a peculiar bone, called the " quadrate 
 bone" or " os quadratum " (fig. 312).
 
 354 REPTILIA. 
 
 These being the common characters of Reptiles and Birds, 
 by which they are collectively distinguished from other Verte- 
 brates, it remains to inquire what are the characters by which 
 they are distinguished from one another. The following, then, 
 are the characters which separate the Reptiles from the Birds : 
 The blood in Reptiles is cold that is to say, slightly warmer 
 than the external medium owing mainly to the fact that the 
 pulmonary and systemic circulations are always directly con- 
 nected together, either within the heart or in its immediate neigJi- 
 bourhood, so that the body is supplied with a mixture of -venous 
 and arterial blood, in place of pure arterial blood alone. The 
 terminations of the bronchi at the surface of the lung are closed, 
 and do not communicate with air-sacs, placed in different parts of 
 the body. When the epidermis develops horny structures, these 
 are in the form of horny plates or scales, and never in the form of 
 feathers. The fore-limbs are formed for -various purposes, includ- 
 ing in some cases even flight, but they are never constructed upon 
 the type of the " wings " of Birds. Lastly, with one or two doubt- 
 ful exceptions, whilst the ankle-joint is placed betiveen the distal 
 and proximal portions of the tarsus, the tarsal and metatarsal 
 bones of the hind-limb are never anchylosed into a single bone. 
 
 These are the leading characters by which Reptiles are dis- 
 tinguished from Birds ; but we must not forget the other dis- 
 tinctive peculiarities in which Reptiles agree with Birds, and 
 differ from other Vertebrates namely, the absence of branchiae 
 at all times of life, the possession of only one occipital con- 
 dyle, and the articulation of the complex lower jaw with the 
 skull by means of a quadrate bone. 
 
 It is now necessary to consider these characteristics of the 
 Reptilia a little more minutely. The class includes the Tor- 
 toises and Turtles, the Snakes, the Lizards, the Crocodiles, and 
 a number of extinct forms ; and with the exception of the Tor- 
 toises and Turtles they are mostly of an elongated cylindrical 
 shape, provided posteriorly with a long tail. The limbs may 
 be altogether absent, as in the Snakes, or quite rudimentary, 
 as in some of the Lizards, but as a general rule both pairs of 
 limbs are present, sometimes in the form of ambulatory legs, 
 sometimes as swimming-paddles, and in some extinct forms 
 modified to subserve an aerial life. The endoskeleton is 
 always well ossified, and is never cartilaginous or semi-cartil- 
 aginous, as in many Fishes and some Amphibians. The skull 
 articulates with the atlas by a single condyle. The lower jaw 
 is complex, each half or ramus being composed of from four to 
 six pieces, united to one another by sutures (fig. 312). In the 
 Tortoises, however, these are anchylosed into a single piece,
 
 GENERAL CHARACTERS OF REPTILES. 355 
 
 and the two rami are also anchylosed. In most Reptiles, how- 
 ever, the two rami of the lower jaw are only loosely united 
 in the Snakes by ligaments and muscles only, in the Lizards 
 by fibre-cartilage, and in the Crocodilia by a regular suture. 
 In all, the lower jaw articulates with the skull by a quadrate 
 bone (fig. 312, a); and as this often projects backwards, the 
 
 6 
 
 Fig. 312. Skull of a Serpent (Python), b Articular portion of the lower jaw ; 
 a Quadrate bone ; c Squamosal portion of the temporal bone. 
 
 opening of the mouth is often very extensive, and may even 
 extend beyond the base of the skull. Teeth are usually pre- 
 sent, but are not sunk in separate sockets or alveoli, except in 
 the Crocodiles and in some extinct forms. In the Tortoises 
 and Turtles alone of living types there are no teeth, and the 
 jaws are simply sheathed in horn, constituting a kind of beak 
 like that of a bird. 
 
 Ribs are always present and always well developed, but they 
 differ much in form. It is not correct, however, to regard the 
 presence of ribs as separating the true Reptiles from the Am- 
 phibia, as is sometimes stated. Some of the most Lizard-like 
 of the Amphibians, such as the Siren, possess short but well- 
 developed ribs, and rudiments of ribs are traceable in other 
 orders; whilst in the Cacilitz they are large and well developed. 
 
 As regards the exoskeleton, all Reptiles have horny epider- 
 mic scales, and they are divided into two great sections called 
 respectively Squamata and Loricata according as the integu- 
 mentary skeleton consists simply of these scales, or there are 
 osseous plates developed in the derma as well. In the Tor- 
 toises, the epidermic plates unite with 1/ie bony exoskeleton 
 and with the true endoskeleton to forfn the case or box in 
 which the body of these animals is enclosed. 
 
 The class Reptilia is divided into the following nine orders, 
 of which the first four are represented by living forms, whilst 
 the remaining five are extinct :
 
 356 REPTILIA. 
 
 1. Chelonia (Tortoises and Turtles). ] 
 
 2. Ophidia (Snakes). I R 
 
 3. Lacertilia (Lizards). 
 
 4. Crocodilia (Crocodiles and Alligators). 
 
 5. Ichthyopterygia. 
 
 6. Sauropterygia. 
 
 7. Anomodontia. 
 
 Extinct. 
 
 Pterosauria. 
 9. Deinosauria. 
 
 As regards their general distribution in time, the Reptilia 
 attained their maximum of development in the Mesozoic 
 period, which has hence often been called the "Age of Reptiles." 
 If the Elgin Sandstones, containing the remains of Telerpeton 
 and Stagonolepis, be of Triassic age as seems almost certain 
 then no Reptile has as yet been discovered in the Devonian 
 Rocks. In the Carboniferous Rocks, the place of the true 
 Reptiles seems to have been taken by the Amphibian group of 
 the Labyrinthodonts. It is possible, however, that the little 
 Hylonomus, of which three species were discovered in the Coal- 
 strata of Nova Scotia by Dr Dawson, may be Lacertian in its 
 affinities. It is also possible that the vertebras from strata of 
 the same age described by Professor Marsh under the name of 
 Eosaurus Acadiensis, may belong to a marine reptile allied to 
 Ichthyosaurus. In the Permian Rocks the first undoubted 
 Reptilian remains occur, the Protorosaurus of this period being 
 probably a Lacertilian. 
 
 Throughout the whole Mesozoic series, Reptilian remains 
 are abundant and belong to numerous and strange types. 
 Chelonians and true Crocodiles, with Lizards allied to existing 
 forms, make their first appearance in deposits belonging to this 
 period. The extinct orders of the Ichthyopterygia, Saurop- 
 terygia, Anomodontia, Pterosauria, and Deinosauria, not only 
 first appear in Mesozoic deposits, but are exclusively confined 
 to rocks of this age. In the Tertiary period, lastly, the 
 remains of Reptiles are comparatively rare, and the number 
 of types is much reduced. The living order of the Ophidia, 
 however, makes its first appearance in the Tertiary deposits. 
 In the following view of the characters and distribution in time 
 of the orders of the Reptiles, it will be advisable to consider 
 the recent orders first, though this is not in accordance with 
 their natural arrangement 
 
 ORDER I. CHELONIA. The first order of living Reptiles is 
 that of the Chelonia, comprising the Tortoises and Turtles, and 
 distinguished by the following characters: There is an osseous 
 exoskeleton which is combined with the endoskeleton to form
 
 CHELONIA. 357 
 
 a kind of bony case or box in which the body of the animal is 
 enclosed, and which is covered by a leathery skin, or, more 
 usually, by horny epidermic plates. The dorsal vertebrae are 
 immovably connected together, and are devoid of transverse 
 processes. The ribs are greatly expanded (fig. 313, r), and 
 
 Fig. 313. Skeleton of Tortoise (Emys Eiiropoea,} the plastron being removed, ca 
 Carapace ; r Ribs, greatly expanded, and united by their edges ; J Scapular arch, placed 
 within the carapace, and carrying the fore-limbs; / Pelvic arch, also placed within the 
 carapace, and carrying the hind-limbs. 
 
 are united to one another by sutures, so that the walls of the 
 thoracic cavity are immovable. All the bones of the skull 
 except the lower jaw and the hyoid bone are immovably united 
 together. There are no teeth, and the jaws are encased in 
 horn so as to form a kind of beak. The heart is three- 
 chambered, the ventricular septum being imperfect. 
 
 Of these characters of the Chelonia, the most important and 
 distinctive are the nature of the jaws, ard the structure of the 
 exoskeleton and skeleton. As regards the first of these points, 
 the lower jaw in the adult appears to consist of a single piece, 
 its complex character being masked by anchylosis. The sepa- 
 rate pieces which really compose each ramus of the jaw are
 
 358 REPTILIA. 
 
 immovably anchylosed together, and the two rami are also 
 united in front by a true bony union. There are also no 
 teeth, and the edges of the jaws are simply sheathed in horn, 
 constituting a sharp beak. As regards the second of these 
 points, the bony case in which the body of a Chelonian is 
 enclosed consists essentially of two pieces, a superior or dorsal 
 piece, generally convex, called the " carapace," and an inferior 
 or ventral piece, generally flat or concave, called the "plastron." 
 The carapace and plastron are firmly united along their edges, 
 but are so excavated in front and behind as to leave apertures 
 for the head, tail, and fore and hind limbs. The limbs and 
 tail can almost always be withdrawn at will under the shelter 
 of the thoracico-abdominal case formed in this way by the 
 carapace and plastron, and the head is also generally re- 
 tractile. 
 
 The carapace or dorsal shield is composed of the flattened 
 spinous processes of the dorsal vertebrae, the expanded ribs, 
 and usually a series of marginal bones the whole covered by 
 horny epidermic plates or by a leathery skin. The plastron 
 or ventral shield is composed of nine bony pieces, which are 
 probably integumentary ossifications, but which are sometimes 
 regarded as composing a modified and greatly - expanded 
 breast-bone. The scapular and pelvic arches, supporting re- 
 spectively the fore and hind limbs, are placed within the cara- 
 pace. As in the Crocodilia, clavicles are wanting. 
 
 From the aquatic habits of many of the members of this order 
 they are by no means uncommon in the fossil condition. The 
 Turtles frequent the sea, and thus come naturally to be fossils 
 in marine deposits ; and the preservation of all the Chelonians 
 alike is rendered easy by the indestructible nature of the case 
 in which their bodies are enclosed. 
 
 The Chelonians may be divided into sections according as 
 the limbs are natatory, are adapted for an amphibious life, or 
 are fitted for terrestrial progression. In the first of these sec- 
 tions are the true Turtles (Chdoniidce), which frequent the 
 sea, and are distinguished by their depressed and flattened 
 carapace, and by their oar-like limbs. In the second section 
 are the River and Marsh Tortoises, comprising the Soft Tor- 
 toises (Trionyddce) and the Terrapins (Emydidee). In the 
 third section are the true Land-tortoises (Testudintdce), distin- 
 guished by their strongly convex carapace, and limbs adapted 
 for walking upon the land. All these three sections are repre- 
 sented in past time, the Turtles, Trionycidce^ and Emydida 
 appearing for the first time, so far as is certainly known, in the 
 Jurassic series, whilst the Testudinida do not appear till the
 
 CHELONIA. 
 
 359 
 
 commencement of the Tertiary epoch. The earliest known 
 traces of Chelonians occur in the Permian Rocks, in the lower 
 portion, that is, of the New Red Sandstone of older geologists. 
 These traces, however, are not wholly satisfactory, since they 
 consist solely of the footprints of the animal upon the ripple- 
 marked surfaces of the sandstone. Of this nature is the 
 Chclichnus Dnncani, described by Sir William Jardine in his 
 classical work on the 
 ' Ichnology ' of Annan- 
 dale in Dumfriesshire. 
 With doubtful excep- 
 tions, the first unequi- 
 vocal remains of Che- 
 lonians appear in the 
 Jurassic series. The 
 Chcloniida make their 
 first undoubted ap- 
 pearance with the Che- 
 lone planiceps of the 
 Portland stone (Upper 
 Oolite). In the Cre- 
 taceous series are seve- 
 ral turtles, one of which 
 is figured below (fig. 
 314). In the Tertiary 
 Rocks the remains of 
 Turtles are abundant, 
 and especially so in the 
 London Clay (Eocene). 
 Species of Emydida 
 
 have been Cited from F 'S- y-^Cltelone Benstedi. Lower Chalk. 
 
 the Jurassic series, 
 
 some of which appear to be free from doubt. A species of 
 Emys occurs in the Wealden, and numerous forms of this 
 family have been detected in formations of Tertiary age, es- 
 pecially in the Eocene and Miocene. The Trionycida, except 
 for a femur described by Owen from the Lias, are not known 
 to have existed prior to the commencement of the Tertiary 
 period. Numerous species of Trionyx, however, occur in the 
 Eocene, and others have been described from the Miocene 
 and Pliocene. The Testudinida or Lar/d-tortoises appear to 
 have commenced their existence in me Miocene Tertiary. 
 The most remarkable form of this group is the great Colosso- 
 chelys Atlas of the Tertiary deposits of the Sivalik Hills, which 
 is believed to have reached the gigantic length of twenty feet.
 
 360 REPTILIA. 
 
 ORDER II. OPHIDIA. The second order of Reptiles is 
 that of the Ophidia, comprising the Snakes and Serpents, and 
 distinguished by the following characters : 
 
 The body is always more or less elongated, cylindrical, and 
 worm-like, and whilst possessing a covering of horny scales, is 
 always unprovided with a bony exoskeleton. The dorsal ver- 
 tebrae are concave in front (proccelous), with rudimentary trans- 
 verse processes. There is never any sternum, nor pectoral 
 arch, nor fore-limbs, nor sacrum, and as a rule there are no 
 traces of hind-limbs. Rudimentary hind-limbs, however, are 
 occasionally present (e. g., in Python and Tortrix). There are 
 always numerous ribs. The two halves or rami of the lower 
 jaw are composed of several pieces, and the rami are united 
 anteriorly by ligaments and muscles only, and not by cartilage 
 or suture. The lower jaw, further, articulates with the skull by 
 means of a quadrate bone (fig. 312, a), which is always more 
 or less movable, and is in turn united with the squamous por- 
 tion of the temporal bone ("mastoid bone"), which is also 
 movable, and is not firmly united with the skull. The superior 
 maxillae are united with the praemaxillae by ligaments and mus- 
 cles only, and the palatine arches are movable and armed with 
 pointed recurved teeth. Hooked conical teeth are always pre- 
 sent, but they are never lodged in distinct sockets or alveoli. 
 Functionally, they are capable of performing nothing more 
 than merely holding the prey fast, and the Snakes are provided 
 with no genuine masticatory apparatus. The heart has three 
 chambers, two auricles and a ventricle, the latter imperfectly 
 divided into two cavities by an incomplete septum. The lungs 
 and other paired organs are mostly not bilaterally symmetrical, 
 one of each pair being either rudimentary or absent. 
 
 The three most important groups of the existing Ophidians 
 are the Colubrine Snakes, the Constricting Snakes, and the 
 Viperine Snakes. In the first of these the upper jaws carry 
 solid teeth, with or without canaliculated fangs as well. In 
 the second group are the Boas and Pythons, distinguished by 
 their great size, enormous muscular power, and numerous 
 strong recurved teeth. In the third group are Snakes, in which 
 the upper jaws carry only a pair of perforated poison-fangs. 
 
 Most of the existing Snakes are terrestrial in their habits, 
 and are therefore not likely to be preserved in stratified de- 
 posits. Many of these, however, take to the water occasionally, 
 and some habitually frequent rivers or the sea itself. All the 
 above-mentioned groups of Ophidians are represented in past 
 time, but they are neither abundant nor of importance as fossils. 
 No remains of Ophidians are known to occur in any Palaeozoic
 
 LACERTILIA. 361 
 
 or Mesozoic deposit. The earliest known traces of any ser- 
 pent are in the Lower Kainozoic Rocks, the oldest being the 
 Palaophis toliapicus of the London Clay of Sheppey. The 
 nearly-allied Palaophis typfuzus of the Eocene beds of Brackle- 
 sham appears to have been a Boa-constrictor-like snake of 
 about twenty feet in length. Other species of Palceophis have 
 been described from the Tertiary Rocks of the United States, 
 and the genus Dinophis has been formed for the reception of 
 another gigantic constricting Serpent from the same formation. 
 In some of the later deposits have been found the poison- 
 fangs of a venomous snake. Upon the whole, however, the 
 Snakes must be looked upon as a comparatively modern group, 
 and not as one of any great geological antiquity. 
 
 ORDER III. LACERTILIA. The third order of Reptiles is 
 that of the Lacerfilia, comprising all those animals which are 
 commonly known as Lizards, together with some serpentiform 
 animals such as the Blind-worms. The Lacertilia are dis- 
 tinguished by the following characters : 
 
 As a general rule, there are two pairs of well-developed 
 limbs, but there may be only one pair, or all the limbs may be 
 absent. A scapular arch is always present, whatever the con- 
 dition of the limbs may be. An exoskeleton, in the form of 
 horny scales like those of the Snakes, is almost always present. 
 The vertebrae of the dorsal region are procoelous or concave in 
 front, rarely amphiccelous or concave at both ends. There is 
 a single transverse process at each side, and the heads of the 
 ribs are simple and undivided. There is either no sacrum, or 
 the sacral vertebrae do not exceed two in number. The teeth 
 are not lodged in distinct sockets. The eyes are generally 
 furnished with movable eyelids, and are always so in the com- 
 pletely snake-like forms. The heart consists of two auricles 
 and a ventricle, the latter partially divided by an incomplete 
 partition. There is a urinary bladder, and the aperture of the 
 cloaca is transverse. 
 
 As a general rule, the animals included under this order 
 have four well-developed legs, and would therefore be popu- 
 larly called " Lizards." In some (Chirotes) there are no hind- 
 feet ; in some (Bipes] the fore-limbs are wanting ; and others 
 (Angitis, Pseudopus, and Amphisbcena] are entirely destitute 
 of limbs, thus coming closely to resemble the true Snakes 
 or Ophidians in external appearance. .' These serpentiform 
 Lizards, however, can be distinguished 'irom the true Snakes, 
 amongst other characters, by the structure of the jaws. In 
 the Snakes, as before said, the two rami of the lower jaw are 
 loosely united in front by ligaments and muscles, and are
 
 362 REPTILIA. 
 
 attached behind to a movable quadrate bone, which is in turn 
 connected with a movable squamosal, this giving an enormous 
 width of gape to these animals. In the Lizards, however, even 
 in those most like the Snakes, the halves of the lower jaw are 
 firmly united to one another in front, and though the quadrate 
 bone is usually more or less movable, the jaws can in no case 
 be separated to anything like the extent that characterises the 
 Ophidia. 
 
 The Lizards are distinguished from the Crocodiles, amongst 
 other characters, by the fact that the integumentary covering is 
 in the form of horny scales, never with bony " scutes," whilst 
 the teeth are rarely or never sunk into distinct sockets. In many 
 cases the teeth are anchylosed to the summit of the margin of 
 the jaw ("acrodont" dentition); in other cases they are at- 
 tached by their sides to the inner surface of the jaw (" pleuro- 
 dont" dentition). 
 
 The whole order of the Lacertilia is very often united with 
 the next group of the Crocodilia, under the name of Sauria. 
 The term " Saurian," however, is an exceedingly convenient 
 one to designate all the reptiles which approach the typical 
 Lizards in external configuration, whatever their exact nature 
 may be ; and from this point of view it is often very useful as 
 applied to many fossil forms, the structure of which is only im- 
 perfectly known. It is therefore perhaps best to employ this 
 term merely in a loose general sense. 
 
 It is hardly possible, with our present knowledge, to speak 
 very positively as to the exact range of the Lacertilia in time. 
 This uncertainty arises from two causes firstly, that there is 
 some doubt as to the exact age of some deposits which have 
 yielded Lacertilian remains ; and secondly, that the affinities of 
 some extinct Reptiles are a matter of considerable question. 
 Upon the whole, the oldest known Lacertilian would appear to 
 be the Protorosaurus of the Middle Permian Rocks ; though 
 good authorities have placed this form in the Crocodilian group 
 of the Thecodontia. Protorosaurus attained a length of between 
 three and four feet, and differs from all existing Lizards in 
 having its teeth implanted in distinct sockets this being a 
 Crocodilian character. In other respects, the Permian reptile 
 approximates closely to the living Monitors ( Vdranidie), and its 
 slightly-cupped vertebrae would lead to the belief that it was 
 aquatic in its habits. 
 
 In rocks known, or supposed, to be of Triassic age, nume- 
 rous Lacertilian reptiles have been discovered, of which the 
 most important are Telerpeton, Hyperodapedon, and Rhyneho- 
 saurus. Telerpeton occurs in strata near Elgin, in Scotland,
 
 LACERTILIA. 363 
 
 which have been variously referred to the Upper Devonian 
 and to the Trias, but which almost certainly belong to the latter. 
 Professor Huxley concludes that Tderpeton " presents not a 
 single character approximating it towards the type of the Per- 
 mian Protosauria, nor to the Triassic Rhynchosaurus, and other 
 (probably Triassic) African and Asiatic allies of that genus, 
 nor to the Mesozoic Dinosauria; still less can it be considered 
 a ' generalised ' form, or as, in any sense, a less perfectly organ- 
 ised creature than the Gecko, whose swift and noiseless run 
 over walls and ceilings, surprises the traveller in warmer cli- 
 mates than our own." In its dentition, Telerpeton seems to 
 have been " acrodont," and it differs from most existing Lizards 
 merely in having amphiccelous, and not proccelous, vertebrae. 
 
 Hyperodapedon was originally discovered in the " Elgin Sand- 
 stones " along with Telerpeton, and it has since been found in 
 strata of Triassic age in India. It was described by Professor 
 Huxley as " a Saurian reptile about six feet long, remarkable 
 for the flattened or slightly concave articular surfaces of the 
 centra of its vertebrae, and for its well-developed costal system 
 and fore and hind limbs ; but more particularly characterised 
 by its numerous series of sub-cylindrical palatal teeth." Upon 
 the whole, Huxley concludes that Hyperodapedon is most 
 nearly allied to the living Sphenodon (Hatterid) of New Zealand, 
 upon the grounds that both " have amphicoelous vertebras 
 (those of the ancient reptile being far less fish-like than those 
 of the modern one, be it noted) ; both have beak-like prasmax- 
 illae, not anchylosed together ; both have the inferior zygoma 
 complete ; both have similarly-formed lower jaws ; in each a 
 single row of teeth in the mandible bites between two rows of 
 teeth fixed to a plate, which is formed by a union of the maxil- 
 la with the palatine bone a structure which is quite anom- 
 alous amongst Lacertilians j and, finally, in both, these teeth 
 wear down to the bone of the jaw by masticatory attrition." 
 
 The genus Rhynchosanrus is in a doubtful position, but 
 may conveniently be considered 
 here. By Huxley its affinities 
 are regarded as being Lacertili- 
 an, but by Owen it is looked 
 upon as belonging to the Ano- 
 modontia, and as being most 
 nearly allied to Oudenodon. In 
 many points Rhynchosaurus ap- Fig. 3 t 5 . sk\i\\o(Rhynchosaurusarti- 
 proaches the existing Lizards, ^ < AfterOwen -> Tnas ' 
 
 but its vertebrae are amphicoelous, and the structure of the 
 mouth is quite unlike that of any living Lacertilian. The skull
 
 364 REPTILIA. 
 
 (fig. 315) is pyramidal, and the jaws do not exhibit any traces 
 of teeth. If the mouth be really edentulous, then Rhynchosau- 
 rus should probably be removed from the Lcuertilia; but this 
 point cannot in the meanwhile be definitely decided in the 
 affirmative. 
 
 Amongst other Triassic, or supposed Triassic, Lacertilians, 
 may be mentioned Saurosternon and Pristerodon, from strata 
 believed to be of Triassic age in Africa, and Clcpsysaurus and 
 Centemodon from deposits of the same age in North America. 
 
 In the Jurassic period, the remains of Lacertilians are not 
 unknown, but call for little special notice. Several forms of 
 little importance have been described from the Middle Oolites. 
 In the fresh-water strata of the Pnrbeck series (Upper Oolites), 
 occur the remains which have been referred to the genera 
 Nuthetes, Macellodon, Saurillus, and Echinodon. These are, 
 perhaps, the first traces in the stratified series of remains, the 
 affinities of which to the typical Lacertidce cannot be disputed. 
 
 In the Cretaceous series occur the small Lizards which con- 
 stitute the genera Raphiosaurus, Coniosanrns, and Dolichosau- 
 rus. Here also, and almost exclusively confined to strata of 
 this age, occur the singular Lacertilians which form the group 
 of the " Mosasauroids." These remarkable Reptiles were of 
 gigantic size, Mosasaurus princeps being believed to have at- 
 tained the enormous length of not less than seventy-five feet. 
 The teeth in these reptiles (fig. 316) are long, pyramidal, and 
 
 Fig. 316. Skull of Mosasaurus Camftrt, much reduced. Maestricht Chalk. 
 
 slightly curved ; but they are anchylosed to the jaw, and are 
 not sunk into distinct sockets, as in the living Crocodiles.
 
 CROCODILIA. 365 
 
 From the shortness of the humerus, and the indications that 
 the vertebral column was unusually flexible, and that the tail 
 was laterally compressed, it was early conjectured that the 
 Mosasauroids were marine and aquatic in their habits. This 
 conjecture has been raised to the rank of a certainty by the 
 discovery that the fore and hind limbs of the Mosasauroids 
 were in the form of fin-like paddles, like those of the Ichthyo- 
 saur and Plesiosaur. There can therefore be no doubt that 
 Mosasaurus like the living Amblyrhynchus was aquatic in its 
 habits, and frequented the sea-shore, coming, in fact, only oc- 
 casionally to the land. The best-known genus is Mosasaurus, 
 of which the most celebrated species is the M. Camperi (fig. 
 316) of the Maestricht Chalk. Other genera belonging to this 
 group are Leiodon, Baptosaurus, and Halisaurus. Recently, 
 Marsh has described bony dermal scutes as present in several 
 Mosasauroids (e.g., Holcodus, Leiodon, and Edestosaurus), thus 
 rendering their Lacertilian affinities doubtful. 
 
 In the Tertiary Rocks the remains of Lacertilians are not by 
 any means unknown, but none of the forms of this period are 
 sufficiently important to demand especial attention. Most of 
 the Tertiary Lacertilians, however, are of small size, and ap- 
 pear to have been terrestrial in their habits, thus approximating 
 to the typical existing Lizards. 
 
 ORDER IV. CROCODILIA. The last and highest order of 
 the living Reptilia is that of the Crocodilia, including the living 
 Crocodiles, Alligators, and Gavials, and characterised by the 
 following peculiarities : 
 
 The body is covered with an outer epidermic exoskeleton 
 composed of horny scales, and an inner dermal exoskeleton 
 consisting of squared bony plates or scutes, which may be con- 
 fined to the dorsal surface alone, or may exist on the ventral 
 surface as well, and which are disposed on the back of the 
 neck into groups of different form and number in different 
 species. The bones of the skull and face are firmly united to- 
 gether, and the two halves or rami of the lower jaw are united 
 in front by a suture. There is a single row of teeth, which are 
 implanted in distinct sockets, and hollowed at the base for the 
 germs of the new teeth, by which they are successively pushed 
 out and replaced during the life of the animal. The centra of 
 the dorsal vertebrae in all living Crocodilia are procoelous, or 
 concave in front, but in the extinct forms,'' they may be either 
 amphicoelous (concave at both ends) or' opisthocoelous (con- 
 cave behind). The vertebral ends of the anterior trunk-ribs 
 are bifurcate. There are two sacral vertebras. The cervical 
 vertebrae have small ribs (hence the difficulty experienced by
 
 366 REPTILIA. 
 
 the animal in turning quickly) ; and there are generally false 
 abdominal ribs produced by the ossification of the tendinous 
 intersections of the recti muscles. There are no clavicles. 
 The heart consists of four completely distinct and separate 
 cavities, two auricles, and two ventricles, the ventricular sep- 
 tum as in no other Reptiles being complete. The right and 
 left aortse, however, or, in other words, the pulmonary artery 
 and systemic aorta, are connected together close to their origin 
 by a small aperture (foramen Panizzcz), so that the two sides 
 of the heart communicate with one another. The aperture of 
 the cloaca is longitudinal, and not transverse, as in the Lizards. 
 All the four limbs are present, the anterior ones being penta- 
 dactylous, the posterior tetradactylous. All are oviparous. 
 
 The chief points by which the Crocodiles are distinguished 
 from their near allies, the Lacertilians, are the possession of 
 a partial bony dermal exoskeleton in addition to the ordinary 
 epidermic covering of scales, the lodgment of the teeth in 
 distinct sockets, and the fact that the mixture of venous and 
 arterial blood, which is so characteristic of Reptiles, takes 
 place, not in the heart itself, but in its immediate neighbour- 
 hood, by a communication between the pulmonary artery and 
 aorta directly after their origin. 
 
 The order Crocodilia is divided into three sub-orders, termed 
 Procxlia, Amphicalia, and Opisthocalia according as the dorsal 
 vertebrae are concave in front, concave at both ends, or con- 
 cave behind. The sub-order PrococKa comprises all the living 
 forms namely, the Crocodiles proper, the Alligators, and the 
 Gavials. The first of these have the fourth tooth in the lower 
 jaw (fig. 317) larger than the others, forming a canine tooth, 
 
 Fig- 317- Skull of young Crocodilns biporcatus v afier Van der Hoven). 
 
 which is received into a notch excavated in the alveolar border 
 of the upper jaw, so that it is visible externally when the mouth 
 is closed. In the Alligators (fig. 318), the fourth tooth in the 
 lower jaw forms a canine which is received into a pit in the 
 palatal surface of the upper jaw, where it is completely con- 
 cealed when the mouth is shut. In the Gavials the snout is
 
 CROCODILIA. 
 
 367 
 
 greatly prolonged, and the teeth are pretty nearly equal in size 
 and similar in form in the two jaws. 
 
 The Procoelian Crocodiles occur for the first time in the 
 Greensand (Cretaceous Series) of North America. In Europe, 
 however, the earliest remains of Proccelian Crocodiles are from 
 the Lower Tertiary Rocks (Eocene). It is a curious fact that 
 in the Eocene Rocks of the south-west of England, there occur 
 fossil remains of all the three living types of the Crocodilia 
 namely, the Gavials, true Crocodiles, and Alligators ; though 
 at the present day these forms are all geographically restricted 
 in their range, and are never associated together. 
 
 Fig. 318. Lower jaw of an Alligator. Eocene Tertiary, Isle of Wight. 
 
 The Amphicoelian Crocodiles are characterised by their 
 biconcave vertebras, and are entirely extinct, being confined 
 altogether to the Mesozoic period. The biconcave vertebras 
 show a decided approach to the structure of the backbone in 
 fishes ; and as the rocks in which they occur are mostly marine, 
 there can be little doubt but that these Crocodiles were, in 
 the majority of cases at any rate, inhabitants of the sea. The 
 typical members of this sub-order range from the Lias to the 
 Chalk ; and the most important genera are Teleosaurus, Steneo- 
 saurus, Dakosatirus, Makrospondylus, Goniopholis, and Sucho- 
 saurus, the two last mentioned occurring in the fresh-water 
 deposits of the Wealden (Cretaceous). 
 
 The Stagonolepis of the Elgin Sandstone, with its pitted dermal 
 bony scutes, is now believed to be truly referable to the Croco- 
 dilia. As before said, the Elgin Sandstone/ are probably Triassic. 
 
 We may briefly consider here a grdiip of Reptiles which 
 have been regarded as Crocodilian, but which are placed by 
 Owen in a separate order under the name of Thecodontia, and 
 which are looked upon by Huxley as being Deinosaurian, The
 
 368 REPTILIA. 
 
 "Thecodont" Reptiles are defined as follows: "Vertebral 
 bodies biconcave ; ribs of the trunk long and bent, the anterior 
 ones with a bifurcate head ; sacrum of three vertebrae ; limbs 
 ambulatory, femur with a third trochanter. Teeth with the 
 crown more or less compressed, pointed, with trenchant and 
 finely serrate margins, implanted in distinct sockets." (Owen.) 
 
 The Thecodont Reptiles are Triassic, and the three most im- 
 portant genera are Thecodontosaurus, Palaosaurus, and Belodon, 
 the last from undoubted Triassic strata, whilst the two former 
 occur in a dolomitic conglomerate near Bristol, which has 
 sometimes been thought to be Permian, but which is also 
 almost certainly Triassic. In some respects these reptiles 
 make an approach to the Lacertians ; but, on the whole, little 
 doubt can be entertained as to their truly belonging to the 
 Amphicoelian Crocodiles. 
 
 The sub-order of the Opisthocxlian Crocodiles, including 
 those forms in which the anterior trunk vertebrae are concave 
 behind, is one which can be only provisionally retained. Pro- 
 fessor Owen includes in this section the two genera Strepto- 
 spondylus and Cetiosaurus; but the latter is referable to the 
 Deinosauria, and will be treated of when that order is con- 
 sidered. The genus Streptospondylus has been founded on 
 vertebrae obtained from the Oolitic and Wealden formations ; 
 but there are doubts as to the true position of the reptile to 
 which these belonged. 
 
 CHAPTER XXXIII. 
 EXTINCT ORDERS OF REPTILES. 
 
 IT remains now to consider briefly the leading characters of 
 five wholly extinct orders of Reptiles, the peculiarities of which 
 are very extraordinary, and are such as are exhibited by no 
 living forms. 
 
 ORDER V. ICHTHYOPTERYCJIA, Owen ( = Ichthyosauria, Hux- 
 ley). The gigantic Saurians forming this order were distin- 
 guished by the following characters : 
 
 The body was fish-like, without any distinct neck, and pro- 
 bably covered with a smooth or wrinkled skin, no horny or 
 bony exoskeleton having been ever discovered. The vertebrae 
 were numerous, deeply biconcave or amphicoelous, and having 
 the neural arches united to the centra by a distinct suture. 
 The anterior trunk-ribs possess bifurcate heads. There is no
 
 ICHTHYOPTERYGIA. 
 
 369 
 
 sacrum, and no sternal ribs or sternum, but clavicles were pre- 
 sent, as well as an interclavicle (episternum) ; and false ribs 
 were developed in the walls of the abdomen. The skull had 
 enormous orbits separated by a septum, and an elongated 
 snout. The eyeball was protected by a ring of bony plates in 
 the sclerotic. The teeth were not lodged in distinct sockets, 
 but in a common alveolar groove. The fore and hind limbs 
 were converted into swimming-paddles, the ordinary number 
 of digits (five) remaining recognisable, but the phalanges being 
 greatly increased in number, and marginal ossicles being added 
 as well. A vertical caudal fin was in all probability present. 
 
 Fig. 319. Ichthyostwrus commu 
 
 Lias. 
 
 The order Ichthyopterygia includes only the gigantic and 
 fish-like Ichthyosauri (fig. 319), all exclusively Mesozoic, and 
 abounding in the Lias, Oolites, and Chalk, but especially char- 
 
 rus Acadiensis (Marsh). Coal-measures of 
 Nova Scotia. (After Dawson.); 
 
 acteristic of the Lias. There is no doubt ^whatever but that the 
 Ichthyosauri were essentially marine animals, and they have 
 been often included with the next order (Sauropterygia) in a 
 common group, under the name of Enaliosauria or Sea-lizards.
 
 37O REPTILIA. 
 
 In 1 86 1 Professor Marsh discovered in the Coal-measures 
 of Nova Scotia two large amphicoelous vertebrae, which he 
 described under the name of Eosaurns Acadiensis. These 
 vertebrae (fig. 320) are of very large size (about two and a half 
 inches in diameter), and they are deeply excavated at both 
 ends. They are regarded by Professor Marsh as indicating 
 the existence in the later Carboniferous period of a gigantic 
 reptile allied to Ichthyosaurus. By Huxley, however, it is 
 believed that these remains may truly belong to some large 
 Labyrinthodont. 
 
 In the biconcave vertebrae and probable presence of a ver- 
 tical tail-fin, the Ichthyosaurus approaches the true Fishes. 
 There is, however, no doubt as to the fact that the animal 
 was strictly an air-breather, and its reptilian characters cannot 
 be questioned, at the same time that the conformation of the 
 limbs is decidedly Cetacean in many respects. Much has 
 been gathered from various sources as to the habits of the 
 Ichthyosaurus, and its history is one of great interest. From 
 the researches of Buckland, Conybeare, and Owen, the fol- 
 lowing facts appear to be pretty well established : That the 
 Ichthyosauri kept chiefly to open waters may be inferred from 
 their strong and well-developed swimming-apparatus. That 
 they occasionally had recourse to the shore, and crawled upon 
 the beach, may be safely inferred from the presence of a strong 
 and well-developed bony arch, supporting the fore-limbs, and 
 closely resembling in structure the scapular arch of the Orni- 
 thorhytichus or Duck-mole of Australia. That they lived in 
 stormy seas, or were in the habit of diving to considerable 
 depths, is shown by the presence of a ring of bony plates in 
 the sclerotic, protecting the eye from injury or pressure. That 
 they possessed extraordinary powers of vision, especially in 
 the dusk, is certain from the size of the pupil, and from the 
 enormous width of the orbits. That they were carnivorous 
 and predatory in the highest degree is shown by the wide 
 mouth, the long jaws, and the numerous, powerful, and pointed 
 teeth. This is proved, also, by an examination of their petri- 
 fied droppings, which are known to geologists as " coprolites," 
 and which contain numerous fragments of the scales and bones 
 of the Ganoid fishes which inhabited the same seas. 
 
 ORDER VI. SAUROPTERYGIA, Owen ( = Plcsiosauria, Huxley). 
 This order of extinct reptiles, of which the well-known Ple- 
 siosaurus may be taken as the type, is characterised by the 
 following peculiarities : 
 
 The body, as far as is known, was naked, and not furnished 
 with any horny or bony exoskeleton. The bodies of the ver-
 
 SAUROPTERYGIA. 
 
 371 
 
 tebrse were either flat or only slightly cupped at each end, and 
 the neural arches were anchylosed with the centra, and did 
 not remain distinct during life. The transverse processes of 
 the vertebrae were long, and the anterior trunk-ribs had simple, 
 not bifurcate, heads. No sternum or sternal ribs are known 
 to have existed, but there were false abdominal ribs. The 
 neck, in most, was greatly elongated, and composed of numer- 
 ous vertebras. The sacrum was composed of two vertebrae. 
 The orbits were of large size, and there was a long snout, as 
 in the Ichthyosauri, but there was no circle of bony plates in 
 the sclerotic. The limbs agree with those of the Ichthyosauri 
 in being in the form of swimming-paddles (fig. 321), but differ 
 in not possessing any supernumerary marginal ossicles. A 
 pectoral arch, formed of two clavicles and an interclavicle 
 (episternum), appears to have been sometimes, if not always, 
 present. The teeth were simple, and were inserted into dis- 
 tinct sockets, and not lodged in a common groove. 
 
 The most familiar and typical member of the Sauropterygia 
 is the Plesiosaums (fig. 321), a gigantic marine reptile, chiefly 
 characteristic of the Lias and Oolites. As regards the habits 
 of the Plesiosaurus, Dr Conybeare arrives at the following con- 
 clusions : "That it was aquatic is evident from the form of 
 its paddles ; that it was marine is almost equally so from the 
 remains with which it is universally as/ociated ; that it may 
 have occasionally visited the shore, the resemblance of its ex- 
 tremities to those of the Turtles may lead us to conjecture ; 
 its movements, however, must have been very awkward on 
 land ; and its long neck must have impeded its progress
 
 372 REPTILIA. 
 
 through the water, presenting a striking contrast to the organi- 
 sation which so admirably fits the Ichthyosaurus to cut through 
 the waves." As its respiratory organs were such that it must 
 of necessity have required to obtain air frequently, we may 
 conclude " that it swam upon or near the surface, arching 
 back its long neck like a swan, and occasionally darting it 
 down at the fish which happened to float within its reach. It 
 may perhaps have lurked in shoal water along the coast, con- 
 cealed amongst the sea-weed ; and raising its nostrils to a 
 level with the surface from a considerable depth, may have 
 found a secure retreat from the assaults of powerful enemies ; 
 while the length and flexibility of its neck may have com- 
 pensated for the want of strength in its jaws, and its incapacity 
 for swift motion through the water." 
 
 The geological range of the Plesiosaurus is from the Lias to 
 the Chalk inclusive, and specimens have been found indicat- 
 ing a length of from eighteen to twenty feet. 
 
 About twenty species of Plesiosaurus have been described 
 in all. Of the remaining genera of the Sauropterygia, Notho- 
 saurus, Simosaurus, Placodus, Pistosaurus, and Conchiosaurus 
 are Triassic. In Nothosaurus the neck is long, composed of 
 at least twenty vertebrae. The dorsal vertebrae are biconcave, 
 and the limbs are converted into swimming-paddles. The 
 teeth are numerous and conical, and are implanted into dis- 
 tinct sockets. Several species are known, all Triassic, and 
 especially characteristic of the Muschelkalk. Shnosaurus had 
 a large head with enormous orbits, and teeth sunk into dis- 
 tinct sockets. This genus is exclusively confined to the Mus- 
 chelkalk. In Placodus (fig. 322), the teeth are in distinct 
 sockets, and resemble those of 
 many fishes in being round- 
 ed and obtuse, forming broad 
 crushing plates adapted for the 
 comminution of shell-fish. The 
 upper jaw contains a double 
 series of these teeth, an outer 
 or maxillary series, and an in- 
 ternal or palatal series ; but 
 the under jaw has only a sin- 
 gle row of teeth. 
 
 Lastly, in Pliosaurus we 
 
 have a hu e e re P. tile ' allied to 
 
 the Plesiosaurus in its fin-like 
 paddles, but having an enormous head supported upon a short 
 neck. The teeth are simple and conical, and in large speci-
 
 ANOMODONTIA. 
 
 373 
 
 mens attain a great size. Pliosaurus is confined to the Middle 
 and Upper Oolites. 
 
 ORDER VII. ANOMODONTIA. The members of this order 
 are especially characterised by the structure of the mouth, the 
 jaws being converted into a kind of beak, which was pro- 
 bably sheathed in horn, and resembled the jaws of a Turtle. 
 Sometimes the mouth appears to have been wholly destitute 
 of teeth, but in other cases there was a single pair of teeth 
 implanted in the upper jaw, growing from persistent pulps, 
 and assuming the character of great tusks. The dorsal verte- 
 brae are biconcave, and the anterior trunk-ribs have bifurcate 
 heads. The sacrum is large, composed of several vertebrae. 
 The animal seems to have been organised for terrestrial pro- 
 gression, the pectoral and pelvic arches being strong, and the 
 limbs well developed. 
 
 By Owen the genera Dicynodon, Oudenodon, and Rhyncho- 
 saurus are included in this order; but the last of these is 
 regarded by Huxley as a Lacertilian. In Dicynodon (fig. 323, 
 
 Fig. 323. A, Skull of Dicynodon lacerticeps, showing tfie maxillary tusk. B, Skull 
 of Oudenodon Bainii. From the Trias of South/ Africa. (After Owen.) 
 
 A), the anterior portions of the jaws appear to have been al- 
 together toothless j and they form a kind of beak, which was 
 probably sheathed in horn. The lower jaw has no teeth ; but
 
 374 REPTILIA. 
 
 each superior maxilla carries an enormous tusk-like tooth 
 growing from a persistent pulp. In Oudenodon, on the other 
 hand, the mouth is beak-shaped (fig. 323, B), and seems to 
 have possessed no teeth of any kind. Dicynodon and Oudeno- 
 don are known only from strata of supposed Triassic age in 
 India and South Africa. Rhynchosaurus also, if truly refer- 
 able here, is Triassic, occurring in Europe. 
 
 ORDER VIII. PTEROSAURIA. This order includes a group 
 of extraordinary flying Reptiles, all belonging to the Mesozoic 
 epoch, and exhibiting in many respects a very extraordinary 
 combination of characters. The most familiar members of 
 the order are the so-called " Pterodactyles," and the following 
 are the characters of the order : 
 
 No exoskeleton is known -to have existed. The dorsal 
 vertebrae are procoelous, and the anterior trunk-ribs are double- 
 headed. There is a broad sternum with a median ridge or 
 keel, and ossified sternal ribs. The jaws are always armed 
 with teeth, and these were implanted in distinct sockets. In 
 some forms (Rampfwrhynchus} there appear to have been no 
 teeth in the anterior portion of the jaws, and these parts seem 
 to have been sheathed in horn, so as to constitute a kind of 
 beak. A ring of bony plates occurs in the sclerotic coat of 
 the eye. The pectoral arch consists of a scapula and distinct 
 coracoid bone, articulating with the sternum as in Birds, but 
 no clavicles have hitherto been discovered. The fore-limb 
 (fig. 324) consists of a humerus, ulna and radius, carpus, and 
 hand of four fingers, of which the inner three are short and 
 unguiculate, whilst the outermost is clawless and is enormous- 
 ly elongated. Between this immensely-lengthened finger, the 
 side of the body, and the comparatively small hind-limb, there 
 must have been supported an expanded flying-membrane or 
 " patagium," which the animal must have been able to employ 
 as a wing, much as the Bats of the present day. Lastly, most 
 of the bones were "pneumatic" that is to say, were hollow 
 and filled with air. 
 
 By the presence of teeth in distinct sockets, and, as will be 
 seen hereafter, especially in the structure of the limbs, the 
 Pterodactyles differed from all known Birds, and there can 
 be little question as to their being genuine Reptiles. The only 
 Reptile, however, now existing, which possesses any power of 
 sustaining itself in the air, is the little Draco volans, but this 
 can only take extended leaps from tree to tree, and cannot be 
 said to have any power of flight properly so called. That 
 the Pterodactyles, on the other hand, possessed the power of 
 genuine flight, is shown by the presence of a median keel upon
 
 PTEROSAURIA. 375 
 
 the sternum, proving the existence of unusually-developed 
 pectoral muscles ; by the articulation of the coracoid bones 
 with the top of the sternum, providing a fixed point or fulcrum 
 for the action of the pectoral muscles ; and, lastly, by the exist- 
 ence of air-cavities in the bones, giving the animal the neces- 
 sary degree of lightness. The apparatus, however, of flight was 
 not a " wing," as in Birds, but a flying-membrane, very similar 
 in its mode of action to the patagium of the Mammalian order 
 of the Bats. The patagium of the Bats, however, differs from 
 that of the Pterodactyles in being supported by the greatly- 
 elongated fingers, whereas in the latter it is only the outermost 
 finger which is thus lengthened out. 
 
 Fig. 324. Pterodactylus crassirostris. From the Lithographic Slates of Solenhofen. 
 (Upper Oolite). 
 
 The difficulty as to the position of the Pterosauria is evaded 
 by Mr Seeley by placing them in a distinct class, which he 
 terms Ornithosauria, and which he regards as most nearly 
 related to, but coequal with, the class Aves. 
 
 The Pterosauria are exclusively Mesozoic, being found from 
 the Lower Lias to the Middle Chalk inclusive, the Lithographic 
 Slate of Solenhofen (Upper Oolite) being particularly rich in 
 their remains. Most of them appear tfi have attained no very 
 great size, but the remains of a species from the Cretaceous 
 Rocks have been considered to indicate an animal with more 
 than twenty feet expanse of wing, counting from tip to tip. 
 
 In the genus Pterodactylus proper, the jaws are provided
 
 3/6 REPTILIA. 
 
 with teeth to their extremities, all the teeth being long and 
 slender. 
 
 In Dimorphodon, the anterior teeth are large and pointed, 
 the posterior teeth small and lancet-shaped. 
 
 In Ramphorhynchus, the anterior portion of both jaws is 
 edentulous, and may have formed a horny beak, but teeth are 
 present in the hinder portion of the jaws. 
 
 ORDER IX. DEINOSAURIA. The last order of the Reptiles 
 is that of the Deinosauria, comprising a group of very remark- 
 able extinct forms, which are in some respects intermediate in 
 their characters between the Cursorial birds and the typical 
 Reptiles ; whilst they have been supposed to have affinities 
 to the Pachydermatous Mammals. Most of the Dtinosauria 
 were of gigantic size, and the order is defined by the following 
 characters : 
 
 The skin was sometimes naked, sometimes furnished with a 
 well-developed exoskeleton, consisting of bony shields, much 
 resembling those of the Crocodiles. A few of the anterior ver- 
 tebrae were opisthocoelous, the remainder having flat or slightly 
 biconcave bodies. The anterior trunk-ribs were double-headed. 
 The teeth were confined to the jaws and implanted in distinct 
 sockets. There were always two pairs of limbs, and these 
 were strong, furnished with claws, and adapted for terrestrial 
 progression. In some cases the fore-limbs were very small in 
 proportion to the size of the hind-limbs. No clavicles have 
 been discovered. 
 
 The teeth are sometimes implanted in distinct sockets, and 
 they are never anchylosed with the jaws. The ischium and 
 pubes are much elongated ; the inner wall of the acetabulum 
 is formed by membrane ; the tibia has its proximal end pro- 
 longed anteriorly into a strong crest ; and the astragalus is 
 bird-like (Huxley). 
 
 The most remarkable points in the organisation of the 
 Deinosauria are connected with the structure of the pelvis and 
 hind-limb, the characters of which, as pointed out by Huxley, 
 approximate to those of the same parts in the Birds, and 
 especially in the Struthioas Birds. This approximation is 
 especially seen in the prolongation of the ilium in front of the 
 acetabulum (fig. 325), the elongation and slenderness of form 
 of the ischium, and the slenderness of the pubes. The astra- 
 galus is like that of a bird, and in some cases appears to have 
 become anchylosed with the distal end of the tibia. The 
 metatarsal bones, however, remain distinct, and are not an- 
 chylosed with any of the tarsal bones to form a " tarso-meta- 
 tarsus."
 
 DEINOSAURIA. 
 
 377 
 
 The Deinosauria are exclusively Mesozoic, ranging from the 
 Triassic to the Cretaceous formation, but abounding especially 
 in the Oolitic and the 
 earlier portion of the Cre- 
 taceous period. By Pro- 
 fessor Huxley the "The- 
 codont" Reptiles are re- 
 garded as belonging here, 
 as has been already re- 
 marked. The same high 
 authority has also pro- 
 posed the establishment 
 of a new order termed 
 OrnitJwscelida to include 
 the ordinary Deinosaurian 
 Reptiles along with the 
 singular Compsognathus. 
 
 A large number of gen- 
 eric types are included in 
 the Deinosauria, of which 
 Iguanodon, Megalosaurus, 
 Cetiosatirus, and Compsog- 
 nathus may be especially 
 mentioned. Other less 
 important forms are Poi- 
 kilopleuron, Lcelaps, Euske- 
 lesaurus, Hyltzosaurus , Hy- 
 psilophodon, and Hadro- 
 
 Fig 32 -._ Z<r O f Deinosaur. il Ilium ; is 
 The Iglianodon is mam- Ischium ;/ Femur ; t Tibia ; * Fibula ; as Astra- 
 
 ly, if not exclusively, Cre- f^T Calcaneum; m Metatarsus ' (j 
 taceous, being especially 
 
 characteristic of the great delta-deposit of the Wealden. The 
 length of the Iguanodon has been estimated as being probably 
 from fifty to sixty feet, and from the close resemblance of its 
 teeth to those of the living Iguanas, there is little doubt that 
 it was herbivorous and not carnivorous. The femur of a large 
 Iguanodon measures from four to five feet in length, with a cir- 
 cumference of twenty-two inches in its smallest part. From 
 the disproportionately small size of the fogs-limbs, and from the 
 occurence of pairs of gigantic three-toed'' footsteps in the same 
 beds, it has been concluded, with much probability, that Igu- 
 anodon, in spite of its enormous bulk, must have walked tem- 
 porarily or permanently upon its hind-legs, thus coming to pre- 
 sent a most marked and striking affinity to the Birds.
 
 3/8 REPTILIA. 
 
 The teeth of Iguanodon (fig. 326) present a singularly close 
 resemblance in shape to those of the comparatively pigmy 
 Iguanas of the present day. Their crown is obtusely sub-tri- 
 angular, with longitudinal ridges, and having the surface of the 
 
 Fig 326. Teeth of Iguanca'oii Mantellii. Wealden. 
 
 enamel crenated on one or both sides. They present the ex- 
 traordinary feature that the crown became worn down flat by 
 mastication, showing that Iguanodon employed the teeth in the 
 actual trituration of the vegetable matter on which it fed. 
 
 The gigantic Cdiosaurus of the Oolitic and Cretaceous 
 Rocks was originally placed amongst the Crocodilia ; but the 
 researches of Professor Phillips have shown that it belongs 
 really to the Deinosauria. Having obtained a magnificent 
 series of remains of this reptile, Professor Phillips has been 
 able to determine many very interesting points as to the 
 anatomy and habits of this colossal animal, the total length 
 of which he estimates as being probably not less than sixty 
 or seventy feet. As to its mode of life, this accomplished 
 writer remarks : 
 
 " Probably when ' standing at ease ' not less than ten feet in 
 height, and of a bulk in proportion, this creature was un- 
 matched in magnitude and physical strength by any of the 
 largest inhabitants of the Mesozoic land or sea. Did it live in 
 the sea, in fresh waters, or on the land ? This question can- 
 not be answered, as in the case of Ichthyosaurus, by appeal to 
 the accompanying organic remains ; for some of the bones lie
 
 DEINOSAURIA. 3/9 
 
 in marine deposits, others in situations marked by estuarine 
 conditions, and, out of the Oxfordshire district, in Sussex, in 
 fluviatile accumulations. Was it fitted to live exclusively in 
 water ? Such an idea was at one time entertained, in conse- 
 quence of the biconcave character of the caudal vertebrae, and 
 it is often suggested by the mere magnitude of the creature, 
 which would seem to have an easier life while floating in water, 
 than when painfully lifting its huge bulk, and moving with slow 
 steps along the ground. But neither of these arguments is 
 valid. The ancient earth was trodden by larger quadrupeds 
 than our elephant ; and the biconcave character of vertebrae, 
 which is not uniform along the column in Cetiosaurus, is perhaps 
 as much a character of a geological period as of a mechanical 
 function of life. Good evidence of continual life in water is 
 yielded in the case of Ichthyosaurus, and other Enaliosaurs, 
 by the articulating surfaces of their limb-bones, for these, all of 
 them, to the last phalanx, have that slight and indefinite adjust- 
 ment of the bones, with much intervening cartilage, which fits 
 the leg to be both a flexible and forcible instrument of nata- 
 tion, much superior to the ordinary oar-blade of the boatman. 
 On the contrary, in Cetiosaur, as well as in Megalosaur and 
 Iguanodon, all the articulations are definite, and made so as 
 to correspond to determinate movements in particular direc- 
 tions, and these are such as to be suited for walking. In par- 
 ticular, the femur, by its head projecting freely from the ace- 
 tabulum, seems to claim a movement of free stepping more 
 parallel to the line of the body, and more approaching to the 
 vertical than the sprawling gait of the crocodile. The large 
 claws concur in this indication of terrestrial habits. But, on 
 the other hand, these characters are not contrary to the belief 
 that the animal may have been amphibious ; and the great 
 vertical height of the anterior part of the tail seems to support 
 this explanation, but it does not go further. For the later 
 caudal vertebne, instead of being much compressed, as in 
 Teleosaurus, are nearly circular in the cross section, and are 
 interlocked by posterior zygapophyses, extended over half or 
 the whole length of a vertebrae. We have therefore a marsh- 
 loving or river-side animal, dwelling amidst filicine, cycadace- 
 ous, and coniferous shrubs and trees full of insects and small 
 mammalia. What was its usual diet? If ex ungue leonem, 
 surely ex denteribum. We have indeed ty(t one tooth, and that 
 small and incomplete. It resembles more the tooth of Iguan- 
 odon than that of any other reptile ; for this reason it seems 
 probable that the animal was nourished by similar vegetable 
 food which abounded in the vicinity, and was not obliged to
 
 380 REPTILIA. 
 
 contend with Megalosaurus for a scanty supply of more stimu- 
 lating diet." 
 
 Megalosaurus is a gigantic Oolitic Reptile, which occurs also 
 in the Cretaceous series (Weald Clay). Its length has been 
 estimated at between forty and fifty feet, the femur and tibia 
 each measuring about three feet in length. As the head of 
 the femur is set on nearly at right angles with the shaft, whilst 
 all the long bones contain large medullary cavities, there can 
 be no doubt but that Megalosaurus was terrestrial in its 
 habits. That it was carnivorous and destructive in the highest 
 degree is shown by the powerful, pointed, and trenchant teeth. 
 
 The teeth in Megalosaurus are conical, compressed, with 
 finely -serrated edges. The fore -limbs are extraordinarily 
 
 Fig. 327. Cranium of Megalosaurus, restored (After Professor Phillips.) 
 
 smaller than the hind-limbs. The teeth do not become worn 
 by mastication ; and there appears to have been no exoskeleton. 
 One of the most remarkable of the Deinosauria is the little 
 Compsognathus longipes of the Lithographic Slate of Solenhofen, 
 regarded by Professor Huxley as the type of a special group 
 (Compsognatha] of his order Ornit/ioscclida. The special 
 characters distinguishing this group are, that the cervical region 
 of the spine is long, and the femur is shorter than the tibia ; 
 whereas in the typical Deinosauria the neck is relatively short, 
 and the femur is as long as, or longer than, the tibia. Comp- 
 sognathus is not remarkable for its size, which does not seem 
 to have been much more than two feet, but for the striking 
 affinities which it exhibits to the true Birds. The head of 
 Compsognathus was furnished with toothed jaws, and supported
 
 BIRDS. 381 
 
 upon a long and slender neck. The fore-limbs were very short, 
 but the hind-limbs were long and like those of Birds. The 
 proximal portion of the tarsus resembled that of Birds in being 
 anchylosed to the lower end of the tibia ; but the distal portion 
 of the tarsus unlike that of Birds was free, and was not an- 
 chylosed with the metatarsus. Huxley concludes that " it is 
 impossible to look at the conformation of this strange Reptile, 
 and to doubt that it hopped or walked in an erect or semi- 
 erect position, after the manner of a bird, to which its long 
 neck, slight head, and small anterior limbs must have given it 
 an extraordinary resemblance." 
 
 CHAPTER XXXIV. 
 BIRDS. 
 
 THE fourth class of the Vertebrata is that of Aves, or Birds. 
 The Birds may be shortly denned as being " oviparous 
 Vertebrates with warm blood, a double circulation, and a 
 covering of feathers " (Owen). More minutely, however, the 
 Birds are denned by the possession of the following char- 
 acters : 
 
 The skull articulates with the vertebral column by a single oc- 
 cipital condyle. Each half or ramus of the lower jaw consists of 
 a number of pieces, which are separate from one another in the 
 embryo ; and the jaw is united with the skull, not directly, but by 
 the intervention of a quadrate bone (as in the Reptiles}. The fore- 
 limb in no existing birds possesses more than three fingers or 
 digits, and the metacarpal bones are anchylosed together. In all 
 living Birds the fore-limbs are useless as regards prehension, and 
 in most they are organs of flight. The hind-limbs in all Birds 
 have the ankle-joint placed in the middle of the tarsus, the proxi- 
 mal portion of the tarsus coalescing with the tibia, and the distal 
 portion of the tarsus being anchylosed with the metatarsus to con- 
 stitute a single bone known as the " tarso-metatarsus" 
 
 The heart consists of four chambers, two auricles and two ven- 
 tricles ; and not only are the right and left sides of the heart com- 
 pletely separated from one another, but ther) is no communication 
 between the pulmonary and systemic circulations, as there is in 
 Reptiles. 
 
 The respiratory organs are in the form of spongy cellular lungs, 
 which are not freely suspended in pleural sacs ; and the bronchi
 
 382 BIEDS. 
 
 open on their surface into a number of air-sacs, placed in different 
 parts of the body. 
 
 All birds are oviparous, none bringing forth their young alive, 
 or being even ovo-viviparous. All birds are, lastly, provided 
 with an epidermic covering, so modified as to constitute what are 
 known as feathers. 
 
 The entire skeleton of the Birds is singularly compact, r and at 
 the same time singularly light. The compactness is due to the 
 presence of an unusual amount of phosphate of lime ; and the 
 lightness, to the absence in many of the bones of the ordinary 
 marrow, and its replacement by air. 
 
 As regards the vertebral column, Birds exhibit some very in- 
 teresting peculiarities. The cervical region of the spine is 
 unusually long and flexible, since the fore-limbs are useless as 
 organs of prehension and all acts of grasping must be exer- 
 cised either by the beak or by the hind-feet, or by both acting in 
 conjunction. The number of vertebrae in the neck varies from 
 nine to twenty-four, and their structure is always such as to 
 allow of considerable freedom of motion one upon the other. 
 The dorsal vertebras vary from six to ten in number, and of 
 these the anterior four or five are generally anchylosed with 
 one another, so as to give a base of resistance to the wings. 
 In the Cursorial Birds, however (such as the Ostrich and 
 Emeu), and in some others (such as the Penguin), in which 
 the power of flight is wanting, the dorsal vertebrae are all more 
 or less freely movable one upon another. There are no lumbar 
 vertebrae, but all the vertebrae between the last dorsal and 
 the first caudal (varying from nine to twenty) are anchylosed 
 together to form a bone which is ordinarily known as the 
 " sacrum." To this, in turn, the iliac bones are anchylosed 
 along its whole length, giving perfect immobility to this region 
 of the spine and to the pelvis. 
 
 The coccygeal or caudal vertebrae vary in number from 
 eight to ten, and are movable upon one another. The most 
 noticeable feature about this part of the spinal column is what 
 is known as the " ploughshare-bone." This is the last joint of 
 the tail, and is a long, slender, ploughshare-shaped bone, de- 
 stitute of lateral processes, and without any medullary canal 
 (fig. 330, B). In reality it consists of two or more of the 
 caudal vertebrae, completely anchylosed, and fused into a 
 single mass. It is usually set on to the extremity of the spine 
 at an angle more or less nearly perpendicular to the axis of the 
 body ; and it affords a firm basis for the support of the great 
 quill-feathers of the tail (" rectrices "). In the Cursorial Birds, 
 which do not fly, the terminal joint of the tail is not plough-
 
 CHARACTERS OF BIRDS. 383 
 
 share-shaped. In the extraordinary Mesozoic bird, the Archa- 
 opteryx macrura, there is no ploughshare-bone, and the tail 
 consists of twenty separate vertebrae, all distinct from one 
 another, and each carrying a pair of quill -feathers, one on 
 each side. As the vertebrae of the ploughshare-bone are 
 distinct from one another in the embryos of existing birds, the 
 tail of the Arcfueopteryx is to be regarded as a case of the per- 
 manent retention in the adult of an embryonic character. In 
 the increased number of caudal vertebrae, however, and in some 
 other characters, the tail of the Archaopteryx makes a decided 
 approach to the true Reptiles. 
 
 The various bones which compose the skull of Birds are 
 amalgamated in the adult so as to form a single piece, and the 
 sutures even are obliterated, the lower jaw alone remaining 
 movable. The occipital bone carries a single occipital condyle 
 only, and this is hemispherical or nearly globular in shape. The 
 "beak" (fig. 328), which forms such a conspicuous feature in all 
 
 Fig. 328. Skull of Spur-winged Goose (Plectropterus Gambetisis). 
 
 birds, consists of an upper and lower half, or a " superior " and 
 " inferior mandible." The upper mandible is composed almost 
 entirely of the greatly-elongated intermaxillary bones, flanked 
 by the comparatively small superior maxillae. The inferior 
 mandible is primitively composed of twelve pieces, six on each 
 side ; but in the adult these are all indistinguishably amal- 
 gamated with one another, and the lower jaw forms a single 
 piece. As in the Reptiles, the lower jaw articulates with the 
 skull, not directly, but through the intervention of a distinct 
 bone the quadrate bone or tympanic bone which always re- 
 mains permanently movable, and is never anchylosed with the 
 skull. In no bird are teeth ever developed in either jaw, but 
 both mandibles are encased in horn, forming the beak, and 
 the margins of the bill are sometimes serrated. 
 
 The thoracic cavity is bounded by the dorsal vertebrae, which
 
 384 BIRDS. 
 
 are usually, as before said, anchylosed with one another to a 
 greater or less extent. Laterally, the thorax is bounded by 
 the ribs, which vary in number from six to ten pairs. In most 
 birds each rib carries a peculiar process the " uncinate pro- 
 cess " which arises from its posterior margin, is directed up- 
 wards and backwards, and passes over the rib next in succes- 
 sion behind, where it is bound down by ligament. The first 
 and last dorsal ribs carry no uncinate processes, and in some 
 cases the processes continue throughout life as separate pieces 
 (fig. 329, B). Anteriorly, the ribs articulate with a series of 
 
 Fig. 329. A, Breast-bone, shoulder-girdle, and fore-limb of Penguin (after Owen) : 
 b Sternum, with the sternal keel ; s s Scapula: ; k k Coracoid bones ; c Furculum or 
 merry-thought, composed of the united clavicles ; h Humerus ; Ulna ; r Radius ; / 
 Thumb; m Metacarpus ; / Phalanges of the fingers. B, Ribs of the Golden Eagle: a a 
 Ribs giving off (6 b) uncinate processes ; c c Sternal ribs. 
 
 straight bones, which are called the " sternal ribs," but which 
 in reality are to be looked upon as the ossified " costal carti- 
 lages." These sternal ribs (fig. 329, B) are in turn movably 
 articulated to the sternum in front, and " they are the centres 
 upon which the respiratory movements hinge " (Owen). In 
 front the thoracic cavity is completed by an enormously-ex- 
 panded sternum or breast-bone, which in some birds of great 
 powers of flight extends over the abdominal cavity as well, in 
 some cases even reaching the pelvis. The sternum of all 
 birds which fly, is characterised by the presence of a greatly- 
 developed median ridge or keel (fig. 329, A), to which are
 
 CHARACTERS OF BIRDS. 385 
 
 attached the great pectoral muscles, which move the wings. 
 As a general rule, the size of this sternal crest allows a very 
 tolerable estimate to be formed of the flying powers of the 
 bird to which it may have belonged ; and in the Ostriches and 
 other birds which do not fly, there is no sternal keel. At its 
 anterior angles the sternum exhibits two pits for the attach- 
 ment of the coracoid bones. 
 
 The scapular or pectoral arch consists of the shoulder-blade 
 or scapula, the collar-bone or clavicle, and the coracoid bone, 
 on each side. The scapula, as a rule (fig. 329, A, s s) is a 
 simple elongated bone, not flattened out into a broad plate, 
 and carrying no transverse ridge, or spinous process. Only a 
 portion of the glenoid cavity for the articulation with the head 
 of the humerus is formed by the scapula, the remainder being 
 formed by the coracoid. The coracoid bones (fig. 329, A, k k) 
 correspond with the coracoid processes of man, but in birds 
 they are distinct bones, and are not anchylosed with the scap- 
 ula. The coracoid bone on each side is always the strongest 
 of the bones forming the scapular arch. Superiorly it articu- 
 lates with the clavicle and scapula, and forms part of the gle- 
 noid cavity for the humerus. Inferiorly each coracoid bone 
 articulates with the upper angle of the sternum. The position 
 of the coracoids is more or less nearly vertical, so that they 
 form fixed points for the action of the wings in their down- 
 ward stroke. The clavicles (fig. 329, A, c) are rarely rudimen- 
 tary or absent, and are in some few cases separate bones. In 
 the great majority, however, of birds, the clavicles are anchy- 
 losed together at their anterior extremities, so as to form a 
 single bone, somewhat V-shaped, popularly known as the 
 "merry-thought," and technically called the "furculum." The 
 outer extremities of the furculum articulate with the scapula 
 and coracoid ; and the anchylosed angle is commonly united 
 by ligament to the top of the sternum. The function of the 
 clavicular or furcular arch is " to oppose the forces which tend 
 to press the humeri inwards towards the mesial plane, during 
 the downward stroke of the wing " (Owen). Consequently the 
 clavicles are stronger, and their angle of union is more open, 
 in proportion to the powers of flight possessed by each bird. 
 
 As regards the structure of the wing proper, the humerus is 
 short and strong, and articulates superiorly with an articular 
 cavity formed partly by the coracoid and partly by the scapula. 
 The fore-arm is composed of a radius and ulna, of which the 
 former is the smallest and most slender. The carpus is reduced 
 to two small bones wedged in between the distal end of the 
 fore-arm and the metacarpus. The metacarpus consists of 
 2 B
 
 386 BIRDS. 
 
 two bones which in all existing birds are anchylosed at both 
 ends, but which are free in the remarkable extinct Archaop- 
 teryx. The metacarpal, which corresponds to the radius, is the 
 larger of the two, and it carries the digit which has the greatest 
 number of phalanges. At the proximal end of the radial 
 metacarpal is generally attached a single phalanx, constituting 
 the so-called " thumb." The digit which is attached to the 
 ulnar metacarpal never consists of more than a single phalanx. 
 
 As regards the structure of the posterior extremity or hind- 
 limb, the pieces which compose the innominate bones (namely, 
 the ilium, ischium, and pubes) are always anchylosed with one 
 another ; and the two innominate bones are also always an- 
 chylosed, by the medium of the greatly-elongated ilia, with the 
 sacral region of the spine. In no living bird, however, with 
 the single exception of the Ostrich, are the innominate bones 
 united in the middle line in front by a symphysis pubis. The 
 stability of the pelvic arch, necessary in animals which sup- 
 port the weight of the body on the hind-limbs alone, is amply 
 secured in all ordinary cases by the anchylosis of the ilia with 
 the sacrum. 
 
 As in the higher Vertebrates, the lower limb (fig. 330, A) 
 consists of a femur, a tibia and fibula, a tarsus, metatarsus, 
 and phalanges ; but some of these parts are considerably ob- 
 scured by anchylosis. The femur or thigh-bone (fig. 330, A,/) 
 is generally very short, comparatively speaking. The chief 
 bone of the leg is the tibia (^), to which a thin and tapering 
 fibula (r) is anchylosed. The upper end of the fibula, how- 
 ever, articulates with the external condyle of the femur. The 
 ankle-joint is placed, as in Reptiles, between the proximal and 
 distal portions of the tarsus. The proximal portion of the 
 tarsus is undistinguishably amalgamated with the lower end of 
 the tibia. The distal portion of the tarsus is anchylosed with 
 the whole of the metatarsus to constitute the most character- 
 istic bone in the leg of the Bird the " tarso-metatarsus " (mi). 
 In most of the long-legged birds, such as the Waders, the dis- 
 proportionate length of the leg is given by an extraordinary 
 elongation of the tarso-metatarsus. 
 
 The tarso-metatarsus is followed inferiorly by the digits of 
 the foot In most birds the foot consists of three toes directed 
 forwards and one backwards four toes in all. In no wild 
 bird are there more than four toes, but often there are only 
 three, and in the Ostrich the number is reduced to two. In 
 all birds which have three anterior and one posterior toe, it is 
 the posterior thumb or hallux (that is to say, the innermost 
 digit of the hind-limb) which is directed backwards ; and it
 
 CHARACTERS OF BIRDS. 387 
 
 invariably consists of two phalanges only. The most internal 
 of the three toes which are directed forwards, consists of three 
 phalanges ; the next has four phalanges ; and the outermost 
 toe is made up of five phalanges (fig. 330, A). This in- 
 crease in an arithmetical ratio of the phalanges of the toes, 
 in proceeding from the inner to the outer side of the foot, 
 obtains in almost all birds, and enables us readily to detect 
 which digit is suppressed, when the normal four are not all 
 
 Fig. 330. A, Hind-limb of the Loon (Colymbm glacialis) after Owen: z Innominate 
 bone ; / Thigh-bone or femur ; t Tibia, with the proximal portion of the tarsus anchy- 
 losed with its lower end ; r Fibula ; m Tarso-metatarsi 
 of the tarsus anchylosed with the metatarsus ; p p Pha 
 Golden Eagle : .r Ploughshare-bone, carrying the grea 
 
 losed with its lower end ; r Fibula ; m Tarso-metatarsus, consisting of the distal portion 
 of the tarsus anchylosed with the metatarsus ; // Phalanges of the toes. B, Tail of the 
 
 eat tail-feathers. 
 
 present. Variations of different kinds exist, however, in the 
 number and disposition of the toes. In many birds such as 
 the Parrots the outermost toe is turned backwards, so that 
 there are two toes in front and two behind. In others, again, 
 the outer toe is normally directed forwards, but can be turned 
 backwards at the will of the animal. In the Swifts, on the 
 other hand, all four toes are present, but they are all turned 
 forwards. In many cases especially amongst the Natatorial
 
 388 BIRDS. 
 
 birds the hallux is wholly wanting, or is rudimentary. In the 
 Emeu, Cassowary, Bustards, and other genera, the hallux is 
 invariably absent, and the foot is three-toed. In the Ostrich 
 both the hallux and the next toe (" index ") are wanting, and 
 the foot consists simply of two toes, these being the outer toe 
 and the one next to it. 
 
 As regards the geological distribution of Birds, there are 
 many reasons why we should be cautious in reasoning upon 
 merely negative evidence, and more than ordinarily careful not 
 to infer the non-existence of birds during any particular geolo- 
 gical epoch, simply because we can find no positive evidence 
 for their presence. As Sir Charles Lyell has well remarked, 
 " the powers of flight possessed by most birds would insure 
 them against perishing by numerous casualties to which quad- 
 rupeds are exposed during floods ; " and, " if they chance to 
 be drowned, or to die when swimming on water, it will scarcely 
 ever happen that they will be submerged so as to become pre- 
 served in sedimentary deposits," since, from the lightness of the 
 bones, the carcase would remain long afloat, and would be 
 liable to be devoured by predaceous animals. As, with a few 
 utterly trivial exceptions, all the deposits in which fossils are 
 found have been laid down in water, and more especially as 
 they are for the most part marine, these considerations put for- 
 ward by Sir Charles Lyell afford obvious ground against the 
 anticipation that the remains of birds should be either of fre- 
 quent occurrence or of a perfect character in any of the fossil- 
 iferous rocks. In accordance with these considerations, as a 
 matter of fact, most of the known remains of birds are either 
 fragmentary, or belong to forms which were organised to live a 
 terrestrial life, and were not adapted for flight. 
 
 The earliest remains which have been generally referred to 
 birds are in the form of footprints (fig. 331) impressed upon 
 certain sandstones in the valley of the Connecticut River in 
 the United States. These sandstones are almost certainly 
 Triassic, and if the ornithic character of these footprints be 
 admitted, then Birds date their existence from the commence- 
 ment of the Mesozoic period, and, for anything we know to 
 the contrary, may have existed during the Palaeozoic epoch. 
 
 The evidence as to the ornithic character of the footprints 
 in the American Trias is as follows : 
 
 Firstly, The tracks are, beyond all question, those of a biped 
 that is to say, of an animal which walked upon two legs. 
 No living animals walk habitually upon two legs except Man 
 and Birds, and therefore there is a prima facie presumption 
 that the authors of these prints were birds.
 
 DISTRIBUTION OF BIRDS. 389 
 
 Secondly, The impressions are mostly tridactylous that is to 
 say, formed by an animal with three toes on each foot, as is 
 the case in many Waders and most Cursorial Birds. 
 
 Fig. 331. Footprint supposed to belong to a Bird. Triassic Sandstones 
 of Connecticut. 
 
 Thirdly, The impressions of the toes show the same numeri- 
 cal progression in the number of phalanges as exists in living 
 birds that is to say, the innermost of the anterior toes has 
 three phalanges, the middle one has four, and the outermost 
 toe has five phalanges. 
 
 Taking this evidence collectively, it would have seemed, till 
 lately, tolerably certain that these impressions were formed by 
 Birds. We must not, however, lose sight of the possibility 
 that these impressions may have been formed by Reptiles 
 more bird-like in their characters than any of the living forms 
 with which we are acquainted. The recent researches of 
 Huxley, Cope, and others, go to show that the Deinosaurian 
 Reptiles possessed the power of walking, temporarily or per- 
 manently, on the hind-legs, and many curious affinities to the 
 true Birds have been pointed out. It is therefore by no means 
 impossible that these footprints of the Connecticut valley are 
 truly Reptilian.* 
 
 The size and other characters of the above-mentioned im- 
 pressions vary much, and they have certainly been produced 
 
 * The occurrence of many^/wr-fo^/impressions in these same Sandstones, 
 and the further discovery of the bones of Deinosaurian Reptiles in the same 
 beds, have rendered the Reptilian nature of many of these footprints almost 
 certain ; but some may possibly have been formed by Birds.
 
 390 BIRDS. 
 
 by several different animals. In the largest hitherto discov- 
 ered, each footprint is twenty-two inches long, and twelve 
 inches wide, showing that the feet were four times as large as 
 those of the African Ostrich. The animal, therefore, which 
 produced these impressions whether Avian or Reptilian 
 must have been of gigantic size. 
 
 The first unmistakable remains of a bird have been found 
 in the Solenhofen Slates of Bavaria, of the age of the Upper 
 Oolites. A single unique specimen, consisting of bones and 
 feathers, but unfortunately without the skull, is all that has 
 hitherto been discovered ; and it has been named the Archa- 
 opteryx macrura. The characters of this singular and aberrant 
 bird, which alone constitutes the order Saurura, will be shortly 
 given, and need not be repeated here. 
 
 Other doubtful remains of birds have been alleged to occur 
 in the Mesozoic series, but many of these certainly belong in 
 reality to Pterodactyles. In the Cretaceous Rocks, however, 
 of the United States, occur the bones of several Wading Birds 
 (Laornis, Telmatornis, and Palaotringa). Recently, Professor 
 Marsh has described some additional remains of Birds from 
 the Cretaceous Rocks. Some of these belong to a new genus, 
 Graculavus, allied to the existing Cormorants. Others belong 
 to a gigantic swimming bird of remarkable affinities, but hav- 
 ing its nearest allies in the living Colymbida. The genus 
 Hesperornis and family Hesperornidce are proposed for its re- 
 ception. 
 
 In the Tertiary Rocks there are, comparatively speaking, 
 many remains of birds. In the Eocene Rocks of France has 
 been found a large bird, as big as an Ostrich, the so-called 
 Gastornis Parisiensis ; and in England, in the same formation, 
 we have a small Vulture (Lithornis vulturinus), and a King- 
 fisher (Halcyornis toliapicus}. In the Eocene of Claris, in Swit- 
 zerland, occurs also the oldest known Insessorial or Passerine 
 bird, the Protornis Glarisiensis, which was about as big as a lark. 
 
 Numerous remains of birds have likewise been found in the 
 Miocene and Pliocene deposits. Amongst these we have Par- 
 rots, Trogons, Secretary Birds, Petrels, Cranes, Guillemots, 
 &c. With the exception, however, of the Mesozoic Archaop- 
 tcryx, by far the most remarkable remains of birds have been 
 found in the Post-tertiary or Pleistocene deposits. All the 
 remains now alluded to are those of gigantic wingless birds ; 
 and it is worthy of notice that they are almost exclusively 
 found in regions now tenanted by smaller wingless birds, 
 whilst there is reason to believe that some of them have been 
 in existence during the human period. Most of the remains
 
 NATATORES. 391 
 
 in question have been found in New Zealand, where there 
 have been obtained the bones of several species of large wing- 
 less birds, referred by Owen to the genera Dinornis, Palap- 
 teryx, and Aptornis. The Dinornis giganteus must have been 
 one of the most gigantic of the whole class of birds, the tibia 
 measuring upwards of a yard in length, and the skeleton indi- 
 cating a bird which stood at least ten feet in height. In an- 
 other species, the Dinornis elephantopus, the " framework of 
 the skeleton is the most massive of any in the whole class of 
 birds/' and " the toe-bones almost rival those of the Elephant " 
 (Owen). The feet were furnished with three anterior toes, 
 and are of interest as presenting us with an undoubted bird 
 big enough to produce the largest of the footprints of the 
 Triassic Sandstones of Connecticut. There is reason to be- 
 lieve, from the traditions of the Maories, that the Dinornis was 
 living at no very remote period, and that it has been exter- 
 minated by man. 
 
 In Madagascar, bones have been discovered of a bird as 
 large as, or larger than, the Dinornis giganteus, which has been 
 described under the name of the sEpiornis maximus. With 
 the bones have been found eggs measuring from thirteen to 
 fourteen inches in diameter, and computed to be as big as 
 three ostrich-eggs, or one hundred and forty-eight hens' eggs. 
 Unlike New Zealand, where there is the Apteryx, Madagascar 
 itself has no living wingless birds ; but in the neighbouring 
 island of Mauritius the Dodo has been exterminated less than 
 three hundred years ago ; and the little island of Rodriguez, in 
 the same geographical province, has in a similar period lost 
 the wingless Solitaire (Pezophaps). 
 
 In the following are given the characters of the orders of the 
 Birds, with the range of each in time, so far as known : 
 
 ORDER I. NATATORES. The order of the Natatores, or 
 Swimmers, comprises a number of birds which are as much or 
 even more at home in the water than upon the land. In 
 accordance with their aquatic habit of life, the Natatores have 
 a boat-shaped body, usually with a long neck. The legs are 
 short, and placed behind the centre of gravity of the body, 
 this position enabling them to act admirably as paddles, at the 
 same time that it renders the gait upon dry land more or less 
 awkward and shuffling. In all cases the toes are " webbed," 
 or united by membrane to a greater or less extent. In many 
 instances the membrane or web is stretched completely from 
 toe to toe ; but in others the web is divided or split up between 
 the toes, so that the toes are fringed with membranous borders, 
 and the feet are only imperfectly webbed.
 
 3Q2 BIRDS. 
 
 Amongst the more important families of the Natatores may 
 be enumerated the Penguins (Spheniscida), the Auks (Alcidce), 
 the Gulls and Terns (Larida], the Petrels (Procel/arida), the 
 Pelicans (Pelicanus), the Cormorants (Phalacrocorax}, the Gan- 
 nets (Su/a), the Ducks (Anatida), the Geese (Anserirue), and 
 the Swans (Cygnida). 
 
 As might have been expected, the remains of Natatorial 
 Birds are, speaking comparatively, not uncommon as fossils. 
 The earliest traces of this order in past time appear in the 
 Cretaceous series, which has yielded in Europe the Cimolornis 
 (supposed to be allied to the Albatross), and in North America 
 the genera Gracttlavus, Hesperornis, Laornis, Tehnatornis, and 
 Palaotringa, The Eocene Tertiary has a form believed to be 
 nearly allied to the living Pelicans, and another supposed to be 
 related to the Mergansers. The Ducks and Flamingos appear 
 for the first time in the Miocene, and the Post-tertiary deposits 
 have yielded remains of Geese, Gulls, Terns, Divers, and Guil- 
 lemots, or of birds allied to these. 
 
 ORDER II. GRALLATORES. The birds comprising the order 
 of the Grallatores, or Waders, for the most part frequent the 
 banks of rivers and lakes, the shores of estuaries, marshes, 
 lagoons, and shallow pools, though some of them keep almost 
 exclusively to dry land, preferring, however, moist and damp 
 situations. In accordance with their semi-aquatic, amphibious 
 habits, the Waders are distinguished by the great length of 
 their legs ; the increase in length being mainly due to the 
 great elongation of the tarso-metatarsus. The legs are also 
 unfeathered from the lower end of the tibia downwards. The 
 toes are elongated and straight, and are never completely 
 palmate, though sometimes semi-palmate. There are three 
 anterior toes, and usually a short hallux, but the latter may be 
 wanting. The wings are long, and the power of flight usually 
 considerable ; but the tail is short, and the long legs are 
 stretched out behind in flight to compensate for the brevity 
 of the tail. The body is generally slender, and the neck and 
 beak usually of considerable length. 
 
 Amongst the more important Grallatorial Birds are the Rails 
 (Rallida), Water-hens (Gallinula), Cranes (Gruida), Herons 
 \Ardt 'idee), Storks (Ciconitue), Snipes (Scokpacidtz), Sandpipers 
 (Tringidce), Curlews (Numenius\ Plovers (Charadriid<z\ and 
 Bustards (Otida). 
 
 As in the case of the Natatores, the earliest traces of the 
 Waders appear to belong to the Cretaceous period. These 
 consist of bones which have been referred to a Snipe-like bird 
 (Scolopax\ and which have been obtained from the Greensand
 
 CURSORES. 
 
 393 
 
 of New Jersey. In the Eocene Rocks, the most important form 
 is the Niunenius gypsorum, which has been discovered in the 
 Gypseous series of Montmartre, and which is supposed to have 
 been allied to the Ibis. In the later Tertiary deposits occur 
 the remains of birds allied to, if not identical with, the living 
 Cranes ( Grits), Bustards ( Otis), Rails (Rallus), and Coots (Fulica). 
 ORDER III. CURSORES. The third order of Birds is that of 
 the Cursores, or Runners, comprising the Ostriches, Rheas, 
 Cassowaries, Emeus, and the singular Apteryx of New Zealand. 
 In many respects the Cursores are to be looked upon as an 
 artificial assemblage; but in the meanwhile it will be most 
 convenient to consider them as forming a distinct division. 
 The Cursores are characterised by the rudimentary condition 
 of the wings, which are so short as to be useless for flight, and 
 by the compensating length and strength of the legs. In ac- 
 cordance with this condition of the limbs, many of the bones 
 retain their marrow, and the sternum is destitute of the pro- 
 minent ridge or keel, to which the great pectoral muscles are 
 attached (hence the name of Ratita, applied by Huxley to the 
 
 Fig. 332. Apteryx Australis. (Gould.) 
 
 order). In the Ostrich, the pubic bones of the pelvis unite to 
 form a symphysis pubis as they do in no other bird, and in all 
 the pelvic arch possesses unusual strength and stability. The
 
 394 BIRDS. 
 
 legs are extremely robust and powerful, and the hind-toe is 
 entirely wanting, except in the Aptcryx, in which it is rudimen- 
 tary. The anterior toes are two or three in number, and are 
 provided with strong blunt claws or nails. The plumage pre- 
 sents the remarkable peculiarity that the barbs of the feathers, 
 instead of being connected to one another by hooked barbules, 
 as is usually the case, are remote and disconnected from one 
 another, presenting some resemblance to hairs. 
 
 The living Cursorial Birds are the Ostrich (Struthio camelus\ 
 the American Ostriches (Rhea), the Emeu (Dromaius), the 
 various species of Cassowary (Casuarius), and the Aptcryx 
 (fig. 332). Of the extinct forms of the Cursores, the most ancient 
 appears to be the Gastornis Parisiensis of the Eocene Tertiary. 
 This bird seems to have attained the size of an Ostrich, and it 
 appears to have points of affinity with the Natatorial and Gral- 
 latorial Birds. In the superficial deposits of New Zealand have 
 been found, as already mentioned, the remains of several species 
 of Dinornis and Palapteryx, along with bones of the now ex- 
 isting Apteryx. In similar deposits in Madagascar occur the 
 bones of the gigantic sEpiornis ; and in the bone-caves of 
 Brazil have been found remains of the American Ostriches 
 or Rheas. 
 
 ORDER IV. RASORES. The fourth order of Birds is that of 
 the Rasores, or Scratchers, often spoken of collectively as the 
 " Gallinaceous" Birds, from the old name of "Gallinae," given 
 to the order by Linnaeus. The Rasores are characterised by 
 the convex, vaulted upper mandible, having the nostrils pierced 
 in a membranous space at its base. The nostrils are covered 
 by a cartilaginous scale. The legs are strong and robust, 
 mostly covered with feathers as far as the joint between the 
 tibia and tarso-metatarsus. There are four toes, three in front 
 and one behind, the latter being short, and placed generally at 
 a higher level than the other toes. All the toes terminate in 
 strong blunt claws suitable for scratching (Gattinaca), or in 
 more slender claws adapted for perching (Columbacd). The 
 order Rasores comprises the various species of Grouse (Tctra- 
 onida], the Partridges, Francolins, and Quails (PerdicidcE), the 
 Turkeys, Fowls, Pheasants, and Pea-fowl (Phasianida), the 
 Pigeons and Doves (Colnmbid<z\ and the recently extinct Dodo 
 (Didus inept us). 
 
 The earliest remains of the Rasorial Birds appear in the 
 Eocene Tertiary, where traces of a Partridge have been found. 
 In Post-Tertiary deposits occur the remains of birds more or 
 less closely allied to the existing Pigeons, Grouse, Quail, 
 Pheasant, Fowl, and Tinamou.
 
 SCANSORES INSESSORES RAPTORES. 39$ 
 
 ORDER V. SCANSORES. The order of the Scansorial or 
 Climbing Birds is easily and very shortly defined, having no 
 other distinctive and exclusive peculiarity except the fact that 
 the feet are provided with four toes, of which two are turned 
 backwards and two forwards. Of the two toes which are 
 directed backwards, one, of course, is the hallux, or proper 
 hind-toe, and the other is the outermost of the normal three 
 anterior toes. This arrangement of the toes enables the Scan- 
 sores to climb with unusual facility. Their powers of flight, on 
 the other hand, are generally only moderate and below the 
 average. 
 
 The most important families of the Scansores are the Cuckoos 
 (Cuculidce), the Woodpeckers and Wry-necks (Picid<z), the Par- 
 rots (Psittaridce), the Toucans (Rhamphastidce), and the Tro- 
 gons (Trogonida). 
 
 The Scansores are of small importance as fossils, but the 
 remains of Parrots, Trogons, Woodpeckers, and Cuckoos have 
 been detected in the later Tertiary and Post-tertiary deposits. 
 
 ORDER VI. INSESSORES. The sixth order of Birds is that of 
 the Insessores, or Perchers often spoken of as the Passeres, 
 or "Passerine" Birds. They are defined by Owen as fol- 
 lows : 
 
 " Legs slender, short, with three toes before and one behind, 
 the two external toes united by a very short membrane." 
 
 The Insessores form the largest order of existing birds, com- 
 prising all the ordinary "song-birds," and including a great 
 number of families. The earliest known representatives of the 
 order in past time are the Protornis Glarisiensis of the Eocene 
 Schists of Claris, and the Haley ornis toliapicus of the London 
 Clay of Sheppey the former somewhat resembling the living 
 Larks, whilst the latter is supposed to be related to the King- 
 fishers. Besides these, a few unimportant forms have been 
 discovered in the later Tertiary and Post-tertiary deposits. 
 
 ORDER VII. RAPTORES. All the members of this order are 
 characterised by the shape of the bill, which is "strong, curved, 
 sharp-edged, and sharp-pointed, often armed with a lateral 
 tooth " (Owen). The upper mandible is the longest, and is 
 strongly hooked at the tip. The body is very muscular ; the 
 legs are robust, short, with three toes in front and one behind, 
 all armed with long, curved, crooked claws or talons ; the 
 wings are commonly pointed, and of considerable size, and the 
 flight is usually rapid and powerful. 
 
 The order Raptores is divided into the two sections of the 
 Nocturnal and Diurnal Raptores, comprising respectively the 
 forms which fly by night and those which fly by day. In the
 
 396 
 
 BIRDS. 
 
 former are only the Owls, and in the latter are the Hawks, 
 Falcons, Eagles, and Vultures. The earliest representative of 
 the Raptores in past time is the Lithornis vulturinus of the Lon- 
 don Clay of Sheppey, a bird probably related to the existing 
 vultures. In the Gypseous series of Montmartre (Eocene), 
 there are also remains of an Owl (Strix), and of a Harrier 
 (Circus). In later Tertiary and Post-tertiary deposits occur 
 unimportant remains of Eagles, Hawks, and Vultures. 
 
 ORDER VIII. SAURURJE. This order includes only the ex- 
 tinct bird, the Archaopteryx macrura, a single specimen of 
 which and that but a fragmentary one has been discovered 
 in the Lithographic Slates of Solenhofen (Upper Oolites). 
 This extraordinary bird (fig. 333), appears to have been about 
 as big as a Rook ; but it differs from all known birds in having 
 two free claws belonging to the wing, and in having a long 
 lizard-like tail, longer than the body, and composed of separate 
 vertebrae. 
 
 Fig. 333. Arthaopteryx tttacrum, showing tail and tail-feathers, 
 with detached bones. 
 
 The tail was destitute of any ploughshare-bone, and each 
 vertebra carried a single pair of quill-feathers. The metacar- 
 pal bones also were not anchylosed, as they are in all other 
 known birds, living or extinct. Milne Edwards concludes 
 that Archceopteryx was probably a vegetable feeder, and that it 
 ordinarily perched upon trees.
 
 MAMMALIA. 397 
 
 CHAPTER XXXV. 
 
 MAMMALIA. 
 GENERAL CHARACTERS OF THE MAMMALIA. 
 
 THE last and highest class of the Vertebrata, that of the Mam- 
 malia, may be shortly defined as including Vertebrate animals 
 in which some part or other of the integtiment is always provided 
 with hairs at some time of life ; and the young are nourished for 
 a longer or shorter time, by means of a special fluid the milk 
 secreted by special glands the mammary glands. These two 
 characters are of themselves sufficient broadly to separate the 
 Mammals from all other classes of the Vertebrate sub-kingdom. 
 In addition, however, to these two leading peculiarities, the 
 Mammals exhibit the following other characters of scarcely less 
 importance : 
 
 1. The skull articulates with the vertebral column by means 
 of a double articulation, the occipital bone carrying two con- 
 dyles, in place of the single condyle of the Reptiles and Birds. 
 
 2. The lower jaw or mandible consists of two halves or 
 rami, united anteriorly by a symphysis, but not necessarily an- 
 chylosed ; but these are each composed of a single piece, 
 instead of being complex and consisting of several pieces, as 
 in the Reptiles and Birds. Further, the lower jaw always ar- 
 ticulates directly with the squamosal element of the skull, and 
 is never united to an os quadratum, as in the Sauropsida. 
 
 3. The two hemispheres of the cerebral mass, or brain proper, 
 are united together by a more or less extensively developed 
 " corpus callosum " or commissure. 
 
 4. The heart consists as in Birds of four cavities or cham- 
 bers, two auricles and two ventricles. The right and left sides 
 of the heart are completely separated from one another, and 
 there is no communication between the pulmonary and systemic 
 circulations. 
 
 5. The cavities of the thorax and abdomen are completely 
 separated from one another by a muscular partition the dia- 
 phragm or midriff. 
 
 6. The respiratory organs are in the form of two lungs placed 
 in the thorax, but none of the bronchi end in air-receptacles, 
 distributed through the body, as in Birds. 
 
 As regards the Osteology of the Mammals, the following 
 points should be noticed : 
 
 With the exception of the Whales and Dolphins (Cetacea\
 
 398 MAMMALIA. 
 
 and the Dugongs and Manatees (Sirenia}, the vertebral column 
 is divisible into the same regions as in man namely, into a 
 cervical, dorsal, lumbar, sacral, and caudal or coccygeal region 
 (see fig. 269). In the Cetacea and Sirenia the dorsal region of 
 the spine is followed by a number of vertebrae which compose 
 the hinder extremity of the body, but which cannot be separ- 
 ated into lumbar, sacral, and caudal vertebras. 
 
 In spite of the great difference which is observable in the 
 length of the neck in different Mammals, the number of verte- 
 brae in the cervical region is extraordinarily constant, being 
 almost invariably seven, as in man. In this respect there is no 
 difference between the Whale and the Giraffe. The only ex- 
 ceptions to this law are the Manatus anstralis, one of the Sea- 
 cows, which has usually six cervical vertebras ; and the three- 
 toed Sloth (Bradypus tridactylus), which is commonly regarded 
 as possessing nine, though competent anatomists would refer 
 the posterior two of these to the dorsal region. 
 
 The dorsal vertebras are mostly thirteen in number, but they 
 vary from ten to twenty-four. In Man there are twelve, in one 
 of the Armadillos only ten, and in the three-fingered Sloth the 
 maximum is attained. The lumbar vertebras are usually six or 
 seven in number, rarely fewer than four. In Man they are five 
 in number, and they are reduced to two in the two-toed Sloth, 
 one of the Ant-eaters, and the Duck-mole. 
 
 The first vertebra, or atlas, always bears two articular cavi- 
 ties for the reception of the two condyles of the occipital bone, 
 and the second vertebra, or axis, usually has an " odontoid " 
 process on which the head rotates. In the true Whales, how- 
 ever, in which the cervical vertebras are anchylosed together to 
 a greater or less extent, and the neck is immovable, the odon- 
 toid process is also wanting. 
 
 The number of lumbar and sacral vertebras, as we have seen, 
 varies in different Mammals; but ordinarily some of the verte- 
 bras are anchylosed into a single bone, and have the iliac bones 
 abutting against them, thus constituting the "sacrum" of human 
 anatomists. In the Cetacea and Sirenia, in which the hind- 
 limbs are wanting, and the pelvis rudimentary, there is no 
 " sacrum." 
 
 The thoracic cavity or chest in Mammals is always enclosed 
 by a series of ribs, the number of which varies with that of the 
 dorsal vertebras. In most cases each rib articulates by its head 
 with the bodies of two vertebras, and by its tubercle with the 
 transverse process of one of these vertebras (the lower one). 
 In the Monotremata (e.g., the Duck-mole), the ribs articulate 
 with the body of the vertebra only ; and in the Whales, the
 
 GENERAL CHARACTERS OF THE MAMMALIA. 399 
 
 hindermost of the ribs, or all of them, articulate with the trans- 
 verse processes only, and not with the centra at all. 
 
 There are usually no bony pieces uniting the ribs with the 
 sternum or breast-bone in front, as in Birds ; but the so-called 
 " sternal ribs " of Aves are represented by the " costal carti- 
 lages" of the Mammals. In some cases, however, the carti- 
 lages of the ribs do become ossified and constitute sternal ribs. 
 Sometimes, as in the Armadillos, there is a joint between the 
 vertebral rib and costal cartilage. More rarely, as in the Mono- 
 tremes, an intermediate piece is found between the vertebral 
 and costal portions of the rib. Only the anterior ribs reach 
 the sternum, and these are called the "true" ribs; the poste- 
 rior ribs, which fall short of the breast-bone, being known as 
 the " false " ribs. 
 
 The sternum or breast-bone is formed of several pieces placed 
 one behind the other, but usually anchylosed together to form 
 a single bone. It is placed upon the ventral surface of the 
 body, and is united with the vertebral column by the ribs and 
 their cartilages. It is generally a long and narrow bone, but in 
 the Cetacea it is broad. It is only in some burrowing animals 
 (such as the Moles) and in the true flying Mammals (the Bats), 
 that the sternum is provided with any ridge or keel for the at- 
 tachment of the pectoral muscles, as it is in Birds. The ster- 
 num is primitively composed of three pieces, an anterior piece 
 or prtzsternum, a middle piece or mesosternum, and a posterior 
 piece or xiphisternum. The praesternum is the " manubrium 
 sterni " of human anatomy, and is the portion of the sternum 
 which lies in front of the attachment of the second pair of ribs. 
 All the other ribs are connected with the mesosternum. The 
 xiphisiernum is the " xiphoid cartilage " of human anatomy, and 
 it commonly remains throughout life more or less unossified. 
 In the Monotremes there is a T-shaped bone above or in front 
 of the praesternum, but this is probably to be regarded as be- 
 longing to the shoulder-girdle, and as representing the " epi- 
 sternum " or " interclavicle" of the Reptiles. 
 
 The normal number of limbs in the Mammalia is four, two 
 anterior and two posterior ; and hence they are often spoken 
 of as "quadrupeds," though all the limbs are not universally 
 present, and other animals have four limbs as well. The ante- 
 rior limbs are not known to be wanting in any Mammal, but 
 the posterior limbs are absent in the Cetacea and Sirenia. 
 
 As regards the structure of the anterior limb, the chief 
 points to be noticed concern the means by which it is con- 
 nected with the trunk. The scapula or shoulder-blade is never 
 absent, and it is in the form of a broad flat bone, applied to the
 
 400 MAMMALIA. 
 
 outer aspect of the ribs, and much more developed than in the 
 Birds. The coracoid bone, which forms such a marked feature 
 in the scapular arch of Ares, is fused with the scapula, and 
 only articulates with the sternum in the Duck-mole and Echidna 
 (Monotremata). In all other Mammals the coracoid forms 
 merely a process of the scapula, and does not reach the top of 
 the breast-bone. The collar-bones or clavicles never unite in 
 any Mammal to form a " furculum," as in Birds : but in the 
 Monotremes they unite with an " inter-clavicle " placed in front 
 of the sternum. The clavicles, in point of fact, are not present 
 in a well-developed form in any Mammals except in those 
 which use the anterior limbs in flight, in digging, or in prehen- 
 sion. The Cetacea, the Hoofed Quadrupeds (Ungulata), and 
 some of the Edentata, have no clavicles. Most of the Carni- 
 vora and some Rodents possess a clavicle, but this is imperfect, 
 and does not articulate with the top of the sternum. The In- 
 sectivorous Mammals, many of the Rodents, the Bats, and all 
 the Quadrumana, have (with man) a perfect clavicle articulat- 
 ing with the anterior end of the sternum. 
 
 The humerus, or long bone of the upper arm (brachiuni), is 
 never wanting, but is extremely short in the Whales, in which 
 the anterior limbs are converted into swimming-paddles. 
 
 In the fore-arm of all Mammals the ulna and radius are re- 
 cognisable, but they are not necessarily distinct; and the radius, 
 as being the bone which mainly supports the hand, is the only 
 one which is always well developed, the ulna being often rudi- 
 mentary. In the Cetacea the ulna and radius are anchylosed 
 together ; and in most of the Hoofed Quadrupeds they are an- 
 chylosed towards their distal extremities. 
 
 The fore-arm is succeeded by the small bones which com- 
 pose the wrist or " carpus." These are eight in number in man, 
 but vary in different Mammals from five to eleven. 
 
 The metacarpus in man and in most Mammals consists of 
 five cylindrical bones, articulating proximally with the carpus, 
 and distally with the phalanges of the fingers. The most re- 
 markable modification of this normal state of things occurs in 
 the Ruminants and in the Horse. In the Ruminants, in which 
 the foot is cleft, and consists of two perfect toes only, there are 
 two metacarpal bones in the embryo ; but these are anchylosed 
 together in the adult, and form a single mass which is known 
 as the " canon-bone " (fig. 334, ca). In the Horse, in which 
 the foot consists of no more than a single digit, there is only a 
 single metacarpal bone, on each side of which are two little 
 bony spines the so-called "splint-bones" which are attached 
 superiorly to the carpus. These are to be regarded as nidi-
 
 GENERAL CHARACTERS OF THE MAMMALIA. 4OI 
 
 mentary metacarpals ; but by Cuvier they were looked upon as 
 imperfect fingers. In most of the other Ungulates there are at 
 least three metacarpals, and in the Elephants there are five. 
 
 The normal number of digits 
 is five, but they vary from one 
 to five. The middle finger is 
 the longest and most persistent 
 of the digits of the fore-limb ; 
 and in the Horse it is the only 
 one which is left (fig. 334, A). 
 The thumb is very frequently 
 absent. In the Ruminants there 
 are only two fingers which are 
 functionally useful, these carry- 
 ing the hoofs. In many Rumi- 
 nants, however, there are two 
 rudimentary and functionally 
 useless digits in addition. 
 
 Normally each digit has three 
 phalanges, except the thumb, 
 which has only two. In the 
 Whales and Dolphins( Cetacea), 
 in which the anterior limbs form 
 swimming - paddles very like 
 those of the Ichthyosaurus and 
 Plesiosaurus, the phalanges are 
 considerably increased in num- 
 ber as they are in those Rep- 
 tiles. In all the Mammalia, 
 too, except the Cetacea, it is the 
 rule that the terminal phalanx 
 in each digit should carry a 
 nail, claw, or hoof. 
 
 Whilst the anterior limbs are never absent in any Mammal, 
 the posterior limbs are occasionally wholly wanting, as in the 
 Cetacea and Sirenia. Generally speaking, however, the poste- 
 rior limbs are present, and the pelvic arch has much the same 
 structure as in man. The two halves of the pelvis the ossa 
 innominata consist each of three pieces in the embryo (viz., 
 the ilium, ischium, and pubes), which meet to form the cup- 
 shaped cavity known as the " acetabulum," with which the head 
 of the thigh-bone articulates. In the adult Mammal these 
 three bones are anchylosed together, and the two ossa inno- 
 minata unite in front by means of a symphysis pubis, con- 
 stituted either by a cartilaginous union (synchondrosis), or by 
 2 c 
 
 A B 
 
 Fig. 334. A, Fore-leg of the Horse : 
 
 Radi 
 
 Splint-bon 
 
 pastern 
 
 c Carpus ; ca Canon-bon 
 e ; a First phalanx or " great 
 b Second phalanx or " small 
 pastern ; " c Ungual phalanx or " coffin- 
 bone." B, Fore-limb of a Deer : r Radi- 
 us ; c Carpus ; ca Canon-bone ; s Supple- 
 mentary toe.
 
 402 MAMMALIA. 
 
 merely ligamentous attachment In some Mammals, however, 
 such as the Mole, and many of the Bats, the pubic bones re- 
 main disunited during life. As a rule also, the ossa innomin- 
 ata are firmly united with the vertebral column. In the Ceta- 
 ceans, in which the hind-limbs are wanting, and there is no 
 sacrum, the innominate bones are rudimentary, and are not 
 attached in any way to the spine. 
 
 The only other bones which are ever connected with the 
 pelvis are two small bones which are directed upwards from 
 the brim of the pelvic cavity in Marsupials and Monotremes. 
 These are the so-called " marsupial bones " regarded generally 
 as not forming parts of the skeleton properly so called, but 
 as being ossifications of the internal tendons of the " external 
 oblique" muscles of the abdomen (fig. 336). 
 
 In those Mammals which possess hind-limbs, the normal 
 composition of the member is of the following parts : i. A 
 thigh-bone or femur ; 2. Two bones forming the shank, and 
 known as the tibia and fibula ; 3. A number of small bones 
 constituting the ankle or tarsus ; 4. The " root " of the foot, 
 made up of the " metatarsus ; " 5. The phalanges of the toes 
 (see fig. 271). 
 
 The thigh-bone or femur articulates with the pelvis, usually 
 at a very open angle. In Man it is distinguished by being the 
 longest bone of the body, and by having the axis of its shaft 
 nearly parallel to that of the vertebral column. In most Mam- 
 mals the femur is relatively shorter, and the axis of its shaft 
 deviates considerably from that of the spine, being sometimes 
 at right angles, or even at an acute angle. 
 
 Of the bones of the leg proper the tibia corresponds to the 
 radius in the fore-limb, as shown by its carrying the tarsus ; 
 and the fibula is the representative of the ulna. The articula- 
 tion between the tibia and fibula on the one hand, and the 
 femur on the other, constitutes the " knee-joint," which is usu- 
 ally defended in front by the " knee-pan " or patella, a large 
 sesamoid bone developed in the tendons of the great extensor 
 muscles of the thigh. The patella is of small size in the Car- 
 nivora, but does not appear to be wanting in any except the 
 Marsupials. In many cases the tibia and fibula are anchylosed 
 towards their distal extremities. In the Horse the fibula has 
 much the same character as in Birds, being a long splint-like 
 bone which only extends about half-way down the tibia. In 
 the Ruminants the reverse of this obtains, the upper half of the 
 fibula being absent, and only the lower half present. 
 
 The tibia articulates with the tarsus, consisting in Man of 
 seven bones, but varying in different Mammals from four to nine.
 
 GENERAL CHARACTERS OF THE MAMMALIA. 403 
 
 The foot consists normally of five toes connected with the 
 tarsus by means of five metatarsal bones, which closely re- 
 semble the metacarpals. In the Ruminants there are only two 
 metatarsals, and these are anchylosed in the adult, and carry 
 two toes. In the Horse there is only one complete metatarsal 
 supporting a single toe. As a rule, the number of digits in the 
 hind-limb or foot is the same as that in the fore-limb or hand ; 
 but this is not always the case. 
 
 The cranial bones are invariably connected with one another 
 by sutures, and in no other examples than the Monotremes are 
 these sutures obliterated in the adult The occipital bone 
 carries two condyles for articulation with the first cervical 
 vertebra. The lower jaw is composed of two halves or rami, 
 which are distinct from another in the embryo, and may or 
 may not be anchylosed together in the adult. However this 
 may be, in no Mammal is the ramus of the lower jaw composed 
 of several pieces, as it is in Birds and Reptiles, nor does it 
 articulate with the skull by the intervention of an os quadratum. 
 On the other hand, each ramus of the lower jaw in the Mam- 
 mals is composed of only a single piece, and articulates with 
 the squamosal element of the skull, or, in other words, with the 
 squamous portion of the temporal bone. 
 
 Teeth are present in the great majority of Mammals ; but 
 they are only present in the embryo of the Whalebone Whales, 
 and are entirely absent in the genera Echidna, Manis, and 
 Myrmecophaga. In the Duck-mole (Ornithorhynchus) the teeth 
 are horny, and the same was the case in the extinct Rhytina 
 amongst the Sirenia. In all other Mammals the teeth have 
 their ordinary structure of dentine, enamel, and crusta petrosa, 
 these elements being variously disposed in different cases. In 
 no Mammals are the teeth ever anchylosed with the jaw, and 
 in all the teeth are implanted into distinct sockets or alveoli, 
 which, however, are very imperfect in some of the Cetacea. 
 
 Many Mammals have only a single set of teeth throughout 
 life, and these are termed by Owen " monophyodont." In 
 most cases, however, the first set of teeth called the " milk " 
 or " deciduous " teeth is replaced in the course of growth by 
 a second set of " permanent " teeth. The deciduous and per- 
 manent sets of teeth do not necessarily correspond to one 
 another ; but no Mammal has ever more than these two sets. 
 The Mammals with two sets of teeth are called by Owen 
 " diphyodont." 
 
 In Man and in many other Mammals the teeth are divisible 
 into four distinct groups, which differ from one another in 
 position, appearance, and function ; and which are known
 
 404 MAMMALIA. 
 
 respectively as the incisors, canines, prcemolars, and molars 
 (fig. 335)- "Those teeth which are implanted in the prae- 
 maxillary bones, and in the corresponding part of the lower 
 jaw, are called ' incisors,' whatever be their shape or size. 
 The tooth in the maxillary bone which is situated at or near 
 to the suture with the prasmaxillary, is the ' canine,' as is also 
 that tooth in the lower jaw which, in opposing it, passes in 
 front of its crown when the mouth is closed. The other teeth 
 of the first set are the ' deciduous molars ; ' the teeth which 
 displace and succeed them vertically are the ' praemolars ; ' 
 the more posterior teeth, which are not displaced by vertical 
 successors, are the ' molars ' properly so called." (Owen.) 
 The deciduous dentition, therefore, of a diphyodont Mammal, 
 consists of only three kinds of teeth incisors, canines, and 
 
 PI* 
 
 Fig. 335. Teeth of the right side of the lower jaw of the Chimpanzee (after Owen). 
 * Incisors ; c Canine ; fm Praemolars ; m Molars. 
 
 molars. The incisor and canine teeth of the deciduous set are 
 replaced by the teeth which bear the same names in the per- 
 manent set. The deciduous " molars," however, are replaced 
 by the permanent " praemolars," and the " molars " of the per- 
 manent set of teeth are not represented in the deciduous series, 
 only existing once, and not being replaced by successors. 
 
 All these four kinds of teeth are not necessarily present in 
 all Mammals, and, as will be afterwards seen, the characters of 
 the teeth are amongst the most important of the distinctions by 
 which the Mammalian orders are separated from one another. 
 The variations which exist in the number of teeth in different 
 Mammals are usually expressed by a " dental formula," which 
 presents the " dentition " of both jaws in a condensed and 
 easily-recognised form.
 
 GENERAL CHARACTERS OF THE MAMMALIA. 405 
 
 According to Owen, the typical permanent dentition of a 
 diphyodont Mammal would be expressed by the following 
 formula : 
 
 Z -3 = 3 ; ,!Z1 I ;^4-4 ;W 3 = 3 = 
 33 i i 44 33 
 
 The four kinds of teeth are indicated in such a formula by the 
 letters incisors i, canines c, praemolars pm, molars m. The 
 numbers in the upper line indicate the teeth in the upper jaw, 
 those in the lower line stand for those in the lower jaw; and 
 the number of teeth on each side of the jaw is indicated by 
 the short dashes between the figures. 
 
 As regards their general distribution in time, as a matter of 
 course, the remains of Mammals are scanty, and occupy but 
 a small space in the geological record ; since the greater 
 number of the Mammalia are terrestrial, and the greater 
 number of the stratified fossiliferous deposits are marine. The 
 Mammals, too, are the most highly organised of the entire 
 sub-kingdom of the Vertebrata ; and therefore, in obedience to 
 the well-known law of succession, they ought to make their 
 appearance upon the globe at a later period than any of the 
 lower classes of the Vertebrata. Such, in point of fact, is to a 
 great extent the case ; and if the geological record were perfect, 
 the law would doubtless be carried out to its full extent. 
 
 It is in the upper portion of the Triassic Rocks that is to 
 say, not long after the commencement of the Mesozoic or 
 Secondary epoch that Mammals for the first time make their 
 appearance ; three or four species being now known in a zone 
 of rocks which are placed at the summit of the Trias, just where 
 this formation begins to pass into the Lias. The earliest of these 
 the oldest known of all the Mammals appears at the upper 
 part of the Upper Trias (Keuper) and also at its very summit 
 (Penarth beds), and has been described under the name of 
 Microlestes antiquus. The nearest ally of Microlestes amongst 
 existing Mammals would seem to be the Marsupial and insec- 
 tivorous Myrmecobius, or Banded Ant-eater of Australia. As 
 only the teeth, however, of Microlestes have hitherto been dis- 
 covered, it is impossible to decide positively whether this 
 primeval Mammal was Marsupial or Placental. 
 
 The next traces of Mammals occur in the Stonesfield Slate 
 (Lower Oolites), and here four species, all of small size, are 
 known to occur. Most of these were Marsupial, but it is 
 possible that one was Placental. They form the genera Amphi- 
 lestes, Amphitherium, Phascolotherium, and Stereognathus. After 
 the Stonesfield Slate another interval succeeds, in which no
 
 406 ORDERS OF MAMMALIA. 
 
 Mammalian remains have hitherto been found ; but in the fresh- 
 water formation of the Middle Purbeck, at the top, namely, of 
 the Oolitic series, as many as fourteen small Mammals have 
 been discovered. These constitute the genera Plagiaulax, 
 Spalacotherium, Triconodon, and Galestes. Another gap then 
 follows, no Mammal having hitherto been discovered in any 
 portion of the Cretaceous series (with doubtful exceptions). 
 
 Leaving the Mesozoic and entering upon the Kainozoic 
 period, remains of Mammals are never absent from any of the 
 geological formations. From the base of the Eocene Rocks 
 up to the present day remains of Mammals commonly occur, 
 constantly increasing in number and importance, till we arrive 
 at the fauna now in existence upon the globe. 
 
 In the following are given the characters of each order of 
 the Mammalia, with the range in time, and, so far as known, 
 the more important fossil forms of each. The number, how- 
 ever, of known fossil Mammals is so great, and in many cases 
 they exhibit so many peculiarities and divergences from exist- 
 ing forms, that nothing more can be attempted here than to 
 give a brief and general sketch of the palaeontological history of 
 the class ; attention being drawn, where it may seem necessary, 
 to extinct types of special interest. 
 
 CHAPTER XXXVI. 
 ORDERS OF MAMMALIA. 
 
 ORDER I. MONOTREMATA. The first and lowest order of the 
 Mammalia is that of the Monotremata, containing only two 
 genera, both belonging to Australia namely, the Duck-mole 
 \Ornithorhynchus) and the Porcupine Ant-eater (Echidna). 
 
 The order is distinguished by the following characters : 
 The intestine opens into a "cloaca," which receives also the 
 products of the urinary and generative organs, which discharge 
 themselves into a urogenital canal the condition of parts 
 being very much the same as in Birds. The jaws are either 
 wholly destitute of teeth (Echidna], or are furnished with horny 
 plates which act as teeth. The pectoral arch has some highly 
 bird-like characters, the most important of these being the 
 extension of the coracoid bones to the anterior end of the 
 sternum. The females possess no marsupial pouch, but the 
 pelvis is furnished with the so-called " marsupial bones," be-
 
 MARSUPIALIA. 407 
 
 lieved to be ossifications of the internal tendon of the external 
 oblique muscle of the abdomen. The corpus callosum is very 
 small, and has been asserted to be altogether wanting. There 
 are no external ears. The mammary glands have no nipples, 
 and their ducts open either into a kind of integumentary pouch 
 (Echidna^ or simply on a flat surface (Ornithorhynchus\ The 
 young are said to be destitute of a placenta, or, in other words, 
 no vascular connection is established between the foetus and 
 the mother. The feet have five toes each, armed with claws, 
 and the males carry perforated spurs on the back of the tarsus 
 (attached to a supplementary tarsal bone). 
 
 As regards their geological history, the Monotremes are not 
 known to be represented at all in past time ; and this need not 
 excite any surprise, seeing that the order is represented at the 
 present day by no more than two genera, both confined to a 
 single geographical region. Upon theoretical grounds, how- 
 ever, it may be expected that we shall ultimately discover that 
 the antiquity of the order Monotremata is extremely high. 
 
 ORDER II. MARSUPIALIA. The order Marsiipialia forms 
 with the Monotremata the division of the Non-placental Mam- 
 mals. With the single exception of the genus Didelphys, which 
 is American, all the Marsupialia belong to the Melanesian pro- 
 vince ; that is to say, they all belong to Australia, Van Diemen's 
 Land, New Guinea, and some of the neighbouring islands. 
 
 The following are the characters which distinguish the 
 order : 
 
 The skull is composed of distinct cranial bones united by 
 sutures, and they all possess true teeth ; whilst the angle of 
 the lower jaw is almost always inflected. The pectoral arch 
 has the same form as in the higher Mammals, and the coracoid 
 no longer reaches the anterior end of the sternum. All pos- 
 sess the so-called "marsupial bones" (fig. 336), attached to 
 the brim of the pelvis. The corpus callosum is very small, 
 and has been asserted to be absent. The young Marsupials 
 are born in a very imperfect condition, of very small size, and 
 at a stage when their development has proceeded to a very 
 limited degree only. It is believed that there is no placenta 
 or vascular communication between the mother and foetus, 
 parturition taking place before any necessity arises for such an 
 arrangement. As the young are born in such an imperfect 
 state of development, special arrangements are required to 
 secure their existence. When born, they are therefore, in the 
 great majority of cases, transferred by the mother to a peculiar 
 pouch formed by a folding of the integument of the abdomen. 
 This pouch is known as the " marsupium," and gives the name
 
 4 o8 
 
 ORDERS OF MAMMALIA. 
 
 to the order. Within the marsupium are contained the nipples, 
 which are of great length. Being for some time after their 
 birth extremely feeble, and unable to perform the act of suc- 
 tion, the young within the pouch are nourished involuntarily, 
 the mammary glands being provided with special muscles 
 which force the milk into the mouths of the young. At a 
 later stage the young can suckle by their own exertions, and 
 they leave the pouch and return to 
 it at will. In a few forms there is 
 no complete marsupium as above 
 described ; but the structure of the 
 nipples is the same, and the young 
 are carried about by the mother, 
 adhering to the lengthy teats. 
 
 The so-called " marsupial bones " 
 (fig. 336) doubtless serve to support 
 the marsupial pouch and its con- 
 tained young, but this cannot be 
 their sole function, since they occur 
 in the Monotremes, in which there 
 is no pouch. 
 
 They consist of two small bones, 
 which spring from the brim of the 
 pelvis, and which are merely ossi- 
 fications of the internal tendons of 
 the "external oblique" muscles of 
 the abdomen. 
 
 The Marsupialia may be pri- 
 marily divided into the vegetable- 
 eating and the rapacious or car- 
 nivorous forms the former characterised by the rudimentary 
 condition or absence of the canine teeth, the molars mostly 
 having broad grinding crowns ; whilst in the latter there are 
 well-developed canines, and the molars mostly have trenchant 
 edges. In the phytophagous section are the living Kangaroos 
 (MacropodidcR\ the Wombat (Phascofotnys), the Kangaroo-rats 
 (Hypsiprymnus), and the Phalangers (Phalangistidcf). In the 
 carnivorous section are the true Opossums (Didelphida), the 
 Banded Ant-eater (Myrmecobius), the T/tytacinus, and the 
 " native devil " or Dasyurus. 
 
 As regards their distribution in time, the Marsupialia pro- 
 bably constitute the oldest of the Mammalian orders. Owing, 
 however, to the detached and fragmentary condition of almost 
 all Mammalian remains consisting in many cases of the 
 ramus of the lower jaw, or of separate teeth it is not possible 
 
 Fig. 336. One side of the pel- 
 5 of a Kangaroo, showing the 
 After 
 
 "marsupial bones" (>) 
 Owen.
 
 MARSUPIALIA. 
 
 409 
 
 to state this with absolute certainty. The oldest known 
 European Mammal is the Microlestes antiquus of the Upper 
 Trias, only a few teeth of which have been as yet detected. 
 The earliest horizon on which Microlestes occurs is in a " bone- 
 bed " in the Keuper of Wiirtemberg ; but it has also been 
 detected in the higher " Rhaetic " beds. Professor Owen 
 believes that the Hypsiprymnopsis of Mr Boyd Dawkins, from 
 the Rhsetic marls of Somersetshire, is also referable to Micro- 
 lestes. Upon the whole, it is most probable that Microlestes 
 was Marsupial ; and it appears to be most nearly related to 
 the little insectivorous Myrmecobius or Banded Ant-eater of 
 New South Wales (fig. 337). 
 
 cobius fasciaiu'!. 
 
 Nearly allied to Microlestes is a small Mammal, a lower jaw 
 of which has been obtained from the Trias of North America, 
 and which has been described under the name of Dromatherium 
 sylvestre. This little animal (fig. 338) appears also to be Mar- 
 supial, and to be most nearly related to Myrmecobius. Each 
 
 Fig. 338. Lower jaw of Dromatherinm sylvestre (after Emmons). From rocks 
 supposed to be of Triassic age, in North Carolina. 
 
 ramus of the lower jaw contains " ten small molars in a con- 
 tinuous series, one canine, and three conical incisors the 
 latter being divided by short intervals " (Owen).
 
 4IO ORDERS OF MAMMALIA. 
 
 The next Mammaliferous horizon above the Trias is the 
 Stonesfield Slate in the Lower Oolites ; and there is no doubt 
 that some, if not all, of the Mammalian remains of this belong 
 to small Marsupials. Four genera of small Mammals are 
 known from this horizon viz., Amphilestes, Amphitherium, 
 Phascolotherium, and Stereognathus. In Amphitherium (fig. 
 339), the molars are cuspidate, and the animal was doubtless 
 
 Fig. 339- Ramus of the lower jaw of Amphitheritim(ThylacotIuriuni) 
 Prevostii. Stonesfield Slate. 
 
 insectivorous. It is believed by Owen to be Marsupial, and 
 to be most nearly related to Myrmecobius. Amphilestes and 
 Phascolotherium (fig. 340) are also believed by the same high 
 authority to have been insectivorous Marsupials, and the latter 
 is supposed to find its nearest living ally in the Opossums of 
 America. Lastly, the Stereognathus of the Stonesfield Slate is 
 in a dubious position. It may have been Marsupial ; but, 
 upon the whole, Professor Owen is inclined to believe that it 
 was placental, hoofed, and herbivorous. 
 
 With the occurrence of small Marsupials in England within 
 the Oolitic period, it is interesting to notice how the fauna of 
 that time approached in other respects to that now inhabiting 
 Australia. At the present day, Australia is almost wholly 
 tenanted by Marsupials ; upon its land-surface flourish Arau- 
 carice and Cycadaceous plants, and in its seas swims the Port- 
 Jackson Shark (Cestradon Philippi) ; whilst the Molluscan 
 genus Trigonia is nowadays exclusively confined to the Aus- 
 tralian coasts. In England at the time of the deposition of 
 the Stonesfield Slate, we must have had a fauna and flora very 
 closely resembling what we now see in Australia. The small 
 Marsupials Amphitherium and Phascolotherium prove that the 
 Mammals were the same in order ; cones of Araucarian pines, 
 with tree-ferns and fronds of Cycads, occur throughout the 
 Oolitic series; spine-bearing fishes, like the Port -Jackson 
 Shark, are abundantly represented by genera such as Acrodus 
 and Strophodus ; and lastly, the genus Trigonia, now exclu- 
 sively Australian, is represented in the Stonesfield Slate by 
 species which differ little from those now existing. 
 
 Another singular point of resemblance is established by the
 
 MARSUPIALIA. 
 
 411 
 
 occurrence in the rivers of Queensland of the " Barramunda," 
 which is referred to the genus Ceratodus a genus which, though 
 pre-eminently Triassic, nevertheless extended its range into 
 the Jurassic period. 
 
 Towards the close of the Oolitic period, in the Middle Pur- 
 beck beds, we have evidence of a number of small Mammals, all 
 of which are probably referable to the Mamipialia. Fourteen 
 species are known, all of small size, the largest being no bigger 
 than a polecat or hedgehog. The genera to which these little 
 quadrupeds have been referred are Plagiaulax, Spalacotherium, 
 Triconodon, and Galestes. The first of these viz., Plagiaulax 
 (fig. 340, 4) is believed to be most nearly allied to the living 
 
 Fig. 340. Oolitic Mammals, natural size. i. Lower jaw and teeth of Phascolotherium ; 
 2. of Triconodon; 3. of A mphitlierium ; 4. of Plagiaulax. 
 
 Kangaroo-rats (Hypsiprymnus) of Australia ; and it is held by 
 good authorities to have been phytophagous, as are its living 
 relatives. Professor Owen, on the other hand, maintains that 
 Plagiaulax was carnivorous. The remaining three genera 
 viz., Spalacotherium, Triconodon (fig. 340, 2), and Galestes ap- 
 pear to have been certainly insectivorous, and find their nearest 
 living allies in the Australian Phalangers and the American 
 Opossums. 
 
 In the older Tertiary Rocks the remains of Marsupials are 
 not abundant. In the Eocene Tertiary (Gypseous series of 
 Montmartre), however, occurs an Opossum, which is very 
 closely allied to the existing American forms, and which has 
 been named the Didelphys Gypsorum. Other species of the 
 same genus have also been discovered in deposits of Miocene 
 age. 
 
 In the later Tertiary and Post-tertiary period the order of 
 the Marsupialia is represented by some very remarkable forms. 
 The remains in question have been found in the bone-caves of 
 Australia the country in which Marsupials now abound above 
 every other part of the globe ; and they show that Australia,
 
 4 I2 
 
 ORDERS OF MAMMALIA. 
 
 at no distant geological period, possessed a Marsupial fauna, 
 much resembling that which it has at present, but compara- 
 tively of a much more gigantic size. In the remains from the 
 Australian bone-caves, almost all the most characteristic living 
 Marsupials of Australia and Van Diemen's Land are repre- 
 sented ; but the extinct forms are usually of much greater size. 
 We have Wombats, Phalangers, Flying Phalangers, and Kan- 
 garoos, with carnivorous Marsupials resembling the recent 
 Thylacinus and Dasyurus. The two most remarkable of these 
 extinct forms are Diprotodon and Thylacoleo, In most essen- 
 tial respects Diprotodon resembled the Kangaroos, the denti- 
 tion, especially, showing many points of affinity. The hind- 
 limbs, however, of Diprotodon 
 were by no means so dispro- 
 portionately long as in the 
 Kangaroos. In size, Dipro- 
 todon must have many times 
 exceeded the largest of the 
 living Kangaroos, since the 
 skull measures three feet in 
 length (fig. 341). 
 Fig. 341. skull of Diprotodon Austraiis. Smaller than Diprotodon'^ 
 Nototherium, a genus which is 
 also most nearly allied to the living Kangaroos. 
 
 Thylacoleo (fig. 342), like Plagiaulax, is in a disputed posi- 
 
 Fig. 342. Skull of Thylacolte. Post-Tertiary deposits of Australia. (After Flower.)
 
 EDENTATA. 413 
 
 tion. By Professor Owen it is regarded as being strictly car- 
 nivorous, and as finding its nearest living ally in the Thylacine. 
 The great feature in the dentition is the presence in either jaw 
 of one huge, compressed, and trenchant prsemolar. This is 
 regarded by Owen as a " carnassial ; " but Professor Flower, 
 with greater probability, regards it as corresponding to the 
 great cutting prsemolar of the Kangaroo-rats (Hypsiprymnus), 
 a view which is further borne out by the small size of the 
 canines in Thylacoleo. Upon the whole, therefore, Flower 
 concludes that " Thylacoleo is a highly-modified and aberrant 
 form of the type of Marsupials now represented by the Macro- 
 podidce and Phalangistidce, though not belonging to either of 
 these families as now restricted," and he believes that its diet 
 was of a vegetable nature. Under any view of its habits, 
 Thylacoleo is a very remarkable type of the Marsupials ; and it 
 must have attained a very great size, since the length of the 
 crown of the great praemolar is not less than two inches and a 
 quarter. 
 
 ORDER III. EDENTATA, or BRUTA. The lowest order of the 
 placental or monodelphous Mammals is that of the Edentata, 
 often known by the name of Bruta. The name Edentata is 
 certainly not an altogether appropriate one, since it is only in 
 two genera in the order that there are absolutely no teeth. 
 The remaining members of the order have teeth, but these are 
 always destitute of true enamel, are never displaced by a 
 second set, and have no complete roots. Further, in none of 
 the Edentata are there any median incisors, and in only one 
 species (one of the Armadillos) are there any incisor teeth at 
 all. Canine teeth, too, are almost invariably wanting. Cla- 
 vicles are usually present, but are absent in the Scaly Ant- 
 eater (Mams). All the toes are furnished with long and 
 powerful claws. The mammary glands are usually pectoral, 
 but are sometimes abdominal in position. The testes are 
 abdominal in position. The skin is often covered with bony 
 plates or horny scales. 
 
 The order Edentata is conveniently divided into two great 
 sections, in accordance with the nature of the food, the one 
 section being phytophagous, the other insectivorous. In the 
 former section is the single group of the Sloths (Bradypodidce). 
 In the latter are the two groups of the Armadillos (Dasypodidce), 
 and the various species of Ant-eaters (the latter constituting 
 Owen's group of the Edmtula). 
 
 The Edentates, like the Marsupials, are singularly circum- 
 scribed at the present day. No member of the order is at the 
 present time indigenous in Europe. Tropical Asia and Africa
 
 4H ORDERS OF MAMMALIA. 
 
 have the Scaly Ant-eaters or Pangolins ; and in Africa occurs 
 the Edentate genus Orycteropus. South America, however, is 
 the metropolis of the Edentata, the order being there repre- 
 sented by the Sloths, the Armadillos, and the true Ant-eaters. 
 It is also in South America that by far the greater number of 
 extinct Edentates have been found ; and, as in the case of the 
 Australian Marsupials, the fossil forms are gigantic in size 
 as compared with their living representatives. 
 
 The oldest known representative of the Edentata is the 
 Macrotherium of the Miocene Tertiary of France. This is a 
 gigantic Edentate, intermediate in some respects between the 
 Pangolins (Manis] and the Aardwark (Orycteropus). There 
 does not appear to have been any dermal armour, and the 
 teeth are rootless and destitute of enamel. The ungual pha- 
 langes are bent like those of the Pangolins, and the animal 
 doubtless possessed long curved claws. From the Upper 
 Miocene of Attica, M. Gaudry has also described a gigantic 
 Edentate, allied to Macrotherium, and larger than a Rhino- 
 ceros. The name assigned to this singular form is Ancylo- 
 therium Penteliri. 
 
 In comparatively recent deposits in South America are 
 found remains of Edentates corresponding to the three groups 
 which now inhabit that continent viz., the Sloths, Armadillos, 
 and Hairy Ant-eaters. The Sloths (Bradypodidcz) are repre- 
 sented in the Post-tertiary deposits of South America by a 
 group of gigantic forms, the most important of which belong 
 to the genera Megatherium, Mylodon, and Megalonyx. 
 
 Megatherium (fig. 343) was a colossal Sloth-like Edentate, 
 
 Fig. "n^. Megatherium CuvUn. Post-Pliocene, South America.
 
 EDENTATA. 415 
 
 which attained a length of eighteen feet, with bones as mas- 
 sive as, or more so than, those of the Elephant. The jaws are 
 destitute of canine and incisor teeth, but there are five upper 
 and four lower molars on each side. All the molars have the 
 form of quadrangular prisms, the crowns of which are furnished 
 with well-marked transverse ridges : and they grew from per- 
 manent pulps. The limbs are extremely massive, and the 
 pectoral arch has a clavicle. The digits are very large and 
 strong, and some of them are furnished with well-developed 
 claws. The tail is enormously thick. Unlike the living 
 Sloths, Megatherium must have been terrestrial in its habits, 
 and must have lived upon the foliage of trees which it up- 
 rooted for itself. 
 
 The genus Mylodon comprises large Sloth-like animals, of 
 which the best known is the Mylodon robustus (fig. 344). In 
 its size, Mylodon robustus was smaller than the Megatherium, 
 but it reached a length of eleven feet. In many respects 
 
 Fig. 344. Skeleton of Mylodon robustus. Post-Pliocene, South America. 
 
 Mylodon is very like Megatherium, and the number of the 
 teeth is the same viz., five upper and four lower molars on 
 each side. The crowns of the molars, however, were flat, 
 instead of being ridged. The fore -feet are pentadacty-
 
 416 ORDERS OF MAMMALIA. 
 
 lous, and the posterior tetradactylous, the two external digits 
 being nailless. 
 
 Megalonyx, unlike the preceding, has been found in both 
 North and South America. It has the same number of teeth as 
 Megatherium and Mylodon, but the crowns of these are exca- 
 vated centrally and have a prominent margin. The fore-limbs 
 are shorter than the hind-limbs, and the calcaneum is unusually 
 long. Megalonyx was probably about the size of an ox. 
 
 Just as the Sloths of the present day were formerly repre- 
 sented in the same geographical area by the gigantic Megathe- 
 roids, so the little banded and cuirassed Armadillos of South 
 America were formerly represented by gigantic species, con- 
 stituting the genus Glyptodon. The Glyptodons (fig. 345) 
 differed from the living Armadillos in having no bands in their 
 armour, so that they must have been unable to roll themselves 
 up. It is rare at the present day to meet with any Armadillo 
 over two or three feet in length ; but the length of the Glypto- 
 don clavipes, from the tip of the snout to the end of the tail, 
 was more than nine feet. 
 
 Fig- 345- Glyptodon clavifes. Post Pliocene, South America. 
 
 There are no canine or incisor teeth in the Glyptodon, but 
 there are eight molars on each side of each jaw, and the crowns 
 of these are fluted and almost trilobed. The head is covered 
 by a helmet of bony plates, and the trunk was defended by an 
 armour of almost hexagonal bony pieces united by sutures, and 
 exhibiting special patterns of sculpturing in each species. The 
 tail was also defended by a similar armour, arid the vertebrae 
 were mostly fused together so as to form a cylindrical bony 
 rod. The feet are massive, and the ungual phalanges short and 
 compressed. 
 
 Besides the various species of Glyptodon, South America has 
 also yielded the remains of several true species of Dasypus, 
 nearly allied to the living Armadillos. These have been found
 
 SIRENIA. 417 
 
 in the ossiferous caverns of Brazil ; in which occur also other 
 Edentates, which have been referred to separate genera, but the 
 affinities of which are somewhat dubious. 
 
 CHAPTER XXXVII. 
 ORDERS OF MAMMALIA Continued. 
 
 ORDER IV. SIRENIA. This order comprises no other living 
 animals except the Dugongs and Manatees, which are often 
 placed with the true Cetaceans (Whales and Dolphins) in a 
 common order. There is no doubt, in fact, but that the Sirenia 
 are very closely allied to the Cetacea, and though they are to 
 be regarded as separate orders, yet they may be advantage- 
 ously considered as belonging to a single section, which has 
 been called Mutilata, from the constant absence of the hind- 
 limbs. 
 
 The Sirenia agree with the Whales and Dolphins in their 
 complete adaptation to an aquatic mode of life (fig. 346); 
 especially in the presence of a powerful caudal fin, which differs 
 from that of Fishes in being placed horizontally and in being 
 a mere expansion of the integuments, not supported by bony 
 rays. The hind-limbs are wholly wanting, and there is no sa- 
 crum. The anterior limbs are converted into swimming-paddles 
 or " flippers." The snout is fleshy and well developed, and 
 the nostrils are placed on its upper surface, and not on the top 
 of the head, as in the Whales. Fleshy lips are present, and 
 the upper one usually carries a moustache. The skin is covered 
 with fleshy bristles. The head is not disproportionately large, 
 as in the true Whales, and is not so gradually prolonged into 
 the body as it is in the latter. There may be only six cervical 
 vertebrae. The teats are two in number and are " thoracic," 
 i. <?., are placed on the chest. There are no clavicles, and 
 the digits have no more than three phalanges each. The testes 
 are retained throughout life within the abdomen, but vesiculge 
 seminales are present. The animal is diphyodont, the perma- 
 nent teeth consisting of molars with flattened crowns adapted 
 for bruising vegetable food, and incisors, which are present in 
 the young animal, at any rate. In the extinct Rhytina it does 
 not appear that there were any incisor teeth. 
 
 The only existing Sirenia are the Manatees (Manatus) and 
 
 I 2 D
 
 41 8 ORDERS OF MAMMALIA. 
 
 the Dugongs (Halicore), often spoken of collectively as " sea- 
 cows," and forming the family of the Manatida. 
 
 Fig. 346. Sirenia. Dugong (Halicore). 
 
 The most important, if not the only, fossil remains which 
 can be referred with certainty to the Sirenia, are those upon 
 which the genus Halitherium has been founded. The upper 
 incisors in this genus are tusk-like, the lower incisors small, 
 and the molars furnished with tubercular crowns. Halitherium 
 appears to be in some respects intermediate between the 
 Dugongs and Manatees ; and several species of the genus are 
 known, ranging from the Eocene to the Pliocene Tertiary. 
 
 The genus Deinotherium referred to this order by De Blain- 
 ville, and still retained in this position by Pictet, will be here 
 considered as belonging to the order of the Proboscidca. 
 
 ORDER V. CETACEA. In this order are the Whales, Dol- 
 phins, and Porpoises, all agreeing with the preceding in their 
 complete adaptation to an aquatic life. The body is com- 
 pletely fish-like in form ; the anterior limbs are converted into 
 swimming-paddles or " flippers ; " the proximal bones of the 
 fore-limbs are much reduced in length, and the succeeding 
 bones are shortened and flattened, and are enveloped in a 
 tendinous skin, thus reducing the limbs to oar-like fins ; there 
 are no external ears ; the posterior limbs are completely absent; 
 and there is a powerful, horizontally-flattened, caudal fin, some- 
 times accompanied by a dorsal fin as well. In all these char- 
 acters the Cetacea agree with the Sirenia, except in the one 
 last mentioned. On the other hand, the nostrils, which may 
 be single or double, are always placed at the top of the head, 
 constituting the so-called " blow-holes " or " spiracles ; " and 
 they are never situated at the end of a snout. The body is 
 very sparingly furnished with hairs, or the adult may be com- 
 pletely hairless. The teats are two in number and are placed 
 upon the groin. The head is generally of disproportionately 
 large size, and is never separated from the body by any distinct 
 constriction or neck. The lumbar region of the spine is long,
 
 CETACEA. 419 
 
 and, as in the Sirenia, there is no sacrum, and the pelvis is 
 only present in a rudimentary form. There are no clavicles, 
 and some of the digits may possess more than three phalanges 
 each. Lastly, the adult is either destitute of teeth or, with ex- 
 ception of the Zeuglodonts, is monophyodont that is to say, 
 possesses but a single set of teeth, which are never replaced by 
 others. When teeth are present, they are usually conical and 
 numerous, and they are almost always of one kind only. 
 
 The Cetacea may be divided into the two sections of the 
 Balcenida, comprising only the "Whalebone Whales," in which 
 true teeth are absent ; and the "Toothed Whales " or Odonto- 
 ceti, comprising the living families of the Delphinidce (Dolphins 
 and Porpoises), the Catodontidce. (Sperm Whales), and the Rhyn- 
 choceti (" Ziphioid " Whales), with the extinct family of the 
 Zeuglodontidce. 
 
 Fig- 347. Skull of the Right Whale (Balana mysticetus] after Owen. 
 
 Fam. i. Balcenida. The Balanida or Toothless Whales are 
 characterised by the total absence of teeth in the adult (fig. 
 347). Teeth, however, are present in the fcetal Whale, but 
 they never cut the gum. The place of teeth is supplied by a 
 number of plates of whalebone or " baleen " attached to the 
 palate \ hence the name of " Whalebone Whales " often given 
 to this family. They are the largest of living animals, and may 
 be divided into the two sections of the Smooth Whales, in which 
 the skin is smooth, and there is no dorsal fin (as in the Green- 
 land Whale), and the Furrowed Whales, in which the skin is 
 furrowed, and a dorsal fin is present (as in the so-called Finner 
 Whales and Hump-backed Whales). 
 
 The Balcznida are of little geological importance. In Plio- 
 cene deposits have been found remains referred to the Rorquals; 
 and bones of the Whalebone Whales have also been found 
 in various Post-Tertiary accumulations. It is probable, like-
 
 420 ORDERS OF MAMMALIA. 
 
 wise, that the ear-bones or " cetotolites " which occur in the 
 Red Crag (Pliocene) are, in some instances at any rate, refer- 
 able to members of the Balanidce. 
 
 Fam. 2. Catodontida. The family of the Catodontidce, or 
 Physeteridce, comprises the Sperm Whales or Cachalots, with 
 which we commence the series of the Toothed Whales (Odon- 
 toceti). They are characterised by the fact that the palate is 
 destitute of baleen plates, and the lower jaw possesses a series 
 (about fifty-four) of pointed conical teeth, separated by inter- 
 vals, and sunk in a common alveolar groove, which is only im- 
 perfectly divided by septa. The upper jaw is also in reality 
 furnished with teeth but, with a single partial exception, these 
 do not cut the gum. 
 
 Remains of Cachalots (Physeter) occur in the Pliocene and 
 Post-Tertiary deposits, and their existence has even been indi- 
 cated in the Miocene Tertiary. They are, however, of no 
 special importance. 
 
 Fam. 3. DelphinidcR. This family includes the Dolphins, 
 Porpoises, and Narwhal, and is characterised by usually pos- 
 sessing teeth in both jaws ; the teeth being numerous, and 
 conical in shape. The nostrils, as in the last family, are united, 
 but they are placed further back, upon the top of the head. 
 The single blow-hole or nostril is transverse and mostly cres- 
 centic or lunate in shape. The head is by no means so dispro- 
 portionately large as in the former families, usually forming 
 about one-seventh of the entire length of the body. 
 
 Fig. 348. The common Dolphin (Delphinus delphis). 
 
 The genus Delphinus, comprising the common Dolphins, 
 appears to date from the Miocene Tertiary, and is well repre- 
 sented in deposits of Pliocene age. In Miocene strata also 
 occur the Delphinoid remains which have been referred to the 
 genera Stcreodclphis and Champsoddphis. 
 
 Fam. 4. RhynchocctL This family is allied to the Cacha- 
 lots or Sperm Whales, and includes the so-called "Ziphioid 
 Whales." They are distinguished by the possession of a
 
 CETACEA. 421 
 
 pointed snout (the "beak" or "rostrum"), single blow-hole, 
 and small dorsal fin ; and by their dentition. The upper jaw 
 is edentulous, any teeth which may be present not cutting the 
 gum. The lower jaw, on the other hand, possesses usually a 
 single pair of teeth, which are sometimes tusk-like, but which 
 in other cases are concealed by the gum. 
 
 The rostrum of these Cetaceans is of great density, and has 
 often been preserved in a fossil state, usually presenting itself 
 as a bony cylinder or elongated cone, generally more or less 
 water-worn. Upon fossils of this nature have been founded 
 the genera Choneziphius and Belemnoziphius, both of which 
 occur in the so-called " Crags " (Pliocene). The genus Ziphius 
 also occurs in the Crag, but unlike the preceding it is repre- 
 sented by existing species. Besides the "beaks," some fossil 
 teeth have been found, which may perhaps be referable to mem- 
 bers of this family. 
 
 Fam. 5. Zeugfodontida. The members of this family differ 
 from all existing Odontoceti in the possession of molar teeth im- 
 planted by two distinct fangs. The Zeuglodonts are entirely 
 extinct, and they are exclusively confined to the Eocene, Mio- 
 cene, and Pliocene periods. The chief genera are Zeuglodon 
 and Squalodon, 
 
 Zeuglodon (fig. 349) is distinguished by its elongated snout, 
 conical incisors, and molar teeth with triangular serrated 
 crowns, implanted in the jaw by two roots. Each molar looks 
 
 Fig. 340. Zeuglodon cetoides. A, Molar tooth, natural size ; B, Vertebra, reduced. 
 From the Middle Eocene of North America. (After Lyell.) 
 
 as if it were composed of two separate teeth united on one side 
 by their crowns ; and it is this peculiarity which is expressed 
 by the generic name. The species of Zeuglodon are Eocene 
 and Miocene, one of the best known being the great Z.
 
 422 ORDERS OF MAMMALIA. 
 
 cetoides of the Middle Eocene (Jackson Beds) of the United 
 States, which attained a length of seventy feet. 
 
 By Professor Huxley, Zeuglodon is regarded as intermediate 
 between the true Cetaceans and the Carnivorous family of the 
 Seals. On this point, this eminent naturalist remarks : "The 
 skull of this great Eocene sea-monster, in fact, shows, by the 
 narrow and prolonged interorbital region ; the extensive union 
 of the parietal bones in a sagittal suture ; the well-developed 
 nasal bones ; the distinct and large incisors implanted in prae- 
 maxillary bones, which take a full share in bounding the fore- 
 part of the gape ; the two-fanged molar teeth with triangular 
 and serrated crowns, not exceeding five on each side in each 
 jaw ; and the existence of a deciduous dentition, its close re- 
 lation with the Seals. While, on the other hand, the produced 
 rostral form of the snout, the long symphysis, and the low cor- 
 onary process of the mandible, are approximations to the 
 Cetacean form of those parts." 
 
 The genus Squalodon is nearly related to Zeuglodon, but the 
 teeth are more numerous ; and the double-fanged molars are 
 more compressed and pyramidal in form. " The nasal bones 
 are very short, and the upper surface of the rostrum presents 
 the groove, filled up during life by the prolongation of the eth- 
 moidal cartilage, which is so characteristic of the majority of 
 Cetaceans " (Huxley). The species of Squalodon all belong 
 to the Miocene and Pliocene Tertiary. 
 
 The genus Saurocetes has been founded for the reception of 
 another Zeuglodont, in which there were double-fanged teeth 
 with conoid crowns. The remains on which this genus are 
 based, are from strata of Tertiary age, near Buenos Ayres, and 
 they indicate an animal much smaller than the true Zeuglodons. 
 
 Lastly, it would appear probable that the genus Balcenodon^ 
 founded upon teeth from the Red Crag (Pliocene), is really re- 
 ferable to this family, and probably to the genus Squalodon. 
 In part, however, teeth of Ziphioid Whales have also been in- 
 cluded under this title. By Owen Balanodon is regarded as 
 comprising teeth of a Cetacean nearly allied to the living 
 Sperm Whale.
 
 UNGULATA. 423 
 
 CHAPTER XXXVIII. 
 
 ORDERS OF MAMMALIA Continued. 
 
 ORDER VI. UNGULATA. The order of the Ungulata, or 
 Hoofed Quadrupeds, is one of the largest and most important 
 of all the divisions of the Mammalia. It comprises three 
 entire old orders namely, the Pachydermata, Solidungula, and 
 Ruminantia. 
 
 The first of these old divisions that of the Pachydermata 
 included the Elephants, Rhinoceros, Hippopotamus, Tapirs, 
 and the Pigs, all characterised, as the name implies, by then- 
 thick integuments. The name is still used to express this fact, 
 though the order is now abandoned, and is merged with that 
 of the Ungulata; the Elephants alone being removed to a 
 separate order under the name of Probosddea. 
 
 The second old order that of the Solidungula or Solipedes 
 included the Horse, Zebra, and Ass, all characterised by the 
 fact that the foot terminates in a single toe, encased in an 
 expanded hoof. The name Solidungula is still retained for 
 these animals, as a section of the Ungulata. 
 
 The third old order that of the Ruminantia includes all 
 those animals, such as Oxen, Sheep, Goats, Camels, Giraffes, 
 Deer, and others, which chew the cud or " ruminate," and have 
 two functional toes to each foot, encased in hoofs. The name 
 Ruminantia is still retained for these animals, as constituting 
 a most natural group of the Ungulata. 
 
 All these various animals, then, are now grouped together 
 into the single order of the Ungulata, or Hoofed Quadrupeds, 
 and the following are the characters of the order : 
 
 All the four limbs are present, and that portion of the toe 
 which touches the ground is always encased in a greatly-ex- 
 panded nail, constituting a "hoof." There are never more 
 than four full-sized toes to each limb. Owing to the encase- 
 ment of the toes in hoofs, the limbs are useless for prehension, 
 and only subserve locomotion ; hence clavicles are always want- 
 ing in the entire order. There are always two sets of enamelled 
 teeth, so that the animal is diphyodont. The molar teeth are 
 massive and have broad crowns, adapted for grinding vegetable 
 substances. 
 
 The order Ungulata is divided into two primary sections : 
 the Perissodactyla, in which the toes or hoofs are odd in num- 
 ber (one or three), and the Artiodactyla, in which the toes are 
 even in number (two or four).
 
 424 ORDERS OF MAMMALIA. 
 
 SECTION A. PERISSODACTYLA. The section of the Perisso- 
 dactyle Ungulates includes the Rhinoceros, the Tapirs, the 
 Horse and its allies, and some extinct forms, all agreeing in 
 the following characters : 
 
 The hind-feet are odd-toed in all, and the fore-feet in all 
 except the Tapirs. The dorso-lumbar vertebras are never less 
 than twenty-two in number. The femur has a third trochanter. 
 The horns, if present, are not paired. Usually there is only 
 one horn, but if there are two, these are placed in the middle 
 line of the head, one behind the other. In neither case are 
 the horns ever supported by bony horn-cores. The stomach 
 is simple, and is not divided into several compartments ; and 
 there is a large and capacious caecum. 
 
 The three existing genera of Perissodactyle Ungulates 
 namely, the Horse, Tapir, and Rhinoceros, are widely removed 
 from one another in many important characters ; but the inter- 
 vals between them are filled up by an extensive series of fossil 
 forms, commencing in the Lower Tertiary Strata. 
 
 Fam. i. Rhinocerida. This family comprises only a single 
 genus, the genus Rhinoceros. The Rhinoceroses are extremely 
 large and bulky brutes, having a very thick skin, which is 
 usually thrown into deep folds. The muzzle is rounded and 
 
 n _,,_,.- * 
 
 blunt, and there are -^- molars, with tuberculate crowns. 
 
 There are no canines, but there are usually incisor teeth in both 
 jaws. The skull is pyramidal, and the nasal bones are enor- 
 mously developed. The feet are furnished with three toes each, 
 encased in hoofs. The nasal bones usually support one or two 
 horns, which are not paired. The horn is composed of longi- 
 tudinal fibres, which are agglutinated together, and are of the 
 nature of epidermic growths, somewhat analogous to hairs. 
 When two horns are present, the hinder one is carried by the 
 frontal bones, and is placed in the middle line of the head 
 behind the anterior horn. The posterior horn is usually much 
 shorter than the anterior one, and if not, it differs in shape. 
 The Rhinoceroses live in marshy places, and subsist chiefly on 
 the foliage of trees. They are exclusively confined at the pre- 
 sent day to the warmer parts of the Old World ; but an extinct 
 species (Rhinoceros tidiorhinus) formerly inhabited England, 
 and ranged over the greater part of Europe. 
 
 The fossil species of Rhinoceros are numerous, commencing 
 in the Miocene Tertiary, and ranging through the Pliocene 
 and Post-Pliocene deposits. The species of Rhinoceros may 
 be divided into groups, as follows : 
 
 i. Those in which the nostrils are separated by a bony sep-
 
 UNGULATA. 425 
 
 turn (" cloison "), and the incisor teeth are wanting in the adult 
 (R. tichorhinus}. 
 
 2. Those in which there is no bony partition between the 
 nostrils, and the incisors are of medium size (Rhinoceros mega- 
 rhinus). 
 
 3. Those in which there is no " cloison," and the incisors 
 are of large size (Rhinoceros incisivus). 
 
 4. Those in which there is an imperfect bony partition be- 
 tween the nostrils (Rhinoceros Etruscus and R. hemitcechus). 
 
 The most important extinct forms of the genus Rhinoceros 
 are the ft. tichorhinus, R. megarhinus, R, hemitcechus ( = 7?. 
 leptorhinus, Owen), R. Etruscus, and the hornless species con- 
 stituting the sub-genus Acerotherium. 
 
 The Rhinoceros tichorhinus is generally known as the 
 " Woolly Rhinoceros," from its possession of a woolly cover- 
 ing. Its skin was foldless, and it possessed two horns, of 
 which the anterior one was very large. The limbs are ex- 
 tremely stout, and the nostrils are completely separated by an 
 osseous septum. R. tichorhinus is essentially a northern form, 
 and has the same distribution in space as the Mammoth, except 
 that it did not cross Behring Straits, and is therefore not 
 found in America. In time, it is younger than the Mammoth, 
 not being found in the prse-glacial forest-bed of Norfolk, and 
 occurring for the first time in the Lower Brick-earths of the 
 Thames valley (prae-glacial, but younger than the '* forest- 
 bed"). It is, therefore, essentially a Post-glacial Mammal, 
 and it is mainly found in quaternary cave-deposits and valley- 
 gravels. A molar tooth of this well-known form is figured 
 below (fig. 351). 
 
 Fig- 350. Penultimate molar of the Fig. 351. Penultimate molar of the 
 lower jaw of Rhinoceros megarhinus, lower jaw of Rhinoceros tichorhinus, 
 two-thirds of the natural size. Post- two-thirds of the natural size, Post- 
 Pliocene. Pliocene. 
 
 The Rhinoceros hemitachus of Falconer ( = the R. leptorhinus 
 of Owen) is also provided with two horns, but is of a much
 
 426 ORDERS OF MAMMALIA. 
 
 more slender build than the Tichorhine form. The nasal 
 bones are slender, and the nostrils are separated by a partially- 
 ossified septum. The adult animal possesses neither incisor 
 nor canine teeth. Like the preceding, R. hemitcechus is ex- 
 clusively Post-Pliocene in its distribution, and is found in 
 cave-deposits and in the Thames-valley Brick-earths. 
 
 The Rhinoceros megarhinus of Christol ( = the R, leptorhinus 
 of Cuvier and Falconer) is also bicorn, and resembles R. hemi- 
 tachus in being of comparatively slender build. It is dis- 
 tinguished, however, by the enormous development of the 
 nasal bones and the absence of the " cloison " or bony parti- 
 tion between the nostrils. This form (fig. 350) is found in the 
 Pliocene beds of Italy and France, and also occurs in the 
 prae-glacial forest-bed of Cromer and the Lower Brick-earths 
 of the Thames valley. 
 
 Rhinoceros Etruscus is also bicorn, and has the nostrils par- 
 tially separated by a " demi-cloison " or incomplete bony par- 
 tition, which "strengthened the basement of the anterior horn." 
 This species is found in deposits of Pliocene age, and occurs 
 also in the Post-Pliocene (as in the Cromer forest-bed). 
 
 In the Miocene period occur various remains of hornless 
 species of Rhinoceros, which have often been united into a 
 separate genus, or sub-genus, under the name of Acerotherium. 
 Some of these forms have all the feet three-toed, and they 
 constitute the Rhinoceros incisivus of Cuvier. The typical 
 species of Acerotherium, on the other hand, are stated to agree 
 with the living Tapirs in having the fore-feet four-toed. 
 
 Fam. 2. Tapiridce. The Tapirs are characterised by the 
 possession of a short movable proboscis or trunk. The skull 
 is pyramidal, and the nasal bones project over the nasal cavity. 
 The skin is hairy and very thick. The tail is extremely short. 
 The fore-feet have four toes each, but these are unsymmetrical, 
 and the hind-feet have only three toes, all encased in hoofs. 
 
 The jaws are furnished with incisor teeth, (- -), small can- 
 
 7 7 3 3 
 
 ines, and , , molars. 
 
 The genus Tapirus, including the existing Tapirs, appears for 
 the first time in deposits of Miocene age, and is represented 
 by various species in Pliocene and Post-Pliocene strata. The 
 genus Lophiodon comprises Tapiroid Ungulates, which are 
 essentially, if not exclusively, of Miocene age. They differ 
 from the Tapirs almost solely in the characters of some of the 
 molar and prsemolar teeth. Lastly, the genus Coryphodon, 
 likewise nearly related to the Tapirs, is found exclusively in 
 the Eocene Tertiary.
 
 UNGULATA. 427 
 
 Fam, 3. Palceotherida. This family includes certain ex- 
 tinct Ungulates from the Eocene and Miocene Tertiary. They 
 are characterised by the possession of three toes to all the feet, 
 by having canines, and by the fact that the lower molars have 
 a doubly crescentic form. The canines are longer than the 
 other teeth, and the dental formula is 
 
 3-3 1-1 44 33 
 
 The chief, if not the only, genus in this family is Palaotherium 
 itself. Several species of this genus are known, varying in size 
 from a sheep up to a horse. From the size and form of the 
 nasal bones, it is deduced, with great probability, that the Palae- 
 othere possessed a short movable proboscis or trunk (fig. 352). 
 
 Fig. 352. Outline of Palceotherium magnum, restored, after Cuvier. Upper Eocene. 
 
 All the known species of Palceotherium are Eocene or Miocene, 
 and the genus attained its maximum in the former period. 
 
 Fam. 4. Solidimgula or Equida. This family comprises the 
 Horses, Asses, and Zebras, characterised by the fact that the 
 feet have only a single perfect toe each, enclosed in a single 
 broad hoof. There is a discontinuous series of teeth in each 
 jaw; and in the males, canines are present, but these are 
 wanting in the females. The dental formula is 
 
 ,*=*; .^^^ 3__3 
 33 i i 33 33 
 
 The skin is covered with hair, and the neck is furnished with
 
 428 ORDERS OF MAMMALIA. 
 
 Three fossil genera of this family are known viz., Anchi- 
 therium, Hipparion, and Equus, the last of which is represented 
 at the present day by the existing Horses, Asses, and Zebras. 
 
 Anchitherium comprises some singular forms from the Upper 
 Eocene and Lower Miocene. In this genus each foot is fur- 
 nished with a single functional hoofed toe, flanked by two 
 small hoofed digits, which are sufficiently developed to touch 
 the ground. Anchitherium is nearly related to Palizotherium. 
 
 Hipparion is confined to the Upper Miocene and Pliocene 
 deposits, and is distinguished by the fact that each foot pos- 
 sessed a single fully-developed toe, bordered by two function- 
 ally useless toes, which did not touch the ground, but simply 
 dangled on each side of the central toe. 
 
 In the genus Equus, the foot consists of a single developed 
 toe, but there are two rudimentary toes in the form of little 
 bony spines the so-called " splint-bones " which are attached 
 to the carpus on either side of the metacarpal of the single 
 functional toe. In the Pliocene period appear, for the first 
 time, remains of horses which, like the present form, possessed 
 only a single toe encased in a single hoof. It is interesting to 
 observe that one of the Pliocene horses (Equus curvideiis) 
 occurs in South America, though this continent certainly pos- 
 sessed no native horse at the time of its discovery by the 
 Spaniards. About twenty horses one of them standing no 
 more than two and a half feet in height have been described 
 from North America, in which continent no indigenous horse 
 existed at the time of its discovery. The Equus fossilis of the 
 Post-Pliocene and Recent deposits is specifically undistinguish- 
 able from the common horse (Equus caballus). 
 
 SECTION B. ARTIODACTYLA. In this section of the Ungu- 
 lates the number of the toes is even either two or four and 
 the third toe in each foot forms a symmetrical pair with the 
 fourth. The dorso-lumbar vertebrae are nineteen in number, 
 and there is no third trochanter on the femur. If true horns 
 are present, these are always in pairs, and are supported by 
 bony horn-cores. The antlers of the Deer are also paired, but 
 they are not to be regarded as true horns. The stomach is 
 always more or less complex, or is divided into separate com- 
 partments, and the caecum is comparatively small and simple. 
 
 The section Artiodactyla comprises the Hippopotamus, the 
 Pigs, and the whole group of the Ruminants, including Oxen, 
 Sheep, Goats, Antelopes, Camels, Llamas, Giraffes, Deer, &c. 
 Besides these there is an extensive series of fossil forms com- 
 mencing in the Eocene or Lower Tertiary period, and in many 
 respects filling up the gaps between the living forms.
 
 UNGULATA. 429 
 
 The group of the Artiodactyle Ungulates may be divided 
 into two sections termed respectively Omnivora and Rumi- 
 nant ia, according as they live upon a miscellaneous (but chiefly 
 vegetable) diet, or are exclusively vegetable-feeders and chew 
 the cud. In the former are the living families of the Hippo- 
 potamidce and Suida (Swine), with the extinct group of the 
 Anoploiherida. In the latter are the Camelidcz, Moschidiz 
 (Musk-deer), Cervida (Deer), Camelopardalida (Giraffes), and 
 Cavicornia (Antelopes, Sheep, Goats, and Oxen). 
 
 OMNIVORA. 
 
 i. Hippopotamidce, This group contains only the single 
 genus Hippopotamus, characterised by the massive heavy body, 
 the short blunt muzzle, the large head, and the presence of 
 
 teeth of three kinds in both jaws. The incisors are > the 
 
 canines extremely large, - ?, and the molars, 'L or - - 
 i i y 7 o o 
 
 with crowns adapted for grinding vegetable substances. The 
 upper canines are short, but the lower canines are in the form 
 of enormous tusks, with a chisel-shaped edge. The feet are 
 massive, and are terminated by four hoofed toes each. The 
 eyes and ears are small, and the skin is extremely thick, and 
 is furnished with few hairs. The tail is very short. 
 
 Several extinct species of Hippopotamus are known, but 
 there is only one well-established living form, the Hippopo- 
 tamus amphibius or River-horse, and this is confined to the 
 African continent. 
 
 The genus Hippopotamus may be divided into two sub- 
 genera, in accordance with the number 
 of the incisor teeth. In the sub-genus 
 Tetraprotodon, comprising the living 
 species and most of the fossil forms, 
 there are four incisors in each jaw. In 
 the sub-genus Hexaprotodon, compris- 
 ing several Miocene species from 
 India, there are six incisors in each 
 jaw. 
 
 The best -known fossil species of 
 
 Hippopotamus in Europe is the H. Fig. 353 .-Moiar tooth of H 
 
 $%%. 
 
 ip- 
 major, which is found both in Pliocene * t 
 
 and in Post-Tertiary deposits. This 
 
 species is very nearly allied to the living H. amphibius; but it 
 
 extended its range over the whole of the south of Europe.
 
 43O ORDERS OF MAMMALIA. 
 
 In the Tertiary deposits of the Siwalik Hills in India (Mio- 
 cene) have been discovered several species of Hippopotamus, 
 belonging to the sub-generic type, Hexaprotodon. 
 
 2. Suida. The group of the Suida, comprising the Pigs, 
 Hogs, and Peccaries, is very closely allied to the preceding ; 
 but the feet have only two functional toes, the other two toes 
 being much shorter, and hardly touching the ground. All the 
 three kinds of teeth are present, but they vary a good deal. 
 The canines always are very large, and in the males they usu- 
 ally constitute formidable tusks projecting from the sides of 
 the mouth. The incisors are variable, but the lower ones are 
 always inclined forwards. The molars vary from three to 
 
 seven on each side of the mouth (* 3 or 7 7\ ^he stom- 
 
 33 77 
 
 ach is mostly slightly divided, and is not nearly so complex as 
 in the Ruminants. The snout is truncated and cylindrical, 
 fitted for turning up the ground, and is capable of consider- 
 able movement. The skin is more or less abundantly covered 
 with hair, and the tail is very short, or represented only by a 
 tubercle. 
 
 The most important genera of the Suida are Sus (Pigs), 
 Dicotyks (Peccaries), Chceropotamus, Hyopotamus, and Anthra- 
 cotherium, of which the three last are extinct. 
 
 The genus Sus, comprising the true Pigs, appears to have 
 commenced its existence in the Miocene Tertiary. Several 
 species are known from Pliocene deposits ; and the Wild 
 Boar (Sus scrofa) has been found in Post-Pliocene accumula- 
 tions (commencing in the prae-glacial forest-bed of Norfolk). 
 
 The genus Dicotyles, comprising the existing Peccaries, is 
 at present confined to the American continent. The same 
 country also has yielded five fossil species, which have been 
 found in the bone-caves of Brazil, and two of which appear to 
 have been much larger than the living forms. 
 
 Charopotamus comprises some Upper Eocene Suida, which 
 possess seven molars on each side of each jaw, the first of 
 these (praemolars) being compressed, whilst the others are 
 tuberculate. The canines are short, and are not exserted, as 
 they are in the Wild Boar. Hyopotamus is another genus, in 
 which the canines are short. All the species of this latter 
 genus belong to the Upper Eocene and Lower Miocene Ter- 
 tiary. Lastly, the genus Anthracotherium is nearly allied to 
 Charopotamus, with which it agrees in the number and general 
 form of the praemolar and molar teeth. All the known species 
 of this genus belong to the Lower Miocene. 
 
 3. Anoplotherida. Forming a kind of transition between
 
 UNGULATA. 43 1 
 
 the Swine and the true Ruminants, is the extinct group of the 
 Anoplotheridce, from the Lower Tertiary Rocks. The Anoplo- 
 theria (fig. 354) were slender in form, with long tails, and feet 
 terminated by two hoofed toes each, sometimes with small 
 accessory hoofs. The dentition consisted of six incisors in 
 each jaw, small canines not larger than the incisors, and seven 
 molars on each side, there being no interval or diastema be- 
 tween the molars and the canines. 
 
 Fig. 354. Anoplotherium commune. Eocene Tertiary. 
 
 There was thus a continuous series of teeth in each jaw, the 
 dental formula being 
 
 i3=3; c-*=*- t im*=*i m ^-44. 
 3-3' i i' J 4-4' 3-3- 
 
 The most important genera of this family are Anoplotherium 
 and Xiphodon of the Upper Eocene, Chalicotherium of the 
 Miocene, and Dichobune of the Middle Eocene ; but many less 
 important genera are known. 
 
 RUMINANTIA. 
 
 The last section of the Artiodactyle Ungulates is the great 
 and natural group of the Ruminantia, or Ruminant animals. 
 This section comprises the Oxen, Sheep, Antelopes, Giraffes, 
 Deer, Camels, &c., and is distinguished by the following char- 
 acters : 
 
 The foot is what is called " cloven," consisting of a symmet- 
 rical pair of toes encased in hoofs, and looking as if produced 
 by the splitting into two equal parts of a single hoof. In addi- 
 tion to these functional toes, there are usually two smaller sup- 
 plementary hoofs placed at the back of the foot. The meta- 
 carpal bones of the two functional toes of the fore-limb, and 
 the metatarsal bones of the same toes of the hind-limb, coalesce
 
 432 ORDERS OF MAMMALIA. ; 
 
 to form a single bone, known as the " canon-bone." The 
 stomach is complex, and is divided into several compartments, 
 this being in accordance with their mode of eating. They all, 
 namely, ruminate or " chew the cud " that is to say, they first 
 swallow their food in an unmasticated or partially-masticated 
 condition, and then bring it up again, after a longer or shorter 
 time, in order to chew it thoroughly. 
 
 The dentition of the Ruminants presents peculiarities almost 
 as great and as distinctive as those to be derived from the di- 
 gestive system. In the typical Ruminants (e.g., Oxen, Sheep, 
 Antelopes), there are no incisor teeth in the upper jaw, their 
 place being taken by a callous pad of hardened gum, against 
 which the lower incisors impinge (fig. 355). There are also no 
 
 *'g- 355. Skull of a hornless Sheep (after Owen). Incisors ; c Canines ; 
 tn Molars and pnemolars. 
 
 upper canine teeth, and the only teeth in the upper jaw are six 
 molars on each side. In the front of the lower jaw is a con- 
 tinuous and uninterrupted series of eight teeth, of which the 
 central six are incisors, and the two outer ones are regarded by 
 Owen as being canines. Upon this view, canine teeth are pre- 
 sent in the lower jaw of the typical Ruminants, and they are 
 only remarkable for being placed in the same series as the in- 
 cisors, which they altogether resemble in shape, size, and direc- 
 tion. Behind this continuous series of eight teeth in the lower 
 jaw there is a vacant space, which is followed behind by six 
 molars on each side.
 
 UNGULATA. 433 
 
 The dental formula, then, for a typical Ruminant animal is 
 o o o o 3 3 3 3 
 
 The departures from this typical formula occur in the Camelidce, 
 the Moschidce, and in some of the Deer. Most of the Deer con- 
 form in their dentition to the above formula, but a few forms 
 (e. g., the Muntjak) have canine teeth in the upper jaw. These 
 upper canines, however, are mostly confined to the males ; and 
 if they occur in the females, they are of a small size. The 
 dentition of the Camelidce (Camels and Llamas) is still more 
 aberrant ; there being two canine-like upper incisors and upper 
 canines as well. The lower canines also are more pointed and 
 stand more erect than the lower incisors, so that they are easily 
 recognisable. 
 
 The group of the Ruminantia includes the families of the 
 Camelidce (Camels and Llamas), the Moschidce (Musk-deer), the 
 Cervidce (Deer), the Camelopardalidce (Giraffe), and the Cavicor- 
 nia (Oxen, Sheep, Goats, Antelopes). 
 
 a. Camelidce. The Camels and Llamas constitute in many 
 respects an aberrant group of the Ruminantia, especially in 
 their dentition, the peculiarities of which have been spoken of 
 above, and need not be repeated here. In their feet, too, the 
 Camelidce are peculiar. The feet are long and terminate in 
 only two toes, which are covered by imperfect nail-like hoofs, 
 covering no more than the upper surface of each toe. The 
 two hinder supplementary toes, which are mostly present in the 
 Ruminants, are here altogether wanting ; and the soles of the 
 feet are covered by a callous horny integument, by which the 
 two toes of each foot are conjoined, and upon which the ani- 
 mal walks. The head in all the Camelidce is destitute of horns, 
 and the nostrils can be closed at the will of the animal. 
 
 The two living genera of the Camelidce are Camelus, compris- 
 ing the trde Camels, and Auchenia, comprising the Llamas and 
 Alpacas of South America. Both of these genera are repre- 
 sented by fossil forms, the former by two species which occur 
 in the Tertiary deposits of the Siwalik Hills, in India, and the 
 latter by two species which occur in the bone-caves of Brazil, 
 and one of which exceeded the horse in size. 
 
 Besides these existing genera, there are the two extinct genera 
 Merycotherium and Macrauchenia. The first of these is only 
 known by some molar teeth, which have been discovered in 
 the drift of Siberia, and which resemble those of the Camel in 
 form. Macrauchenia is a remarkable extinct genus, which is in 
 many respects intermediate between the Perissodactyle and 
 2 E
 
 434 ORDERS OF MAMMALIA. 
 
 Artiodactyle Ungulates. In fact, as the feet appear to be un- 
 doubtedly three-toed, it can only with some violence be consi- 
 dered here as belonging to the Artiodactyles. At the same 
 time, it shows many remarkable points of affinity to the Catne- 
 lidcE, and it may be regarded as a generalised type, presenting 
 resemblances on the one hand to PaltzotJierium, and on the 
 other hand to the Llamas (Auchenia). Only a single species is 
 known, which equals the Rhinoceros in size, and occurs in 
 Post-Tertiary or late Tertiary strata in South America. 
 
 b. Moschidce. The second group is that of the Musk-deer, 
 characterised by the total absence of horns in both sexes, and 
 by the presence of canines in both jaws, those in the upper jaw 
 being in the form of tusks in the males, but being much smaller 
 in the females. 
 
 The family Moschida is a small one, and is of little geologi- 
 cal importance. A species of Moschus, allied to the living 
 Musk-deer, has been found in India, and another form has been 
 indicated as occurring in the later Tertiary deposits of Europe. 
 The genus Amphitragulus has been founded upon remains from 
 the Lower Miocene of France ; and the nearly-allied Dremo- 
 therium has been discovered in the Miocene deposits of France 
 and Attica. 
 
 c. Cervida. This family is of much greater importance than 
 that of the Moschida, including as it does all the true Deer. 
 They are distinguished from the other Ruminants chiefly by 
 the nature of the horns. With the single exception of the 
 Reindeer, these appendages are confined to the males amongst 
 the Cervida, and do not occur in the females. They do not 
 consist, as in the succeeding group, of a hollow sheath of horn 
 surrounding a central bony core, nor are they permanently re- 
 tained by the animal. On the other hand, the horns, or, as 
 they are more properly called, the antlers, of the Cerridce are 
 deciduous, and are solid. They are bony throughout, and are 
 usually more or less branched, and they are annually shed and 
 annually reproduced at the breeding season. They increase 
 in size and in the number of branches every time they are 
 reproduced, until in the old males they may attain an enor- 
 mous size. 
 
 The living Cervida are very generally distributed, but no 
 member of the group has hitherto been discovered in either 
 Australia or South Africa, their place in the latter continent 
 seeming to be taken by the nearly-allied Antelopes (distin- 
 guished by their hollow horns). 
 
 The true Cervida do not seem to make their appearance 
 before the Miocene period, in which they are represented by
 
 UNGULATA. 
 
 435 
 
 the extinct genus Dorcatherium, and by species of the living 
 genus Cervus. The former of these appears to have been 
 furnished with upper canines ; and the animal had antlers 
 supported upon bony peduncles, in both of these respects re- 
 sembling the living Muntjak (Cervus Muntjak} of India. 
 
 The number of known fossil Deer is very considerable, but 
 many forms are only known by fragmentary remains ; and it 
 will be sufficient here to speak of some of the more important 
 examples. 
 
 F g- 35<5. Cervus megaceros (Megaceros Hibernicus). The " Irish Elk. " 
 Post-Pliocene. 
 
 The true Elks, represented by the living Moose (Alces mal- 
 chis, or A. palmatus), are distinguished by their antlers with- 
 out either basal or mesial " tines," but terminated by a great
 
 436 ORDERS OF MAMMALIA. 
 
 palmation digitated on its outer side only. Antlers of a 
 species undistinguishable from the existing Moose have been 
 found not uncommonly in Post-Pliocene deposits in various 
 parts of Europe, but this animal does not make its appearance 
 till after the close of the Glacial period. 
 
 The Reindeer (Cervus tarandus] of Northern Europe and 
 North America is remarkable for being the only member of 
 the Cervidce in which both sexes have horns. The horns are 
 of large size, cylindrical, divided, with basilar and median 
 tynes. Remains of the Reindeer are found, often in con- 
 siderable abundance, in various Post - Pliocene deposits in 
 Europe, extending as far south as the Pyrenees. 
 
 Intermediate between the Reindeer and the Fallow-deer 
 is the celebrated Post-Pliocene species, which is commonly 
 known as the " Irish Elk " ( Cervus megaceros, or Megaceros 
 Hibernicus). This extinct form (fig. 356) is remarkable for its 
 great size and for the enormous dimensions of the spreading 
 antlers, which are expanded towards their extremities, and 
 attain an expanse of as much as ten feet from tip to tip. The 
 Cervus megaceros is exclusively Post-Tertiary, but does not 
 appear, so far as is known with certainty, to have survived into 
 the Prehistoric period. 
 
 The true Stags (Cervus), to which the Irish Elk seems pro- 
 perly to belong, are typified by such species as the Red Deer 
 ( Cervus elaphus) of Europe, and the Wapiti ( Cervus Canadetisis) 
 of North America. The former of these occurs in a fossil 
 state in Post-Pliocene and Recent deposits in Europe, and the 
 latter is represented in accumulations of the same age in 
 America by a closely-allied or identical form. 
 
 The Roebuck (Cervus capreolus), distinguished by its 
 branched antlers, with a median, but without a basilar, tyne, 
 is also known in a fossil condition in Post-Pliocene deposits 
 in Europe, appearing before the commencement of the Glacial 
 period. 
 
 The Miocene and Pliocene deposits, lastly, have yielded 
 remains of Cervidce, which have been referred to various 
 species ; but none of these are sufficiently important to merit 
 especial mention. 
 
 d. CamelopardalidiB. This family includes only a single 
 living animal the Camelopardalis Giraffa, or Giraffe some- 
 times called the Camelopard, from the fact that the skin is 
 spotted like that of the Leopard, whilst the neck is long, and 
 gives it some distant resemblance to a Camel. There are no 
 upper canines in the Giraffe, and both sexes possess two small 
 frontal horns, which, however, are persistent, and remain per-
 
 UNGULATA. 437 
 
 manently covered by a hairy skin, terminated by a tuft of long 
 stiff bristles. The neck is of extraordinary length, but, never- 
 theless, consists of no more than the normal seven cervical 
 vertebrae. The fore-legs appear to be much longer than the 
 hind-legs, and all are terminated by two toes each, the supple- 
 mentary toes being altogether wanting. 
 
 Fossil species of Giraffe have been discovered in the Ter- 
 tiary deposits of the Siwalik Hills in India and in the Upper 
 Miocene of Attica; and a species has also been described 
 from France. This last, however, would seem to be referable 
 to the genus Hettadotherium, founded for the reception of some 
 singular fossils from the Upper Miocene Tertiary of Attica. 
 In this remarkable genus there appear to have been no horns, 
 and 'the teeth present certain resemblances to those of the 
 Antelopes. 
 
 e. Cavicornia. The last family of the Ruminants is that ot 
 the Cavicornia or Bovida, comprising the Oxen, Sheep, Goats, 
 and Antelopes. This family includes the most typical Rumi- 
 nants, and those of most importance to man. The upper jaw 
 in all the Cavicornia is wholly destitute of incisors and canines, 
 the place of which is taken by the hardened gum, against which 
 the lower incisors bite. There are six incisors and two canines 
 in the lower jaw, placed in a continuous series, and the molars 
 are separated by a wide gap from the canines. There are six 
 molars on each side of each jaw. Both sexes have horns, or 
 the males only may be horned, but in either case these ap- 
 pendages are very different from the " antlers " of the Cervida. 
 The horns, namely, are persistent, instead of being deciduous, 
 and each consists of a bony process of the frontal bone or 
 "horn-core" covered by a sheath of horn. The feet are 
 cleft, but are furnished with accessory hoofs placed on the 
 back of the foot. 
 
 The Cavicornia comprise the three families of the Antilopidce, 
 Ovidce, and Bovida. The Antelopes form an extremely large 
 section, with very many species. They are characterised by 
 their slender deer-like form, their long and slender legs, and 
 their simple, cylindrical, annulated, or twisted horns, which are 
 usually confined to the males, but sometimes occur in the 
 females as well. 
 
 The above definition will not apply in all points to some 
 singular extinct forms usually referred to the Antilopidce, nor 
 to one aberrant existing form viz., the Prong-buck (Antilope 
 furcifer, or Antilocapra Americana). This extraordinary and 
 unique species differs from the typical Antelopes in having no 
 accessory hoofs, in having horns which have a snag in front,
 
 438 ORDERS OF MAMMALIA. 
 
 and in the fact that the outer sheath of the horn is deciduous, 
 and not permanent. For these reasons, it has been proposed 
 to place the Prong-buck in a separate family (the Antilocaprida) 
 but it is more convenient here to consider it as an aberrant 
 member of the Antilopida. 
 
 Several species of Antelope have been described from the 
 Miocene and Pliocene deposits of Europe, but none of them 
 are of any special importance. Fossil Antelopes have also 
 been discovered in the bone-caves of Brazil, though no mem- 
 ber of this family is known at the present day as existing in 
 South America. By far the most remarkable fossils, however, 
 which have been generally referred to the Antilopidiz, are those 
 on which the genera Sivatherium and Bramatherium have been 
 founded. 
 
 Sivatherium (fig. 357) is known by the single species S. 
 giganteum, discovered by Dr Falconer and Sir Proby Cautley 
 in the Tertiary deposits of the Siwalik Hills in India. The 
 
 Fig. 357- Skull of Sivatherium gigattttHtn. Pliocene, India. (After Murie.) 
 
 most important peculiarity in Sivatherium is the structure of 
 the horns, of which the animal possessed two pairs. Both 
 pairs of horns were supported by bony " cores," so that there 
 can be no hesitation in referring Sivatherium to the group of
 
 UNGULATA. 439 
 
 the Cavicornia. The anterior horns, as shown by the shape 
 of the horn-cores, were simple; and if the posterior horns had 
 been of a similar form, then Sivatherium might have been 
 fairly regarded as merely a gigantic four -horned Antelope, 
 similar to the living Antilope (Tetraceros) quadricornis of 
 India. The posterior horns, however, are not only much 
 larger than the anterior, but they possess two snags or 
 branches a peculiarity not to be paralleled amongst existing 
 Cavicornia, except in the Prong-buck. Dr Murie, however, in 
 an admirable paper on the affinities of Sivatherium, has drawn 
 attention to the fact that the Prong-buck sheds the sheath of 
 its horns annually, and has suggested that this may have also 
 been the case with the extinct form. This hypothesis is ren- 
 dered probable, amongst other reasons, by the fact that no 
 sheath has as yet been discovered surrounding the horn-cores 
 of either pair of horns in the Sivatherium. Upon the whole, 
 therefore, the above-mentioned zoologist would refer Siva- 
 therium to a distinct group which he terms Sivatheridce, and 
 regards as being most nearly related to the Antilocapridce. 
 
 Bramatherium has been found in deposits of the same age as 
 Sivatherium, with which it agrees in its colossal dimensions 
 and its possession of two pairs of hollow horns. It differs from 
 Sivatherium, however, in certain details of minor importance. 
 
 The Sheep and Goats (Ovidce) have mostly horns in both 
 sexes, and the horns are generally curved, compressed, and 
 turned more or less backwards. The body is heavier, and the 
 legs shorter and stouter, than in the true Antelopes. In the 
 true Goats (Capra) both sexes have horns, and there are no 
 lachrymal sinuses. The true Sheep (Oms) are destitute of a 
 beard, and the horns are generally twisted into a spiral. Horns 
 may be present in both sexes, or in the males only. 
 
 The Sheep and Goats are of no importance as fossils, unless, 
 indeed, as believed by high authorities, the Musk-ox should be 
 referred to the Ovidce. Here, however, it will be considered 
 as belonging to the Bovidcz. Remains of both Sheep and Goats 
 have been discovered in various Post-Tertiary deposits in 
 Europe, but they present nothing of special interest. 
 
 The true Oxen (Bovidce) are distinguished by having simple 
 horns, of a rounded shape, not twisted into a spiral. A few 
 remains of Bovidce, have been found in deposits of Pliocene 
 age, but the Oxen are essentially Post-Pliocene and Recent. 
 The most important Fossil Oxen are the Urus, the Aurochs, 
 the Bos longifrons of Owen, and the Musk-ox. 
 
 The Aurochs or Lithuanian Bison (Bos bison] can hardly be 
 considered as a fossil form, as it occurs in a living state in
 
 440 ORDERS OF MAMMALIA. 
 
 Europe at the present day. Remains, however, of this large 
 ox are found in various prehistoric deposits. 
 
 The Bos longifrons of Owen, or " Small Short-horn," is in a 
 similar position to the Aurochs. According to Mr Boyd 
 Dawkins, this form (which is identical with the Bos frontosus 
 of Nilsson) has not been proved to occur in any Post-Pliocene 
 deposit, though it occurs plentifully in the bone-caves and 
 alluvia of the Recent or prehistoric period. It is believed by 
 the same high authority that the Bos longifrons is the ancestor 
 of our present Welsh or Scotch Cattle. 
 
 The Urus or Wild Bull (Bos primigenius), though much 
 larger than our ordinary oxen, is believed to be specifically 
 undistinguishable from the domestic Ox (Bos taurus), and it 
 was probably the parent of the larger varieties of European 
 
 Fig- 358. Skull of the Urus (Bos frimigenius). Post-Pliocene and Recent. 
 
 Oxen. It was a contemporary of the Mammoth, Woolly 
 Rhinoceros, Cave Lion, Cave Bear, Irish Elk, and other Post- 
 Pliocene Mammals, and it was in existence up to at least the 
 twelfth century. 
 
 The last of the Oxen which deserves notice is the curious 
 Musk-ox (Ovibos moschatus). This singular animal is at the 
 present day a native of Arctic America, and is remarkable for 
 the great length of the hair. It is called the Musk-ox, because 
 it gives out a musky odour. Like the Reindeer, the Musk-ox 
 had formerly a much wider geographical range than it has at 
 present the conditions of climate which are necessary for its 
 existence having at that time extended over a very much
 
 HYRACOIDEA PROBOSCIDEA. 441 
 
 larger area than at present. The Musk-ox, in fact, in Post 
 Tertiary times is known to have extended over the greater part 
 of Europe, remains of it occurring abundantly in certain of the 
 bone-caves of France. As already mentioned, high authorities 
 regard the Musk-ox as being truly a large Sheep, and as being, 
 therefore, referable to the Ovid<z. 
 
 CHAPTER XXXIX. 
 
 ORDERS OF MAMMALIA Continued. 
 
 HYRACOIDEA AND PROBOSCIDEA. 
 
 ORDER VII. HYRACOIDEA. This is a very small order which 
 has been constituted by Huxley for the reception of two or 
 three little animals, which make up the single genus Hyrax. 
 These have been usually placed in the immediate neighbour- 
 hood of the Rhinoceros, to which they have some decided 
 affinities, and they are still retained by Owen in the section of 
 the Perissodactyle Ungulates. 
 
 The order is distinguished by the following characters : 
 There are no canine teeth, and the incisors of the upper jaw 
 are long and curved, and grow from permanent pulps, as they 
 do in the Rodents (such as the Beaver, Rat, &c.) The molar 
 teeth are singularly like those of the Rhinoceros. According 
 to Huxley, the dental formula of the aged animal is 
 
 The fore-feet are tetradactylous, the" hind-feet tridactylous, and 
 all the toes have rounded hoof-like nails, with the exception of 
 the inner toes of the hind-feet, which have an obliquely-curved 
 nail. There are no clavicles. The nose and ears are short, 
 and the tail is represented by a mere tubercle. 
 
 The living species of Hyrax inhabit Syria, Palestine, and 
 South Africa. No fossil representative of the order has as yet 
 been discovered. The Hyracotherium of the Eocene Tertiary, 
 however, received its name from its supposed affinities to the 
 living Hyrax. 
 
 ORDER VIII. PROBOSCIDEA. The eighth order of Mammals 
 is that of the Probostidea, comprising no other living animals
 
 442 
 
 ORDERS OF MAMMALIA. 
 
 except the Elephants, but including also the extinct Mastodon 
 and DeinotJierium. 
 
 The order is characterised by the total absence of canine 
 teeth ; the molar teeth are few in number, large, and trans- 
 versely ridged or tuberculate ; incisors are always present, and 
 grow from persistent pulps, constituting long tusks (fig. 359). 
 
 Fig. 359. Skull of the Indian Elephant (Elefhas Indicia), i Tusk-like upper incisors ; 
 m Lower jaw, with grinding molars, but without incisors ; Nostrils, placed at the ex- 
 tremity of the proboscis. 
 
 In all the Elephants there are two of these tusk-like incisors in 
 the upper jaw, and the lower jaw is without incisor teeth. In 
 the Deinotherium this is reversed, there being two tusk-like 
 lower incisors and no upper incisors. In the Mastodons, the 
 incisors are usually developed in the upper jaw, and form tusks, 
 as in the Elephants ; but sometimes there are both upper^and 
 lower incisors, and both are tusk-like. The nose is prolonged 
 into a cylindrical trunk, movable in every direction, highly 
 sensitive, and terminating in a finger-like prehensile lobe (fig. 
 359). The nostrils are placed at the extremity of the proboscis. 
 The feet are furnished with five toes each, but these are only 
 partially indicated externally by the divisions of the hoof. The 
 feet are furnished with a thick pad of integument, forming the
 
 PROBOSCIDEA. 
 
 443 
 
 palms of the hand and the soles of the feet. There are no 
 clavicles. The testes are abdominal throughout life. There 
 are two teats, and these are placed upon the chest. 
 
 The order Proboscidea comprises the three genera, Elephas 
 (with both living and extinct representatives), Mastodon, and 
 Deinotherium, the two latter being extinct. The order came 
 into existence in the Miocene period, in which it is represented 
 by all these three genera. The genus Elephas comprises the 
 living Asiatic and Indian Elephants. In all the Elephants, 
 whether living or extinct, the " tusks " are formed by an enor- 
 mous development of the upper incisors. The milk-tusks are 
 early shed, and never attain any great size. The permanent 
 tusks, however, grow from persistent pulps, attaining in old 
 males an enormous size. The lower incisors are absent, and 
 there are no other teeth in the jaws except the large molars, 
 which are usually two in number on each side of each jaw. 
 The molar teeth are of very large size, and are composed of 
 a number of transverse plates of enamel united together by 
 dentine. In the Indian Elephant the transverse ridges of 
 enamel are narrow and undulating, whilst in the African 
 Elephant they enclose lozenge-shaped intervals. 
 
 The surfaces of the molars are approximately flat, and the 
 plates of enamel form patterns which are very characteristic of 
 
 Fig. 360. Molar of the Mammoth (ElepJias primigeuius), upper jaw, right side, 
 half natural size. Post- Pliocene, a Grinding surface ; b Side view. 
 
 the different species. Subjoined are illustrations of the molars 
 of three of the most important Post-Pliocene Elephants (figs. 
 360-362).
 
 444 ORDERS OF MAMMALIA. 
 
 No Elephant has as yet been discovered in the Miocene 
 deposits of Europe, but six species are known from strata of 
 this age in India. In the Pliocene period, Europe possessed 
 its Elephants, of which the most important is the Elephas 
 antiquns (fig. 362). This is essentially a southern form, and 
 is found in Pliocene strata in France and Italy. It survived 
 the Glacial period, and is found abundantly in various Post- 
 Pliocene deposits. It abounded in Post-Pliocene times chiefly 
 in Southern Europe, south of the Alps and Pyrenees ; and it is 
 only on the northern edge of this area that its remains are 
 found commingled with those of the Mammoth. 
 
 Fig. 361. Molar tooth of Elephas meridionalis, one-third of natural size. 
 Pliocene and Post-Pliocene. (After Lyell.) 
 
 Fig. 362. Molar tooth of Elephas antiquns. Penultimate molar, one-third 01 
 natural size. Post -Pliocene and Pliocene. (After Lyell.) 
 
 Of the Post-Pliocene Elephants by far the best-known and 
 most important is the Mammoth (Elephas primigenius). This 
 remarkable form (fig. 363) was essentially northern in its dis- 
 tribution, never passing south of a line drawn through the 
 Pyrenees, the Alps, the northern shores of the Caspian, Lake 
 Baikal, Kamschatka, and the Stanovi Mountains (Dawkins). 
 It occurs in the prae-Glacial forest-bed of Cromer in Norfolk, 
 survived the Glacial period, and is found abundantly in Post- 
 Glacial deposits in France, Germany, Britain, Russia in Europe, 
 Asia, and North America, being often associated with the Rein-
 
 PROBOSCIDEA. 
 
 445 
 
 deer, Lemming, and Musk-ox. That it survived into the ear- 
 lier portion of the human period is unquestionable, its remains 
 having been found in a great number of instances associated 
 
 with implements of human manufacture ; whilst in one instance 
 a recognisable portrait of it has been discovered, carved on 
 bone. From its great abundance in Siberia, it might have been 
 safely inferred that the Mammoth was able to endure a much
 
 446 ORDERS OF MAMMALIA. 
 
 colder climate than either of the living species. This inference, 
 however, has been rendered a certainty by the discovery of the 
 body of more than one Mammoth embedded in the frozen soil 
 of Siberia. These specimens had been so perfectly preserved 
 that even microscopical sections of some of the tissues could 
 be made ; and in one case even the eyes were preserved. 
 From these specimens, we know that the body of the Mam- 
 moth was covered with long woolly hair. 
 
 Amongst other Elephants which occur in Post-Pliocene de- 
 posits, may be mentioned, as of special interest, the pigmy 
 Elephants of Malta. One of these the Elephas Melitensis, 
 or so-called " Donkey-Elephant " was not more than four 
 and a half feet in height. The other the Elephas Falconeri, 
 of Busk was still smaller, its average height at the withers not 
 exceeding two and a half to three feet. 
 
 The Mastodons in most respects closely resemble the true 
 Elephants, from which they are distinguished by their denti- 
 tion. As in the Elephants, the upper incisors grow from per- 
 manent pulps, and constitute long tusks; but in the majority 
 of cases the Mastodons also possess lower incisors as well. 
 
 Fig. 364. Third milk-molar of the left side of the upper jaw of Mastodon 
 Arverntnsis, showing the grinding surface. Pliocene. (After Lyell.) 
 
 The two lower incisors, however, though tusk-shaped, did 
 not develop themselves to any extent, and often disappeared 
 in adult life. A more important distinction between the Ele- 
 phants and Mastodons is that the molar teeth of the latter are 
 not only more numerous, but have the peculiarity that their 
 crowns are furnished with nipple-shaped eminences or tubercles 
 placed in pairs (fig. 364). The Mastodons appear to have 
 commenced their existence in the Miocene period, being re-
 
 CARNIVORA. 
 
 447 
 
 presented in strata of this age by four European and three 
 Indian species. In the Pliocene period, also, remains of 
 Mastodon are not infrequent ; 
 and in North America the great 
 M. Ohioticus occurs plentifully in 
 deposits of Post-Pliocene age. 
 
 The last of the Probosridea is 
 the remarkable Miocene Mam- 
 mal known as the Deinotherium, 
 which is still referred by some 
 high authorities to the order 
 Sirenia. 
 
 This extraordinary animal has 
 hitherto only been found in 
 Miocene deposits, and little is 
 known of it except its enormous 
 skull (fig. 365). Molars and 
 praemolars were present in each 
 jaw, and the upper jaw was des- 
 titute of canines and incisors, 
 very large tusk-like incisors, which were not directed forwards 
 as in the true Elephants, but were bent abruptly downwards 
 (fig. 365). The animal must have attained an enormous size, 
 and it is probable that the curved tusks were used either in 
 digging up roots or in mooring the animal to the banks of 
 rivers, for it was probably aquatic or semi-aquatic in its habits. 
 
 Several species of Deinotherium have been indicated as 
 occurring in Europe, and a species has been noticed in the 
 Tertiary deposits of the Siwalik Hills by Dr Falconer and Sir 
 Proby Cautley. 
 
 Fig. 
 
 365. Skull of Deinotherium 
 giganteum. Miocene Tertiary. 
 
 In the lower jaw were two 
 
 CHAPTER XL. 
 
 ORDERS OF MAMMALIA Continued. 
 CARNIVORA. 
 
 ORDER IX. CARNIVORA. The ninth order of Mammals is that 
 of the Carnivora, comprising the Fera, or Beasts of Prey, along 
 with the old order of the Pinnipedia, or Seals and Walruses, 
 these latter being now universally regarded as merely a group 
 of the Carnivora modified to lead an aquatic life.
 
 448 ORDERS OF MAMMALIA. 
 
 The Carnivora are distinguished by always possessing two 
 sets of teeth, which are simply covered by enamel, and are 
 always of three kinds incisors, canines, and molars differ- 
 ing from one another in shape and size. The incisors are 
 
 generally - - (except in some Seals) ; the canines are always 
 3 3 
 
 and are invariably much larger and longer than the in- 
 cisors. The prsemolars and molars are mostly furnished with 
 cutting or trenchant edges ; but they graduate from a cutting 
 to a tuberculate form, as the diet is strictly carnivorous, or 
 becomes more or less miscellaneous. In the typical Carnivores 
 (such as the Lion and Tiger), the last tooth but one in the 
 upper jaw, and the last tooth in the lower jaw, are known as 
 the " carnassial " teeth, having a sharp cutting edge adapted 
 for dividing flesh, and generally a more or less developed tu- 
 berculated heel or process. A varying number, however, of the 
 molars and praemolars may be " tuberculate," their crowns 
 being adapted for bruising rather than cutting. As a general 
 rule, the shorter the jaw, and the fewer the praemolars and 
 molars, the more carnivorous is the animal. The jaws are so 
 articulated as to admit of vertical but not of horizontal move- 
 ments ; the zygomatic arches are greatly developed to give 
 room for the powerful muscles of the jaws ; and the orbits are 
 not separated from the temporal fossae. 
 
 In all the Carnivora the clavicles are either altogether want- 
 ing, or are quite rudimentary. The toes are provided with 
 sharp curved claws. 
 
 The order Carnivora is divided into three very natural sec- 
 tions : 
 
 Section I. Pinnigrada or Pinnipedia. This section comprises 
 the Seals and Walruses, in which the fore and hind limbs are 
 short, and are expanded into broad, webbed swimming paddles 
 (fig. 366, B.) The hind-feet are placed very far back, nearly 
 in a line with the axis of the body, and they are more or less 
 tied down to the tail by the integuments. 
 
 Section //. Plantigrada. This section comprises the Bears 
 and their allies, in which the whole, or nearly the whole, of the 
 foot is applied to the ground, so that the animal walks upon 
 the soks of the feet (fig. 366, A.) 
 
 Section III. Digitigrada. This section comprises the Lions, 
 Tigers, Cats, Dogs, &c., in which the heel of the foot is raised 
 entirely off the ground, and the animal walks upon the tips of 
 the toes (fig. 366, C.) 
 
 As regards their general distribution in time, if the little Mi-
 
 CARNIVORA. 
 
 449 
 
 crolestes of the Upper Trias be Marsupial, as is almost certainly 
 the case, then the order Carnivora is comparatively modern, the 
 earliest undoubted remains having been found in the Eocene 
 Tertiary. In the Eocene period, however, the families of the 
 CanidcR and Felidce appear to have been already differentiated. 
 The Ursidce, Viverrid(z,Mustelid(E,Hy(Ziiid<z, xtAPhocida, do not 
 seem to have made their appearance before the Miocene period. 
 In the Pliocene and Post-Pliocene periods almost all the existing 
 types of the Carnivora are represented by extinct forms, whilst 
 in the latter the remains of various living species are found 
 associated with other animals which have at the present day 
 entirely passed away. In the following are given the charac- 
 ters and chief fossil forms of the families of the Carnivora. 
 
 Fig. 366. Feet of Carnivora (after Owen). A, Plantigrada, Foot of Bear ; 
 B, Pinnigrada, Hind-feet of Seal; C, Digitigrada, Foot of Lion. 
 
 SECTION I. PINNIGRADA. This section of the Carnivora 
 comprises the amphibious Seals and Walruses, which differ 
 from the typical Carnivores merely in points connected with 
 their semi-aquatic mode of life. The body is elongated, some- 
 what fish-like in shape, and terminated by a short conical tail. 
 All the four limbs are present, but they are very short, and the 
 five toes of each foot are united by the integuments, so as to 
 form powerful swimming-paddles. The hind-feet are placed 
 very far back, their axis nearly coinciding with that of the body 
 (fig. 366, B). Owing to this circumstance the hinder end of 
 the body forms an admirable swimming apparatus, similar in 
 its action to the horizontal tail-fin of the Cetacea and Sirenia. 
 The tips of the toes are furnished with strong claws, but the 
 powers of terrestrial locomotion are very limited. The ears are
 
 450 ORDERS OF MAMMALIA. 
 
 of small size, and are mostly only indicated by small apertures, 
 which the animal has the power of closing when under water. 
 The bones are light and spongy, and beneath the skin is a layer 
 of fat or blubber. The dentition varies ; but teeth of three 
 kinds are always present, in the young animal at any rate. 
 The canines are always long and pointed, and the molars are 
 generally furnished with sharp cutting edges. 
 
 The Seals (Photida) are distinguished by having incisor 
 teeth in both jaws, and by the fact that the canines are not 
 immoderately developed. As regards their distribution in 
 time, the Seals are indicated as occurring in the Miocene and 
 Pliocene Tertiary ; but their remains are by no means as 
 abundant as might have been anticipated from their aquatic 
 habits. Remains of Seals, however, are by no means very rare 
 in Post'Tertiary deposits. 
 
 The Walruses (Trichecidce) are distinguished from the Seals 
 by their enormously -developed upper canines, which grow 
 from persistent pulps, and constitute great pointed tusks. 
 Remains of the Walrus have been found in some of the later 
 Tertiary deposits, but they are merely fragmentary, and are of 
 little importance. 
 
 SECTION II. PLANTIGRADA. The Carnivorous animals be- 
 longing to this section apply the whole or the greater part of 
 the sole of the foot to the ground (fig. 366, A) ; and the por- 
 tion of the sole so employed is destitute of hairs in most 
 instances (the sole is hairy in the Polar Bear). 
 
 The typical family of the Plantigrade Carnivora is that of 
 the Ursida or Bears, in which the entire sole of the foot is 
 applied to the ground in walking. The Ursida are much less 
 purely carnivorous than the majority of the order, and, in 
 accordance with their omnivorous habits, the teeth do not 
 exhibit the typical carnivorous characters. The incisors and 
 canines have the ordinary carnivorous form, but the " carnas- 
 sial" or sectorial molar has a tuberculate crown instead of a 
 sharp cutting edge. The dental formula is 
 
 /3=3 ; c *=*-.** 4=4; ; 2 =? = 42. 
 33 i i 44 33 
 
 The claws are large, strong, and curved, but are not retrac- 
 tile. The tongue is smooth ; the ears small, erect, and rounded ; 
 the tail short ; the nose forms a movable truncated snout ; and 
 the pupil is circular. 
 
 The oldest known member of the Ursida is the Atxphicyon 
 of the Miocene Tertiary. In this genus the molars are tuber- 
 culated, as they are in the true Bears ; but, unlike the latter,
 
 CARNIVORA. 
 
 451 
 
 there is an additional molar on each side of the upper jaw. 
 Several species have been described from deposits of Middle 
 Tertiary age. 
 
 The true Bears ( Ursus) do not appear, so far as is certainly 
 known, to have commenced their existence before the Pliocene 
 period, the best-known species of this epoch being the Ursus 
 Arvernensis. In the Post-Tertiary period the two most im- 
 portant species are the Ursus priscus and Wrsus spelaus, of 
 which the former is probably identical with the living Grizzly 
 Bear ( Ursus ferox). The Cave-bear (Ursus spelceus, fig. 367) 
 
 Fig. 367. Skull of Ursiis sfelans. Post-Pliocene. 
 
 is a gigantic Bear, which, as its name implies, has been found 
 mainly in cavern-deposits. The size of this species con- 
 siderably exceeded that of any existing Bear, and it is espe- 
 cially characteristic of the later portion of the Post-Pliocene 
 period. 
 
 More or less nearly allied to the true Bears are the little 
 living animals which are known as Coatis (Nasua), Racoons 
 (Procyon\ and Kinkajous (Cercoleptes}, all of which at the 
 present day are confined to the American continent. The 
 bone-caves of Brazil have yielded remains of two species of 
 Nasua, and a Racoon has been found in Post-Tertiary de- 
 posits in Illinois. No certain remains of Cercoleptes are known ; 
 but the Arctocyon primoevus of the Eocene Tertiary of France 
 has been compared with the existing Kinkajous. 
 
 The only remaining family of the Plantigrada is that of the 
 Melidce or Badgers, characterised by their elongated bodies 
 and short legs, and by the fact that the carnassial tooth has a 
 partly cutting edge, and is not wholly tuberculate as in the 
 Bears.
 
 452 ORDERS OF MAMMALIA. 
 
 Remains of Badgers have been found in Post-Tertiary de- 
 posits in Europe, and they are probably referable to the exist- 
 ing Meles taxus. The Gluttons (Gulo) are also only known 
 from Post-Tertiary accumulations, and the so-called Gulo 
 spekeus of the cavern-deposits of Europe does not appear to 
 be separable from the common Wolverine (Gulo luscus). 
 
 SECTION III. DIGITIGRADA. In this section of the Carni- 
 vora the heel is raised above the ground, with the whole or 
 the greater part of the metacarpus, so that the animals walk 
 more or less completely on the tips of the toes (fig. 366, C). 
 No absolute line, however, of demarcation can be drawn 
 between the Plantigrade and Digitigrade sections of the Car- 
 nivora, since many forms (e.g., Mustelida and Viverrida) ex- 
 hibit transitional characters, and it has even been proposed 
 to place these in a separate section, under the name of Semi- 
 plantigrada. 
 
 The first family of the Digitigrada is that of the Mustelida 
 or Weasels, including a number of small Carnivores, with short 
 legs, elongated worm-like bodies, and a peculiar gliding mode 
 of progression (hence the name of Vermiformes, sometimes 
 applied to the group). 
 
 The most important fossil forms of the Mustelida belong to 
 the genera Mustela (comprising the Weasels and Stoats), and 
 Lutra (comprising the Otters). The Weasels appear to have 
 come into existence in the Miocene period, being represented 
 by several species in deposits belonging to this age. They 
 occur also in Pliocene and Post-Tertiary deposits. The Otters 
 are likewise known by their remains in strata of Miocene and 
 Pliocene age, and they occur in Post-Tertiary times. 
 
 The second family of the Semi-plantigrade Carnivores is that 
 of the Viverrida, the Civets and Genettes. They are all of 
 moderate size, with sharp muzzles and long tails, and more or 
 less striped, or banded, or spotted. The carnassial molar is 
 trenchant ; the canines are long, sharp, and pointed ; and the 
 tongue is roughened by numerous prickly papillae. The claws 
 are semi-retractile, and the pupils can contract, on exposure to 
 light, till they resemble a mere line. 
 
 The genus Palceonyctu of De Blainville has been founded 
 upon a lower jaw obtained from the Eocene Tertiary of France, 
 and apparently referable to this family. The Miocene rocks 
 of France have yielded the remains of several species which 
 have been placed in the existing genus Viverra. Lastly, the 
 Hyanictis and Ictitherium of the Upper Miocene deposits of 
 Attica, appear to be intermediate in their characters between 
 the ViverridcK and Hycenidce.
 
 CARNIVORA. 453 
 
 Forming a transition between the Viverridtz and the Felidce 
 is the family of the Hyanidce, distinguished by the fact that, 
 alone of all the Carni-vora, both pairs of feet have only four 
 toes each. The hind-legs are shorter than the fore-legs, so that 
 the trunk sinks towards the hind-quarters, and the tail is short. 
 The tongue is rough and prickly. The head is extremely 
 broad, the muzzle rounded, and the muscles of the jaw ex- 
 tremely powerful and well developed. The claws are non- 
 retractile. All the molars are trenchant except the last upper 
 molar, which is tuberculate. The upper carnassial has a small 
 internal tubercle, and the lower carnassial is wholly trenchant. 
 
 The earliest fossil member of the Hyanida is the Hyana 
 Hipparionum of the Pliocene of France, and other species have 
 been obtained in the same country from strata of the same age. 
 Of the Post-Tertiary Hyaenas, the best known and most im- 
 portant is the great Cave-hyaena (Hycena spelcea, fig. 368). 
 This species in many respects resembles the Hyana Croatia of 
 
 Fig. 368. Skull of Hycena spelcea. Post-Pliocene. 
 
 South Africa ; and it inhabited Britain and the greater part of 
 Europe during the Post-Pliocene period. Its remains often 
 occur in great abundance, and no doubt can be entertained as 
 to its having survived into the human period. 
 
 Here may be considered the genus Hyanodon, which cannot 
 be referred either to the Hyanidcz or Felidce. This remark- 
 able genus has been detected in the Eocene Tertiary of Eng- 
 land, and the Miocene in France, and is noticeable for the 
 great number of its molars, as compared with the existing 
 Felidcs. The dental formula is 
 
 All the praemolars and molars possessed trenchant edges,
 
 454 ORDERS OF MAMMALIA. 
 
 and were compressed, so that the dentition of this extinct genus 
 is more highly carnivorous than is the case with any existing 
 Carnivore. 
 
 The next family is that of the Canidce, comprising the Dogs, 
 Wolves, Foxes, and Jackals. The members of this family are 
 characterised by having pointed muzzles, smooth tongues, and 
 non-retractile claws. The fore-feet have five toes each, 
 
 the hind-feet have only four. The molar teeth are , 
 
 sometimes , and of these, two or three on each side are 
 
 tuberculate. The carnassial has a tolerably large heel or 
 process. 
 
 Fig. 369. Skull of Jackal (Cants aureus). 
 
 The true Dogs and the Wolves, forming the genus Cants, 
 and the Foxes ( Vulpes), can hardly be distinguished from one 
 another, as fossils, with any certainty. The oldest known 
 member of the Canida is the Canis Parisiensis of the Upper 
 Eocene Tertiary (Gypseous series of Montmartre), which ap- 
 pears to be nearly allied to the existing Arctic Fox ( Vulpes 
 lagopus}. Other species of Canis occur in the Miocene, Plio- 
 cene, and Post-Tertiary deposits ; and the so-called Canis 
 familiaris fossilis of the caves of Germany, Belgium, and France, 
 appears to be very nearly allied to the domestic Dog of the 
 present day. Similarly, the so-called Canis speteus, and Canis 
 vulpes spdcsus are nearly, if not quite, identical with the exist- 
 ing Wolf and Fox of Europe. Lastly, the Galcecynus of the 
 Pliocene schists of Oeningen, and the Palceocyon (Lund) of the 
 Brazilian caves, are two extinct genera which may be provision- 
 ally referred to the Canidas. 
 
 The last group of the Digitigrada is that of the Fclida, or Cat 
 tribe, comprising the most typical members of the whole order 
 of the Carnivora, such as the Lions, Tigers, Leopards, Cat, and 
 Panthers. The members of this family all walk upon the tips
 
 CARNIVORA. 45 5 
 
 of their toes, the soles of their feet being hairy, and the whole 
 of the metacarpus and heel being raised above the ground (fig. 
 366, C). The jaws are short, and, owing to this fact, and to 
 the great size of the muscles concerned in mastication, the head 
 assumes a short and rounded form, with an abbreviated and 
 rounded muzzle. The molars and prsemolars are fewer in 
 number than in any other of the Carnivora (hence the short- 
 ness of the jaws), and they are all trenchant, except the last 
 molar in the upper jaw, which is tuberculate. The upper car- 
 nassial has three lobes, and a blunt heel or internal process. 
 The lower carnassial has two cutting lobes, and no internal 
 process. According to Owen, the dental formula is 
 
 The legs are nearly of equal size, and the hind-feet have only 
 four toes each, whilst the fore-feet have five. All the toes are 
 furnished with strong, curved, retractile claws, which, when not 
 in use, are withdrawn within sheaths by the action of elastic 
 ligaments, so as not to be unnecessarily blunted. 
 
 Fig. 37 o.-Skull of Lion (Felts ho). 
 
 The FelidcB probably came into existence in the Eocene 
 period ; but there is considerable uncertainty as to the remains 
 which have been cited from deposits of this age. Several spe- 
 cies of Felis have been indicated as occurring in Miocene 
 deposits, and still more numerous forms have been determined 
 from Pliocene strata. The most important and best known of 
 the Post-Pliocene Felldce is the great Cave-lion (Felis spelcEa\ 
 which does not appear to be separable by any character of im- 
 portance from the existing Lion (Felis leo). This species in- 
 habited Britain in times subsequent to the Glacial period, and
 
 456 ORDERS OF MAMMALIA. 
 
 was a contemporary of the Cave-hyaena, Cave-bear, Woolly 
 Rhinoceros, and Mammoth. There can also be no doubt but 
 that the Cave -lion survived into the earlier portion of the 
 human period. 
 
 The only other member of the Felida which deserves men- 
 tion, is the " sabre-toothed " Tiger (Machairodus), species of 
 which are known to have existed from the Miocene period up 
 to the Post-Pliocene. In this singular genus the upper canines 
 were greatly elongated, trenchant, and sabre - shaped, with 
 finely-serrated margins. There is no upper true molar, and 
 the praemolars are reduced to two on each side of each jaw. 
 The dental formula is 
 
 3~3 i i , 22 o o _ 
 
 3 3 I 1 ' 2 2 I I 
 
 Species of Machairodus must have been as large as a Lion ; 
 and the genus is not only European, but is also represented by 
 a form in South America, and another in India. 
 
 CHAPTER XLI. 
 
 ORDERS OF MAMMALIA Continued. 
 
 RODENTIA, CHEIROPTERA, AND INSECTIVORA. 
 
 ORDER X. RODENTIA. The tenth order of Mammals is that 
 of the Rodents, often spoken of as Glires, comprising the Mice, 
 Rats, Squirrels, Rabbits, Hares, Beavers, &c. 
 
 The Rodent ia are characterised by the possession of two 
 long curved incisor teeth in each jaw, separated by a wide in- 
 terval from the molars. The lower jaw never has more than 
 two of these incisors, and the upper jaw very rarely; but some- 
 times there are four upper incisors. There are no canine 
 teeth, and the molars and praemolars are few in number (rarely 
 more than four on each side of the jaw). The feet are usually 
 furnished with five toes each, all of which are armed with claws; 
 and the hallux, when present, does not differ in form from the 
 other digits. 
 
 The most characteristic point about the Rodents is to be 
 found in the structure of the incisors, which are adapted for 
 continuous gnawing hence the name of Rodentia. The in- 
 cisor teeth are commonly two in each jaw, and they grow from
 
 RODENTIA. 
 
 457 
 
 persistent pulps, so that they continue to grow throughout the 
 life of the animal. They are large, long and curved (fig. 371, 
 
 Fig. 371. A, Skull of the Beaver (after Owen). B, Diagram of the incisor teeth 01 
 a Rodent, showing the chisel-shaped point : a Enamel ; d Dentine. 
 
 B), and are covered anteriorly by a plate of hard enamel. The 
 back part of each incisor is composed only of the comparatively 
 soft dentine, so that when the tooth is exposed to attrition, the 
 soft dentine behind wears away more rapidly than the hard 
 enamel in front. The result of this is that the crown of the 
 tooth acquires by use a chisel-like shape, bevelled away behind, 
 and the enamel forms a persistent cutting edge (fig. 371). 
 
 The gnawing action of the incisors is assisted by the articu- 
 lation of the lower jaw, the condyle of which is placed longi- 
 tudinally and not transversely, so that the jaw slides backwards 
 and forwards. The molars, consequently, have flat crowns, the 
 enamelled surfaces of which are always arranged in transverse 
 ridges, in opposition to the antero-posterior movement of the 
 jaw. 
 
 The earliest known traces of the Rodents in past time have 
 been discovered in the Eocene Tertiary. The order comprises 
 a large number of families, only the more important of which 
 can be noticed here. 
 
 Fam. i. Leporidce. In this family are the Hares and Rabbits 
 (Lepus), and the Pikas (Lagomys), distinguished amongst the 
 Rodents by the possession of two small incisors in the upper 
 jaw, placed behind the central chisel-shaped incisors, so that 
 there are four upper incisors in all. The molars and prsemolars 
 are rootless, and the dental formula is 
 
 . 2 2 o o T, ^ T, T, 
 
 '!=?; *?%* *"$' *"-* 
 
 The clavicles are imperfect. The fore-legs are furnished
 
 45 8 ORDERS OF MAMMALIA. 
 
 with five toes, and are considerably shorter than the hind-legs, 
 which have only four toes. The two orbits communicate by 
 an aperture in the septum. Generally there is a short erect tail. 
 
 Species of Lepus, more or less nearly allied to the existing 
 Hares and Rabbits, are found in the Miocene and Pliocene 
 Tertiary of Europe ; whilst the Post-Tertiary deposits of the 
 same area have yielded remains almost or quite identical with 
 living species. The cave-deposits of Brazil have also yielded 
 the bones of a hare very nearly allied to the living Lepus 
 Brasiliensis. The Calling Hares or Pikas (Lagomys), which 
 are distinguished by their nearly complete clavicles and rudi- 
 mentary tail, and which at the present day are characteristic of 
 Siberia, are found in the Pliocene of Oeningen and in Post- 
 Tertiary deposits in Britain and Southern Europe. 
 
 Fam. 2. Cavidce. In this family are the living Capybaras 
 (Hydrochcsrus\ Agoutis (Dasyprocta), Pacas (Ccelogenys), &c, 
 characterised by their absence of clavicles, their rudimentary 
 tail, their unguiculate toes, and their general possession of 
 eight rootless molars in each jaw. Almost all the existing 
 members of this family belong to South America, and this 
 continent has been peopled during Post-Tertiary times with 
 numerous species more or less nearly allied to living forms. 
 Thus, the Brazilian bone-caves have yielded to the researches 
 of Lund remains of Guinea-pigs (Ancema), Agoutis, Pacas, and 
 Capybaras, all of which appear to belong to extinct species. 
 
 Fam. 3. Hystricida. In this family are the well-known Por- 
 cupines, distinguished from the other Rodents by the fact that 
 the body is covered with long spines or " quills," mixed with 
 bristly hairs. They have four molars on each side of each jaw, 
 and they possess imperfect clavicles. 
 
 Remains of Porcupines allied to the existing species of 
 Hystrix have been detected in the Pliocene and Post-Pliocene 
 deposits of Europe and Asia. On the other hand, the bone- 
 caves of Brazil have yielded the remains of a Porcupine with 
 a prehensile tail, allied to the living Cercolabes of South 
 America. 
 
 Fam. 4. Castoridce. The best-known example of this family 
 is the Beaver (Castor fiber). The distinctive peculiarities of 
 the family are the possession of distinct clavicles, the posses- 
 sion of five toes to each foot, and the fact that the hinder feet 
 are mostly webbed, adapting the animal to a semi-aquatic life. 
 
 The genus Castor, comprising the existing Beaver, and 
 characterised by the possession of a flattened scaly tail, is re- 
 presented by fossil species in the Miocene and Pliocene de- 
 posits of Europe. The Castor spelaus of the European cave-
 
 RODENTIA. 459 
 
 deposits does not appear to be specifically separable from the 
 existing Beaver (Castor fiber]. The great Trogontherium (fig. 
 372) of the Post-Tertiary de- 
 posits of Europe, also appears 
 to be generically inseparable 
 from Castor. The Castoroides 
 Ohioensis of the Post-Tertiary 
 period of North America 
 seems to be rightly referred 
 to a separate genus. The 
 only known species attained 
 a comparatively gigantic size, 
 reaching a length of about 
 
 five feet. The Chalicomys of the European Miocene and 
 Pliocene deposits appears to be nearly related to the Beavers ; 
 and the bone-caves of Brazil have yielded a species of Myopot- 
 ajmis nearly allied to the existing Coypu (Myopotamus coypus) 
 of South America. 
 
 Fain. 5. Murida. The fifth family of Rodents is that of the 
 Afuruite, comprising the Rats, Mice, and Lemmings. In this 
 family the tail is long, always thinly haired, sometimes naked 
 and scaly. The lower incisors are narrow and pointed, and 
 there are complete clavicles. The hind-feet are furnished with 
 five toes, the fore-feet with four, together with a rudimentary 
 pollex. 
 
 Remains of Rats and Mice have been obtained in the Mio- 
 cene and Pliocene Tertiary of Europe, and the Post-Tertiary 
 forms are in several cases very nearly if not altogether un- 
 distinguishable .from existing forms. The genus Cricetus, com- 
 prising the existing Hamster, is represented in Post-Tertiary 
 deposits by a form probably identical with the living C. vulgaris. 
 The Lemmings (Myodes] are represented by at least one species 
 in Post-Tertiary deposits in Britain, occurring after the Glacial 
 period, and being contemporary with " palaeolithic " man. The 
 Voles or Campagnols (Anricofa) commence in the Pliocene, 
 and are abundantly represented in Post-Tertiary deposits. The 
 Post-Glacial deposits of Britain have yielded remains of the 
 Arvicola pratensis, A. agrestis, and A. amphibia, the last of 
 which (the well-known "Water-rat") occurs also in Prae- 
 Glacial accumulations. 
 
 Fam. 6. Dipodida. The sixth family of the Rodents, which 
 is sufficiently important to need notice, is that of the Dipodida 
 or Jerboas, mainly characterised by the disproportionate length 
 of the hind-limbs as compared with the fore-limbs. The tail 
 also is long and hairy, and there are complete clavicles.
 
 460 ORDERS OF MAMMALIA. 
 
 Remains of a species of Jerboa (Dipus) have been discovered 
 in Miocene deposits in France, but they are of no special im- 
 portance. 
 
 Fam. 7. Myoxidce. The members of this family are com- 
 monly known as Dormice, and they are often included in the 
 following family of the Squirrels and Marmots. 
 
 They resemble the Squirrels in most respects, but they have 
 only four molars on each side of the upper jaw, whereas the 
 latter possess five. Two species of Myoxus have been detected 
 in the Upper Eocene (Gypseous series of Montmartre), and a 
 third species has been determined from beds of Miocene age. 
 Several species have been detected in Post-Tertiary deposits, 
 of which the most remarkable is the comparatively gigantic 
 Myoxus Mditensis of the Maltese Post-Pliocene. 
 
 Fam. 8. Sciurida. This is the last family of Rodents which 
 calls for any special mention, and it comprises the true Squir- 
 rels, the Flying Squirrels, and the Marmots. 
 
 The members of this family are distinguished by their pointed 
 or compressed incisors and their tubercular molars, the upper 
 jaw having five of the latter on each side, whilst the lower jaw 
 has only four. The genus Sciurus, comprising the true Squir- 
 rels, is represented from the Eocene Tertiary upwards, but 
 none of the fossil forms are of special interest. The genus 
 Arctomys, comprising the Marmots, is represented in the Plio- 
 cene by a single species, and by several forms in the Post- 
 Tertiary. The Pouched Marmots (Spcrnwphilus), lastly, ap- 
 pear for the first time in the Miocene ; and Britain possessed 
 two species in times posterior to the Glacial period. 
 
 ORDER XI. CHEIROPTERA. This order is undoubtedly " the 
 most distinctly circumscribed and natural group " in the whole 
 class of the Mammalia. In many respects, however, it would 
 be advantageous to regard the Cheiroptera as a sub-order of 
 the next order (namely the Insectivora), specially modified to 
 lead an aerial life ; just as the Pinnigrada are regarded as a 
 mere section of the Carnivora specially modified to suit an 
 aquatic life. 
 
 The Cheiroptera are essentially characterised by the fact that 
 the anterior limbs are longer than the posterior, the digits ot 
 the fore-limb, with the exception of the pollex, being enor- 
 mously elongated (fig. 373). These elongated fingers are 
 united by an expanded membrane or " patagium," which is 
 also extended between the fore and hind limbs and the sides 
 of the body, and in many cases passes also between the hind- 
 limbs and the tail. The patagium thus formed is naked, or 
 nearly so, on both sides, and it serves for flight Of the fingers
 
 CHEIROPTERA. 
 
 461 
 
 of the hand, the pollex, and sometimes the next finger as well, 
 are unguiculate, or furnished with claws ; but the other digits 
 are destitute of nails. In the hind-limbs all the toes are un- 
 guiculate, and the hallux is not in any respect different from 
 the other digits. Well-developed clavicles are always present, 
 and the radius has no power of rotation upon the ulna. The 
 mammary glands are two in number, and are placed upon the 
 chest. There are teeth of three kinds, and the canines are 
 always well developed. The molars are tuberculate or grooved 
 in the frugivorous forms, and cuspidate in the insectivorous 
 species. The ulna is sometimes quite rudimentary. The 
 bones are not pneumatic. 
 
 '- Fig. 373. Skeleton of Fox-bat (Pteropus) after Owen. 
 
 The living Bats are divided into the two groups of the 
 Frugivorous Bats, comprising the single family of the Pteropida 
 (Fox-bats or Roussettes), and the Insectivorous Bats, com- 
 prising the three families of the Vespertilionidce, the Rhinolo- 
 phid(K (Horse-shoe Bats), and the Phyllostomidcs (Vampire 
 Bats). The Cheiroptera are represented for the first time in 
 the Eocene Tertiary of Europe, and that by a form very 
 similar to the existing European Bats. The fossil in question 
 is the Vespertilio Parisiensis (fig. 374) of the Gypseous series 
 of Montmartre (Upper Eocene). Other species of small In-
 
 462 ORDERS OF MAMMALIA. 
 
 sectivorous Bats ( Vespertilio) have been discovered in Miocene, 
 Pliocene, and Post-Tertiary deposits. The Horse-shoe Bats 
 (Rhinolophus) have as yet only been discovered in cave- 
 deposits. Lastly, the Vampire Bats are represented by no 
 less than five species in the Post-Pliocene cave-deposits of 
 Brazil, in which country is found the living Phyllostoma 
 spectrum. 
 
 Fig. 374. Vespertilio Paristfttsis. Upper Eocene. 
 
 ORDER XII. INSECTIVORA. The twelfth order of Mammals 
 is that of the Inscctivora, comprising a number of small Mam- 
 mals which are very similar to the Rodents in many respects, 
 but want the peculiar incisors of that order, and are likewise 
 always furnished with clavicles. 
 
 In the Insectivora, all the three kinds of teeth are usually 
 present, but the exact nature of the dentition varies consider- 
 ably in different cases. The incisors and canines present 
 little special, but the molars are always serrated with nume- 
 rous, small, pointed eminences or cusps, adapted for crushing 
 insects. With one exception, clavicles are always present in a 
 complete form. All the feet are usually furnished with five 
 toes ; all the toes are furnished with claws ; and the animal 
 walks on the soles of the feet, or is plantigrade. 
 
 The earliest traces of Insectivorous Mammals are in the 
 Eocene Tertiary (the Spalacodon of the Upper Eocene of 
 Hordwell, discovered by Mr Flower). The order, however,
 
 INSECTIVORA. 463 
 
 does not become well represented till we reach the Miocene 
 period. 
 
 The three leading families of the Insectivora are the Talpidce 
 or Moles, the Soriddce or Shrew- 
 mice, and \hzErinaceida or Hedge- 
 hogs. 
 
 Fam. i. Talpidce. The body in 
 this family is covered with hair ; 
 the feet are formed for digging and 
 burrowing, and the toes are fur- 
 nished with strong curved claws. 
 
 The earliest remains of Talpidce Fig. 375- Insectivora. skull of 
 appear for the first time in the S^T Hed s eho * (**< 
 Miocene Tertiary ; but they are of 
 
 little importance. The common Mole (Talpa Europcea) occurs 
 in Post-Pliocene deposits in Britain and on the Continent. 
 Several genera (Dimylus, Palceospalax, Geotrypus, &c.) have 
 been founded upon remains of Mole-like animals from the 
 Miocene and later Tertiary deposits. 
 
 Fam. 2. Soriddce. The Soriddce or Shrew-mice are distin- 
 guished by having the body covered with hair, and the feet 
 not adapted for digging ; whilst there are external ears, and 
 the eyes are well developed. Of all the Insectivora, no divi- 
 sion is more abundant or more widely distributed than that of 
 the Shrew-mice. In general form and appearance the Shrews 
 very closely resemble the true Mice (Muridce) and the Dor- 
 mice (Myoxidce], but they are in reality widely different, and 
 must not be confounded with them. 
 
 Remains of Shrews (belonging to the genera Sorex, Mysa- 
 rachne, and Plesiosorex) have been discovered in the Miocene 
 deposits of Europe. Several existing species (such as Sorex 
 araneus and S. fodiens) occur in Post-Tertiary cave-deposits 
 and ossiferous breccias. Lastly, the Desmans (Mygale) are 
 represented from the Miocene Tertiary onwards. 
 
 Fam. 3. Erinaceidce. The last family of the Insectivora is 
 that of the Hedgehogs, characterised by the fact that the upper 
 part of the body is covered with prickly spines, the feet are 
 not adapted for digging, and the animal has mostly the power 
 of rolling itself into a ball at the approach of danger. 
 
 Several species of Hedgehog have been found in the fossil 
 state, commencing in the Miocene Tertiary. The Erinaceus 
 fossilis of the Post-Tertiary period, does not appear to be 
 separable from the common species (Erinaceus Europaus}.
 
 464 ORDERS OF MAMMALIA. 
 
 CHAPTER XLII. 
 ORDERS OF MAMMALIA Concluded. 
 
 QUADRUMANA AND BlMANA. 
 
 ORDER XIII. QUADRUMANA. The thirteenth order of Mam- 
 mals is that of the Quadrumana, comprising the Apes, Mon- 
 keys, Baboons, Lemurs, &c., characterised by the following 
 points : 
 
 The hallux (innermost toe of the hind-limb) is separated 
 from the other toes, and is opposable to them, so that the 
 hind-feet become prehensile hands. The pollex (innermost 
 toe of the fore-limbs) may be wanting, but when present, it 
 also is usually opposable to the other digits, so that the animal 
 becomes truly quadrumanous, or four-handed. 
 
 2 2 3 3 
 
 The incisor teeth generally are -^-, and the molars ^- 
 
 with broad and tuberculate crowns. Perfect clavicles are 
 present. The teats are two in number, and are pectoral in 
 position. 
 
 The Quadrumana are divided by Owen into three very 
 natural groups, separated from one another by their anato- 
 mical characters and by their geographical distribution as 
 follows : 
 
 STREPSIRHINA. 
 
 This section of the Quadrumana is characterised by the 
 possession of twisted or curved nostrils, placed at the end 
 of the snout. The incisor teeth are generally much modified, 
 
 and are in number | | as a rule ; the praemolars are 
 33 33 
 
 or t and the molars are tuberculate. The second digit 
 
 of the hind-limb has a claw, and both fore and hind feet have 
 five toes each, all the thumbs being generally opposable. In 
 the true Lemurs, all the digits, except the second toe of the 
 hind-feet, are furnished with nails. 
 
 This section is often called that of the Prosimia, and it in- 
 cludes several families, of which the Aye-Ayes, Pottos, and 
 true Lemurs are the most important. 
 
 No member of the Strepsirhine division of the Quadrumana 
 has as yet been discovered in the fossil condition. When,
 
 QUADRUMANA. 465 
 
 however, those regions of the world have been properly ex- 
 plored in which these forms occur at the present day, we shall 
 doubtless find extinct representatives of this group. The 
 Strepsirhine Monkeys, namely, are at present confined to 
 Madagascar, Western Africa, and the Indian Archipelago ; 
 and these regions are as yet almost unknown, palaeontologi- 
 cally speaking. 
 
 PLATYRHINA. 
 
 The section of the Platyrhine Monkeys is exclusively con- 
 fined to South America, and one of its leading characters is to 
 be found in the almost universal possession of a prehensile 
 tail ; this being an adaptive character by which the animal 
 is suited to the arboreal life which so many of the South 
 American Mammals are forced to lead. There are neither 
 cheek-pouches nor natal callosities, and there is an additional 
 praemolar, and sometimes a molar less than in man and the 
 Old World Monkeys. The nostrils are simple, wide apart, 
 and placed nearly at the extremity of the snout. The prae- 
 
 molars are -^j- in number, and have blunt tubercles. The 
 
 thumbs of the fore-hands are either wanting altogether, or, if 
 present, are not opposable, though versatile. 
 
 The fossil remains of Platyrhine Monkeys are only known 
 to occur in South America, to which country all the existing 
 forms are confined. Here, in deposits of late Tertiary or 
 Post-Tertiary age, have been found remains of Monkeys re- 
 ferable to the existing genera Cebus, Callithrix, and lacchus, 
 along with a large form which constitutes the extinct genus 
 Protopithecus, and which is allied to the recent Mycetes. 
 
 CATARHINA. 
 
 The third and highest section of the Quadrumana is that of 
 the Catarhina or Old World Monkeys. In this section the 
 nostrils are oblique, and are placed close together, and the 
 septum narium is narrow. The thumbs of all the feet are 
 opposable, so that the animal is strictly quadrumanous. In 
 Colobus alone the anterior thumbs (pollex) are wanting. The 
 dental formula is the same as in man, viz. : 
 
 ,' ; c 1=1 ; ^ 2 -=?; m *=* - 3 2. 
 22 I I J "22 33 
 
 The incisors, however, are projecting and prominent, and 
 the canines especially in the males are large and pointed. 
 Moreover, the teeth form an uneven series, interrupted by a 
 
 2 G
 
 466 ORDERS OF MAMMALIA. 
 
 diastema or interval. The tail is never prehensile, and is 
 sometimes absent. Cheek-pouches are often present, and the 
 skin covering the tubera ischii is almost always callous and 
 destitute of hair, constituting the so-called " natal callosities." 
 With the single exception of a Monkey which inhabits the 
 Rock of Gibraltar, all the Catarhina are natives of Africa 
 and Asia. 
 
 The earliest traces of the Catarhine Monkeys (constituting 
 the oldest known relics of the entire order of the Quadrumana) 
 appear in the Eocene Tertiary ; and they occur only in the 
 Old World, so far as is yet known. The Macacus eocanus of 
 the London Clay has now been referred to Hyracotherium ; 
 but the Ccenopithecus lenmroides of Riitimeyer, from deposits of 
 Eocene age, appears to be an undoubted Monkey. Ccenopi- 
 thecus, however, cannot be referred with any certainty to the 
 
 Fig. 376. Lower jaw of Pliopithtcus (Pitkecvs) antiguus. Miocene. 
 
 Catarhina, its most marked affinities being with the genus 
 Mycetes on the one hand, and the Lemuridoe on the other. In 
 the Miocene deposits of Greece occur the remains of a Macaque 
 (Mesopithecus Pentelicf); and in deposits of the same age in 
 France have been found the remains upon which have been 
 founded the genera Pliopithecus (fig. 376) and Dryopithecus. 
 The former of these appears to have been most nearly allied 
 to the recent genus Semnopithecus, in which case it must have 
 possessed a tail and cheek-pouches. The latter appears to have 
 been more nearly allied to the living Gibbons (Hylobates}, in 
 which case it must have been destitute of a tail and of cheek- 
 pouches. 
 
 Besides the above, the Pliocene (or Miocene) deposits of 
 India have yielded the remains of Semnopithecus, Macacus,
 
 BIMANA. 
 
 467 
 
 and a form allied to the Orang. The Pliocene deposits of 
 France contain remains of the genera Semnopithecus, Macacus, 
 and Cercopithecus ; and a jaw of Macacus has been obtained 
 from similar deposits in Essex. 
 
 ORDER XIV. BIMANA. This, the last remaining order of 
 the Mammalia, comprises Man (Homo) alone, and it will there- 
 fore require but little notice here, the peculiarities of Man's 
 mental and physical structure properly belonging to other 
 branches of science. 
 
 Zoologically, Man is distinguished from all other Mammals 
 by his habitually erect posture and bipedal progression. The 
 lower limbs are exclusively devoted to progression and to sup- 
 porting the weight of the body. The anterior limbs are shorter 
 than the posterior, and have nothing whatever to do with pro- 
 gression. The thumb is opposable, and the hands are pre- 
 hensile, the fingers being provided with nails. The toes of the 
 hind-limb are also furnished with nails, but the hallux is not 
 opposable to the other digits, and the feet are therefore useless 
 as organs of prehension. The foot is broad and plantigrade, 
 and the whole sole is applied to the ground in walking. 
 
 The dentition consists of thirty-two teeth, and these form a 
 nearly even and uninterrupted series, without any interval or 
 diastema. The dental formula is 
 
 . 2 2 i 
 
 33 
 
 g- 377- A, Skull of the Orangoutang. B, Skull of an adult European. 
 
 The brain is more largely developed and more abundantly 
 furnished with large and deep convolutions than is the case 
 with any other Mammal. The mammae are pectoral, and the 
 placenta is discoidal and deciduate.
 
 468 ORDERS OF MAMMALIA. 
 
 Man is the only terrestrial Mammal in which the body is 
 not provided with a covering of hair. 
 
 Palseontologically, there is little to be said about Man or, 
 rather, so much might be said on this subject that its discus- 
 sion can only be properly taken up in a special treatise. 
 Man appeared upon the earth, so far as we know, only in the 
 last or Post-Tertiary period of Geology, and his remains, in 
 the form of bones or implements of various kinds, have been 
 detected in various Post-Tertiary accumulations, such as valley- 
 gravels and cave-deposits. The chief facts as to the past exist- 
 ence of man which concern the palaeontological student may 
 be briefly stated as follows : 
 
 1. Man unquestionably existed during the later portion of 
 what Sir Charles Lyell has termed the " Post- Pliocene " period. 
 In other words, Man's existence dates back to a time when 
 several remarkable Mammals, to be afterwards mentioned, had 
 not yet become extinct ; but he does not date back to a time 
 anterior to the present Molluscan fauna. 
 
 2. The antiquity of the so-called Post-Pliocene period is 
 a matter which must be mainly settled by the evidence of 
 Geology proper, and need not be discussed here. 
 
 3. The extinct Mammals with which man coexisted in 
 Western Europe are mostly of large size, the most important 
 being the Mammoth (Elephas frimigenius), the Woolly Rhino- 
 ceros (Rhinoceros tichorhinus), the Cave-lion (felts spelaa), 
 the Cave-hyaena (Hycena spd<za\ and the Cave-bear (Ursus 
 spelceus). We do not know the causes which led to the ex- 
 tinction of these Post-Pliocene Mammals ; but we know that 
 no Mammalian species has become extinct during the historical 
 period. 
 
 4. The extinct Mammals with which man coexisted are re- 
 ferable in many cases to species which presumably required a 
 very different climate to that now prevailing in Western Europe. 
 How long a period, however, has been consumed in the bring- 
 ing about of the climatic changes thus indicated we have no 
 means of calculating with any approach to accuracy. 
 
 5. Some of the deposits in which the remains of man have 
 been found associated with the bones of extinct Mammals, are 
 such as to show incontestably that great changes in the phy- 
 sical geography and surface-configuration of Western Europe 
 have taken place since the period of their accumulation. We 
 have, however, no means at present of judging of the lapse of 
 time thus indicated except by analogies and comparisons which 
 may be disputed. 
 
 6. The human implements which are associated with the
 
 BIMANA. 469 
 
 remains of extinct Mammals, themselves bear evidence of an 
 exceedingly barbarous condition of the human species. Post- 
 Pliocene or " Palaeolithic " Man was clearly unacquainted with 
 the use of any of the metals. Not only so, but the workman- 
 ship of these ancient races was much inferior to that of the 
 later tribes, who were also ignorant of the metals, and who 
 also used nothing but weapons and tools of stone. 
 
 7. Lastly, it is only with the human remains of the Post- 
 Pliocene period that the palaeontologist proper has to deal. 
 When we enter the " Recent " period, in which the remains of 
 Man are associated with those of existing species of Mammals, 
 we pass out of the region of pure palaeontology into the do- 
 main of the Archaeologist and the Ethnologist.
 
 PART III. 
 
 PAL^EOBOTANY
 
 PAL^EOBOTANY. 
 
 CHAPTER XLIIL 
 
 GENERAL RELATIONS OF PLANTS TO TIME. 
 
 THE subject of Palagobotany or Palaeophytology is one which 
 is far too vast to be treated of in a work of this nature ; whilst 
 it is one which is of less importance to the general student than 
 that of Palaeozoology. For this reason, nothing further will be 
 attempted here than to give the briefest and most elementary 
 outline of the general distribution of plants in past time, to 
 which will be added a short summary of the chief forms of 
 vegetable life which characterise each of the great formations. 
 The following table shows the leading groups into which the 
 Vegetable Kingdom is divided : 
 
 DIVISIONS OF THE VEGETABLE KINGDOM. 
 
 I. CRYPTOGAMIC PLANTS (Gr. kruptos, concealed ; gamos, marriage), 
 distinguished by having no distinct flowers or fruit. They include 
 
 a. Thallogens. Ex. Sea- weeds (Algce), Lichens, Mushrooms. 
 
 b. Anogens. Ex, Liverworts, Mosses. 
 
 c. Acrogens. Ex. Club-mosses (Lycopodiaiecs) ) '&ras, Horse-tails (Equi- 
 setacecs), 
 
 II. PHANEROGAMIC PLANTS (Gr. pkaneros, conspicuous ; gamos, mar- 
 riage), distinguished by having distinct flowers and seeds. They are 
 divided into 
 
 a. Endogens. Ex. Grasses, Palms, Lilies. These have endogenous stems, 
 showing no rings of growth, and the young plant possesses but a single 
 seed-lobe or " cotyledon." Hence they are often called Monocotyledons. 
 
 b. Exogens. Ex. Pines and Cycads, with most ordinary shrubs, trees, 
 and flowering plants. The Pines and Cycads, with the fossil Sigillari<z, 
 have the seed naked, and are hence called Gymnosperms (Gr. gumnos, naked ; 
 sperma, seed). Ordinary trees and shrubs, on the other hand, have the 
 seed covered, and are therefore called Angiosperms. Both the Gymno- 
 sperms and Angiosperms have an exogenous mode of growth, with a true 
 bark and annual rings of growth. The seed also possesses two seed-lobes or 
 " cotyledons ; " and they are therefore often spoken of as Dicotyledons.
 
 474 PAUEOBOTANY. 
 
 The remains of Plants appear for the first time, so far as yet 
 known, in the Lower Cambrian series (fhz Eophyton of the Fucoi- 
 dal Sandstone of Sweden) ; and from this time onward they are 
 never absent altogether from any of the great geological forma- 
 tions. The affinities of this earliest known plant are so dubi- 
 ous that it cannot be employed as proving the first appearance 
 of any of the great groups of plants. The Upper Cambrian 
 and Lower Silurian Rocks have yielded various remains of an 
 unquestionable vegetable nature, but of doubtful affinities re- 
 ferred, however, with more or less probability, to Sea-weeds 
 (" Fucoids "). In the Upper Silurian Rocks have been detected 
 various Sea-weeds (Spirophyton, &c.), the spore-cases of Lyco- 
 podiaceous plants (Pachytheca), Lcpidodendron, and remains of 
 the remarkable generalised type Psilophyton, which is in some 
 respects intermediate between the Lyeopodiacea (Club-mosses) 
 and the Ferns. In the Devonian period as we now know, 
 from the researches of Dr Dawson of Montreal in particular 
 plants are very abundant, and belong to varied types. The 
 great group of the Gymnospermous Exogens is here represented 
 by remains of various Conifers (Dadoxylon, Ormoxylon, and 
 Prototaxites). The Ferns are represented by numerous species, 
 in many cases not far removed from types now in existence ; 
 and it is interesting to notice that Tree-ferns (Psaronius and 
 Caulopteris) are not wanting amongst these. The Lycopodiaceiz 
 or Club-mosses are represented in the Devonian Series by nu- 
 merous remarkable types, such as Lepidodendron, Lepidophloios^ 
 Cordaites, and Lycopodites. The Sigillarioid plants, regarded 
 by different authorities as being Coniferous, or Lycopodiaceous, 
 or as being intermediate between the Acrogens and Gymno- 
 sperms are represented by species of Sigillaria itself, with its 
 Stigmaria roots. The Horse-tails or Equisetaeea are repre- 
 sented by species of the remarkable genus Catamites. The 
 genus Ant/wHthes, commonly supposed to be the spike of fruc- 
 tification of some phanerogamic plant, and now known to bear 
 the probably Gymnospermous fruit, Cardiocarpon is repre- 
 sented by two species in the Devonian Rocks. Lastly, the 
 Devonian formation of the State of New York has yielded the 
 remains of an Angiospermous Exogen, which has been described 
 by Dr Dawson, under the name of Syringoxylon mirabile. 
 
 We thus see, even from such an imperfect summary as the 
 above, that we must abandon the old view that nothing like a 
 general and varied flora existed in times anterior to the Coal- 
 measures. We see that at a point of Paleozoic time as early 
 as that represented by the Devonian formation, the earth ex- 
 hibited a far from scanty vegetation, composed of true land-
 
 GENERAL RELATIONS OF PLANTS TO TIME. 4/5 
 
 plants, and embracing representatives of almost all the great 
 groups of plants which at present grow upon its surface. Thus, 
 we find in the Devonian Rocks representatives of the groups of 
 the Horse-tails, Club-mosses, Ferns, and Gymnospermous and 
 Angiospermous Exogens. We have, however, no certain re- 
 presentative of the great group of the Endogens, whilst the 
 Angiospermous Exogens are known by a single genus only, 
 represented by a single species. Upon the whole, therefore, 
 the vegetation of the Devonian period is characterised by the 
 predominance of Cryptogams and Gymnospermous Exogens. 
 
 Passing on to the Carboniferous period, we have to consider 
 the largest and most varied of the Palaeozoic floras, but one 
 which is in most respects very similar to that of the Devonian 
 period. Some Devonian genera of plants do not pass up into 
 the over-lying, formation, and some of the Carboniferous genera 
 have not been recognised in the Devonian ; whilst hardly any 
 species are common to the two floras. Still, the general fades 
 of the Carboniferous vegetation is much the same as that of 
 the Devonian ; and the same groups predominate in the former 
 as in the latter, The predominant groups of plants in the Car- 
 boniferous Rocks are the Ferns (Filices), the Sigillarioids, the 
 Lepidodendroids, and the Calamites, of which all except the 
 Sigillarioids are certainly Cryptogams. Here, also, we have 
 the first instance of the occurrence of a Fungus (Archagari- 
 con). The Conifera are well represented by several genera 
 (Araucarioxylon, Dadoxylon, &c.), but no remains of trees 
 belonging to the Angiospermous Exogens have been as yet 
 detected. There are, however, a few flowering plants (such as 
 the Monocotyledonous Pothodtes of the Scotch Carboniferous). 
 Lastly, the Carboniferous Rocks have yielded remains of the 
 genus Ntzggerathia, referred by Brongniart to the peculiar Gym- 
 nospermous group of the Cycadacea, but regarded by others as 
 belonging to the Ferns. 
 
 In the Permian period, the vegetation is nearly related to 
 that of the Coal-measures. We have still numerous Ferns 
 (Neuropteris, Pecopteris, Sphenopteris), Tree-ferns (Psaronius), the 
 Lycopodiaceous Lepidodendron, and Calamites. The Conifers, 
 also, are abundant, and belong to several genera. Some of the 
 Conifers, however (as Ullmania], bear genuine cones, and the 
 Sigillarioids, which are so characteristic of the Carboniferous 
 period, have apparently altogether disappeared in the Permian. 
 
 With the Trias we commence the great series of Mesozoic 
 deposits, and there is a marked change in the vegetation of this 
 period as compared with that of the Carboniferous and Permian 
 epochs. The Lepidodendroids and Sigillarioids have now com-
 
 476 PAL^OBOTANY. 
 
 pletely disappeared. The Calamites of the Coal-measures are 
 represented by true Horse-tails (Equisetites). Ferns and Coni- 
 fers are still abundant, and some of the latter ( Voltzia) are by 
 no means unlike existing forms. Lastly, there is an abundance 
 of remains of Cycadaceous plants (Pterophyllum, Podozamites, 
 &c.) 
 
 The Jurassic and Lower Cretaceous deposits are similarly 
 characterised by an abundance of Cycads, Ferns, and Conifers, 
 the first of these in particular constituting a marked feature in 
 the vegetation. 
 
 In the Upper Cretaceous period we have the first appearance, 
 in any quantity, of ordinary Angiospermous Exogens, similar to 
 those which predominate at the present day in the flora of 
 temperate regions. Besides Ferns and Cycads more or less 
 allied to Jurassic forms, we have now numerous Dicotyledonous 
 trees, such as the Oak, Beech, Fig, Poplar, Walnut, Willow, 
 Alder, &c., belonging to familiar genera now in existence. 
 Here, also, we have the first appearance, so far as is certainly 
 known, of the group of the Palms. 
 
 Of the vegetation of the Tertiary period, it is sufficient to 
 remark here that now there is a marked predominance of 
 Angiospermous Exogens and of Endogens as compared with 
 Cryptogams and Gymnospermous Exogens. Not only is this 
 the case, but many of the Tertiary plants approximate closely 
 to existing forms, this approximation becoming more and more 
 marked as we recede from the Eocene and approach the Re- 
 cent period. 
 
 Before closing this brief review of the succession of plants 
 upon the globe, it may be well to notice shortly a generalisa- 
 tion which was long since made by M. Adolphe Brongniart. 
 This distinguished observer, in dividing the series of stratified 
 deposits in accordance with the fossil plants contained in them, 
 named the Palaeozoic period the " Age of Acrogens," the 
 Secondary period (exclusive of the Cretaceous) the " Age of 
 Gymnosperms," and the Cretaceous and Tertiary periods the 
 " Age of Angiosperms." This generalisation, though still ex- 
 pressing a general truth, can only be accepted with consider- 
 able reservation. Gymnosperms, and even Angiosperms, are 
 not unknown in the Palaeozoic period ; and if the Sigillarioids 
 should be referred to the former group of plants, then the later 
 Palaeozoic period would have as good claim to be called the 
 " Age of Gymnosperms " as the Secondary period. Again, as 
 pointed out by Sir Charles Lyell, the Lower and Upper Creta- 
 ceous floras differ from one another in the most striking manner, 
 the Lower Cretaceous agreeing in this respect with the Jurassic
 
 PRE-CARBONIFEROUS FLORAS. 477 
 
 series, whilst the Upper Cretaceous series is linked on by its 
 plants to the Tertiary formations. The line, therefore, between 
 the Age of Gymnosperms and the Age of Angiosperms must 
 be drawn between the Lower and Upper Cretaceous, and not 
 at the base of the Cretaceous series. 
 
 CHAPTER XLIV. 
 PRE-CARBONIFEROUS FLORAS. 
 
 CAMBRIAN PLANTS. The Laurentian and Huronian deposits 
 have as yet yielded no remains of plants ; but the occurrence 
 of graphite in large quantity in the former of these would 
 strongly support the view that the Laurentian period was not 
 without an abundant vegetation. The Lower Cambrian Rocks 
 have yielded many so-called " fucoids ; " but these are almost 
 invariably to be referred to the tracks and burrows of marine 
 worms. The only apparently unequivocal plant of the Lower 
 Cambrian period is the Eophyton (fig. 378) of the "Fucoidal 
 Sandstone " of Sweden. 
 
 The singular fossils referred to this genus consist of straight, 
 furrowed, and striated stems, which can hardly be anything else 
 than the remains of plants. The affinities, however, of these 
 ancient fossils are quite undetermined, except that it seems 
 pretty certain that they cannot be referred to the Alga. 
 
 In the Upper Cambrian Rocks (Potsdam Sandstone) of 
 North America occur various so-called " Fucoids " (PalcBOphy- 
 cus, &c.) The true nature of these, however, is in many cases 
 very doubtful, and it is questionable if any of them can really 
 be regarded as plants. 
 
 Here, also, we may briefly consider certain remains dis- 
 covered by the author in the Skiddaw Slates of the North of 
 England, a formation which is probably referable to the Upper 
 Cambrian, but which good authorities regard as belonging to 
 the Lower Silurian series. The remains in question were 
 originally referred provisionally to the genera Buthotrephis and 
 Eophyton, and the fossils which led to the former determina- 
 tion appear to be indubitable plants. They are thus described 
 by Dr Dawson in a note communicated to the author : 
 
 I. Biithotrephis Harknessii, This consists of what have been cylindrical 
 branches, given off from a central stem, and producing a few branchlets in 
 the manner of Pinnularia. Under the microscope the branches show a
 
 er- 
 The 
 
 478 PAL^OBOTANY. 
 
 vesicular structure; but this I believe to have been produced by the weath 
 ing out of minute globular concretions, probably of calcareous matter. T 
 appearances are rather those of roots or slender herbaceous stems than of 
 Algse. If found in the Coal-measures it would probably be regarded as an 
 obscure Pinnularia. 
 
 2. Buthotrephis radiatm. This shows radiating branchlets or leaves, 
 with the same vesicular structure as the preceding, and having some re- 
 semblance to the whorls of Annularia, though without any midrib. 
 
 It is auite possible that both of the above may belong to the same species. 
 If a land-plant, allied to Annularia, the first may represent the roots or sub- 
 aquatic stems, and the second its whorls of leaves. If an Alga, the first 
 may represent branching fronds, and the latter the fructification. Under the 
 former supposition, they may be compared with Annularia laxa of the 
 Devonian, and the radiating root-like bodies associated with it. (Dawson, 
 ' Report on Devonian Flora.') Under the supposition that the plants are 
 Algre, they may be compared with Spharococcites Schurtzanus of Goeppert, 
 from the Lower Silurian (Etage D.) of Bohemia, though they do not come 
 under the technical definition of Steinberg's genus Sphcerococcitts. 
 
 Fig. 378. Fragment of Eopkytott Linneanum. Lower Cambrian. 
 
 SILURIAN PLANTS. The remains of plants in the Silurian 
 series are few in number and require little consideration. In
 
 PRE-CARBONIFEROUS FLORAS. 
 
 479 
 
 the Lower Silurian Rocks no undoubted traces of land-plants 
 have hitherto been detected. The deposits of this period, 
 however, have yielded numerous fossils which have been re- 
 ferred to " Fucoids," under the generic titles of Palaophycus, 
 Licrophycus, Buthotrephis, Phytopsis, Sphenothallus, &c. Some 
 of these appear to be nothing more than the tracks of Annel- 
 ides. Others appear to be unquestionable plants; but nothing 
 positive can be stated as to their affinities. They may be Alga, 
 or they may belong to plants higher in the vegetable scale. 
 Subjoined is an illustration of a characteristic Canadian species 
 described by Mr Billings (fig. 379). 
 
 J 
 
 Fig. 379- Licrophycus Ottaivaensis, a " Fucoid" from the Trer 
 (Lower Silurian) of Canada. After Billings. 
 
 Limestone 
 
 In the Upper Silurian Rocks are also numerous remains ot 
 " Fucoids " (ArthrophyatS) Dictuolites, Chondrites, Spirophyton, 
 &c.), which do not differ in any important point from those ot 
 the inferior division. Some of these can hardly be anything 
 but true plants, and would certainly seem to be the remains of
 
 480 PALjEOBOTANY. 
 
 genuine Sea-weeds. Besides these problematical fossils,' how- 
 ever, the Upper Silurian Rocks have been shown to contain 
 the remains of genuine land-plants. Thus, remains of the 
 Lycopodiaceous genus Lepidodetidron (Sagenaria) have been 
 discovered in the Upper Silurian of Germany and Bohemia. 
 At the summit of the Upper Silurian series in Britain have 
 been detected numerous seed-vessels or " sporangia " referred 
 by Hooker to a Lycopodiaceous plant under the generic title 
 of Pachytheca. Lastly, the Upper Silurian of North America 
 has yielded remains of the characteristic Devonian genus Psilo- 
 phyton, which will be described immediately. 
 
 DEVONIAN PLANTS. The plants of the Devonian period 
 belong to the groups of the Eqttisetacece (Horse-tails), Lyco- 
 podiacece (Club-mosses), Filices (Ferns), Sigillarioids, and Coni- 
 fers the whole constituting an abundant terrestrial vegetation. 
 Besides the above, however as already mentioned the re- 
 mains of a true Angiospermous Exogen have in one instance 
 been detected in Devonian strata (Dawson). 
 
 The Equisetacece are represented by species of the remarkable 
 genus Catamites, the characters of which will be briefly spoken 
 of when treating of the Coal-plants. 
 
 The Lycopodiacea are represented by the genera Lepidoden- 
 dron, Lycopodites, Leptophlaum, Lepidophloios, Cordaites, and 
 Psilophyton. The Lepidodendroids will be shortly discussed 
 under the head of the plants of the Carboniferous series ; but 
 Cordaites and Psilophyton merit special notice here. The 
 genus Cordaites is common both to the Devonian and the 
 Carboniferous formations, and includes broad, striated, parallel- 
 veined leaves, which are extremely abundant in certain beds. 
 They possess broad clasping bases, and may attain a length of 
 a foot and a breadth of as much as three inches. Their affini- 
 ties are disputed; but they are regarded by Dr Dawson as 
 referable to some Lycopodiaceous plant. 
 
 The genus Psilophyton of Dawson (fig. 380) commences its 
 existence in the Upper Silurian Rocks ; but it is character- 
 istically Devonian, and is not known to be represented in the 
 Carboniferous period. The following is given by Dr Dawson 
 as the definition of the genus : 
 
 " Stems branching dichotomously, and covered with inter- 
 rupted ridges. Leaves rudimentary, or short, rigid, and pointed ; 
 in barren stems, numerous and spirally arranged ; in fertile 
 stems and branchlets, sparsely scattered or absent ; in decor- 
 ticated specimens represented by minute punctate scars. Young 
 branches circinate ; rhizomata cylindrical, covered with hairs 
 or ramenta, and having circular areoles irregularly disposed,
 
 PRE-CARBONIFEROUS FLORAS. 
 
 /-^r 
 
 481 
 
 Fig 380. Psilofhyton pnnceps (Dawson). a 
 Rhizome ; b Stem ; c Termination of a branch ; 
 d Vernation ; e Fructification, all of the natural 
 size ; g Areole of rhizome enlarged ; h Restoration 
 of the plant, reduced. Devonian of Canada. 
 
 2 H
 
 482 PAL^iOBOTANY. 
 
 giving origin to slender cylindrical rootlets. Internal structure 
 an axis of scalariform vessels, surrounded by a cylinder of 
 parenchymatous cells, and by an outer cylinder of elongated 
 woody cells. Fructification consisting of naked oval spore- 
 cases, borne usually in pairs on slender curved pedicles, either 
 lateral or terminal." 
 
 Species of Psilophyton occur all through the Devonian series 
 of North America, and they are also not wanting in the Old 
 Red Sandstone of Britain. The genus is regarded by Dr 
 Dawson as comprising "synthetic or generalised plants, having 
 rhizomata resembling those of some ferns, stems having the 
 structure of Lycopodium, and rudimentary leaves also resem- 
 bling those of Lycopodiacece, branchlets with circinate verna- 
 tion like that of Ferns, and sporangia of a type quite peculiar 
 to themselves." 
 
 The Ferns of the Devonian period are very numerous, and 
 upon the whole present a close resemblance to those of the 
 Carboniferous period. The smaller forms are represented by- 
 such genera as Cyclopteris, Neuropteris, Sphenopteris, Alethop- 
 tcris, Pecopteris, &c. Besides these, however, there occur the 
 trunks of large Tree-ferns, which are referred to the genera 
 Psaronius, Caulopteris, and Protopteris. Subjoined is an illus- 
 tration of a Fern from the Devonian of Europe (fig. 381). 
 
 The Sigillarioids of the Devonian series comprise forms 
 referable to the well-known genera Sigillaria (with Stigmaria) 
 and Calamodendron ; though the affinities of the last are not 
 well understood. The characters of these genera will be 
 noticed in treating of the plants of the Carboniferous series. 
 
 The Coniferte of the Devonian Rocks belong to the genera 
 Dadoxylon, Ormoxylon, and Prototaxites. All of these are 
 exogenous trees with concentric rings of growth, and the two 
 former are undoubtedly Coniferous, as their woody tissue 
 exhibits discs under the microscope. Prototaxites, unlike the 
 preceding, occurs in the Lower Devonian series, and is there- 
 fore the oldest Exogenous tree at present known to us. The 
 woody fibres do not exhibit punctations, and there is there- 
 fore some doubt as to the exact position of this genus. 
 
 In addition to the preceding forms, the Devonian Rocks have 
 yielded examples of the fossils known as Stcrnbergia, Cyperites, 
 Asterophyllites, Annularia, Pinnularia, Cardiocarpon, and Tri- 
 gonocarpon. Of these, the genus Stembergia comprises cylin- 
 drical, transversely-marked fossils, which are now known to 
 be nothing more than the casts of the pith-cylinders of other 
 plants. They seem chiefly to belong to Conifers of the genus 
 Dadoxylon, but they are referable also to Sigillaria, and even
 
 PRE-CARBONIFEROUS FLORAS. 483 
 
 to Lepidodendron. When the plant to which they belong is 
 itself preserved, there is no difficulty in recognising the true 
 
 Fig. 381. Sphenopteris laxus. Devonian. 
 
 nature of the Sternbergice; but when the outer wood has been 
 denuded, it becomes almost impossible to determine to what 
 plant they may have belonged. The genus Cyperites comprises 
 elongated linear leaves, which appear truly to be the leaves 
 of Sigillarice. The genus Asterophyllites (fig. 382) comprises 
 elegant plants with ribbed and jointed stems. The joints of 
 the stems give off verticils of leaves, or branchlets bearing 
 whorls of leaves, which are narrow, elongated, and furnished 
 with a single midrib. This genus is not only found in the 
 Devonian Series, but is commonly represented in the Coal- 
 measures, to which the species here figured belongs. 
 
 The genus Annularia comprises plants which are of doubt- 
 ful affinities, but which possessed slender stems bearing at in- 
 tervals whorls of leaves. The Annularice appear to have been
 
 484 PAL^OBOTANY. 
 
 floating plants, and they occur in both the Devonian and 
 Carboniferous formations. 
 
 Fig. ^.AsterophyUitesfoliosus. Coal-measures. (After Lindley and Hutton.) 
 
 The fossils known as Pinnularics are slender stem-like bodies, 
 with a smooth or striate surface, producing at right angles long 
 slender branchlets. The genus Pinnularia is regarded by 
 Dawson as being founded upon the roots of other plants, such 
 as Asterophyllites or Catamites. 
 
 Lastly, we find in the Devonian Rocks the little fruits 
 known as Cardiocarpon and Trigonocarpon, which are so abun- 
 dant in the Coal-measures. The Cardiocarpa appear mostly 
 to have been winged achenes or " samaras ; " but it is not 
 altogether certain by what plants they were produced. It is 
 now known, however, that the so-called Antholithes consists of 
 a spike, bearing Cardiocarpa protected by bracts ; and there is 
 a considerable probability that they were produced by Sigil- 
 larioid trees. Trigonocarpon (fig. 383) 
 comprises nut-like fruits, often of 
 considerable size, and commonly 
 three- or six- angled. The exterior of 
 the fruit was probably fleshy, and well- 
 preserved specimens show the integu- 
 ments, and the internal cavity at one 
 time filled by the albumen and em- 
 ' bryo. Trigonocarpon is probably the 
 fruit of a Conifer, and it shows a de- 
 cided resemblance to the solitary fruit of the existing Taxoid 
 genus, Salisburia. Possibly, however, Dr Dawson is correct 
 in his conjecture that most of the Trigonocarpa belonged really 
 to Sigillarioid plants.
 
 THE CARBONIFEROUS AND PERMIAN FLORAS. 485 
 
 CHAPTER XLV. 
 
 THE CARBONIFEROUS AND PERMIAN FLORAS. 
 
 CARBONIFEROUS PLANTS. The most extensive and the best 
 known of the Palaeozoic Floras is that which flourished during 
 the Carboniferous period. At this time were formed those 
 vast accumulations of vegetable matter which we know as 
 coal ; and much of our information as to the Carboniferous 
 plants is due to the value of coal, and to the vigour with which 
 coal-mining has been prosecuted. 
 
 Coal consists of nearly pure carbon, with varying proportions of hydrogen 
 and oxygen and a small quantity of mineral matter. The following are the 
 conclusions arrived at by Dr Dawson as to the minute structure of coal : 
 I. The so-called "mineral charcoal" or "mother coal" consists chiefly of 
 ' ' bast-tissue " or of elongated cells derived from the inner bark of Sigillaria; 
 and Lepidodendra. 2. Besides the above, the mineral charcoal contains in 
 many instances scalariform tissue derived from Ferns, Sigillari<z, Lepido- 
 dendra, &c. 3. The coarse and laminated portions of the coal are made 
 up of vascular bundles, derived apparently in the main from Ferns, along 
 with other vegetable fragments, and in some cases, though not to a great 
 extent, the sporangia of some of the Carboniferous Cryptogams. 4. In 
 many parts of the coal occur discigerous or punctated woody fibres, be- 
 longing to Dadoxylon, Sigillaria, and Calamodendron. 5- A considerable 
 portion of the coal is made up of "epidermal tissue," which is "a dense 
 cellular tissue representing the outer integuments of various leaves, herba- 
 ceous stems, and fruits." 6. The layers of bright shining coal are com- 
 posed of the flattened stems, and chiefly of the bark, of Sigillaria and 
 other trees. 7. Some layers of coal are occasionally composed mainly of 
 the compressed leaves of Cordaites. 8. Sporangia are often present in 
 coal ; but they rarely exist in such a proportion as to any extent actually to 
 form the coal themselves. 
 
 As has been already observed, the types of plants which 
 are found in the Carboniferous Rocks are to a great extent 
 identical with those which composed the Devonian flora. 
 Specifically, however, the coal-plants are almost always distinct 
 from the Devonian forms. The number of plants already 
 known to have existed during the Carboniferous period is so 
 great, that nothing more can be done here than to draw the 
 attention of the student to some of the more important and 
 characteristic types. 
 
 a. Filices. The Ferns of the Carboniferous period are 
 extremely numerous, and include both herbaceous forms like 
 the majority of existing species, and arborescent forms similar 
 to the living Tree-ferns of New Zealand. The latter belong 
 to the genera Psaronius, Caulopteris, and Palceopteris, of which 
 the two former occur in the older Devonian period. Of the
 
 486 PAlwEOBOTANY. 
 
 smaller ferns, the genera Sphenopteris, Pecopteris, Alethopteris, 
 Odontopteris, Neuropteris, Hymetiophyllites, and Cyclopteris may 
 be mentioned as the most important and widely distributed. 
 In the genus Neuropteris (fig. 384) the midrib of the leaflets is 
 
 Fig. 384. Neuropteris heterofhylla. Coal-measures of Europe. The lower figure 
 shows a single leaflet enlarged. 
 
 evanescent, either not distinct, or disappearing towards the 
 apex. Species of this genus are found in the Coal-formation 
 over almost the whole world. In Alethopteris the leaflets are 
 attached by their bases to the stem and to one another, and 
 are provided with a very distinct midrib from which the veins 
 are given off nearly at right angles. The commonest species 
 is the cosmopolitan Alethopteris (Pecopteris) lonchitica, which 
 nearly resembles the living Brackens (Pteris aquilina). Nearly 
 allied to Alethopteris is the genus Pecopteris, which includes a
 
 THE CARBONIFEROUS AND PERMIAN FLORAS. 487 
 
 large number of characteristic Carboniferous species. In 
 Odontopteris (fig. 385) the frond is pinnate, the leaflets being 
 attached by their entire bases, and the veins are generally 
 given off from the base. The species here figured is a widely- 
 distributed one, occurring in both Europe and North America. 
 
 Fig- 385. Odontopteris Schlotheimii. Carboniferous of Europe and North America. 
 
 In the genus Sphenopteris, the leaflets are narrow towards their 
 bases, often assuming a wedge-like form, the nervures dividing 
 in a pinnate manner from the base. 
 
 Lastly, in the genus Hymenophyllites the frond exhibits a 
 general resemblance to Sphenopteris, but the margin is divided 
 into lobes, into each of which a single nervure is continued. 
 
 b. Catamites. Amongst the commonest and most charac- 
 teristic of the plants of the Carboniferous period are the 
 striated fossils which are known as Calamites. Long as these 
 have been known, and carefully as they have been studied, 
 there is still no unanimity of opinion as to the affinities of 
 these plants. The prevalent modern view, however, is that 
 Calamites are truly referable to the Equisetacea, and that they 
 may be regarded as gigantic Horse-tails though they differ 
 in many respects from any existing forms. The Calamites 
 were " slender, ribbed, and jointed externally, and from the 
 joints there proceeded, in some of the species, long, narrow, 
 simple branchlets ; and, in others, branches bearing whorls of 
 small branchlets or rudimentary leaves. The stem was hollow, 
 with thin transverse floors or diaphragms at the joints, and it
 
 4 88 
 
 1'AL^EOBOTANY. 
 
 had no true wood and bark, but only a thin external shell of 
 fibres and scalariform vessels. The Catamites grew in dense 
 
 fig. 386. Calamites cantutformii. Carboniferous of Europe and North America. 
 
 brakes on the sandy and muddy flats, subject to inundation, 
 or perhaps even in the water, and they had the power of 
 budding out from the base of the stem, so as to form clumps
 
 THE CARBONIFEROUS AND PERMIAN FLORAS. 489 
 
 of plants, and also of securing their foot-hold by numerous 
 cord-like roots proceeding from various heights on the lower 
 part of the stem. The fruit was a long cone or spike, bearing 
 spore-cases under scales" (Dawson, Acadian Geology, p. 441). 
 Besides the true Catamites, the Carboniferous Rocks have also 
 yielded the remains of the genus Equisetites, which differed 
 from the Calamites, and agrees with the existing Horse-tails 
 in having sheaths at the joints. 
 
 Calamites often attain a comparatively gigantic size twenty 
 feet or more in length ; and though they generally occur as 
 prostrate and flattened stems, they are not uncommonly found 
 in an erect and uncompressed condition, standing as they grew. 
 The fossils known as Asterophyllites have been referred to 
 Calamites, of which they were at one time supposed to consti- 
 tute the foliage ; but this opinion has been shown to be pro- 
 bably incorrect 
 
 c. Calamodendron. A good deal of the confusion which has 
 prevailed as to the true nature of Calamites appears to have 
 arisen out of the problematic fossils now generally referred to 
 the genus Calamodendron. As ordinarily found, Calamodendra 
 present themselves in the form of jointed and longitudinally- 
 ribbed cylindrical stems, which are hardly separable from 
 Calamites, except that they show no " areoles," or points 
 whence leaves or branchlets have been given off. From the 
 examination, however, of complete specimens, it has been 
 shown that Calamodendron, as thus constituted, is really nothing 
 more than the cast of the pith or medullary cavity of a com- 
 plex woody stem, thus resembling in its nature the fossils 
 known as Sternbergia. Round the internal axis thus consti- 
 tuted there is found in perfect examples a thick woody envel- 
 ope, composed of ligneous wedges arranged concentrically and 
 separated by intervening tracts of cellular tissue (or "medul- 
 lary rays "). The external surface of the stem is not known, 
 but the woody wedges are stated to consist of " elongated 
 cells, and porous, discigerous, or pseudo-scalariform tissue." 
 The affinities of Calamodendron are uncertain. It is regarded 
 by different authorities as belonging to the Gymnospermous 
 Exogens or to the Acrogens, or as a connecting form between 
 these groups. In any case, it is necessary to distinguish very 
 carefully between Calamodendron and Calamites, the latter 
 being clearly separated by the absence of a woody envelope, 
 and the presence of whorled leaves or branchlets at the arti- 
 culations of the stem. 
 
 d. Lepidodendroids. Under this head we have to consider 
 the genera Lepidodendron and Lepidophloios, generally regarded
 
 490 
 
 PAL/EOBOTANY. 
 
 as gigantic extinct members of the Club-moss family (Lycopo- 
 diacea). The genus Lepidodendron (fig. 387) comprises nume- 
 
 Fig. ^.Lepidodendron Stembergii. Carboniferous. 
 
 rous large arborescent plants, which attain their maximum in 
 the Carboniferous period, but which appear to commence in 
 the Upper Silurian, and are well represented in the Devonian. 
 The trunk in some cases reached a length of fifty feet or more,
 
 THE CARBONIFEROUS AND PERMIAN FLORAS. 49! 
 
 and the branches are given off in a regular, bifurcating manner. 
 The bark is marked with numerous rhombic or oval scars, 
 arranged in quincunx order, and indicating the points where 
 leaves were formerly attached. The branches were covered 
 with slender, pointed leaves, closely crowded together; and 
 the fructification was carried at the ends of the branches in 
 the form of cones or spikes. These cones have generally been 
 described under the name of Lepidostrobi ; and they consist of 
 a central axis, surrounded by imbricated scales or bracts, each 
 of which supports a sporangium or spore-case. 
 
 In internal structure, Lepidodendron possesses a large cen- 
 tral pith, surrounded by a continuous sheath of scalariform 
 vessels. Outside this, again, is a thick bark, composed mainly 
 of elongated fibres or " bast-tissue," with a thin dense outer 
 rind. 
 
 The genera, or sub-genera, Sagenaria, Knorria, and Aspidiaria, 
 are properly to be referred to Lepidodendron. The genus Le- 
 pidophloios, however, is represented in both in Devonian and 
 Carboniferous Rocks by forms which are generically distinct 
 from Lepidodendron. The genus includes Lycopodiaceous 
 trees which have " thick branches, transversely elongated leaf- 
 scars, each with three vascular points, and placed on elevated 
 or scale-like protuberances, long one-nerved leaves, and large 
 lateral strobiles in vertical rows or spirally disposed" (Daw- 
 son). 
 
 e. Sigillarioids. The three chief genera included under this 
 head are Sigillaria, Rhytidolepis, and JFhvularia, of which the 
 first is the most important. The Sigillarioids commence their 
 existence, so far as known, in the Devonian period, but they 
 attain their maximum in the Carboniferous ; and unlike the 
 Lepidodendroids they are not known to occur in the Per- 
 mian period. They are comparatively gigantic in size, often 
 attaining a height of from thirty to fifty feet or more; but 
 though abundant and well preserved, great divergence of 
 opinion prevails as to their true affinities. The name of Sigil- 
 larioids (Lat. sigilla, little seals or images) is derived from the 
 fact that the bark is marked with seal-like impressions or leaf- 
 scars (fig. 388). 
 
 According to Dawson, Sigillaria proper is distinguished by 
 its strong ribs, " which are usually much broader than the 
 oval or elliptical tripunctate areoles, and are striated longi- 
 tudinally." The stem consists of a central pith, which is trans- 
 versely partitioned, as in the so-called Sternbergice. The pith 
 is surrounded by a woody cylinder, consisting of ligneous 
 wedges, composed of punctated (discigerous) and scalariform
 
 492 PAL/EOBOTANY. 
 
 vessels, and separated by medullary rays. Outside the woody 
 axis is an inner bark composed of long durable fibres of 
 " bast-tissue," the whole surrounded by a thick outer bark of 
 dense cellular tissue. " The trunk when old lost its regular 
 ribs and scars, owing to expansion, and became furrowed like 
 that of an Exogenous tree." The roots, as will be seen im- 
 mediately, constitute the fossils known as Stigmaria. The 
 
 Fig. 388. Fragment of Sigillaria Greeseri. The left-hand figure shows a small 
 portion enlarged. Carboniferous. 
 
 leaves are believed to be the so-called Cyperitcs, long, narrow, 
 rigid, and two- or three- nerved. The fruits are supposed to 
 be Trigonocarpa, " borne in racemes on the upper part of the 
 stem." Upon the whole, Dr Dawson is disposed to adopt the 
 view, originally put forth by Brongniart, that the Sigillaricc 
 find their nearest living allies in the Cycads, and that if not 
 actually referable to the Gymnospermous Exogens, they may 
 be intermediate between these and the higher Acrogens. 
 
 Mr Carruthers, on the other hand, describes Sigillaria as 
 consisting of a central cellular pith or medulla, surrounded by 
 a sheath consisting wholly of scalariform vessels, the whole 
 enveloped in an external cortical mass of cellular tissue. The 
 medullary sheath is perforated by meshes for the passage out- 
 wards of the vascular bundles which go to the axial appendages 
 (the leaves and branches) ; but there are no true medullary 
 rays. Upon these grounds, Mr Carruthers decides against 
 the view that Sigillaria is a Gymnospermous Exogen, and he 
 regards it as Cryptogamic and Lycopodiaceous. He also dis-
 
 THE CARBONIFEROUS AND PERMIAN FLORAS. 
 
 493 
 
 credits the assertion that discigerous tissue is present, and 
 describes the fruit as consisting of cones or strobiles. 
 
 Leaving the botanical position of Sigillaria thus undecided, 
 we find that it is now almost universally conceded that the 
 fossils originally described under the name of Stigmaria are 
 the roots of Sigillaria, the actual connection between the two 
 having been in numerous instances demonstrated in an un- 
 mistakable manner. The Stigmaria (fig. 389) ordinarily pre- 
 sent themselves in the form of long, compressed or rounded 
 
 Fig. 389. Stigmaria ficoides. Quarter natural size. Carboniferous. 
 
 fragments, the external surface of which is covered with 
 rounded pits or shallow tubercles, each of which has a little 
 pit or depression in its centre. From each of these pits there 
 proceeds, in perfect examples, a long cylindrical rootlet ; but 
 in many cases these have altogether disappeared. In its 
 internal structure, Stigmaria exhibits a central pith surrounded 
 by a sheath of scalariform vessels, the whole enclosed in a 
 cellular envelope. The Stigmaria are generally found ramify- 
 ing in the " underclay," which forms the floor of a bed of coal, 
 and which represents the ancient soil upon which the Sigillaria 
 grew. 
 
 Of the remaining genera of the Sigillarioids, Rhytidolepis is 
 the most important. It is characterised by the possession of 
 large, hexagonal, tripunctate areoles, and narrow, often trans- 
 versely striate ribs. In Favularia, lastly, the smaller branches 
 were destitute of ribs, with elliptical, spirally-disposed areoles. 
 The stem branched dichotomously like that of a Lepidoden- 
 dron and the leaves were broad, with numerous parallel veins, 
 approximating to the leaves of Cordaites. 
 
 f. Conifera. True Conifers have long been known to occur 
 in the Carboniferous Rocks. They belong to the genera 
 Dadoxylon, Palceoxylon, Arancarioxylon, and Pinites. They
 
 494 PAluEOBOTANY. 
 
 are recognised by the great size and concentric rings of their 
 prostrate, rarely erect trunks, and by the fact that the micro- 
 scope exhibits punctated fibres in their wood. Their fruit is 
 unknown, unless, as is very probable, it is constituted by the 
 so-called Trigonocarpa. If this be the case, the Carboniferous 
 Conifers must have been " Taxoid," resembling the recent 
 Yews in producing berries instead of true cones. The so- 
 called Sternbergioe, as has been already pointed out, are " pith- 
 cylinders," or, in other words, casts of the pith, of Dadoxylon. 
 They appear, however, to belong also to Sigillaria and Lepido- 
 phloios. 
 
 g. Cycadacece. The peculiar group of Gymnospermous 
 Exogens represented at the present day by the Cycads is not 
 known with certainty to be represented in the Carboniferous 
 Rocks. Nceggerathia has been referred here, and the Cyca- 
 daceous genus PteropJiyllum has also been alleged to occur. 
 Brongniart has also conjectured that the Sigillarioids are in 
 reality most nearly allied to the Cycadacece ; and this opinion 
 is supported by other high authorities. 
 
 //. Angiospermous Exogens. The occurrence of true Angio- 
 sperms in the Carboniferous period is very doubtful. No 
 Exogenous wood which is not Coniferous has been as yet 
 detected. The fossil known as Antholithes, which was at one 
 time conjectured to be possibly the infloresence of an An- 
 giosperm, has now been shown to be really a raceme bearing 
 the fruit termed Cardiocarpon ; and it remains uncertain to 
 what plant this really belongs. 
 
 i. Monocotyledons. The occurrence of Endogens in the 
 Coal-formation is also attended with some uncertainty. The 
 genus Ncegge rat hia has sometimes been referred to the Palms, 
 and the same group has been asserted to be represented by 
 species of Palmacites. The only apparently unequivocal proof 
 of the occurrence of Carboniferous Endogens is, however, 
 afforded by the so-called Pothocites, which appears to have 
 been the spadix of an Aroideous plant. 
 
 PERMIAN PLANTS. The Permian Flora is, upon the whole, 
 very nearly allied to that of the Coal-measures, though the 
 Permian species are mostly distinct, and there are some new 
 genera. Thus, we find species of Lcpidodendron, Calamites, 
 Equisetites, Asterophyllites, Annularia, c. all genera which 
 are highly characteristic of the Carboniferous period. On the 
 other hand, the Sigillarioids of the Coal appear to have finally 
 passed away with the close of the Carboniferous period. 
 
 Ferns are abundant in the Permian Rocks, and belong for 
 the most part to the well-known Carboniferous genera Alethop-
 
 THE CARBONIFEROUS AND PERMIAN FLORAS. 495 
 
 fen's, Neuropteris, Sphenopteris, and Pecopteris. There are also 
 Tree-ferns referable to the genus Psaronius. The singular 
 
 Fig. 390. Nceggerathia expcmsa. Permian. 
 
 genus Nceggerathia (fig. 390) is also represented in the Permian 
 Rocks. 
 
 Fig. 391. Walchia piniformis ; a Branch ; b Twig. From the Permian of Saxony. 
 (After Gutbier.) 
 
 The Conifers of the Permian period are numerous, and
 
 496 PAL^EOBOTANY. 
 
 belong in part to Carboniferous genera. A characteristic 
 genus, however, is Walchia (fig. 391), distinguished by its lax 
 short leaves. This genus, though not exclusively Permian, is 
 mainly so, the best-known species being the W. piniformis. 
 Here, also, we meet with Conifers which produce true cones, 
 and which differ, therefore, in an important respect from the 
 Taxoid Conifers of the Coal-measures. One of the most 
 characteristic of these is the Ullmania selaginoidcs, which oc- 
 curs in the Magnesian Limestone of Durham, the Middle 
 Permian of Westmorland, and the " Kupfer-schiefer " of 
 Germany. 
 
 CHAPTER XLVI. 
 
 FLORAS OF THE SECONDARY AND TERTIARY 
 PERIODS. 
 
 TRIASSIC PLANTS. With the Trias we commence what has 
 been aptly termed the " Age of Cycads," from the predomi- 
 nance of the plants of this group in the Mesozoic vegetation. 
 The Cycads are a group of Gymnospermous Exogens, the 
 form and habit of growth of which present considerable re- 
 semblance to those of young Palms (fig. 392). The trunk is 
 
 Fig. 392. Zanria spiralii, a living Cycad. Australia. 
 
 unbranched, often shortened, and bearing a crown of pinnate 
 fronds. The leaves are usually " circinate " that is, they un- 
 roll in expanding, like the fronds of Ferns. The ovules are 
 borne upon the edge of altered leaves, or are carried on the 
 scales of a cone. All the existing species of Cycads are
 
 FLORAS OF SECONDARY AND TERTIARY PERIODS. 497 
 
 natives of warm countries, occurring in South America, the 
 West Indies, Japan, Australia, Southern Asia, and South 
 Africa. As has been already remarked, the occurrence of 
 genuine Cycads in the Carboniferous vegetation has not been 
 demonstrated, and the same holds good of all the Palaeozoic 
 floras. True Cycads, therefore, so far as known, make their 
 first appearance in the Trias, at the commencement of the Me- 
 sozoic period, where they are represented by the genera Ptero- 
 phylhim, Zamites, and Podozamites. Cycads continue to be 
 abundantly represented throughout the whole Mesozoic series; 
 but they have only been detected by a single dubious example 
 in strata of Tertiary age. The name " Age of Cycads," as 
 applied to the Secondary epoch, is, therefore, from a botanical 
 point of view, an exceedingly appropriate one. 
 
 Besides Cycads, the Triassic Rocks have yielded the re- 
 mains of Ferns, Eqiiisetites, Calamites, and Conifers. The 
 Ferns belong mostly to the genera 
 Neuropteris, Pecopteris, Acrostichites, 
 Crematopteris, Cydopteris, and Ano- 
 mopteris. A characteristic species of 
 the first of these is figured below 
 (fig. 393). The Conifers of the Trias, 
 lastly, are abundant, the most char- 
 acteristic genus being Voltzia. This 
 genus is related to the existing Cy- 
 presses, and many species of it are 
 found in the Triassic Rocks. 
 
 Fig. 393. Neuropteris elegans. Trias. 
 
 JURASSIC PLANTS. Taken as a whole, the Jurassic period 
 is characterised by the prevalence of Ferns, Cycads, and 
 Conifers ; no Palms or Angiospermous Exogens having been 
 as yet shown to occur. 
 
 The Cycads are extremely abundant, and belong chiefly to 
 the genera Pterophyllum, Otozamites, Zamites, Bucklandia, Cros- 
 sozamia, Williamsonia, Mantdlia, &c. The " dirt-bed," as it 
 
 2 I
 
 498 PAL/EOBOTANY. 
 
 is called, of the Purbeck beds, consists of an ancient soil, in 
 which stand erect the trunks of Conifers and the stems of 
 Cycads of the genus Mantellia (fig. 394). The fronds of 
 
 F'g- y)i,.Mantell 
 
 i, a Cycad Irom the Purbeck 
 
 Fig. y)t > .Coniopteris Mvrravana. Great Oolite. 
 
 Cycads occur also in great abundance in various Jurassic 
 strata, especially in the lower portion of the series ; and the
 
 FLORAS OF SECONDARY AND TERTIARY PERIODS. 499 
 
 cones likewise have been in some instances preserved. The 
 Conifers are represented by various genera more or less nearly 
 allied to the present Araucarice, and cones have been in a 
 few instances detected. 
 
 ferns occur very abundantly in the Jurassic series, the 
 commonest genera being Coniopteris (fig. 395), Odontopteris 
 (fig. 396), Sphenopteris ', Cydopteris, Phlebopteris, Pecopteris, 
 Polypodites, Pachypteris, and Tceniopteris. 
 
 Endogens are by rjo means unknown in the Jurassic series, 
 though no representative of the group of the Palms has been 
 as yet detected. Amongst the most important of the Oolitic 
 Endogens may be mentioned the Aroideous fruit described by 
 Mr Carruthers under the name of Aroides Stutterdi, and the 
 fruits known as Podoearya and Kaidacarpum, both of which 
 belong to the living order of the Pandanece (Screw-pines). 
 
 Fig. 396. Odontopteris cycadea. Lower Lias. 
 
 CRETACEOUS PLANTS. The Lower Cretaceous Plants 
 greatly resemble those of the Jurassic period, consisting 
 mainly of Ferns, Cycads, and Conifers. The Upper Creta- 
 ceous Rocks, however, both in Europe and in North America, 
 have yielded an abundant flora which resembles the existing 
 vegetation of the globe in consisting mainly of Angiospermous 
 Exogens and of Monocotyledons. In Europe, the plant-re- 
 mains in question have been found chiefly in certain sands in
 
 500 PAL^EOBOTANY. 
 
 the neighbourhood of Aix-la-Chapelle, and they consist of 
 numerous Ferns, Conifers (such as Cycadoptcris), Screw Pines 
 (Pandamts), Oaks (Quercus), Walnut (Juglans), Fig (Ficvs), 
 and many ProteacM, some of which are referred to existing 
 genera (I)rya?uira, Banksia, Grevillea, &c.) 
 
 In North America, the Cretaceous strata ol New Jersey, 
 Alabama, Nebraska, Kansas, &c., have yielded the remains of 
 numerous plants, many of which belong to existing genera. 
 Amongst these may be mentioned Tulip-trees (Liriodendroii), 
 Sassafras (fig. 397), Oaks (Quercus), Beeches (Fagus), Plane- 
 
 197. Cretaceous Angiospertns. a, Sassafras Cretafeunt; b, Liriodendron 
 uteekii; c, Leguminosites Marcouanus; d, Salix Meekii. (After Dana.) 
 
 trees (P/afanus), Alders (Alnus), Dog-wood (Cornus), Willows 
 (Salix), Poplars (Populus), Cypresses (Cupressus\ Bald Cy- 
 presses (Taxodium\ Magnolias, &c. Besides these, however, 
 there occur other forms which have now entirely disappeared 
 from North America as, for example, species of Cinnamomum 
 and Araucaria. 
 
 EOCENE PLANTS. The Plants of the Eocene period ap-
 
 FLORAS OF SECONDARY AND TERTIARY PERIODS. $01 
 
 proximate on the whole to the existing vegetation of the earth. 
 They are, however, in the main most closely allied to forms 
 which now are found in tropical or sub-tropical regions. In 
 the London Clay occur numerous fruits of Palms (Nipadites, 
 fig. 398), along with various other plants, most of which in- 
 dicate a warm climate as prevailing in the South of England 
 at the commencement of the Eocene period. In the Eocene 
 strata of North America occur numerous plants, such as Palms, 
 Conifers, Magnolia, Cinnamon, Fig, Dog-wood, Maple, Hick- 
 ory, Poplar, Plane-trees, &c. Upon the whole, the Eocene 
 flora of North America is nearly re- 
 lated to that of the Miocene strata 
 of Europe, as well as to that now 
 existing in the American area. We 
 may conclude, therefore, that " the 
 forests of the American Eocene re- 
 sembled those of the European Mio- 
 cene, and even of modern America" 
 (Dana). 
 
 MIOCENE PLANTS. The deposits 
 of the Miocene period have yielded 
 an extraordinarily large number of 
 plants, only a few of the more im- 
 portant of which can be indicated 
 here. Our chief sources of informa- 
 tion as to the vegetation of the Miocene period are derived 
 from the Brown Coals of Germany and Austria, the Lower 
 
 Fig. zgZ.Nipadites ellip- 
 ticus. London Clay of Shep- 
 
 Fig. 399. Miocene Palms. A, Chamcerops Helvetica; B, Sabal major. 
 Lower Miocene of Switzerland and France. 
 
 and Upper Molasse of Switzerland, and the Miocene strata of 
 Greenland. The lignites of Austria have yielded very numer-
 
 502 
 
 PAL^OBOTANY. 
 
 ous plant-remains, chiefly of a tropical character; one of the 
 most noticeable forms being a Palm of the genus Sabal,(f\g. 
 399, B), now found in America. The plants of the Lower 
 Miocene of Switzerland are also mostly of a tropical character, 
 but include several forms now found in North America, such 
 as a Tulip-tree (Liriodendrori) and a Cypress (Taxodiuni). 
 Amongst the more remarkable forms from these beds may be 
 mentioned Fan-Palms (Chamcerops, fig. 399, A), numerous 
 tropical ferns, and two species of Cinnamon. The plant- 
 remains of the Upper Molasse of Switzerland indicate an 
 extraordinarily rank and luxuriant vegetation, composed 
 mainly of plants which now live in warm countries. Among 
 the commoner plants of this formation may be enumerated 
 many species of Maple (Acer), Plane-trees (Platanus, fig. 400), 
 Cinnamon-trees, and other members of the Lauracece, many 
 species of Proteacea (Banksia, Grevillea, &c.), several species 
 of Sarsaparilla (Smi/ax), Palms, Cypresses, &c. 
 
 Fig. 400. Platanus accroides. a 
 Leaf; 6 The core of a bundle of 
 pericarps ; c A single fruit or peri- 
 carp, natural size. Upper Miocene. 
 
 Fig. 401. Cinnattiti- 
 mum polymorphunt. a 
 Leaf; b Flower. Upper 
 Miocene. 
 
 In Britain, the Lower Miocene strata of Bovey Tracy have 
 yielded remains of Ferns, Vines, Fig, Cinnamon, Proteacece, 
 &c., along with numerous Conifers. The most abundant of 
 these last is a gigantic pine the Sequoia Couttsia which is 
 very nearly allied to the huge Sequoia, ( Wellingtonid) gigantea 
 of California. A nearly-allied form (Sequoia Langsdorffii) has 
 been detected in the leaf-bed of Ardtun in the Hebrides. 
 
 In Greenland, as well as in other parts of the Arctic regions, 
 Miocene strata have been discovered which have yielded a 
 great number of plants, many of which are identical with 
 species found in the European Miocene. Amongst these
 
 FLORAS OF SECONDARY AND TERTIARY PERIODS. 503 
 
 plants are found many trees, such as Conifers, Beeches, Oaks, 
 Maples, Plane-trees, Walnuts, Magnolias, &c., with numerous 
 shrubs, ferns, and other smaller plants. 
 
 Taking the Miocene flora as a whole, Dr Heer concludes 
 from his study of about 3000 plants contained in the European 
 Miocene alone, that the Miocene plants indicate tropical or 
 sub-tropical conditions, but that there is a striking intermixture 
 of forms which are at present found in countries widely re- 
 moved from one another. It is impossible to state with cer- 
 tainty how many of the Miocene plants belong to existing 
 species, but it appears that the larger number are extinct. 
 According to Heer, the American types of plants are most 
 largely represented in the Miocene flora, next those of Europe 
 and Asia, next those of Africa, and lastly those of Australia. 
 Upon the whole, however, the Miocene flora of Europe is 
 mostly nearly allied to the plants which we now find inhabit- 
 ing the warmer parts of the United States ; and this has led 
 to the suggestion that in Miocene times the Atlantic Ocean 
 was dry land, and that a migration of American plants to 
 Europe was thus permitted. This view is borne out by the 
 fact that the Miocene plants of Europe are most nearly allied 
 to the living plants of the eastern or Atlantic seaboard of the 
 United States, and also by the occurrence of a rich Miocene 
 flora in Greenland. As regards Greenland, Dr Heer has de- 
 termined that the Miocene plants indicate a temperate climate 
 in that country, with a mean annual temperature at least 30 
 warmer than it is at present. 
 
 The present limit of trees is the isothermal which gives the 
 mean temperature of 50 Fahr. in July, or about the parallel 
 of 67 N. latitude. In Miocene times, however, the Limes, 
 Cypresses, and Plane-trees reach the 79th degree of latitude, 
 and the Pines and Poplars must have ranged even further 
 north than this. 
 
 PLIOCENE PLANTS. The vegetation of the Pliocene period 
 is, upon the whole, so closely allied to that now existing as to 
 call for no special mention. It is worthy of notice, however, 
 that the Pliocene flora of Europe was strikingly similar to that 
 now existing in North America. Thus, we find in the Plio- 
 cene of Europe genera such as the Locust-trees (Robinid), 
 the Honey-locusts (Gleditschia), the Sumach (Rhus\ the Bald 
 Cypress (Taxodiuni), the Tulip-tree (Liriodendrori), the Sweet- 
 gum Tree (Liquidambar), the Sour-gum Tree (JVyssa), &c., 
 which do not now occur in Europe, but are at present charac- 
 teristic forms in the flora of temperate North America.
 
 PART IV. 
 HISTORICAL PALAEONTOLOGY
 
 HISTORICAL PALAEONTOLOGY. 
 
 CHAPTER XLVI. 
 
 LAURENTIAN AND CAMBRIAN PERIODS. 
 
 IN this portion of the work it will be endeavoured very briefly 
 to give a view of the forms of life which characterised each of 
 the great geological periods. The subject of the fossils which 
 characterise each particular stratum or group of strata in the 
 earth's crust is one far too vast to be grappled with here, and 
 can only be properly considered in a special treatise. All that 
 will be attempted here is to give a short synopsis of the de- 
 posits of each successive era, followed by a general account of 
 the " life " of the period in which those deposits were laid 
 down. Such an account may be advantageously prefaced by 
 a tabular view of the more important fossiliferous deposits, 
 commencing with the most ancient. 
 
 TABULAR VIEW OF FOSSILIFEROUS STRATA. 
 
 I. PALAEOZOIC OR PRIMARY EPOCH. 
 
 ( Terrains Paleozo'iques. ) 
 
 i. LAURENTIAN. 
 
 a. Lower Laurentian. British Wanting. Foreign Great series of 
 
 metamorphic rocks in Canada, gneiss, mica-schist, quartzite, and 
 limestones, with a total thickness of about 20,000 feet. 
 
 b. Upper Laurenttatt.ritis/iFunda.tnent3.l Gneiss of the Hebrides (?) ; 
 
 Hypersthene Rocks of the Isle of Skye (?). Foreign Labrador Series 
 of Canada, having a thickness of 10,000 feet, and resting unconform- 
 ably upon the Lower Laurentian. 
 
 2. HURONIAN. 
 
 British Wanting (?). Foreign About 18,000 feet of metamorphic rocks 
 resting unconformably upon the Laurentian series of Canada. Per- 
 haps the equivalent of the Lower Cambrian of other regions.
 
 508 HISTORICAL PAL/EONTOLOGY. 
 
 3. CAMBRIAN. 
 
 a. Lower Cambrian. British Longmynd group of Shropshire ; Harlech 
 
 Grits ; Llanberis Slates ; Green and purple slaty rocks of Wicklow, 
 containing Oldhamia. Foreign Fucoidal Sandstone of Sweden, with 
 Eophyton ; Etages A and B of Barrande in Bohemia ; Huronian series 
 of Canada (?). 
 
 b. Upper Cambrian. British Lingula Flags of Shropshire and Wales. 
 
 Tremadoc Slates (?). Skiddaw Slates (?). Foreign "Primordial 
 zone" of Bohemia; Alum-schists of Sweden and Norway; Potsdam 
 Sandstone and Calciferous Sand-rock of North America ; Quebec 
 group of Canada (?). 
 
 4. SILURIAN. 
 
 a. Lower Silurian. 
 
 Britain. 
 Lower Llandeilo or Arenig Group. 
 
 2. Upper Llandeilo or Llandeilo Flags. 
 
 3. Caradoc, Bala, or Coniston Group. 
 
 4. Lower Llandovery Group. 
 
 North America. 
 
 1. Trenton Period (comprising the Chazy, Birds-eye, Black River, 
 
 and Trenton Limestones). 
 
 2. Hudson Period (comprising the Utica Shales and Hudson River 
 
 Group). 
 Bohemia. 
 \ Etage D of Barrande. 
 
 b. Upper Silurian. 
 
 Britain. 
 
 /I. Upper Llandovery (comprising the Tarannon Shales and May 
 Hill Sandstone). 
 
 j 2. Wenlock Group (comprising the Woolhope Limestone, Wen- 
 lock Shale, and Wenlock Limestone). 
 
 I 3. Ludlow Group (comprising the Lower and Upper Ludlow 
 
 V formations). 
 
 North America. 
 
 1. Niagara period (comprising the Oneida Conglomerate, Medina 
 
 Sandstone, Clinton Group and Niagara Limestone). 
 
 2. Salina period (comprising the Guelph Limestone and Onondaga 
 
 Salt Group). 
 
 3. Lower Helderberg period (comprising the Tentaculite and Water- 
 
 lime Groups, the Lower Pentamerus Limestone, the Delthyris 
 Shaly Limestone, and the Upper Pentamerus Limestone). 
 Bohemia. 
 Etage E. 
 
 G. , 
 
 H. 
 
 5. DEVONIAN. 
 
 Lower Devonian. British Arbroath Paving Stones of Scotland ; Lin- 
 ton Group of Devonshire. Foreign Oriskany Sandstone (?) and 
 Comiferous series of North America. 
 
 Middle Devonian. British Bituminous Schists of Caithness ; Ilfra- 
 combe Group of Devonshire. Foreign Eifel Limestone of Europe ; 
 Hamilton series of North America.
 
 TABLE OF FOSSILIFEROUS STRATA. 509 
 
 c. UpperDevonian. British Sandstones of Dura Den ; Sandstones of 
 Denholm Hill in Roxburghshire ; Kiltorcan beds of Ireland ; Pilton 
 and Petherwyn Group of South of England. Foreign Clymenien- 
 Kalk, and Cypridinen-Schiefer of Germany ; Portage, Chemung, and 
 Catskill Groups of North America. 
 
 6. CARBONIFEROUS. 
 
 a. Lower Carboniferous. British Carboniferous Slates of Ireland; Moun- 
 tain Limestone ; Yoredale Series. Foreign Sub-Carboniferous Group 
 of North America. 
 
 l>. Upper Carboniferous British Millstone Grit ; Coal- Measures. Foreign 
 Equivalent beds in various parts of the world. 
 
 7. PERMIAN. 
 
 a. Lower Permian. British Lower Red Sandstones of North of Eng- 
 
 land. Foreign Rothliegendes of Germany. 
 
 b. Middle Permian. British Marl Slate and Magnesian Limestone. 
 
 Foreign Mergel-schiefer, Kupfer-schiefer, and Zechstein of Germany. 
 
 c. Upper Permian. British- Gypseous Marls and Red Sandstones of the 
 
 North of England. Foreign Bunter-schiefer of Germany. 
 
 II. MESOZOIC OR SECONDARY EPOCH. 
 (Terrains Secondaires.) 
 
 8. TRIASSIC SERIES. 
 
 a. Lower Trias. British New Red Sandstone of Lancashire and 
 
 Cheshire. Foreign Bunter Sandstein of Germany. 
 
 b. Middle Trias. British Wanting. Foreign Muschelkalk of Germany. 
 
 c. Upper Trias. British Red marls, salt, &c. (Keuper), of Cheshire ; 
 
 Penarth, Rhaetic, or Avicula contorta beds of Somersetshire, Glamor- 
 ganshire, &c. Foreign Keuper beds of Germany ; Kossen (St 
 Cassian) and Hallstadt beds of the Austrian Alps. 
 
 9. JURASSIC SERIES. 
 
 a. Lower Oolites. British Lias, Inferior Oolite, Fuller's Earth, Great 
 
 Oolite, Stonesfield Slate, Cornbrash, and Forest Marble. Foreign 
 The Sinemurien, Liasien, Toarcien, Bajocien, and Bathonien of 
 D'Orbigny. 
 
 b. Middle Oolites. British Kelloway Rock, Oxford Clay, Coral Rag. 
 
 Foreign Nerinean Limestone of the Jura, Diceras Limestone of the 
 Alps. 
 
 c. Upper Oolites British Kimmeridge Clay, Portland Stone, Purbeck 
 
 beds. Foreign Lithographic Slate of Solenhofen. 
 
 10. CRETACEOUS SERIES. 
 
 a. Lower Cretaceous. British Hastings Sands, Weald Clay, Lower 
 
 Greensand, Kentish Rag. Foreign Neocomian of Neufchatel, Weal- 
 den of Hanover. 
 
 b. Upper Cretaceous British Gault, Blackdown beds, Upper Green- 
 
 sand, Chalk Marl, White Chalk. Foreign Quader Sandstein and 
 Planer Kalk of Germany, Hippurite Limestone of the South of 
 Europe, Maestricht Chalk, Faxoe Limestone, Sands and Marls of New 
 Jersey in North America.
 
 510 HISTORICAL PALEONTOLOGY. 
 
 III. KAINOZOIC OR TERTIARY EPOCH. 
 ( Terrains Tertiaires, ) 
 
 11. EOCENE SERIES. 
 
 a. Lower Eocene. British Thanet Sands, Plastic and Mottled Clays of 
 Woolwich, London Clay. Foreign Sables de Bracheux and Argile 
 plastique of France. Claiborne beds of Alabama, United States. 
 
 /'. Middle Eocene. British Bagshot, Bracklesham and Barton beds, 
 Headon Series, St Helens or Osborne Series. Foreign Calcaire 
 Grossier of France ; Nummulitic Limestone of the Alps; Jackson 
 beds of the United States. 
 
 f. Upper Eocene. British Bembridge beds, Hempstead beds (Lower 
 Miocene?). Foreign Gypseous Series of Montmartre in France, 
 Vicksburg and White River beds in the United States. 
 
 12. MIOCENE SERIES. 
 
 a. Lower Miocene. British Bovey Tracy lignites and clays, Leaf-beds of 
 
 Mull in the Hebrides. Foreign Brown Coals of Germany and 
 Croatia, Lower Molasse of Switzerland. 
 
 b. Upper Miocene. British Ferruginous Sands of North Downs (?). 
 
 Foreign Faluns of Touraine, Epplesheim Sands, Upper Molasse of 
 Switzerland, Oeningen beds of Switzerland, Siwalik beds of India. 
 
 13. PLIOCENE SERIES. 
 
 a. Older Pliocene.~BritishVl\i\te Crag and Red Crag of Suffolk. 
 
 Foreign Upper and Middle Crags of Antwerp, Sub-Apennine beds. 
 
 b. Newer Pliocene. British Norwich Crag. Foreign Lacustrine Strata 
 
 of the Val d'Amo, near Florence. 
 
 14. POST-TERTIARY SERIES. 
 a. Post-Pliocene. Cave-deposits, High-level and low-level gravels, Glacial 
 
 deposits, Forest-bed of Cromer, &c. 
 />. Recent. Peat-mosses, recent river-gravels, lacustrine mud,&c. 
 
 LAURENTIAN PERIOD. 
 
 ROCKS OF THE PERIOD. The Laurentian Rocks have their 
 typical development in North America, especially in Canada. 
 In northern New York strata of this age rise into the lofty 
 and rugged elevations of the Adirondacks, and similar rocks 
 occur in another area to the south of Lake Superior. The 
 Laurentian series is of vast thickness, and is divided into 
 a lower and upper division. The Lower Laurentian group 
 attains the enormous thickness of about 20,000 feet, and is 
 composed entirely of metamorphic rocks, consisting mainly of 
 gneiss interstratified with mica-schist, with great beds of quartz, 
 and massive beds of crystalline limestone, of which one varies 
 from 700 to 1500 feet in thickness. Conglomerates also oc- 
 cur, and there are vast deposits of magnetic and specular iron- 
 ore. Graphite or black-lead occurs disseminated in strings, 
 veins, and beds, through hundreds of feet of Lower Laurentian 
 strata, and its amount is calculated by Dr Dawson to be equal
 
 HURONIAN PERIOD. 511 
 
 in quantity to the coal-seams of an equal area of the Carbon- 
 iferous rocks. 
 
 Not only is the Lower Laurentian series of vast thickness 
 and greatly metamorphosed, but it must have been elevated 
 above the sea, and subjected to vast denudation, prior to the 
 deposition of the upper group. This is shown by the fact 
 that the Upper Laurentian lies unconformably upon the trun- 
 cated edges of the Lower Laurentian. The Upper Lauren- 
 tian group is about 10,000 feet thick, and consists wholly of 
 stratified crystalline rocks. These consist mainly of gneissic 
 and felspathic rocks, often characterised by the occurrence of 
 lime-felspar or Labradorite. The series is extensively devel- 
 oped in Labrador, and is sometimes spoken of as the " Labra- 
 dor series." 
 
 In Britain it has been conjectured, with great probability, that 
 the "fundamental gneiss" of the Hebrides and the "hypers- 
 thene rocks " of the Isle of Skye belong to the Laurentian series. 
 
 LIFE OF THE LAURENTIAN PERIOD. The Laurentian rocks 
 are often spoken of as the Azoic series (Gr. a, without ; zoe, 
 life) ', but the name appears to be inappropriate, because there 
 is good evidence to show that living beings were in existence 
 in the Laurentian period. In the first place, it is certain that 
 the Laurentian rocks, though now highly metamorphic, were 
 originally deposited as ordinary sedimentary beds of sandstone, 
 conglomerate, shale, and limestone. There is, therefore, no 
 reason whatever for supposing that the seas of the Laurentian 
 period differed in any respect from modern seas, so far at any 
 rate as to render the existence of living beings impossible ; 
 while we know that one of the results of metamorphic action 
 is the obliteration of the fossils in the rock affected. Secondly, 
 by the researches of Sir William Logan there was discovered 
 in one of the limestones of the Lower Laurentian group, the 
 body which has been described under the name of Eozoon 
 Canadense, and which is believed to be a gigantic Foraminifer. 
 The organic nature of this body was first detected by Dr Daw- 
 son of Montreal, and his opinion as to its nature has since 
 been confirmed by the highest authorities. Thirdly, there is 
 good reason to believe that the graphite of the Laurentian 
 rocks is nothing more than metamorphic coal, and that it is 
 derived from vegetables which flourished during the Lauren- 
 tian period. 
 
 HURONIAN PERIOD. 
 
 The rocks of the Huronian series rest unconformably upon 
 the denuded edges of the Laurentian rocks on the borders of
 
 512 HISTORICAL PALAEONTOLOGY. 
 
 Lakes Superior and Huron. They are about 18,000 feet in 
 thickness, and consist of quartzites (altered sandstones), sili- 
 ceous slates, conglomerates, and limestones. The conglome- 
 rates sometimes contain pebbles derived from the subjacent 
 Laurentian rocks. No fossils have hitherto been found in 
 any part of the Huronian series, and its exact age is therefore 
 doubtful. Not improbably it may correspond with the Lower 
 Cambrian rocks of other regions, but it may represent an 
 independent formation to be intercalated in point of time 
 between the Laurentian and Cambrian groups. 
 
 CAMBRIAN PERIOD. 
 
 ROCKS OF THE PERIOD. The exact limits of the Cambrian 
 Rocks are as yet not well denned, different authorities taking 
 different views as to the strata which should be considered 
 under this head. The name " Cambrian " is derived from the 
 fact that these strata are the lowest rocks visible in North 
 Wales and its borders (Cambria). The Cambrian rocks are 
 generally divided into a Lower and Upper division, and they 
 are well developed in various parts of Europe and America. 
 The following gives a general idea of the nature, distribution, 
 and mineral characters of the Cambrian rocks : 
 
 I. Cambrian Rocks of Britain. The Lower Cambrian rocks 
 of Britain are best seen in the Longmynd Hills in Shropshire, 
 and consist of about 25,000 feet of variously-coloured sand- 
 stones, grits, and shales, often ripple-marked, and exhibiting 
 rain-prints, but with very few fossils. These are succeeded by 
 a great series of micaceous flagstones, slates, and shales, which 
 vary in thickness from 6000 to 2000 feet, and are, in part 
 at any rate, of Upper Cambrian age. They are known as the 
 Lingula flags, from the occurrence in them of a Brachiopod 
 belonging to the genus Lingula. In North Wales the Lower 
 Cambrian strata are often highly metamorphosed, and the cele- 
 brated Welsh roofing-slates are also derived from this division. 
 Cambrian rocks occur in other parts of Britain, and the follow- 
 ing table exhibits their leading members : 
 
 1. Lower Cambrian : 
 
 a. Longmynd beds (25,000 feet). 
 
 b. Llanberis slates (3000 feet). 
 
 c. Harlech grits (6000 feet). 
 
 d. Oldhamia slates of Ireland. 
 
 2. Upper Cambrian: 
 
 e. Lingula Flags of Wales (about 6000 feet). 
 
 / Tremadoc Slates of North Wales (2000 feet). 
 
 g. Skiddaw Slates of the north of England (7000 feet).
 
 CAMBRIAN PERIOD. 513 
 
 The last-mentioned group of rocks, namely, the Skiddaw 
 Slates of the north of England, is in a doubtful position. 
 They consist of about 7000 feet of dark-coloured shales and 
 slates, and they are most clearly the equivalent of the Quebec 
 group of Canada, containing many of the same fossils. Upon 
 the whole, it seems safer in the meanwhile to regard them as 
 Upper Cambrian. 
 
 II. Cambrian Rocks of Bohemia and Sweden. In Bohemia, 
 M. Barrande has succeeded in demonstrating as underlying 
 the Lower Silurian rocks of that country a zone of rocks, 
 which correspond to the Lingula Flags of Britain, and are 
 therefore of Upper Cambrian age. This zone contains many 
 remarkable and characteristic fossils, and is often spoken of as 
 the " Primordial Zone." In Sweden and Norway the Lower 
 Cambrian rocks are represented by a sandstone containing 
 impressions supposed to be referable to sea-weeds or " fucoids." 
 This " Fucoidal sandstone " is succeeded by beds of so-called 
 " alum-schist/' which are of Upper Cambrian age, and corre- 
 spond with the Lingula Flags of Britain. 
 
 III. Cambrian Rocks of North America. The Cambrian 
 rocks are represented in North America by the Potsdam sand- 
 stone and the Calciferous series. The Potsdam Sandstone is 
 mostly a laminated sandstone, or grit in the State of New 
 York, but limestones are present in addition in the Mississippi 
 basin, and it consists of a great thickness (2000 to 7000 feet) 
 of slates, sandstones, and limestones, along the Appalachian 
 chain. It contains a good many fossils, among which are 
 Trilobites resembling those of the " Primordial Zone " in 
 Bohemia. 
 
 The Calciferous series consists of a hard calcareous sand- 
 stone, or " sand-rock " in the State of New York ; but it con- 
 sists of sandstone with well-developed magnesian limestone in 
 the basin of the Mississippi ; and along the Appalachian chain 
 it consists of sandstones and limestones, subordinated to great 
 masses of shale. In their last-mentioned development the 
 Calciferous rocks have been termed the " Quebec group," and, 
 as before said, they are undoubtedly the equivalent of the 
 Skiddaw Slates of Britain. They attain a thickness of from 
 5000 to 7000 feet ; but it is not clear whether they are truly 
 referable to the Upper Cambrian or to the base of the Silurian 
 system. Most probably they are transition beds between the 
 two formations. 
 
 LIFE OF THE CAMBRIAN PERIOD. In the Lower Cambrian 
 Rocks fossils have hitherto proved extremely scarce. The 
 commonest organic remains are the burrows and tracks of 
 2 K
 
 514 HISTORICAL PALEONTOLOGY. 
 
 Annelides (Arenicolites, Histioderma, &c.) Besides these, the 
 Longmynd beds of Shropshire have yielded a supposed Trilo- 
 bite (Palceopyge), The green and purple slaty rocks of Wick- 
 low have yielded two species of the singular fossil Oldhamia 
 (fig. 27), which may be a Hydroid Zoophyte, but which is 
 more probably a calcareous sea-weed. Lastly, the " Fucoidal 
 Sandstone " of Sweden, besides the obscure remains which are 
 known as " fucoids," has yielded the remarkable fossil known 
 as Eophyton (fig. 378), which is most probably a plant, along 
 with a small Lingula, 
 
 In the Upper Cambrian Rocks, fossils become tolerably 
 abundant, and belong to varied types. The most character- 
 istic forms are Trilobites, the characters of which are so 
 peculiar as to have gained them the name of " primordial," 
 applied also to the strata in which they are found. The 
 chief genera are Paradoxides (fig. 114), Conocephalus, Sao, 
 Conocoryphe, Ellipsocephalus, Microdiscus, Agnostus, &c. The 
 " Primordial Zone " of Bohemia has also yielded a few 
 Pteropods, Brachiopods, and Echinoderms. The Potsdam 
 Sandstone of North America contains various primordial 
 Trilobites (especially those of the genus Dikelocepha/us), Bra- 
 chiopods of the genera Obolus, Obolella, and Lingula, Gastero- 
 pods of the genera Pleurotomaria and Ophileta, Annelide-bur- 
 rows (Scolithus), and numerous so-called " fucoids." Lastly, 
 in the Potsdam Sandstone have been detected the earliest 
 footprints, if they may be so termed, which have been as yet 
 discovered These have been described under the names of 
 Protichnites and Climactichnites, and they have probably been 
 produced by large Crustaceans. 
 
 The Lingula Flags of Britain owe their name to the occur- 
 rence in them of a large satchel-shaped Lingula (L. Davisii). 
 Trilobites of the genera Olenus, Agnostus, Paradoxides, &c., 
 occur, and remains of Phyllopodous Crustaceans (Hymeno- 
 caris) are by no means rare. 
 
 The Skiddaw and Quebec groups, as already mentioned, 
 are in a doubtful position, and are often regarded as being 
 referable to the Lower Silurian. They are chiefly noticeable 
 for the great abundance of Graptolites which they have been 
 shown to contain. Many of these belong to genera which 
 pass up into the Silurian rocks (Didymograpsus, Diplograpsiis, 
 and Climacograpsus) ; but others belong to types which are 
 exclusively confined to this horizon, and which are remarkably 
 complex as compared with later forms. Amongst these may 
 be mentioned the genera Tetragrapsus (fig. 32), Dichograpsus 
 (fig. 33), Loganograpsus, and Phyllograpsus.
 
 SILURIAN PERIOD. 515. 
 
 CHAPTER XLVIII. 
 
 SILURIAN PERIOD. 
 
 ROCKS OF THE PERIOD. 
 
 FOLLOWING the Cambrian comes the great Silurian series of 
 rocks, first clearly established and definitely worked out by 
 Sir Roderick Murchison, the founder of the Silurian system. 
 The exact limit between the Cambrian and Silurian formations 
 is one which is not clearly defined, since there does not appear 
 to be t.ny general physical break between the two groups. 
 The line of demarcation between them is, in the present state 
 of our knowledge, an arbitrary line, and is derived chiefly from 
 the characters of the Trilobites. There are rocks, however, 
 such as the Tremadoc Slates, the Skiddaw Slates, and the Cal- 
 ciferous and Quebec groups, in which there is an intermixture 
 of Cambrian with true Lower Silurian types. These rocks, 
 therefore, might be regarded as Upper Cambrian or as Lower 
 Silurian, or as passage-beds between the two. It is to be 
 remembered, also, that the Tremadoc Slates and Lingula Flags 
 are regarded by Sir Roderick Murchison as being the base- 
 ment-beds of the Lower Silurian. 
 
 The name " Silurian " was proposed by Sir R. Murchison 
 for a great series of strata lying below the Old Red Sandstone, 
 and occupying those parts of Wales and England which were 
 at one time occupied by the " Silures," a tribe of ancient 
 Britons. The Silurian rocks are largely developed in Wales, 
 the north of England, Scotland, and Ireland, in various parts 
 of Europe, especially Bohemia, Saxony, Russia, and Sweden, 
 and in the North American Continent. The entire series is 
 divisible into the two sections of the Lower and Upper Silurian 
 rocks, each in turn split up into smaller subdivisions, the names 
 of which have usually been taken from localities where they are 
 unusually well developed, or where they were first studied. 
 
 In Britain the Silurian Rocks are divided into the following 
 groups from below upwards : 
 
 a. Lower Llandeilo group, 1 
 
 b. Upper Llandeilo group, 1 T ower Silurian 
 
 c. Bala, Caradoc, or Coniston group, \ U 
 
 d. Lower Llandovery group, J 
 
 e. Upper Llandovery group, \ 
 
 f. Wenlock group, > Upper Silurian. 
 
 g. Ludlow group, J
 
 5l6 HISTORICAL PALAEONTOLOGY. 
 
 a. The Lower Llandcilo or Arenig group derives its name from 
 ihetown of Llandeilo, in Wales, where it consists of dark-coloured 
 micaceous flags, with earthy shales and gritty sandstones. 
 
 b. The Upper Llandeilo group consists of a great series of 
 micaceous flags and dark-coloured shales, often with inter- 
 stratified igneous matter. In Scotland the group consists of 
 a great assemblage of shales and grits, the former mostly very 
 dark in colour, often anthracitic, and charged with the remains 
 of Graptolites. 
 
 c. The Bala, Caradoc, or Coniston group consists in Wales 
 of slates, grits, and sandstones, with two interstratified lime- 
 stones, the whole attaining a thickness of about 5500 feet. 
 In the north of England this group consists of black flaggy 
 beds, a well-marked limestone with intercalated shales, and 
 black mudstones replete with Graptolites. 
 
 d. The Lower Llandovery group consists of slates and sand- 
 stones, with great beds of conglomerate. 
 
 e. The Upper Llandovery group forms in Britain the base of 
 the Upper Silurians, and rests unconformably upon the Lower 
 Llandovery. It consists of limestones, shales, conglomerates, 
 sandstones, and slates, attaining a total thickness of nearly 
 2000 feet. 
 
 / The Wenlock group consists of a great mass of shale and 
 flagstone (Wenlock Shale), underlaid and surmounted by lime- 
 stones, the whole attaining a thickness of 3000 feet. 
 
 g. The Ludlow group consists of shales, limestones, and 
 sandstones in Wales, and of grits and shales in the north of 
 England, having a total thickness of from 2000 to 4000 or 
 5000 feet. 
 
 In North America the Silurian series is magnificently devel- 
 oped, and is capable, like that of other parts of the world, of 
 being separated into a Lower and Upper division. The 
 annexed table shows the subdivisions of the Silurian series as 
 developed in the State of New York, and their supposed 
 British equivalents the table being in ascending order : 
 
 Silurian Strata of New York. British equwalents. 
 
 1. Trenton period (comprising the Chazy, Bird's i The Lower Silurian 
 eye, Black River, and Trenton limestones. I series (comprising the 
 
 \ Llandeilo, Bala, and 
 
 2. Hudson period (comprising the Utica slates Lower Llandovery 
 and Hudson River shales). ' groups). 
 
 IThe lower portion of 
 the Upper Silurian series 
 
 conglomerate, Medina sandstone, Clinton group, ^(comprising the Upper 
 and Niagara limestone). I Llandovery and \Ven- 
 
 J lock).
 
 SILURIAN PERIOD. 517 
 
 4. Salina period (comprising the Guelph lime- ) AT -p ... , . , . 
 stone and Onondaga salt group). \ N Bntlsh e q uivalen t- 
 
 5. The Lower Helderberg period (comprising'* ^, , . , ,. e 
 the Tentaculite and Water -lime groups, the L Th T ^ hlghe Q r P f 
 Lower Pentamerus limestone, th e g Delthyris V th * i, U PP er . $^". se- 
 
 - 
 
 ,. . 
 
 shaly limestone, and the Upper Pentamerus nes(compnsingtheLiid- 
 limestone). 
 
 In Bohemia, as shown by M. Barrande, the Silurian series 
 likewise admits of a subdivision into an Inferior and a Supe- 
 rior division. The former comprises the single " etage D," 
 and is characterised by a fauna to which M. Barrande has 
 applied the term of " second fauna," the so-called " primordial 
 zone" having yielded the "first fauna" of the same palaeonto- 
 logist. The Upper Silurian series comprises the etages E, F, G, 
 and H, and is characterised by the possession of the " third 
 fauna." 
 
 LIFE OF THE SILURIAN PERIOD. In the lower portion of 
 the Cambrian series, as we have seen, organic remains are ex- 
 ceedingly scanty ; but in the upper portion of the same, fossils 
 are tolerably abundant, and belong in part to types which pass 
 upwards into the overlying Silurian series. The fossils of the 
 Silurian series are almost exclusively marine, the only excep- 
 tions being some remains of land-plants, such as stems of 
 Lepidodendron (Sagenaria) and the sporangia of Lycopodiace- 
 ous plants (Pachytheca), the latter having been discovered in 
 the very highest beds of the system. The only other vegeta- 
 ble remains which have been detected in undoubted Silurian 
 deposits belong to what are loosely termed " fucoids " (Licro- 
 phycus, Arthrophycus, Palceophycus, Buthotrephis, &c.), and 
 these are tolerably abundant in various parts of the series. 
 
 The sub-kingdom of the Protozoa is represented by For- 
 aminiferous shells and by Sponges. The latter are tolerably 
 abundant in both the Lower and Upper Silurian and belong 
 to various genera (Palaospongia, Acanthospongia, Astylospongia, 
 Amphispongia, &c.) Here, also, we meet with the singular 
 genera Receptactilites and Ischadites, which have been variously 
 regarded as gigantic Foraminifers, as Sponges, or as inter- 
 mediate forms between the Foraminifera and the Spongida. 
 
 The sub -kingdom of the Ccelenterata is represented in 
 Silurian times by the Graptolites and by numerous Corals. 
 The typical Graptolites commence their existence in the Skid- 
 daw and Quebec Groups (Upper Cambrian ?), and are highly 
 characteristic of the Silurian Rocks. If we except the genus 
 Dictyonema, which is probably referable to the Sertularians, no 
 species of Graptolite is known to have survived the close of 
 the Silurian period. Neglecting their earlier appearance, the
 
 518 HISTORICAL PALEONTOLOGY. 
 
 genera Didymograpsus and Dicranograpsus are exclusively, 
 and the genera Diplograpsus, C/imacograpsus, and Rastrites are 
 pre-eminently, characteristic of the Lower Silurian period. 
 The genera Graptolites and Retiolites are those which espe- 
 cially characterise the Upper Silurian deposits, though both 
 commence in the inferior division of the series. Corals are 
 exceedingly abundant in many parts of the Silurian series, 
 certain formations, such as the Wenlock Limestone of Eng- 
 land and the Niagara Limestone of North America, being 
 in places so largely composed of these fossils that they have 
 been regarded as ancient coral-reefs. Almost all the Silurian 
 corals belong to the groups of the Rugosa and Tabulata. 
 
 The Echinodermata are largely represented in Silurian de- 
 deposits, more especially by Crinoids and Cystideans. The 
 former are extremely abundant, and belong in many instances 
 to peculiar types. The Cystideans are pre-eminently Lower 
 Silurian, though they occur also in the upper division of the 
 series. They are especially characteristic of the Bala or 
 Caradoc period. The true Star-fishes (Asteroided) are repre- 
 sented even in the Lower Silurian rocks ; whilst the Brittle- 
 stars (Ophiuroidea) are represented by the genus Prof aster. 
 The Sea-urchins (Echinoidea) are not represented at all except 
 in the Upper Silurian, and there only by the aberrant genus 
 Palcechinus. 
 
 The Annelida are represented in the Silurian rocks by the 
 tracks and burrows of Sea-worms (Hclminthites and Scolites), 
 and by the tubes of Tubicola (Serpulites, Ortonia, Conchicolites, 
 Cornnlites, Spirorbis, &c.) The little spiral tubes of Spirorbis 
 are commonly found in the Upper Silurian rocks attached to 
 the shells of Orthocerata and the like. 
 
 The Arthropoda appear to have been represented wholly by 
 Crustaceans, no Arachnids, Myriapods, or Insects being yet 
 known with certainty to occur. The most important Silurian 
 Crustaceans belong to the Trilobita, Phyllopoda, Euryptcrida, 
 and Ostracoda. The Trilobites are extraordinarily abundant, 
 and every subdivision of the Silurian series has its characteristic 
 species. The " primordial Trilobites " are only represented 
 by such forms as Agnostus and Olenus. The Lower Silurians 
 have many types, amongst which Asaphus, Ogygia, Trinucleus 
 Calymene, C/ieirurus, Illcenus, and Phaeops may be mentioned 
 as the most important, though most of these range into the 
 Upper Silurians as well. The Silurian Phyllopods are toler- 
 ably plentiful in both divisions of the series and belong chiefly 
 to the genera Ceratiocaris, Peltocaris, and Discinocaris, The 
 Eurypterids are represented in the Lower Silurians, but they
 
 SILURIAN PERIOD. 519 
 
 are pre-eminently characteristic of the higher beds of the 
 Upper Silurian. Lastly, the Ostracoda are often extremely 
 abundant, and belong chiefly to the genera Leperditia, Pri- 
 mitia, Beyrichia, and Entomis. 
 
 The sub-kingdom Mollusca is very largely represented in 
 Silurian deposits, and the Brachiopods and Tetrabranchiate 
 Cephalopods in particular enjoyed a vast extension and a de- 
 velopment which has never since been attained. The Brachi- 
 opods are so abundant in all parts of the series that the 
 Silurian period has been spoken of as the " Age of Brachi- 
 opods." The chief families are the Strophomenidce, Rhyn- 
 chonellida, Spiriferidce, and Lingulidcz. The genus Pentamerus 
 is especially characteristic of the Llandovery Rocks, or of what 
 has been termed the " Middle Silurian " by Sir Charles Lyell. 
 The Caradoc period is noticeable for the great number of 
 Orthides, mostly belonging to simple plaited forms. The ex- 
 clusively Silurian genera, however, are very few, but Obolus, 
 Siphonotreta, and Trematis are not known to have survived 
 into the Devonian period. Bivalves, such as Modiolopsis, 
 Ctenodonta, Lyrodesma, Ambonychia, Pterinea, Cardiola, &c., 
 are far from uncommon ; whilst the Gasteropods are largely 
 represented by such forms as Pleurotomaria, Metoptoma, 
 Holopea, Cydonema, and Murchisonia. The Heteropods are 
 represented by Madurea, Bellerophon, Cyrtolites, and Ecculiom- 
 phalus ; and the Pteropods abounded under the generic forms of 
 Theca (Hyolithes}, Conularia, Tentaculites ; and Pterotheca. The 
 Tetrabranchiate Cephalopods are extraordinarily abundant ; 
 but they belong almost exclusively to the sections of the 
 Nautilida and Orthoceratidce ; the Ammonitidce being repre- 
 sented only by the genus Goniatites, which has not as yet been 
 recognised in the Lower Silurian deposits. The family of the 
 Orthoceratidce attains here its maximum of development, over 
 one thousand species having been described by M. Barrande 
 from the Silurian basin of Bohemia alone. Their highest de- 
 velopment, however, is in the upper and not in the lower 
 division of the series. 
 
 The sub-kingdom Vertebrata is not known to be represented 
 in the Lower Silurian period at all ; but remains of various 
 fishes have been detected in the Upper Silurian series. In 
 Britain, the earliest fish-remains have been discovered in the 
 Lower Ludlow Shale, and consist of the cephalic bucklers of 
 Pteraspidean fishes. In the well-known stratum at the summit 
 of the Ludlow Rocks, familiar under the name of the " bone- 
 bed," have been discovered the defensive spines on which the 
 genus Onchus has been founded, and the shagreen-scales
 
 52O HISTORICAL PALEONTOLOGY. 
 
 which constitute the genera Thelodus and Sphagodus. These 
 spines are believed to indicate the existence in the Upper 
 Silurian seas of Cestraciont fishes allied to the living Port- 
 Jackson Shark, whilst the latter may have belonged to some 
 form like the existing Dog-fishes. It must be admitted, how- 
 ever, that the true nature of these fossils is still open to ques- 
 tion. From the Upper Silurian series of Bohemia M. Bar- 
 rand e describes no less than five fishes viz., Coccosteus primus, 
 C. Agassizi, Asterolepis Bohemicus, Gompholepis Panderi, and 
 Ctenacanthus Bohemicus, of which the first four belong to the 
 Ganoids, whilst the last is supposed to be a Cestraciont or a 
 Selachian. 
 
 CHAPTER XLIX. 
 
 DEVONIAN PERIOD. 
 
 ROCKS OF THE PERIOD. 
 
 THE Silurian Rocks are succeeded upward by a great system of 
 rocks, mainly of the nature of sandstones and conglomerates, 
 to which the name of Old Red Sandstone has been applied. 
 The name Devonian formation is also employed to designate 
 these same strata, rocks supposed to belong to this period 
 being largely developed in Devonshire, in England. It is 
 probable, however, that the Devonian rocks represent a por- 
 tion only of the Old Red Sandstone, and that they cannot be 
 regarded as the full equivalent of the Old Red Sandstone of 
 other regions. The term " Devonian " may, however, when 
 thus understood, be usefully employed as a general term for 
 all the strata which intervene between the Silurian System and 
 the succeeding formation of the Carboniferous rocks. 
 
 The uncertainty as to the exact position of the Devonian 
 Rocks of Devonshire in the series of the Old Red Sandstone, 
 or the uncertainty as to whether they represent the Old Red 
 Sandstone in whole or in part, arises from this that though 
 both formations are fossiliferous, the peculiar fossils of each 
 are never found associated together. The peculiar fossils of 
 the Old Red Sandstone proper are not found in the rocks of 
 Devonshire; and the fossils of the latter, though found in 
 equivalent strata on the Continent of Europe, do not occur in 
 the beds to which the name of Old Red Sandstone was origi- 
 nally applied. This, however, may be largely due to the fact
 
 DEVONIAN PERIOD. 521 
 
 that, while the Devonian strata are undoubtedly marine in 
 their origin, there seems reason to conclude that the Old Red 
 Sandstone proper was, in part at any rate, a fresh-water de- 
 posit. The two groups, therefore, might be truly contempora- 
 neous, and yet might not contain the same fossils. 
 
 The Old Red Sandstone is pre-eminently a British forma- 
 tion, and is divisible into three groups the Lower, Middle, 
 and Upper Old Red. 
 
 The Lower Old Red reposes with perfect conformity upon 
 the highest beds of the Upper Silurians, the two formations 
 appearing to pass into one another by an intermediate series 
 of " passage-beds," which contain large Crustaceans of the 
 family of the Eurypterids. The Lower Old Red consists 
 mainly of massive conglomerates, with sandstones, shales, and 
 concretionary limestones. Its organic remains consist chiefly 
 of plants, Crustaceans, and fishes. 
 
 The Middle Old Red of Scotland consists of dark -grey flag- 
 stones, bituminous, flaggy shales, and conglomerates, some- 
 times accompanied by shales having irregular calcareous no- 
 dules embedded in them. The fossil remains are chiefly fishes, 
 with one Crustacean, and a few plants. 
 
 The Upper Old Red of Scotland consists of pebbly con- 
 glomerates, sandstones, and shales, and contains many fishes, 
 a good many fragments supposed to belong to sea-weeds, and 
 some undoubted land-plants. 
 
 In North and South Devon there occurs, underlying the 
 Carboniferous Rocks, a great series of strata which has been 
 regarded as the equivalent of the Old Red Sandstone. Though 
 certainly referable, in great part at any rate, to the period of 
 the Old Red Sandstone, it does not appear that the Devonian 
 Rocks can be regarded as the equivalent of the Old Red 
 Sandstone of Scotland. The Devonian Rocks, however, are 
 largely represented on the continent of Europe, and they are 
 richly fossiliferous ; though they do not contain any of the 
 characteristic Crustaceans, and only one or two generic re- 
 presentatives of the characteristic fishes of the Scotch Old 
 Red. 
 
 The Devonian Rocks of Devonshire consist essentially of 
 greenish slates, alternating with sandstones, conglomerates, 
 and well-developed bands of blue crystalline limestone and 
 calcareous slates. 
 
 In no country in the world probably is there a finer and 
 more complete exposition of the strata intervening between 
 the Silurian and Carboniferous formations than in the United 
 States. The following are the main subdivisions of the Devo-
 
 Upper Devonian. 
 
 522 HISTORICAL PALAEONTOLOGY. 
 
 nian Rocks of the State of New York, in which, probably, the 
 series is most typically displayed : 
 
 1. Oriskany period (Oriskany Sandstone),* \ 
 
 2. Corniferous period (comprising the ( T 
 
 Cauda-Galli grit, Schoharie grit, and / Lower Devonian. 
 Upper Helderberg group), 
 
 3. Hamilton period (comprising the Mar- 
 
 cellus, Hamilton, arid Genesee 
 groups), 
 
 4. Chemung period (comprising the Por- 
 
 tage and Chemung groups), 
 
 5. Catskill period (Catskill Sandstone), 
 
 LIFE OF THE DEVONIAN PERIOD. Taken as a whole, the 
 life of the Devonian period may be regarded as transitional 
 between that of the underlying Silurian and overlying Carboni- 
 ferous period. As far, however, as our present knowledge 
 allows of our forming a definite opinion, the Devonian fauna 
 and flora approximate more nearly to those of the succeed- 
 ing Carboniferous than to those of the antecedent Silurian 
 period. This is especially shown in the Devonian plants, 
 which, as has been already pointed out, in almost all cases 
 agree generically with those of the Carboniferous ; whilst 
 in some cases they are even specifically identical. Thus, the 
 Devonian land supported an abundant vegetation, in which 
 Lepidodendroids, Sigillarioids, Calamites, Ferns, and Conifers, 
 mostly of Carboniferous types, play a prominent part. There 
 are, however, some forms, which, like Psilophyton, are as yet 
 not known to have occurred in the Carboniferous deposits. 
 
 The Protozoa are represented in the Devonian rocks byTvr- 
 aminifera and Sponges. Of the latter, Sparsispongia is the 
 most characteristic genus. (Steganodictyum is the buckler of a 
 Pteraspidean fish.) 
 
 The Ccclenterata are represented by the Hydrozoal genus 
 Dictyonema, which has often been referred to the Graptolites, 
 and by very numerous and varied forms of corals. No true 
 Graptolites have been as yet detected, unless Dictyonema be 
 one. The corals still belong mainly to the groups of the 
 Rugosa and Tabulata. The section of the Tubulosa (Aulopor- 
 ida) is represented here for the first time. Here also occur 
 the singular operculate Rugose corals upon which the genus 
 Calceola is founded. 
 
 The Echinodermata are represented in the Devonian period 
 by numerous Crinoids (Cupressocrinus, Aplocrinus, Platycri- 
 
 * The Oriskany Sandstone, though here placed in the Devonian, is pro- 
 bably really the summit of the Upper Silurian.
 
 DEVONIAN PERIOD. 523 
 
 nus, &c.), along with Pentremites ; whilst Cystideans are stated 
 to make their last appearance here. 
 
 The Articulates are represented by numerous Crustaceans, 
 and by a few insects the latter being the first of their class. 
 The Crustaceans are abundant, the chief forms being Trilobites 
 (Phaeops, Bronteus, Homalonotus, &c.), large Eurypterids (Ptery- 
 gotus, Stylonurus, Eurypterus, &c), and Ostracodes (Entomis, 
 Leper ditia, Beyrichia, &tc.) The bivalved carapaces of the last 
 mentioned of these groups are very abundant in certain De- 
 vonian beds, and the so-called " Cypridinen-schiefer " of the 
 Devonian series of Germany derives its name from the occur- 
 rence in it of vast numbers of the little Entomis ( Cypridina] 
 serrato-striata. In certain Devonian beds, also, the remains of 
 the Crustacean genus Estheria are very abundant. The Devo- 
 nian Insects appear on the whole to have the closest affinity 
 with certain of the existing Neuroptera or Pseudo-neuroptera. 
 
 The Mollusca are largely represented in Devonian time, and 
 the Brachiopods are especially abundant. The most charac- 
 teristic forms are those of the genera Stringocephalus (fig. 144) 
 and {Incites, along with numerous broad-winged Spirifers (such 
 as S. mucronata, fig. 148). Lamellibranchs (such as Megalo- 
 don and Pterinea), Gasteropods (Macrocheihis, Trochus, Pleuro- 
 tomaria, &c.), and Pteropods (Conularia) are well represented 
 in the Devonian Rocks. As in the case of the Silurian period, 
 no certain traces of the existence of Dibranchiate Cephalo- 
 pods have been as yet detected in the Devonian. The Tetra- 
 branchiate Cephalopods, however, are known by true Nautili 
 and Orthocerata, and by the genus Clymenia. The family of 
 the Ammonitidce is also represented by the genera Goniatites 
 and Bactrites. 
 
 The sub-kingdom of the Vertebrata is still represented by 
 fishes only ; but these are so abundant that the Devonian 
 period has been commonly called the " Age of Fishes." Most 
 of the Devonian Fishes belong to the order of the Ganoids, 
 and especially to the two groups of the Crossopterygida and 
 Ostracostei. The genera Cephalaspis, Pteraspis, Pterichthys, 
 and Coccosteus, do not survive this period, and there are many 
 other peculiar Lepidoganoids as well. Besides Ganoids, nu- 
 merous remains of Elasmobranchii have been detected, these 
 being referable both to the Cestraphori and to the Selachii. It 
 is probable, also, that some of the Devonian fishes are rightly 
 referable to the order Dipnoi, finding their nearest living 
 allies in the Mud-fishes of South America and Africa, and the' 
 Barramunda of Australia.
 
 524 HISTORICAL PAL/EONTOLOGY. 
 
 CHAPTER L. 
 
 CARBONIFEROUS PERIOD. 
 ROCKS OF THE PERIOD. 
 
 OVERLYING the great formation of the Old Red Sandstone, or 
 Devonian Rocks, sometimes unconformably but more often in 
 perfect conformity, we have the large and important series of 
 the Carboniferous Rocks, so called because workable beds of 
 coal are more commonly developed in this than in any other 
 formation. It must not be forgotten, however, that coal is not 
 exclusively a Carboniferous product, but that workable seams 
 of coal occur in several formations younger than the Carboni- 
 ferous. In all cases, too, the coal forms but a very small pro- 
 portion of the actual thickness of the Carboniferous Rocks, 
 occurring in comparatively thin beds intercalated in a great 
 series of sandstones, shales, and limestones. 
 
 The Carboniferous Rocks are largely developed in Britain, 
 on the continent of Europe, and in North America, and are 
 known to occur in other parts of the world also. Their general 
 composition, however, is, comparatively speaking, so uniform, 
 that it will be sufficient to take a general view of the formation 
 without considering each area separately. As a general rule, 
 the Carboniferous Rocks may be divided into the following 
 three groups, from below upward : 
 
 1. The Carboniferous Slates and Mountain Limestone, mainly 
 and most typically calcareous. Sometimes termed the Sub- 
 carboniferous group. 
 
 2. The Millstone Grit, essentially arenaceous and conglome- 
 ratic. 
 
 3. The Coal-measures, composed of alternating shales, sand- 
 stones, and other strata, with workable beds of coal. 
 
 I. The CARBONIFEROUS, SUB-CARBONIFEROUS, or MOUNTAIN, 
 LIMESTONE constitutes ordinarily the base of the Carboniferous 
 system. In Ireland, however, and elsewhere, the lowest beds 
 of the Carboniferous series are slates and grits, which attain a 
 maximum thickness of 5000 feet, and have been termed the 
 Carboniferous Slates. Their fossils are partially referable to 
 good Carboniferous types, and partly to Devonian forms, so 
 that they may be regarded as passage-beds. The Carboni- 
 'ferous limestone proper in its most typical development, as in 
 Wales and the west of England, consists of a great mass of 
 nearly pure limestone, from 1000 to 2000 feet thick, with a
 
 CARBONIFEROUS PERIOD. 525 
 
 few beds of shale. In other places, however, it is more or 
 less broken up into a series of different beds of limestone, 
 alternating with sandstones, grits, and shales, and sometimes 
 containing beds of coal. In North America it is never purely 
 calcareous, but consists mainly, or entirely, of sandstones and 
 shales, sometimes with thin beds of coal, or deposits of clay 
 iron-ore. Westward, however, it becomes more highly cal- 
 careous. 
 
 II. THE MILLSTONE GRIT. The highest beds of the Car- 
 boniferous limestone are succeeded, usually conformably but 
 sometimes unconformably, by a series of sandy and gritty beds 
 which have been termed the Millstone Grit. In its most 
 typical form the Millstone Grit consists of a series of hard 
 quartzose sandstones, the component grains of which are some- 
 times so large as to be more properly called small pebbles, 
 when the rock becomes a fine conglomerate. In other cases 
 regular conglomerates are present, and there are sometimes 
 shales, limestones, and thin beds of coal. The thickness of 
 the Millstone Grit varies from 1000 to 1700 feet as a rule; 
 but sometimes its thickness is very greatly diminished. Fos- 
 sils are scarce, and offer no peculiarity. 
 
 III. THE COAL-MEASURES. The Coal-measures proper 
 succeed the Millstone Grit conformably, and consist of a great 
 series of shale, sandstone, grit, and coal, attaining a total 
 thickness, when well developed, of from 7000 to 15,000 feet. 
 Except in Scotland, where workable coal-seams occur below 
 the horizon of the Millstone Grit, it is mostly from the true 
 Coal-measures that coal is obtained ; the largest and most 
 productive coal-fields of the world occurring in Britain, North 
 America, and Belgium. In their mineral nature, the Coal- 
 measures, all over the world, exhibit a wonderful general uni- 
 formity of composition. They consist, namely, of dark, often 
 nearly black, earthy and laminated shales, yellow, brown, and 
 purple sandstones, sometimes spotted, but very rarely red in 
 colour, along with occasional beds of limestone and clay iron- 
 ore, and beds of coal of varying thickness. These alternating 
 beds may follow one another in any order, and may be re- 
 peated over and over again, the total thickness sometimes 
 reaching the enormous amount of 14,000 feet, or nearly three 
 miles. In the South Wales coal-field the series consists as 
 usual of sandstones, shales, and coals, alternating with one 
 another, and indicating a slow, but probably intermittent, 
 depression of the area which they now occupy. In this coal- 
 field there are about 80 distinct beds of coal, each of which 
 represents an ancient land-surface. Each of these beds re-
 
 526 HISTORICAL PALAEONTOLOGY. 
 
 poses upon a sandy shale or clay, which is known as the 
 "underclay" or "floor" of the coal, and through which spread 
 numerous fossils referred to the genus Stigmaria, and now 
 known to be the roots of plants (Sigillaria). Each seam is 
 also surmounted by a bed of shale, forming the so-called 
 " roof" of the coal, and in this are found numerous flattened 
 and compressed branches and stems of plants. 
 
 LIFE OF THE PERIOD. The vegetation of the Carboniferous 
 period is exceedingly luxuriant ; but its characters have been 
 already so fully discussed as to render unnecessary anything 
 further here than a mere allusion to its chief members. The 
 chief feature in the Carboniferous flora is the great predominance 
 of Cryptogams as compared with Phanerogams. The former 
 are amply represented by numerous Ferns, Calamites, Lepido- 
 dendroids, and, perhaps, Sigillarioids. The latter, with few 
 exceptions, are represented only by Gymnospermous Exogens. 
 
 The Protozoa are represented in the Carboniferous rocks by 
 a few Sponges and by the shells of Foraminifera, of which the 
 genus Fusulina (fig. 1 1 ) is the most characteristic. The tests 
 of this form are sometimes so abundant as almost to make up 
 the whole of certain limestones. 
 
 The Cceletiterates are represented almost exclusively by 
 Corals, which abound especially in some of the limestones of 
 the Lower Carboniferous series. Most of the Carbonifer- 
 ous Corals belong to the Tabulate division of the Zoantharia 
 Sderodermata, or to the Rugosa, and amongst the more impor- 
 tant genera may be mentioned Lithostrotion, Syringopora, Lons- 
 daleia, Cyathophyllum, Amplexus, Farosites, and Chatties, 
 
 Of the Echinodcrmata the most abundant are the Crinoids, 
 which occur in vast profusion in most of the limestones of the 
 Carboniferous series. The most important genera are Aetino- 
 crimts, Platycrinus, Cyathocrinus, Poleriocrinus, and Rhodocri- 
 nus. In some parts of the Carboniferous, Pentremites are also 
 exceedingly abundant. Lastly, the Echinoids are represented 
 by the two aberrant genera, Archceocidaris and Palcechinus, 
 
 Annelides are not abundant, with the single exception of 
 the little Spirorbis, pr Microconchus, earbonarius, which some- 
 times occurs in great plenty. The Crustaceans belong chiefly 
 to the groups of the Ostracoda and Phyllopoda. The Trilo- 
 bites make here their last appearance ; the genera Phittipsia, 
 Griffithides, and Brachymetopus, being the last of the race. 
 The Eurypterids also appear to die out finally in the Carbon- 
 iferous. On the other hand, the Xiphosura are now repre- 
 sented by the genera Bdinurns and Preslwichia (fig. 119); and 
 the Macrourous Decapods appear to commence their existence
 
 CARBONIFEROUS PERIOD. 527 
 
 at this point. Of the Phyllopods, the best-known genera are 
 Dithyrocaris and Leaia. The little Ostracoda are often exceed- 
 ingly abundant, some of them belonging to marine, and others 
 to fresh-water or brackish-water forms. About thirteen genera 
 have been already detected in rocks of Carboniferous age, the 
 most important being Leperditia, Bairdia, Cypridina, Cythere, 
 Candona, and Beyrichia, of which the last appears to die out 
 here. Besides Crustaceans, the Arthropods are represented 
 by Arachnida, Myriapoda, and Insecta. 
 
 The Mollusca are very largely represented in Carboniferous 
 seas. Polyzoa are very abundant, the most characteristic forms 
 belonging to the genera Fenestella, Ptilopora, Retepora, and Ar- 
 chimedipora. Brachiopods occur in profusion, and belong as 
 a rule to very well marked types. The great family of the 
 Productidtz attains here its maximum, most of the remaining 
 forms belonging to the genera Spirifera, Strophomena, Orthis, 
 Lingula, Terebratula, and Distinct. Bivalves are very numerous, 
 and the family of the Aviciilidce reaches here its maximum of 
 development. Other well-known Carboniferous Bivalves be- 
 long to the genera Edmondia, Posidonomya, Conocardiuin, and 
 Cardiomorpha. The Gasteropods are represented mainly by 
 the characteristically Palaeozoic genera Macrocheilus and Lox- 
 onema, the almost exclusively Palaeozoic Euomphalus, and the 
 persistent genus Pleiirotomaria. Heteropods (Bellerophon and 
 Porcellid) and Pteropods {Conularia} are also not unknown. 
 No Dibranchiate Cephalopods are as yet known to occur, but 
 the Tetrabranchiates are well represented the Nautilidcz by 
 forms of Orthoceras and Cyrtoceras, and the Ammonitidce by 
 Goniatites. 
 
 The Vertebrates are now represented by Amphibians, in 
 addition to Fishes. The latter are still chiefly Ganoid, the 
 commonest forms belonging to the genera Palaoniscus, Rhizo- 
 dus, and Holoptychius. Besides these occur numerous teeth 
 and fin-spines referred to Elasmobranchii, the most important 
 genera founded on these remains being Psammodus, Orodus, 
 Cochliodns, Cladodus, Ctenacanthus, Pleuracanthus, Gyracanthus, 
 Lept acanthus, and Orthacanthus. The Amphibians appear to 
 belong exclusively to the extinct order of the Labyrinthodon- 
 tia, referred to many genera, of which the most important are 
 Archegosaurus, Anthracosaurus, and Baphetes. Some of the 
 remains, however, of the air-breathing Vertebrates of the Car- 
 boniferous period are perhaps higher in the scale than Laby- 
 rinthodonts ; and they have been supposed to indicate the 
 existence at this time of true Reptiles.
 
 528 HISTORICAL PALEONTOLOGY. 
 
 PERMIAN PERIOD. 
 
 ROCKS OF THE PERIOD. The Carboniferous series is suc- 
 ceeded by a group of beds, which complete the Palaeozoic 
 formations, and which were termed Permian Rocks by Sir 
 Roderick Murchison, from the province of Perm, in Russia, 
 where they are extensively developed. Formerly these rocks 
 were grouped with the succeeding formation of the Trias under 
 the common name of " New Red Sandstone." This name 
 was given them because they contain a good deal of red sand- 
 stone, and because they are superior to the Carboniferous 
 rocks, while the Old Red Sandstone is inferior. Nowadays, 
 however, the term " New Red Sandstone " is rarely employed, 
 unless it be for red sandstones and associated rocks, which are 
 seen to overlie the Coal-measures, but which contain no fossils 
 by which their exact age may be made out. Under these 
 circumstances it is sometimes convenient to employ the term 
 " New Red Sandstone." The New Red, however, of the older 
 geologists is now broken up into the two formations of the 
 Permian and Triassic rocks, the former being the top of the 
 Palaeozoic series, and the latter constituting the base of the 
 Mesozoic. 
 
 The Permian rocks, as a rule, repose unconformably upon 
 the underlying Carboniferous rocks, but seem to pass upward 
 conformably into the Trias, in most instances. The division, 
 therefore, between the Permian and Triassic rocks, and, con- 
 sequently, between the Palaeozoic and Mesozoic series, is not 
 founded upon any marked or universal physical break, but 
 upon the difference in the life of the two periods. 
 
 The Permian rocks exhibit their most typical features in 
 Russia and Germany, though they are very well developed in 
 parts of Britain, and they occur in North America. When 
 well developed, they exhibit three main divisions : a lower set 
 of sandstones, a middle group, generally calcareous, and an 
 upper series of sandstones, constituting respectively the Lower, 
 Middle, and Upper Permians. 
 
 In Russia, Germany, and Britain, the Permian rocks con- 
 sist of the following members : 
 
 i. The Loiver Permians consisting mainly of a great series 
 of sandstones, of different colours, but usually red. The base 
 of this series is often constituted by massive breccias with 
 included fragments of the older rocks, upon which they may 
 happen to repose ; and similar breccias sometimes occur in 
 the upper portion of the series as well. The thickness of this
 
 PERMIAN PERIOD. 529 
 
 group varies a good deal, but may amount to 3000 or 4000 
 feet. 
 
 2. The Middle Permians, consisting, in their typical de- 
 velopment, of laminated marls, or " marl-slate," surmounted 
 by beds of magnesian limestone (the " Zechstein" of the Ger- 
 man geologists). Sometimes the limestones are degenerate or 
 wholly deficient, and the series may consist of sandy shales 
 and gypsiferous clays. The magnesian limestone, however, of 
 the Middle Permians is, as a rule, so well marked a feature 
 that it was long spoken of as the Magnesian Limestone. 
 
 3. The Upper Permians, consisting of a series of sandstones 
 and shales, or of red or mottled marls, often gypsiferous, and 
 sometimes including beds of limestone. 
 
 In North America, the Permian rocks appear to be confined 
 to the region west of the Mississippi, being especially well de- 
 veloped in Kansas. Their exact limits have not as yet been 
 made out, and their total thickness is not more than a few 
 hundred feet. They consist of sandstones, conglomerates, 
 limestones, marls, and beds of gypsum. 
 
 LIFE OF THE PERIOD. The Permian Rocks have yielded 
 a very considerable number of plants, most of which are speci- 
 fically distinct from those of the Coal-measures. Though the 
 species, however, are distinct, many of the Permian genera 
 date back to the antecedent Carboniferous period. Thus, 
 besides several genera of Carboniferous Ferns, the Permian 
 Rocks contain the well-known genera Lepidodendron and Cala- 
 mites. The Sigillarioids, however, seem to have finally dis- 
 appeared. Conifers are by no means uncommon, and some 
 of these ( Ullmanid) produce true cones. The genus Walchia 
 comprises the most characteristic of the Permian Conifers. 
 
 The Protozoa are represented in the Permian deposits by a 
 few Sponges and Foraminifera. The Coelenterates are repre- 
 sented by Corals, but these are rarely abundant. The Rugosa 
 are reduced here to the single genus Polycoelia. Crustaceans 
 are also by no means largely represented. The Trilobita 
 have disappeared, as have the Eurypterids. The King-crabs 
 (Limulus} are, however, represented by one species. Ostracoda 
 are tolerably abundant, and the genus Prosoponiscus has been 
 regarded as referable to either the Isopoda or the Amphipoda. 
 Lastly, the genus Hemitrochiscus has been founded for the 
 reception of a Permian fossil which has been regarded as the 
 remains of a true Crab. If this determination be correct, the 
 tribe of Brachyurous Decapods has its commencement here. 
 
 Molluscs occur in greater abundance than any of the pre- 
 ceding. The genera Fenestella and Acanthodadia represent the 
 2 L
 
 530 HISTORICAL PALAEONTOLOGY. 
 
 Polyzoa. The most important genera of Brachiopods are 
 Spin/era, Producta, Strophalosia, Camaroptioria, and Lingula. 
 Bivalves are moderately numerous, the commonest forms be- 
 longing to the family Trigoniadce and to the genus Axinus 
 (Schizodus). Other forms belong to the genera Mytilus, Bake- 
 wellia, and Avicula. Gasteropods and Cephalopods are, upon 
 the whole, very poorly represented in the Permian series. 
 
 The most important Permian fossils are referable to the 
 Vertebrata. Fishes are comparatively very abundant, and be- 
 long almost entirely to the order of the Ganoids. The most 
 characteristic genera are Palceoniscus, Platysomus, Pygopterus, 
 Gyropristis, Acrolepis, and Ccelacanthus. The Amphibians are 
 represented by various forms belonging to the Labyrinthodontia. 
 True Reptiles are represented by the Proiorosaurus of the 
 " Kupfer-schiefer " of Germany, and somewhat doubtfully by 
 the Chelonian footprints (Chelichnus) from the Permian Sand- 
 stones of Dumfriesshire. 
 
 CHAPTER LI. 
 
 TRIASSIC PERIOD. 
 ROCKS OF THE PERIOD. 
 
 WE come now to the consideration of the great Afesozoic, or 
 Secondary series of formations, consisting, in ascending order, 
 of the Triassic, Jurassic, and Cretaceous systems. The Trias- 
 sic group forms the base of the Mesozoic series, and corre- 
 sponds with the higher portion of the New Red Sandstone of 
 the older geologists. Like the Permian Rocks, and as implied 
 by its name, the Trias admits of a subdivision into three 
 groups a Lower, Middle, and Upper Trias. Of these sub- 
 divisions the middle one is wanting in Britain ; and all have 
 received German names, being more largely and typically de- 
 veloped in Germany than in any other country. Thus, the 
 Lower Trias is known as the Bunter Sandstein; the Middle 
 Trias is called the Muscficlkalk, and the Upper Trias is known 
 as the Keuper. 
 
 I. The lowest division of the Trias is known as the Bunter 
 Sandstein, from the generally variegated colours of the beds 
 which compose it (German, bunt, variegated). The Bunter 
 Sandstein of the continent of Europe consists of red and
 
 TRIASSIC PERIOD. 53! 
 
 white sandstones, with red clays, and thin limestones, the 
 whole attaining a thickness of about 1500 feet. The term 
 " marl " is very generally employed to designate the clays of 
 the Lower and Upper Trias, but the term is inappropriate, as 
 they contain no lime, and are therefore not genuine marls. 
 In Britain the Bunter Sandstein consists of red and mottled 
 sandstones, with unconsolidated conglomerates, or " pebble- 
 beds," the whole having a thickness of about 1200 feet. The 
 Bunter Sandstein, as a rule, is very barren of fossils. 
 
 II. The Middle Trias is not developed in Britain, but it 
 is largely developed in Germany, where it constitutes what is 
 known as the Muschclkalk (Germ. Muschel, mussel ; kalk, lime- 
 stone), from the abundance of fossil shells which it contains. 
 The Muschelkalk consists of compact grey or yellowish lime- 
 stones, sometimes dolomitic, and including occasional beds of 
 gypsum and rock-salt. 
 
 III. The Upper Trias, or Keuper, as it is generally called, 
 occurs in England ; but is not so well developed as it is in 
 Germany. In Britain the Keuper is about 1000 feet in thick- 
 ness, and consists of white and brown sandstones, with red 
 marls, the whole topped by red clays with rock-salt and 
 gypsum. 
 
 The Keuper in Britain is extremely unfossiliferous ; but it 
 passes upwards with perfect conformity into a very remarkable 
 group of beds, at one time classed with the Lias, and now 
 known under the names of the Penarth beds (from Penarth, in 
 Glamorganshire), the Rhastic beds (from the Rhastic Alps), or 
 the Avicula contorta beds (from the occurrence in them of 
 great numbers of this peculiar Bivalve). These singular beds 
 have been variously regarded as the highest beds of the Trias, 
 or the lowest beds of the Lias, or as an intermediate group. 
 The phenomena observed on the Continent, however, render 
 it best to consider them as Triassic, as they certainly agree 
 with the so-called St Cassian or Kossen beds which form the 
 top of the Trias in the Austrian Alps. 
 
 The Penarth beds occur in Glamorganshire, Gloucestershire, 
 Warwickshire, Staffordshire, and the north of Ireland; and 
 they generally consist of a small thickness of dark grey and 
 black shales, surmounted conformably by the lowest beds of 
 the Lias. The most characteristic fossils which they contain 
 are the three Bivalves Cardium Rh&ticum, Avicula contorta, 
 and Peden Valoniensis ; but they have yielded many other 
 fossils, amongst which the most important are the remains of 
 Fishes and small Mammals (Microlestes). 
 
 In the Austrian Alps the Trias terminates upwards in an
 
 532 
 
 HISTORICAL PALEONTOLOGY. 
 
 Koessen beds. 
 
 (Synonyms, Upper St 
 Cassian beds of Escher 
 and Merian). 
 
 2. Dachstein beds. 
 
 Hallstadt beds 
 (or St Cassian). 
 
 4. A. Guttenstein beds. 
 B. Werfen beds, base of 
 
 Upper Trias? 
 Lower Trias of some 
 geologists. 
 
 extraordinary series of fossiliferous beds, replete with marine 
 fossils. Sir Charles Lyell gives the following table of these 
 remarkable deposits : 
 
 Strata below the Lias in the Austrian Alps, in Descending Order. 
 
 /Grey and black limestone, with calcareous 
 marls having a thickness of about 50 
 feet. Among the fossils, Brachiopoda 
 very numerous ; some few species com- 
 mon to the genuine Lias ; many pecu- 
 liar. Avicula contorta, Pecten Valo- 
 niensis, Cardiunt Rhtzticum, Avicula 
 inaquivalvis, Spirifer Afunsteri, Dav. 
 Strata containing the above fossils al- 
 ternate with the Dachstein beds, lying 
 next below. 
 
 White or greyish limestone, often in beds 
 three or four feet thick. Total thick- 
 ness of the formation above 2000 feet. 
 Upper part fossiliferous, with some 
 strata composed of corals. (Lithoden- 
 dron.) Lower portion without fossils. 
 Among the characteristic shells are He- 
 micardium Wulferii, Megalodon triqueter, 
 and other large bivalves. 
 Red, pink, or white marble, from 800 to 
 icoo feet in thickness, containing more 
 than 800 species of marine fossils, for 
 the most part mollusca. Many species 
 of Orthoceras. True Ammonites, besides 
 Ceratites and Gtmiatites, Belemnites (rare), 
 Porcellia, Pleurotomaria, Trochus, Mono- 
 tis salinaria, &c. 
 
 A. Black and grey lime- 
 stone 1 50 feet thick, al- 
 ternating with the un- 
 derlying Werfen beds. 
 
 B. Red and green shale 
 and sandstone, with 
 salt and gypsum. 
 
 In the United States, rocks of Triassic age occur in several 
 areas between the Appalachians and the Atlantic seaboard ; 
 but they show no such triple division as in Germany, and their 
 exact place in the system is uncertain. The rocks of these 
 areas consist of red sandstones, sometimes shaly or conglomer- 
 atic, occasionally with beds of impure limestone. Other more 
 extensive areas where Triassic rocks appear at the surface, are 
 found west of the Mississippi, on the slopes of the Rocky Moun- 
 tains, where the beds consist of sandstones and gypsiferous 
 marls. The American Trias is chiefly remarkable for having 
 yielded the remains of a small Marsupial (Dromatherium] and 
 
 Among the fossils 
 are Ceratitet 
 cassian us. My- 
 acitfs fassfitn- 
 sis, Naticella 
 costata^ c.
 
 TRIASSIC PERIOD. 
 
 533 
 
 numerous footprints, which have generally been referred to 
 Birds (Brontozoum), along with the tracks of undoubted Rep- 
 tiles (Otozoum, Anisopus, &c.) 
 
 LIFE OF THE TRIASSIC PERIOD. The Triassic period, as 
 regards its plants and animals, is in many respects intermedi- 
 ate between the Palaeozoic and the later Mesozoic deposits, 
 whilst being itself decidedly Mesozoic. Amongst the plants 
 there are some Palaeozoic types (such as Catamites) but there 
 is no longer a marked predominance of Cryptogams, and the 
 leading forms are Ferns (Pecopteris, Neuropteris, Acrostichites, 
 &c.), Cycads (Pterophyllum, Podozamites, &c.), and Conifers 
 (chiefly belonging to the genus Voltzia). 
 
 The Protozoa are represented in Triassic times by several 
 sponges (Amorphospongia, Cupulispongia, Leiospongia, &c.) 
 Corals are by no means infrequent in the Muscheikalk, and in 
 some of the limestones of the Upper Trias ; but they are other- 
 wise rare. They belong mostly to Secondary types, such as 
 Montlivaltia, Synastrcea, Acrosmilia, Eunomia, &c. The Echi- 
 noderms are rarely abundant, but two forms are exceedingly 
 characteristic of the Muscheikalk. These are the beautiful 
 Lily-encrinite, Encrinus liliiformis (fig. 80), and the little 
 Ophiurid, Aspidura loricata (fig. 71). 
 
 Articulates are not abundant, with the exception of Ostra- 
 coda, which are sometimes very plentiful. The other common 
 forms are referable to Estheria; but Macrurous Decapods have 
 also been detected. Besides Crustaceans, several forms of 
 Insects have been discovered. 
 
 The Mollusca are exceedingly abundant in parts of the Tri- 
 assic series, and they exhibit an extraordinary intermixture of 
 Palaeozoic and Mesozoic types. This is shown in a synoptical 
 manner in the following table of the Mollusca of the Upper 
 Trias of the Austrian Alps, given by Sir Charles Lyell in his 
 ' Elements of Geology : ' 
 
 Genera of Fossil Mollusca in the St Cassian and Hallstadt Beds. 
 
 Common to Older Rocks. 
 
 Cyrtoceras. 
 
 Orthoceras. 
 
 Goniatites. 
 
 Loxonema. 
 
 Holopella. 
 
 Murchisonia. 
 
 Euomphalus. 
 
 Porcellia. 
 
 Megalodon. 
 
 Cyrtia. 
 
 Characteristic Triassic 
 
 Common to Newer Rocks. 
 
 Genera. 
 
 
 Ceratites. 
 
 Ammonites. 
 
 Scoliostoma (or 
 
 Belemnites. 
 
 Cochlearia). 
 
 Nerinsea. 
 
 Naticella. 
 
 Opis. 
 
 Platystoma. 
 
 Cardita. 
 
 Isoarca. 
 
 Trigonia. 
 
 Pleurophorus. 
 
 Myoconchus. 
 
 Myophoria. 
 
 Ostrea. I sp. 
 
 Monotis. 
 
 Plicatula. 
 
 Koninckia. 
 
 Thecidium.
 
 534 HISTORICAL PALEONTOLOGY. 
 
 From the above table it will be seen, that amongst the Gas- 
 teropoda the Trias has yielded the characteristically Palaeozoic 
 Loxonema, Holopdla, Murchisonia, and Euomphalus, all of 
 which commence their existence in the Silurian period. With 
 these are forms like Scoliostoma and Platystoma, which are 
 characteristically Triassic, and these are associated with such 
 a typical Jurassic genus as Nerincea. Amongst the Bivalves, 
 we find the Palaeozoic Megalodon side by side with the Triassic 
 Monotis and Myophoria, these being associated with the Tri- 
 gonice, Plicatulce, and Oysters of later deposits. The Brachi- 
 opods exhibit the Palaeozoic Cyrtia, with the Triassic Koninc- 
 kia, and the modern genus Thecidium. Lastly, amongst the 
 Cephalopods, this same intermingling of old and new types is 
 shown in its most striking form. The ancient genera Orthoceras, 
 Cyrtoceras, and Goniatites appear here for the last time upon 
 the scene. With these are the first Dibranchiate Cephalopods, 
 represented by the great Mesozoic genus Belemnites. The 
 Amntonitidce, with the disappearance of the comparatively 
 simple Goniatites, are represented by the more complex Cera- 
 iites, which is exclusively Triassic ; whilst the still more com- 
 plicated genus Ammonites makes its first appearance here, and 
 is never again wanting till we reach the close of the Mesozoic 
 period. 
 
 The Vertebrata are represented in the Triassic period ap- 
 parently by members of all the existing classes. Fishes are 
 very numerous, and belong chiefly to the Hybodonts, Acro- 
 donts, and Ganoids. Amongst the more important forms we 
 find the Palaeozoic genera Palaoniscus and AmMypterus, with 
 the Secondary Hybodtis and Acrodus, and the Triassic genus 
 Saurichthys. We may also assert now with tolerable safety, 
 that the order of the Dipnoous Fishes was represented in 
 Triassic times by various species of the genus Ceratodus. 
 
 The Amphibians of the Trias are known both by the actual 
 bones and teeth, and still more commonly by their footprints. 
 They belonged exclusively to the order of the Labyrinthodon- 
 tia, which disappears finally at the close of this period. 
 
 Of the living orders of the Reptiles, the Chelonians are only 
 known by more or less doubtful footprints ; the Lacertilians 
 are represented by Telerpeton and Rhynchosaurus (the last often 
 referred to the Dicynodonts) ; the Crocodilia are represented 
 by Stagonolepis, Belodon, Thecodontosaurus, and Palceosaurus 
 (the last two referred by Huxley to the Deinosaurs) ; and the 
 Ophidians do not appear to have yet commenced their exist- 
 ence. Of the extinct orders of Reptiles, the Pterosaurs are 
 unknown in the Trias, and the Ichthyosaurs are not with cer-
 
 JURASSIC PERIOD. 535 
 
 tainty known to have existed. The Plesiosaurs are represented 
 by species of Plesiosaurus itself, and by the allied genera Sitno- 
 saurus, Nothosaurus, Pistosaurus, &c. The Anomodontia are 
 represented by the genera Dicynodon and Oudenodon ; whilst 
 Rhynchosaurus is referred by Owen to this group. Lastly, the 
 Deinosaurs are represented, according to Huxley, by several 
 forms, amongst which the most important are the "Thecodont" 
 Palceosaurus and Thecodontosaurus, both of which have been 
 referred by other writers to different groups of the Reptilia. 
 
 The existence of Birds during the Triassic period must, as 
 yet, be regarded as uncertain. The only evidence as to their 
 existence which has been hitherto obtained, consists in the 
 paired footprints which have been already spoken of as occur- 
 ring in the Triassic strata of the Connecticut Valley. These 
 footprints are very numerous, and are often of very large size ; 
 and there is no doubt but that many of them were produced 
 by animals walking upon two legs. Some of them, however, 
 have been unquestionably produced by Reptiles ; and it must 
 at present remain uncertain whether all have been thus formed, 
 or whether some may not have been formed by Birds. The 
 probabilities, however, are in favour of the view that some of 
 these tracks are truly ornithic. 
 
 Lastly, the Mammals are represented in the Trias only by 
 the small forms referred to the genera Microlestes and Droma- 
 therium, both of which are probably referable to the order of 
 the Marsupials. 
 
 CHAPTER LII. 
 
 JURASSIC PERIOD. 
 ROCKS OF THE PERIOD. 
 
 SUCCEEDING to the Trias, we have a great series of Rocks 
 which are known as the Oolitic Rocks, from their commonly 
 containing oolitic limestones, or as the Jurassic Series, from 
 their being largely developed in the mountain -range of the 
 Jura, on the western borders of Switzerland. The Jurassic 
 rocks are very extensively developed in Britain, where they 
 consist of the following members in ascending order : 
 
 I. Lias. 
 
 II. Lower Oolites (consisting of the Inferior Oolite, Fuller's 
 
 Earth, Great Oolite, Stonesfield Slate, &c.)
 
 536 HISTORICAL PALEONTOLOGY. 
 
 III. Middle Oolites (Oxford Clay and Coral-rag). 
 
 IV. Upper Oolites (Kimmeridge Clay, Portland Stone, and 
 
 Purbeck beds). 
 
 I. The Lias succeeds the uppermost beds of the Trias with 
 perfect conformity, and passes upward, generally conformably, 
 into the lowest beds of the Lower Oolites. It consists essen- 
 tially of a great series of bluish or greyish laminated clays, 
 alternating with thin bands of blue or grey limestone, the 
 whole assuming at a distance a characteristically striped and 
 banded appearance. 
 
 II. The Lower Oolites consist of calcareous freestones (In- 
 ferior Oolite), shales, clays, and marls (Fuller's earth), fine- 
 grained Oolitic limestones (Great Oolite), with calcareous 
 flags at the base (Stonesfield slate), and superiorly shelly lime- 
 stones and calcareous sandstones (Forest - marble and Corn- 
 brash), the whole having a thickness of from 400 to 500 feet. 
 In Yorkshire the Lower Oolites consist of limestones with car- 
 bonaceous shales and thin seams of coal, which are sufficiently 
 extensive and constant to be worked for coal. Of this age, 
 also, is probably the coal-field of Brora, in Sutherlandshire, in 
 the north of Scotland. 
 
 III. The Middle Oolites are composed of a great mass of 
 dark-blue tenacious clay (Oxford clay), with a maximum thick- 
 ness of 700 feet, surmounted by from 150 to 250 feet of lime- 
 stones, known as the Coral-rag, from the number of corals con- 
 tained in them. 
 
 IV. The Upper Oolites consist in Britain of laminated, some- 
 times carbonaceous or bituminous clays (Kimmeridge clay), 
 forming the base of the group, and having a thickness of 500 
 or 600 feet. These are succeeded by sandstones and lime- 
 stones (Portland stone) of about 120 feet in thickness; and 
 the formation is capped by a remarkable group of alternating 
 strata of fresh-water, brackish-water, and marine beds, with old 
 land-surfaces, the whole known as the Purbeck beds, and 
 having a united thickness of about 150 feet. Of the same age 
 as the Upper Oolites in Britain is the Solenhofen slate of 
 Bavaria, an exceedingly fine-grained stone, which is largely 
 used in lithography, and is celebrated for the number and 
 beauty of its organic remains, especially those of Vertebrates. 
 
 Rocks belonging to the Jurassic series, in the form of lime- 
 stones and marls, have been detected by their fossils in the 
 Laramie Mountains and in other portions of the Rocky Moun- 
 tains, and also at various points in Arctic America. The ex- 
 tent, however, of these beds is unknown, and no subdivisions 
 have hitherto been established in them.
 
 JURASSIC PERIOD. 537 
 
 LIFE OF THE PERIOD. The vegetation of the Jurassic 
 period is characterised by the abundance of Ferns, Cycads, 
 and Conifers the Cycadacece attaining here their maximum of 
 development. 
 
 The Protozoa are represented by numerous Foraminifera 
 and by Sponges. Of the former the genera Involuting Nodo- 
 saria, Cristellaria, Dentalina, and Frondicularia may be men- 
 tioned as amongst the most important. Of the latter the chief 
 forms belong to Cribrospongia, Actinospongia, Porospongia, 
 Goniospongia, Perispongia, Chenendopora, and Scyphia. 
 
 The Ccelenterates are represented in the Jurassic period by 
 numerous corals, which are exceedingly abundant in some of 
 the limestones of the series (such as the Coral-rag and the 
 Great Oolite). The number of Oolitic genera of Corals is 
 very large, but the commonest and most characteristic forms 
 belong to Thamnastrtza, Isastrcca, Prionastr&a, Anabaaa, Mont- 
 livaltia, T/iecosmilia, Eunomia, Protoseris, Comoseris, Den- 
 drarea, Dactylarea, Loboccenia, Aplophyllia, Trochocyathus, and 
 Stylina. 
 
 The Echinoderms are very largely represented all through 
 the Jurassic Series. The Crinoids are represented both by 
 stalked forms (Pentacrinus, Extracrinus, Apiocrinus, &c.) and 
 by free forms (Saccosomd). Echinoids are extremely abundant 
 in many parts of the series, the commonest generic types being 
 HetnictdariS) Diadema, Pseudodiadema, Nucleolites, Dysaster 
 (Colly rites), Acrosalenia, and Cidaris. True Star-fishes ( Uraster, 
 Tropidaster, Plumaster, Solaster, and Astropecteri) are not un- 
 known, and Ophiuroids (Ophioderma, Ophiolepis, Acroura, &c.) 
 are far from uncommon. 
 
 As regards the' Arthropods, Crustaceans are abundantly 
 found in certain beds (especially in the Solenhofen Slates). 
 The orders which are most largely represented are the Decapoda 
 (with many forms, both Macrurous and Brachyurous), the Cir- 
 ripedia, and the Ostracoda. Besides Crustaceans, the Oolitic 
 rocks have yielded numerous Insects, belong to the orders 
 Coleoptera, Neuroptera, Orthoptera, Hemiptera, Diptera, and 
 Hymenoptera. True Spiders have also been detected. 
 
 Coming to the Mollusca, Brachiopods are still abundant, 
 though they do not fill such a predominant place in the marine 
 fauna as in many Palaeozoic deposits. The Palaeozoic genera 
 Leptcena and Spirifera appear here (in the Lias) for the last 
 time ; and most of the Jurassic forms belong to the modern 
 genera Terebratula and Rhynchonella. Bivalves are very abun- 
 dant, and approximate in many respects to existing forms. 
 The sub-genera Gryphaa and Exogyra amongst the Oysters,
 
 538 HISTORICAL PALEONTOLOGY. 
 
 along with numerous forms of Ostrea itself, and the genera 
 Trigonia, Lima (Plagiostomd), Pholadomya, Cardinia, and 
 Avicula may be mentioned as comprising most of the com- 
 moner forms. One of the most remarkable, however, of the 
 Oolitic genera of Lamellibranchs is Diceras (fig. 189), com- 
 prising certain singular shells allied to the existing Chatna. 
 These are so abundant in a limestone of the Alps of the age 
 of the Coral-rag as to have gained for this formation the name 
 of " Diceras Limestone." 
 
 Of the Gasteropoda there are many examples of the ancient 
 genus Pleurotomaria ; but on the whole the Univalves have a 
 modern aspect. Holostomatous Univalves, such as Nerita, 
 Patella, Natica, Turritella, Chemnitzia, and Nerinaa, still hold 
 a predominant place ; and species of the last-named genus are 
 especially characteristic of parts of the series. The Tertiary 
 and modern genus, Cerithium, also makes its first appearance 
 here. Though the Holostomata still predominate, there is now 
 a fair proportion of the carnivorous siphonostomatous Univalves, 
 and many of these are referable to existing genera. Thus, 
 with the extinct Purpuroidea are found forms belonging to 
 such' genera as Pteroceras, Rostellaria, Buccinum, Fusus, Murex, 
 and Pleurotoma. The Cephalopoda are exceedingly abundant 
 all through the Jurassic series, and are represented by both 
 Dibranchiate and Tetrabranchiate types. The Dibranchiate 
 Belemnitida here attained their maximum of development, 
 many beds being literally charged with the guards of these 
 extinct cuttle-fishes. The Tetrabranchiates are represented 
 by various species of the persistent genus Nautilus, but more 
 especially by species of Ammonites, which are extraordinarily 
 plentiful and of the most varied forms. Speaking generally, 
 Ammonites and Belemnites may be stated to be the charac- 
 teristic fossils of the Jurassic period. 
 
 In the fresh-water strata of the Oolites (Purbeck beds), the 
 Molluscs, as a matter of course, belong to forms which now 
 inhabit fresh water. Thus, amongst the Bivalves we have the 
 genus Cyrena, and amongst the Gasteropods we meet with the 
 genera Planorbis, Physa, Paludina, and Melanopsis. As regards 
 the Vertebrates, little need be said about the Jurassic fishes, 
 which belong to the Ganoidei and Elasmobranchii. The Ganoids 
 now possess, many of them, symmetrical tails, and the most 
 important genera are Tetragonolepis, Dapeditis, sEehmodus, 
 Pycnodus, Leptolepis, and Aspidorhynchus. The Cestraphon 
 are represented by Hybodonts (Hybodus and Strophodus) and 
 Acrodus. Lastly, the true Sharks are not without Jurassic 
 representatives (Notidanus).
 
 JURASSIC PERIOD. 539 
 
 The Reptilia have an enormous development in Oolitic 
 times, and are represented both by forms allied to those now 
 in existence and by types which are now altogether extinct. Of 
 the living forms there are as yet no Ophidians, but the Che- 
 lonians are represented by various genera (Idiochelys, Eury- 
 sternum, and Chelone). The Lacertilians are represented by 
 several forms of no special importance, and the Crocodilia were 
 represented by species with amphiccelous vertebras ( Teleosaurus 
 and Steneosaurus). Of the extinct orders of Reptiles, the Ichthyop- 
 terygia, comprising only the genus Ichthyosaurus, form a very 
 marked feature in the Reptilian fauna of the Jurassic period. 
 Numerous species of Ichthyosaurus are known ; and the remains 
 of individuals are very abundant in certain beds, especially in 
 the Lias. The Sauropterygia are represented by numerous 
 species of Plesiosaurus, remains of which are also very abun- 
 dant in the Lias and in other parts of the Oolitic series. The 
 Pterosauria are represented by all their chief genera (Ptero- 
 dactylus, Dimorphodon, and Ramphorhynchus) ; and though 
 commencing in the Lias, they are most abundant in the Solen- 
 hofen Slate. The Dicynodonts appear to have died out ; but 
 the Deinosaurs are largely represented, chiefly by the genera 
 Megalosaurus and Cetiosaurus. 
 
 The Birds have no other representative in the Oolitic period 
 than the extraordinary Archtzopteryx, macrura of the Solenhofen 
 Slates the first undoubted indication of birds in the geolo- 
 gical record. As has been before pointed out, this Jurassic 
 bird differed in several most important characters from all 
 known members of the class, whether living or extinct ; its 
 most striking peculiarity being the possession of a long, lizard- 
 like tail composed of free vertebrae, of which each supported a 
 pair of quill-feathers. 
 
 The Mammals, taking all things into consideration, are well 
 represented in the Jurassic series, their remains belonging to 
 the two horizons of the Stonesfield Slate (Lower Oolites) and 
 the Purbeck beds (Upper Oolites). The Stonesfield Mammals 
 viz., Amphitherium, Amphilestes, Phascolotherium, and Stereog- 
 nathus are all of small size ; and the first three appear to be 
 certainly Marsupial. Stereognathus may be also a Marsupial, 
 but its true affinities are uncertain. The Purbeck Mammals 
 Triconodon, Spalacotherium, Galestes, and Plagiaulax were 
 likewise all of small size, and they appear to have been all 
 Marsupial ; the three first-named being probably insectivorous, 
 whilst the last appears to have been a vegetable-feeder.
 
 540 HISTORICAL PALEONTOLOGY. 
 
 CHAPTER LIII. 
 
 CRETACEOUS PERIOD. 
 
 ROCKS OF THE PERIOD. 
 
 THE next series of rocks in ascending order is the great and 
 important series of the Cretaceous Rocks, so called from the 
 general occurrence in the system of chalk (Lat. creta, chalk). 
 As developed in Britain and Europe generally, the following 
 leading subdivisions may be recognised in the Cretaceous 
 
 2. Ltoeensand or Neocomian, } Lower Cretaceous - 
 
 3. Gault, 1 
 
 5'. ChS GfeenSand ' Upper Cretaceous. 
 
 6. Maestricht beds, 
 
 I. The Wealden formation, though of considerable impor- 
 tance, is a local group, and is confined to the south-east of 
 England, France, and some other parts of Europe. Its name 
 is derived from the Weald, a district comprising parts of 
 Surrey, Sussex, and Kent, where it is largely developed. Its 
 lower portion, for a thickness of from 500 to 1000 feet, is 
 arenaceous, and is known as the Hastings Sands. Its Upper 
 portion, for a thickness of 150 to nearly 300 feet, is chiefly 
 argillaceous, consisting of clays with sandy layers, and occa- 
 sionally courses of limestone. The geological importance of the 
 Wealden formation is very great, as it is undoubtedly the 
 delta of an ancient river, being composed almost wholly of 
 fresh-water beds, with a few brackish-water and even marine 
 strata, intercalated in the lower portion. Its geographical 
 extent, though uncertain, owing to the enormous denudation 
 to which it has been subjected, is nevertheless great, since it 
 extends from Dorsetshire to France, and occurs also in North 
 Germany. Still, even if it were continuous between all these 
 points, it would not be larger than the delta of such a modern 
 river as the Ganges. The river which produced the Wealden 
 series must have flowed from an ancient continent occupying 
 what is now the Atlantic Ocean ; and the time occupied in 
 the formation of the Wealden must have been very great, 
 though we have, of course, no data by which we can accu- 
 rately calculate its duration.
 
 CRETACEOUS PERIOD. 54! 
 
 The fossils of the Wealden series are, naturally, mostly the 
 remains of such animals as we know at the present day as in- 
 habiting rivers. We have, namely, fresh-water mussels ( Unio), 
 river-snails (Paludina), and other fresh-water shells, with nume- 
 rous little bivalved Crustaceans, and some fishes. 
 
 II. The Wealden beds pass upward, often by insensible 
 gradations, into the Lower Greensand. The name Lower 
 Greensand is not an appropriate one, for green sands only 
 occur sparingly and occasionally, and are found in other for- 
 mations. For this reason it has been proposed to substitute 
 for Lower Greensand the name Neocomian, derived from the 
 town of Neufchatel anciently called Neocomum in Switzer- 
 land. If this name were adopted, as it ought to be, the 
 Wealden beds would be called the Lower Neocomian. 
 
 The Lower Greensand or Neocomian of Britain has a thick- 
 ness of about 850 feet, and consists of alternations of sands, 
 sandstones, and clays, with occasional calcareous bands. The 
 general colour of the series is dark brown, sometimes red, and 
 the sands are occasionally green, from the presence of silicate 
 of iron. 
 
 The fossils of the Lower Greensand are purely marine, and 
 among the most characteristic are the shells of Cephalopods. 
 
 The most remarkable point, however, about the fossils of 
 the Lower Cretaceous series, is their marked divergence from 
 the fossils of the Upper Cretaceous rocks. Of 280 species of 
 fossils in the Lower Cretaceous series, only 51, or about 18 
 per cent, pass on into the Upper Cretaceous. This break in 
 the life of the two periods is accompanied by a decided phy- 
 sical break as well, for the Gault is often, if not always, uncon- 
 formably superimposed on the Lower Greensand. At the 
 same time, the Lower and Upper Cretaceous groups form a 
 closely-connected and inseparable series, as shown by a com- 
 parison of their fossils with those of the underlying Jurassic 
 Rocks and the overlying Tertiary beds. Thus, in Britain no 
 marine fossil is known to be common to the marine beds of 
 the Upper Oolites and the Lower Greensand; and of more 
 than 500 species of fossils in the Upper Cretaceous Rocks, 
 almost every one died out before the formation of the lowest 
 Tertiary strata, the only survivors being one Brachiopod and a 
 few Foraminifera. 
 
 III. The lowest member of the Upper Cretaceous series is 
 a stiff, dark-grey, blue, or brown clay, often worked for brick- 
 making, and known as the Gault, from a provincial English 
 term. It occurs chiefly in the south-east of England, but can 
 be traced through France to the flanks of the Alps and Ba-
 
 542 HISTORICAL PALEONTOLOGY. 
 
 varia. It never exceeds 100 feet in thickness ; but it con- 
 tains many fossils, usually in a state of beautiful preservation. 
 
 IV. The Gault is succeeded upward by the Upper Green- 
 sand, which varies in thickness from three up to 100 feet, and 
 which derives its name from the occasional occurrence in it of 
 green sands. These, however, are local and sometimes want- 
 ing, and the name " Upper Greensand " is to be regarded as a 
 name and not a description. The group consists, in Britain, 
 of sands and clays, sometimes with bands of calcareous grit or 
 siliceous limestone, and occasionally containing concretions of 
 phosphate of lime, which are largely worked for agricultural 
 purposes. 
 
 V. The top of the Upper Greensand becomes argillaceous, 
 and passes up gradually into the base of the great formation 
 known as the true Chalk, divided into the three subdivisions 
 of the chalk-marl, white chalk without flints, and white chalk 
 with flints. The first of these is simply argillaceous chalk, 
 and passes up into a great mass of obscurely-stratified white 
 chalk in which there are no flints. This, in turn, passes up 
 into a great mass of white chalk, in which the stratification is 
 marked by nodules of black flint arranged in layers. The 
 thickness of these three subdivisions taken together is some- 
 times over 1000 feet, and their geographical extent is very 
 great. White Chalk, with its characteristic appearance, may 
 be traced from the north of Ireland to the Crimea, a distance 
 of about 1140 geographical miles, and, in an opposite direc- 
 tion, from the south of Sweden to Bordeaux, a distance of 
 about 840 geographical miles. 
 
 VI. In Britain there occur no beds containing Chalk fossils, 
 or in any way referable to the Cretaceous period, above the 
 true White Chalk with flints. On the banks of the Maes, 
 however, near Maestricht, in Holland, there occurs a series of 
 yellowish limestones, of about 100 feet in thickness, and un- 
 doubtedly superior to the White Chalk. These Maestricht 
 beds contain a remarkable series of fossils, the characters of 
 which are partly Cretaceous and partly Tertiary. Thus, with 
 the characteristic Chalk fossils, Belemnites, Baculites, Sea-Ur- 
 chins, &c., are numerous Univalve Molluscs, such as Cowries 
 and Volutes, which are otherwise exclusively Tertiary or Re- 
 cent. 
 
 Holding a similar position to the Maestricht beds, and 
 showing a similar intermixture of Cretaceous forms with later 
 types, are certain beds which occur in the island of Seeland, 
 in Denmark, and which are known as the Faxoe Limestone. 
 
 VII. In North America, the Lower Cretaceous Rocks are
 
 CRETACEOUS PERIOD. 543 
 
 not represented at all, or very feebly; but there is a very 
 extensive development of rocks of Upper Cretaceous age in 
 the United States. According to Dana, " the Cretaceous 
 Eocks occur i. At intervals along the Atlantic border, south 
 of New York, from New Jersey to South Carolina ; 2. Exten- 
 sively over the States along the Gulf 'border ; and 3. Through 
 a large part of the Western interior region, over the slopes of 
 the Rocky Mountains, from Texas northward, to the head- 
 waters of the Missouri on the east of the summit of the chain, 
 and far into the Colorado region on the west. Still farther 
 north-west in British America, they appear on the Saskat- 
 chewan and Assiniboine, and also on the Arctic Sea, near the 
 mouth of the Mackenzie." The rocks of these areas consist 
 chiefly of sands, marls, clays, and limestones ; but it is to be 
 remembered that there is no white Chalk. Green sands are 
 often present, as in New Jersey, where they are called " marls," 
 and are largely worked for agricultural purposes, their fertilis- 
 ing properties being due to the presence of a small percentage 
 of phosphate of lime. 
 
 LIFE OF THE CRETACEOUS PERIOD. As regards the vegeta- 
 tion of the Cretaceous period, the plants of the Inferior divi- 
 sion of the series agree with those of the antecedent Jurassic 
 period in consisting chiefly of Ferns, Cycads, and Conifers. 
 In the Upper Cretaceous Rocks, on the other hand, we find a 
 vegetation composed largely of Angiospermous Exogens, many 
 of which belong to existing genera. 
 
 The Protozoa are very largely represented in the Cretaceous 
 period by Foraminifera and Sponges. The microscopic shells 
 of the former are often excessively abundant ; and the white 
 chalk is to a large extent composed of the exuvia of these 
 minute organisms. Amongst the more important genera may 
 be mentioned Textularia, Globigerina, Rotalia, Lituola, Nodo- 
 saria, Flabellina, Cuneolina, Cristellaria, Bulimina, Dentalina, 
 &c. Sponges are very numerous, especially in the Upper 
 Greensand and White Chalk. The most important genera are 
 Siphonia, Ventriculites, Manon, Choanites, Cliona, Scyphia, 
 Chenendopora, Giiettardia, and Polypothecia ; but many other 
 forms might be mentioned. 
 
 The Ccelenterates are represented by Corals, belonging 
 mainly to the genera Trochocyathus, Cyclocyathus, Trochosmilia, 
 Parasmilia, Cyathina, Micrabacia, Stephanophyllia, &c. In the 
 Upper Greensand, also, occurs the little Holocystis elegans, long 
 believed to be the last of the Rugose Corals. 
 
 The Echinoderms are exceedingly abundant in the Creta- 
 ceous rocks, but belong mainly to the Echinoids. Crinoids,
 
 544 HISTORICAL PALEONTOLOGY. 
 
 though not altogether rare, are very perceptibly reduced in 
 numbers, the more important forms being Marsupites, Penta- 
 crinus, Bourgueticrinus, and Comatula. Sea-urchins, on the 
 other hand, are so numerous as to constitute one of the most 
 marked features in the Cretaceous fauna. The leading genera 
 are Micraster, Ananchytes, Galerites, Hemipneustes, Diadema, 
 Discoidea, Saletiia, Cidaris, Catopygus, Pygaster, Pygaulus, 
 Holaster, &c. 
 
 The Arthropods are represented by various Crustaceans be- 
 longing mainly to the Macrurous and Brachyurous Decapods, 
 and to the Cirripedes. The little Ostracodes are also abun- 
 dant in many parts of the series, especially in the fresh-water 
 strata of the Wealden. 
 
 Coming to the Mollusca, the Polyzoa have a great develop- 
 ment in the Cretaceous deposits, the family of the Escharida 
 here attaining its maximum. Amongst the more characteristic 
 Cretaceous genera may be mentioned Eschara, Escharina, 
 Vincularia, Membranipora, Flustra, Reticulipora, Homer a, 
 Tubulipora, &c. 
 
 Brachiopods are not especially numerous, and belong mainly 
 to Terebratula, Terebratella, Terebratulina, Rhynchonella, and 
 Crania. Bivalves are very abundant, and some of them are 
 very characteristic. Amongst these are numerous species of 
 Ostrea, Exogyra, Lima, Plicatula, Pecten, and Spondylus, with 
 the various species of Inoceramus, and the great family of the 
 Hippuritida. With the exception of a few Jurassic species, 
 the genus Inoceramus is exclusively Cretaceous, being repre- 
 sented in deposits of this period by numerous species, and not 
 being known to have survived it. The Hippuritidce, or Rudis- 
 tes of Lamarck, comprise a great number of very aberrant 
 Bivalves, all of which were attached and lived associated in 
 beds, like Oysters. The two valves of the shell are always 
 unlike in sculpturing, in appearance, and in shape, and the cast 
 of the interior is often very unlike the form of the outer surface 
 of the shell. A great many species of this family are known, 
 chiefly referable to the genera Hippurites, Radiolites, and Ca- 
 prina. The family appears to be exclusively Cretaceous ; and 
 the most characteristic members of the Cretaceous series of the 
 south of Europe consists of certain compact marbles, which 
 are known as " Hippurite Limestone," from the abundance of 
 shells of this family. 
 
 Gasteropods are not particularly numerous in the Cretace- 
 ous Rocks, and belong chiefly to such modern genera as Turri- 
 tella, Natica, Solarium, Sea/aria, Rostellaria. Dentalium, P/iorus, 
 &c. Along with these are species of the persistent genus Pleu-
 
 CRETACEOUS PERIOD. 545 
 
 rotomaria, and the Mesozoic Nerintza. Towards the close of the 
 Cretaceous period, we meet for the first time with Gasteropods 
 of the existing genera Valuta, Mitra, Cypraa, Fasdolaria, 
 Strombus, &c. 
 
 The most characteristic Molluscs of the Cretaceous period 
 are Cephalopods. The Dibranchiate section of this order is 
 represented by species of Belemnites itself and by the genus 
 Belemnitella. Of the Tetrabranchiates we find species of the 
 old genus Nautilus ; but this section is represented mainly by 
 complex and beautiful forms of the Ammonitida. The genus 
 Ammonites itself, dating its existence from the Upper Trias, is 
 represented by many Cretaceous species, and finally disappears 
 with the close of this period. Ancyloceras dates from the 
 commencement of the Jurassic period, and also dies out in the 
 Chalk. Finally, the AmmonitidcB are represented by the genera 
 Baculites, Turrilites, Scaphites, Hamites, Ptychoceras, Toxoceras, 
 and Crioceras, which make their first appearance in the Creta- 
 ceous rocks, but which are not known at present to occur in 
 any later deposit. 
 
 Remains of Fishes are by no means rare in the Cretaceous 
 rocks. Teleostean Fishes appear here, and are well represented 
 by forms more or less allied to existing types (Beryx, Osmero- 
 ides, &c.) Ganoids (such as Lepidotus, Caturus, Pycnodus, &c.) 
 are plentiful ; but are of little special importance. Of the 
 Cestracionts, we have the old genus Acrodus, and the Creta- 
 ceous genus Ptychodus. Hybodonts also occur, and teeth of 
 true Selachians (Lamna, Carcharias, Odontaspis, &c.) are not 
 wanting. 
 
 The Reptiles of the Cretaceous belong mostly to the orders 
 of the Pterosauria, Ichthyopterygia, Sauropterygia, and Deino- 
 sauria all of which die out with the Cretaceous period. The 
 best known of the Deinosaurs is Iguanodon, which is confined 
 exclusively to the Lower Cretaceous period, but the genera 
 Ichthyosaurus, Plesiosaurus, and Pterodactylus, extend their 
 range into the Upper Cretaceous. The only exclusively Cre- 
 taceous group of Reptiles is that of the Mosasauroids, which 
 are known to have existed up to the last phase of this period 
 (Maestricht beds). The Mosasauroids are found in Europe, 
 but more abundantly in North America ; and the recent dis- 
 covery by Professor Marsh, that the body was, in some cases, 
 furnished with a covering of bony scutes, would seem to re- 
 move them from the Lizards, amongst which they have been 
 generally placed. 
 
 Birds have not been shown with certainty to have existed 
 during the Cretaceous period in Europe, though various re- 
 
 2 M
 
 546 HISTORICAL PALEONTOLOGY. 
 
 mains of this age have been with more or less probability re- 
 garded as being Ornithic. The Upper Cretaceous rocks of 
 the United States have, however, yielded the remains of un- 
 doubted birds (Laornis,Telmatornis, Scolopax, and Palceotringa). 
 More remarkable than any of the above are the recently-dis- 
 covered Hesperornis and Ichthyornis, of which the former is a 
 large Diver-like bird, whilst the latter exhibits the singular 
 peculiarity that the vertebrae are biconcave. Mammals have 
 not hitherto been detected in any Cretaceous deposit. 
 
 CHAPTER LIV. 
 
 EOCENE PERIOD. 
 
 BEFORE commencing the study of the subdivisions of the 
 Kainozoic series, there are some general considerations to be 
 noted. In the first place, there is a complete and entire phy- 
 sical break between the rocks of the Mesozoic and Kainozoic 
 periods. In no instance are Tertiary strata to be found rest- 
 ing conformably upon any Secondary rock. The Chalk has 
 invariably suffered much erosion and denudation before the 
 lowest Tertiary strata were deposited upon it. This is shown 
 by the fact that the actually eroded surface of the Chalk can 
 often be seen, or, failing this, that we can point to the presence 
 of the chalk-flints in the Tertiary strata. This last, of course, 
 affords unquestionable proof that the Chalk must have been 
 subjected to enormous denudation prior to the formation of 
 the Tertiary beds, all the chalk itself having been removed, 
 and nothing left but the flints, while these are all rolled and 
 rounded. 
 
 In the second place, there is a complete break in the life 
 of the Mesozoic and Kainozoic periods. With the excep- 
 tion of a few foraminifera, and one Brachiopod (the latter 
 doubtful), no Cretaceous species is known to have survived the 
 Cretaceous period ; while several characteristic families, such 
 as the Ammonitida and Hippuritidce, died out entirely with the 
 close of the Cretaceous rocks. In the Tertiary rocks, on the 
 other hand, not only are all the animals and plants more or 
 less like existing types, but we meet with a constantly-increas- 
 ing number of living species as we pass from the bottom of the 
 Kainozoic series to the top. Upon this last fact is founded
 
 EOCENE PERIOD. 547 
 
 the modern classification of the Kainozoic rocks, propounded 
 by Sir Charles Lyell. 
 
 It follows from the constant want of conformity between 
 the Cretaceous and Tertiary rocks, and still more from the 
 entire difference in life, that the Cretaceous and Tertiary 
 periods are separated by an enormous lapse of unrepresented 
 time. How long this interval may have been, we have no 
 means of judging exactly, but it very possibly was as long as 
 the whole Kainozoic epoch itself. Some day we shall doubt- 
 less find, at some part of the earth's surface, strata which were 
 deposited during this period, and which will contain fossils 
 intermediate in character between the organic remains which 
 respectively characterise the Secondary and Tertiary periods. 
 At present, we have only slight traces of such deposits, as, for 
 instance, the Maestricht beds. 
 
 CLASSIFICATION OF THE TERTIARY ROCKS. The classifica- 
 tion of the Tertiary rocks is a matter of unusual difficulty, in 
 consequence of their occurring in disconnected basins, form- 
 ing a series of detached areas, which hold no relations of 
 superposition to one another. The order, therefore, of the 
 Tertiaries in point of time, can only be determined by an 
 appeal to fossils ; and in such determination Sir Charles Lyell 
 proposed to take as the basis of classification the proportion of 
 living or existing species of Mollusca which occurs in each stratum 
 or group of strata. Acting upon this principle, Sir Charles 
 Lyell divides the Tertiary series into four groups : 
 
 i. The Eocene formation (Gr. eos, dawn; kainos, new), con- 
 taining the smallest proportion of existing species, and being, 
 therefore, the oldest division. In this classification only the 
 Mollusca are taken into account; and it was found that of 
 these about three and a half per cent were identical with 
 existing species. 
 
 II. The Miocene formation (Gr. meion, less ; kainos, new), 
 with more recent species than the Eocene, but less than the 
 succeeding formation, and less than one-half the total number 
 in the formation. As before, only the Mollusca are taken into 
 account, and about 17 per cent of these agree with existing 
 species. 
 
 III. The Pliocene formation (Gr. pleion, more ; kainos, new), 
 with more than half the species of shells identical with existing 
 species ; the proportion of these varying from 35 to 50 per 
 cent in the lower beds of this division, up to 90 or 95 per cent 
 in its higher portion. 
 
 IV. The Post-Tertiary Formations, in which all the shells 
 belong to existing species. This, in turn, is divided into two
 
 548 HISTORICAL PALAEONTOLOGY. 
 
 minor groups the Post-Pliocene and Recent Formations. In 
 the Post-Pliocene formations, while all the Mollusca belong to 
 existing species, most of the Mammals belong to extinct 
 species. In the Recent period, the quadrupeds, as well as the 
 shells, belong to living species. 
 
 The above, with some modifications, was the original classi- 
 fication proposed by Sir Charles Lyell for the Tertiary rocks, 
 and now universally accepted. More recent researches, it is 
 true, have somewhat altered the proportions of existing species 
 to extinct, as stated above. The general principle, however, 
 of an increase in the number of living species, still holds good ; 
 and this is as yet the only satisfactory basis upon which it has 
 been proposed to arrange the Tertiary deposits. 
 
 EOCENE FORMATION. 
 
 The Eocene rocks are the lowest of the Tertiary series, and 
 comprise all those Tertiary deposits in which there is only a 
 small proportion of existing Mollusca from three and a half 
 to five per cent. The Eocene rocks occur in several basins in 
 Britain, France, the Netherlands, and other parts of Europe, 
 and in the United States. The subdivisions which have been 
 established are extremely numerous, and it is often impossible 
 to parallel those of one basin with those of another. It will 
 be sufficient, therefore, to accept the division of the Eocene 
 formation into three great groups Lower, Middle, and Upper 
 Eocene and to consider some of the more important beds 
 comprised under these heads in Europe and in North America. 
 
 I. LOWER EOCENE. The base of the Eocene series in 
 Britain is constituted by about 90 feet of light-coloured, some- 
 times argillaceous sands (Thanet Sands), which are of marine 
 origin. Above these, or forming the base of the formation 
 where these are wanting, come mottled clays and sands with 
 lignite (Woolwich and Reading series), which are estuarine or 
 fluvio-marine in origin. The highest member of the Lower 
 Eocene of Britain is the " London Clay," consisting of a 
 great mass of dark-brown or blue clay, sometimes with sandy 
 beds, or with layers of " septaria," the whole attaining a thick- 
 ness of from 200 to as much as 500 feet. The London Clay 
 is a purely marine deposit, containing many marine fossils, 
 with the remains of terrestrial animals and plants ; all of which 
 indicate a high temperature of the sea and tropical or sub- 
 tropical conditions of the land. 
 
 II. MIDDLE EOCENE. The inferior portion of the Middle 
 Eocene of Britain consists of marine beds, chiefly consisting
 
 EOCENE PERIOD. 549 
 
 of sands, clays, and gravels, and attaining a very considerable 
 thickness (Bagshot and Bracklesham beds). The superior 
 portion of the Middle Eocene of Britain, on the other hand, 
 consists of deposits which are almost exclusively fresh-water 
 or brackish-water in origin (Headon and Osborne series). 
 
 The chief Continental formations of Middle Eocene age are 
 the " Calcaire grossier " of the Paris basin, and the "Num- 
 mulitic Limestone " of the Alps. 
 
 III. UPPER EOCENE. If the Headon and Osborne beds of 
 the Isle of Wight be placed in the Middle Eocene, the only 
 British representatives of the Upper Eocene are the Bern- 
 bridge and Hempstead beds though the latter are regarded 
 by Sir Charles Lyell as being of Lower Miocene age. These 
 strata consist of limestones, clays, and marls, which have for 
 the most part been deposited in fresh or brackish water. 
 
 IV. EOCENE BEDS OF THE PARIS BASIN. The Eocene 
 strata are very well developed in the neighbourhood of Paris, 
 where they occupy a large area or basin scooped out of the 
 Chalk. The beds of this area are partly marine, partly fresh- 
 water in origin ; and the following table (after Sir Charles 
 Lyell) shows their subdivisions and their parallelism with the 
 English series : 
 
 GENERAL TABLE OF FRENCH EOCENE STRATA. 
 UPPER EOCENE. 
 
 French Subdivisions. ' English Equivalents. 
 
 A. I. Gypseous series of Mont- I. Bembridge series. 
 
 martre. 
 
 A. 2. Calcaire silicieux, or Tra- 2. Osborne and Headon series, 
 vertin Inferieur. 
 
 A. 3. Gres de Beauchamp, or 3. White sand and clay of Barton 
 
 Sables Moyens. Cliff, Hants. 
 
 MIDDLE EOCENE. 
 
 B. i. Calcaire Grossier. I. Bagshot and Bracklesham beds. 
 
 B. 2. Soissonnais Sands, or Lits 2. Wanting. 
 
 Coquilliers. 
 
 LOWER EOCENE. 
 
 C. I. Argile de Londres at base of I. London Clay. 
 
 Hill of Cassel, near Dun- 
 kirk. 
 
 C. 2. Argile plastique and lignite. 2. Plastic clay and sand with lig- 
 nite (Woolwich and Reading 
 series). 
 C. 3. Sables de Bracheux. 3. Thanet sands. 
 
 V. EOCENE STRATA OF THE UNITED STATES. In North 
 America, Lower Eocene Rocks are extensively developed at
 
 550 HISTORICAL PALAEONTOLOGY. 
 
 Claiborne, Alabama, and consist of clays, lignites, marls, and 
 impure limestones. The fossils of the Claiborne series are 
 much the same in their characters as those of the London 
 clay, and the lignites contain numerous plant-remains. 
 
 The Middle Eocene group is represented in North America 
 by lignitic clays and marls which occur at Jackson, Mississippi. 
 Amongst the more remarkable fossils of the Jackson beds are 
 the teeth and bones of Cetaceans of the genus Zeuglodon. 
 
 Rocks of Upper Eocene age occur in North America at 
 Vicksburg, Mississippi, and consist of lignites, clays, marls, 
 and limestones. On the White River they are about 1000 
 feet thick, and consist of clays, sandstones, and limestones, of 
 fresh-water origin. Among their most remarkable fossils are 
 the remains of Mammals, of which about forty species have 
 been already determined. 
 
 LIFE OF THE EOCENE PERIOD. 
 
 Little need be added here as to the life of the Eocene 
 period, fossils being so abundant as to render it impossible to 
 do more than indicate some general considerations. Upon 
 the whole, the plants and animals of the Eocene period closely 
 resemble those now in existence upon the globe ; not, how- 
 ever, necessarily in the exact localities in which they are now 
 found. Thus, the modern representatives of the plants and 
 animals of the Eocene Rocks of Europe are not to be found 
 in Europe itself, but in some tropical or sub-tropical region. 
 The climatic conditions of Europe in the Eocene period were 
 very different to those at present subsisting, and the animals 
 and plants were correspondingly different. Still, there are 
 few Eocene fossils which have not their modern representa- 
 tives in warm countries. 
 
 The Protozoa are represented in Eocene times chiefly by 
 Foraminifera, which are often extraordinarily abundant, and 
 the shells of which may in some cases be said without exagge- 
 ration to compose whole mountain-masses. The great and 
 widespread formation of the Nummulitic Limestone is largely 
 made up of the shells of Nummulites and Orbitoides, some of 
 the former occasionally reaching a size of more than an inch 
 in diameter. One of the limestones of the Paris basin is 
 largely composed of the shells of a species of Miliola. Nume- 
 rous other forms occur ; and the genus Nummulites is exclu- 
 sively confined to this formation. 
 
 Corals are not particularly abundant in the Eocene rocks, 
 but they are mostly of types identical with, or nearly allied to,
 
 EOCENE PERIOD. 551 
 
 those now existing. The Tabulata are represented by no 
 more than one genus, and the Eocene forms belong mainly to 
 the Zoantharia, Aporosa, and Perforata. Besides Zoantharia, 
 the family of the Pennatulidce (Sea-pens, &c.) is represented 
 by the genus Graphularia, and the family of the Gorgonidce 
 (sea-shrubs), by the genera Mopsea and Websteria. 
 
 As regards the Mollusca, Brachiopods and Polyzoa are not 
 abundant, and the former are represented in Eocene times 
 chiefly by the existing genera Terebratula and Rhynchonella, 
 Lamellibranchs and Gasteropods, the latter especially, are 
 exceedingly abundant, and almost all existing genera are now 
 represented ; though less than five per cent are identical with 
 existing species. The Gasteropods are chiefly siphonostoma- 
 tous, and belong to such familiar genera as Valuta, Mitra, 
 Conus, Pleurotoma, Fusus, Cyprcza, Oliva, Ancillaria, Rostel- 
 laria, &c. The fresh-water and brackish-water beds of the 
 formation have also yielded numerous species of Cerithium, 
 along with Limncea, Planorbis, Melania, &c. The Ammonites, 
 Turrilites, B acuities, Belemnites, &c., of the Cretaceous period 
 have now disappeared, and the Cephalopoda are represented 
 mainly by the genus Nautilus, though Dibranchiates (such as 
 Belosepid) are not unknown. 
 
 The most important fossils of the Eocene Rocks belong to 
 the sub-kingdom of the Vertebrata. Fishes are numerous, 
 sometimes (as in the limestone of Monte Bolca) extraordinarily 
 so. They belong in the vast majority of instances to the 
 Teleostei, the remains of Ganoid fishes being comparatively 
 very rare. True Sharks are represented by numerous teeth, 
 referable to the genera Carcharodon, Otodus, Lamna, Galeo- 
 cerdo, &c. ; and Rays are represented by their pavement-like 
 dental plates (Myliobatis}. 
 
 The Reptiles of the Eocene period all belong to the existing 
 orders of the Chelonians, Ophidians, Lacertilians, and Croco- 
 dilians. The Chelonians are very abundant, and belong for 
 the most part to existing genera. The Ophidians make their 
 first appearance in the Eocene (Palceophis). The Crocodilians, 
 lastly, are very abundant, speaking comparatively ; and Eng- 
 land possessed in Eocene times representatives of the three 
 existing genera of this order viz., Crocodilus, Alligator, and 
 Gavialis. 
 
 As regards the Birds, it is sufficient to say that all the exist- 
 ing orders of Aves appear to have been represented in Eocene 
 times, often by forms which differ little from existing types. 
 
 As regards the Mammals, the Eocene deposits have yielded 
 remains of Marsupialia, Sirenia, Cetacea, Ungulata, Carnivora,
 
 552 HISTORICAL PALEONTOLOGY. 
 
 Cheiroptera, Rodentia, and Insectivora. No traces, however, have 
 hitherto been found in the Eocene of the orders Probostidea 
 and Edentata, and the Quadrumana are represented only by 
 two doubtful forms. The Marsupials are represented in 
 the Eocene by Didelphys, the Sirenia by Halitherium, and 
 the Cetaceans by the singular and aberrant family of the Zeu- 
 glodonts. The Ungulates are represented by a great series of 
 forms, of which the most important are the two extinct groups 
 of the Palaotherida and Anoplotherida, the former representing 
 the Perissodactyles, the latter the Artiodactyles. Besides these, 
 however, there occur numerous other extinct forms, chiefly 
 referable to the genera Coryphodon, Lophiodon, Chceropotatnus , 
 Anthracotherium, Hyopotamus, Pliolophus, Dichodon, Dichobune, 
 Xiphodon, &c. 
 
 The Carnivora are represented by the extinct Hyanodon, 
 the Cheiroptera by species of the existing genus Vespertilio, the 
 Rodentia by Shrew-mice (Myoxus), and the Insectivora by 
 Spalacodon. 
 
 CHAPTER LV. 
 
 MIOCENE PERIOD. 
 
 ROCKS OF THE PERIOD. 
 
 THE Miocene formations comprise those Tertiary deposits 
 which contain less than about 35 per cent of existing species 
 of Mollusca, and more than 5 per cent, or those deposits in 
 which the proportion of living shells is less than of extinct 
 species. The Miocene formations are divisible in Europe into 
 a Lower Miocene and Upper Miocene group. 
 
 I. LOWER MIOCENE. The Miocene formations are very 
 poorly represented in Britain, their leading development being 
 at Bovey Tracy, in Devonshire, where there occur sands, clays, 
 and beds of lignite or woody coal. These strata contain nume- 
 rous plants, among which are Vines, Figs, the Cinnamon-tree, 
 Palms, and a number of Coniferce. Other plant-bearing strata 
 in the Hebrides, on the west coast of Scotland, have been 
 referred to the Miocene age. 
 
 In France, the Lower Miocene is represented in Auvergne, 
 Cantal, and Velay, by a great thickness of nearly horizontal 
 strata of sand, sandstone, clays, marls, and limestones, all of
 
 MIOCENE PERIOD. 553 
 
 fresh-water origin. Other Miocene deposits occur in Austria, 
 Germany, Switzerland, and the Siwalik hills in India. 
 
 II. UPPER MIOCENE. The typical European deposits of 
 Upper Miocene age occur in the valley of the Loire, in France, 
 and are known as the " Faluns," a provincial term given to 
 shelly sands employed to spread upon soils which are deficient 
 in lime. The Faluns occur in scattered patches, which are 
 rarely more than 50 feet in thickness, and consist of sands 
 and marls. The fossils are chiefly marine, but there occur 
 also land and fresh-water shells, and the remains of numerous 
 Mammals. 
 
 In Switzerland, between the Alps and the Jura, there occurs 
 a great series of Miocene deposits, known collectively as the 
 " Molasse," from the soft nature of a greenish sandstone, 
 which constitutes one of its chief members. It attains a thick- 
 ness of many thousands of feet, and rises into lofty mountains, 
 some of which as the Rigi are more than 6000 feet in 
 height. The middle portion of the Molasse is of marine 
 origin, and is shown by its fossils to be of the age of the 
 Faluns ; but the lower and upper portions of the formation 
 are mainly or entirely of fresh-water origin. The Lower 
 Molasse (of Lower Miocene age) has, yielded about 500 species 
 of plants, mostly of tropical or sub-tropical forms. The Upper 
 Molasse has yielded about the same number of plants, with 
 about 900 species of Insects, such as wood-eating Beetles, 
 Water-beetles, White Ants, Dragon-flies, &c. 
 
 MIOCENE OF NORTH AMERICA.- Miocene deposits are 
 found in the United States in New Jersey, Maryland, Virginia, 
 California, Oregon, &c., and they attain sometimes a thickness 
 of 1500 feet. They consist chiefly of clays, sands, and sand- 
 stones: and in Virginia there is a bed of what is wrongly 
 called " Infusorial Earth," which attains a thickness of many 
 feet, and consists almost wholly of the siliceous cases of cer- 
 tain low forms of plants (Diatoms). The strata of the White 
 River, with remains of numerous Mammals, formerly spoken 
 of as Upper Eocene, are sometimes referred to the Miocene 
 formation. The fossils of the American Miocene are chiefly 
 Molluscs (of which 15 to 30 per cent are living species). 
 
 LIFE OF THE MIOCENE PERIOD. The vegetation of the 
 Miocene period has been already spoken of, and need not be 
 again discussed here. The Invertebrates of the Miocene also 
 need no special mention, since they are very similar in type to 
 those now in existence, though mostly specifically distinct. 
 The Fishes, Reptiles, and Birds of the Miocene likewise call 
 for no special comment. The Miocene Mammals, on the
 
 554 HISTORICAL PALEONTOLOGY. 
 
 other hand, belong in great part to extinct types, and are 
 sufficiently remarkable in their characters to demand some 
 notice. In addition to the orders known to be represented in 
 the Eocene Tertiary, we meet now with remains referable to 
 the Edentata, Proboscidea, and Quadrumana ; whilst some 
 existing groups of the older orders are now represented for the 
 first time. 
 
 The Edentates are represented by the gigantic Macrotherium, 
 which appears to have been nearly allied to the Scaly Ant- 
 eaters or Pangolins, and by the still more gigantic Ancylotherium. 
 
 Of the Sirenia we have the genus Halitherium, and of the 
 true Cetacea we have the remains of Squalodonts and Dolphins. 
 
 Of the Ungulates the Rhinocerida are represented in Miocene 
 times by Acerotherium, the Equida by Anchitherium and Hip- 
 parion, the Hippopotamidce by species of Hippopotamus itself, 
 the Suida by species of Sus, the Moschida by Dremotherium, 
 the Cervidce by Dorcatherium, the Camelopardalida by Hellado- 
 therium, and the Cavicornia by the extraordinary SwatJierium 
 and Bramatherium. The Bovidcs do not appear as yet to 
 have come into existence. 
 
 The Proboscidea are represented in the Miocene period by 
 all the known sections of the order namely, by Elephants, 
 Mastodons, and the Deinotherium. 
 
 Of the Carnnora we have Miocene representatives of the 
 Felidce {Machairodus\ the Canidce, Hycenida, Viverridce, and 
 Mustelida. The Insectivora are represented by species of 
 Erinaceus and Talpa, and the Rodents by species of Castor, 
 Mus, Lepus, &c. Lastly, the Quadrumana are represented by 
 the two extinct genera Pliopithecus and Dryopithecus. 
 
 CHAPTER LVI. 
 
 PLIOCENE AND POST-PLIOCENE PERIODS. 
 ROCKS OF THE PLIOCENE PERIOD. 
 
 THE Pliocene formations contain from 40 to 95 per cent of 
 existing species of Mollusca, the remainder belonging to extinct 
 species. They are divided by Sir Charles Lyell into two 
 divisions, the Older Pliocene and Newer Pliocene. 
 
 The Pliocene deposits of Britain occur in Suffolk, and are 
 known by the name of " Crags," this being a local term used
 
 PLIOCENE AND POST-PLIOCENE PERIODS. 555 
 
 for certain shelly sands, which are employed in agriculture. 
 Two of these Crags are referable to the Older Pliocene viz., 
 the White and Red Crags, and one belongs to the Newer 
 Pliocene, viz., the Norwich Crag. 
 
 The White or Coralline Crag of Suffolk is the oldest of the 
 Pliocene deposits of Britain, and is an exceedingly local for- 
 mation, occurring in but a single small area, and having a 
 maximum thickness of not more than 50 feet. It consists of 
 soft sands, with occasional intercalations of flaggy limestone. 
 Though of small extent and thickness, the Coralline Crag is of 
 importance from the number of fossils which it contains. The 
 name "Coralline" is a misnomer; since there are few true 
 Corals, and the so-called "Corals" of the formation are really 
 Potyzoa, often of very singular forms. The shells of the Coral- 
 line Crag are mostly such as inhabit the seas of temperate 
 regions ; but there occur some forms usually looked upon as 
 indicating a warm climate. 
 
 The Upper or Red Crag of Suffolk like the Coralline Crag 
 has a limited geographical extent and a small thickness, 
 rarely exceeding 40 feet. It consists of quartzose sands, usu- 
 ally deep red or brown in colour, and charged with numerous 
 fossils. 
 
 Altogether more than 200 species of shells are known from 
 the Red Crag, of which 60 per cent are referable to existing 
 species. The shells indicate upon the whole a temperate or 
 even cold climate, decidedly less warm than that indicated by 
 the organic remains of the Coralline Crag. It appears, there- 
 fore, that a gradual refrigeration was going on during the 
 Pliocene period, commencing in the Coralline Crag, becoming 
 intensified in the Red Crag, being still more severe in the 
 Norwich Crag, and finally culminating in the Arctic cold of the 
 Glacial period. 
 
 Besides the Mollusca, the Red Crag contains the ear-bones 
 of Whales, the teeth of Sharks and Rays, and remains of the 
 Mastodon, Rhinoceros, and Tapir. 
 
 The Newer Pliocene deposits are represented in Britain by 
 the Norwich Crag, a local formation occurring near Norwich. 
 It consists of incoherent sands, loams, and gravels, resting in 
 detached patches, from 2 to 20 feet in thickness, upon an 
 eroded surface of Chalk. The Norwich Crag contains a mix- 
 ture of marine, land, and fresh-water shells, with remains of 
 fishes and bones of mammals ; so that it must have been de- 
 posited as a local sea-deposit near the mouth of an ancient 
 river. It contains altogether more than 100 marine shells, of 
 which 89 per cent belong to existing species. Of the Mam-
 
 55^ HISTORICAL PALEONTOLOGY. 
 
 mals, the two most important are an Elephant (Elephas meri- 
 dionalis), and the characteristic Pliocene Mastodon (M. An>er- 
 nensis), which is hitherto the only Mastodon found in Britain. 
 
 The following are the more important Pliocerfe deposits 
 which have been hitherto recognised out of Britain : 
 
 1. In the neighbourhood of Antwerp occur certain " crags," 
 which are the equivalent of the White and Red Crag in part. 
 The lowest of these contains less than 50 per cent, and the 
 highest 60 per cent, of existing species of shells, the remainder 
 being extinct. 
 
 2. Bordering the chain of the Apennines, in Italy, on both 
 sides are a series of low hills made up of Tertiary strata, which 
 are known as the Sub-Apennine beds. Part of these is of 
 Miocene age, part is Older Pliocene, and a portion is Newer 
 Pliocene. The Older Pliocene portion of the Sub-Apennines 
 consists of blue or brown marls, which sometimes attain a 
 thickness of 2000 feet. 
 
 3. In the valley of the Arno, above Florence, are both 
 Older and Newer Pliocene strata. The former consist of blue 
 clays and lignites, with an abundance of plants. The latter 
 consist of sands and conglomerates, with remains of large Car- 
 nivorous Mammals, Mastodon, Elephant, Rhinoceros, Hippo- 
 potamus, &c. 
 
 4. In Sicily, Newer Pliocene strata are probably more largely 
 developed than anywhere else in the world, rising sometimes 
 to a height of 3000 feet above the sea. The series consists 
 of clays, marls, sands, and conglomerates, capped by a com- 
 pact limestone, which attains a thickness of from 700 to 800 
 feet. The fossils of these beds belong almost entirely to living 
 species, one of the commonest being the Great Scallop of the 
 Mediterranean (Pecten Jacobaus). 
 
 5. Occupying an extensive area round the Caspian, Aral, 
 and Azof Seas, are Pliocene deposits known as the " Aralo- 
 Caspian " beds. The fossils in these beds are partly fresh- 
 water, partly marine, and partly intermediate in character, and 
 they are in great part identical with species now inhabiting 
 the Caspian. The entire formation appears to indicate the 
 former existence of a great sheet of brackish water, forming an 
 inland sea, like the Caspian, but as large as, or larger than, the 
 Mediterranean. 
 
 6. In the United States, strata of Pliocene age are found in 
 North and South Carolina. They consist of sands and clays, 
 with numerous fossils, chiefly Molluscs and Echinoderms. 
 From 40 to 60 per cent of the fossils belong to existing 
 species. On the Loup Fork of the river Platte, in the Upper
 
 POST-PLIOCENE PERIOD. 557 
 
 Missouri region, are strata which are also believed to be refer- 
 able to the Pliocene period, and probably to its upper division. 
 They are from 300 to 400 feet thick, and contain land-shells, 
 with the bones of numerous Mammals, such as Camels, Rhino- 
 ceroses, Mastodons, Elephants, the Horse, Stag, &c. 
 
 LIFE OF THE PLIOCENE PERIOD. As regards the life of 
 the Pliocene period, it is sufficient to indicate two general 
 considerations. In the first place, we have to notice that the 
 introduction upon the globe of existing species of animals was 
 carried on rapidly during this period. In the older Pliocene 
 deposits the number of shells of existing species is only from 
 40 to 60 per cent ; but in the Newer Pliocene the proportion 
 of existing species rises to as much as 80 to 95 per cent. The 
 Mammals still all belong to extinct species, but modern types 
 gradually supersede the more antique forms of the Eocene and 
 Miocene periods. In the second place, there is good evidence 
 to show that the Pliocene period was one in which the climate 
 of the northern hemisphere gradually became colder. In the 
 Miocene period, as we have seen, Europe possessed a climate 
 probably very similar to that now enjoyed by the Southern 
 States of the Union, and certainly very much warmer than its 
 present climate. In the Older Pliocene, northern forms, on 
 the other hand, predominate among the shells, though some 
 of the types of warmer regions still survive. In the Newer 
 Pliocene, the Molhisca are almost exclusively such as inhabit 
 the seas of temperate or even cold regions. It might be 
 thought that the occurrence of Mammals such as the Elephant, 
 Rhinoceros, and Hippopotamus, would prove that the climate 
 of Europe and the United States must have been a hot one 
 during the later portion of the Pliocene period. We have, 
 however, reason to believe that many of these extinct quadru- 
 peds were more abundantly furnished with hair, and more 
 adapted to withstand a cool temperature, than any of their 
 living congeners. 
 
 Amongst the Pliocene Mammals may be mentioned the 
 following, as comprising the more important forms : 
 Mastodon Arvernensis. 
 
 Elephas meridionalis. 
 Elephas antiquus. 
 Rhinoceros megarhinus. 
 Hippopotamus major. 
 
 Tapi 
 Mac 
 
 hairodus cultridens. 
 Ursus Arvernensis. 
 Equus plicidens. 
 
 POST-PLIOCENE PERIOD. 
 
 Later than any of the Tertiary formations are a series of de- 
 posits which are spoken of as Post-Tertiary or Quaternary, 
 and which are characterised by the fact that all the contained
 
 558 HISTORICAL PALEONTOLOGY. 
 
 shells belong to existing species. The Post-Tertiary deposits 
 are divided by Sir Charles Lyell into Post-Pliocene, in which 
 the shells belong entirely to existing species, but some of the 
 Mammals are extinct; and the Recent, in which the shells and 
 the Mammals alike belong to existing species. 
 
 The Recent deposits do not properly concern the Palaeonto- 
 logist, but the Zoologist, since they contain the remains of none 
 but existing animals. The Post-Pliocene deposits, on the 
 other hand, contain the remains of various extinct Mammals, 
 and therefore properly form part of the domain of the palaeon- 
 tologist. The deposits of the Post-Pliocene period may be 
 divided into those which preceded the Glacial period, those 
 which were formed during the Glacial epoch, and those which 
 are Post-Glacial. 
 
 I. PRE-GLACIAL DEPOSITS. The chief pre-glacial deposit of 
 Britain is found on the Norfolk coast, reposing upon the Newer 
 Pliocene (Norwich Crag), and consists of an ancient land-sur- 
 face which is known as the " Cromer Forest-bed." 
 
 This consists of an ancient soil, having embedded in it the 
 stumps of many trees, still in an erect position, with remains 
 of living plants, and the bones of recent and extinct quadru- 
 peds. It is overlaid by fresh-water and marine beds, all the 
 shells of which belong to existing species, and it is finally sur- 
 mounted by true "glacial drift." While all the shells and 
 plants of the Cromer Forest-bed and its associated strata belong 
 to existing species, the Mammals are partly living, partly ex- 
 tinct. Thus, we find the existing Wolf, Bison, Reindeer, 
 Beaver, Walrus, &c., side by side with three extinct Elephants, 
 the Rhinoceros, and Hippopotamus, and a gigantic extinct 
 Beaver. Among the Elephants are two Pliocene species, viz., 
 Elephas meridionalis and Elephas antiquus. The third species 
 is the Mammoth (Elephas primigenius), which has not as yet 
 been detected in strata of Pliocene age. The following list is 
 given by Mr Boyd Dawkins as comprising the most important 
 Mammals as yet known in the " Forest-bed : "- 
 
 LIST OF PRE-GLACIAL MAMMALS. 
 
 Ursus Arvfrnensis. 
 
 Ursus speltrus (? Elruscus). 
 
 Sorex. 
 
 Mygale mosehata, 
 
 Talpa Europaa. 
 
 C trims megaceros ? 
 
 Cervus capreolus. 
 
 Cenms elaphus. 
 
 Cervus Sedgwickii. 
 
 Cervus ardcus. 
 
 Bos primigenius. 
 Hippopotamus major. 
 Eauus fossilis. 
 Rhinoceros megarhinus. 
 Rhinoceros Etruscus. 
 Elephas antiquus. 
 Elephas meridionalis. 
 Arvicola amphibia. 
 Castor fiber. 
 Trogontherium Cuvieri.
 
 POST-PLIOCENE PERIOD. 559 
 
 II. GLACIAL DEPOSITS. Under this head is included a 
 great series of deposits which are widely spread over both 
 Europe and America, and which were formed at a time when 
 the climate of these countries was very much colder than it is at 
 present, and approached more or less closely to what we see at 
 the present day in the Arctic regions. These deposits are 
 known by the general name of the Glacial deposits, or by the 
 more specialised names of the Drift, the Northern Drift, the 
 Boulder-clay, the Till, &c. 
 
 These glacial deposits are found in Britain as far south as 
 the Thames, over the whole of Northern Europe, in all the 
 more elevated portions of Southern and Central Europe, and 
 over the whole of North America, as far south as the 39th par- 
 allel. They generally occur as sands, clays, and gravels, 
 spread in widely-extended sheets over all the geological forma- 
 tions alike, except the most recent, and are commonly spoken 
 of under the general term of " Glacial drift." They vary much 
 in their exact nature in different districts, but they universally 
 consist of one, or all, of the following members : 
 
 1. Unstratified clays, or loams, containing numerous angular 
 or sub-angular blocks of stone, which have often been trans- 
 ported for a greater or less distance from their parent rock, 
 and which often exhibit polished, grooved, or striated surfaces. 
 These beds are what is called Boulder-clay, or Till. 
 
 2. Sands, gravels, and clays, often more or less regularly 
 stratified, but containing erratic blocks, often of large size, and 
 with their edges unworn, derived from considerable distances 
 from the place where they are now found. In these beds it is 
 not at all uncommon to find fossil shells ; and these, though of 
 existing species, are mostly of an Arctic character, comprising 
 a majority of forms which are now exclusively found in the icy 
 waters of the Arctic seas. These beds are often spoken of as 
 "Stratified Drift." 
 
 3. Stratified sands and gravels, in which the pebbles are 
 worn and rounded, and which have been produced by a re- 
 arrangement of ordinary glacial beds by the sea. These beds 
 are commonly known as " Drift-gravels," or " Regenerated 
 Drift." 
 
 The fossils of the Glacial deposits are almost exclusively 
 shells, which belong to existing species, but are referable to 
 species now inhabiting cold regions. The most important 
 Glacial shells are the following :
 
 560 HISTORICAL PALAEONTOLOGY. 
 
 Pecten Islandicus. 
 Astarte borealis. 
 Leda oblonga. 
 Saxicava rugosa. 
 Tellina proximo. 
 Tellina solidula. 
 Leda truncata. 
 Astarte compressa. 
 
 Trophon dathratum. 
 Natica clausa. 
 Sea /aria Greenland ica. 
 Buccinum undatnm. 
 Purpura lapillus. 
 fusus Islandicus. 
 Littorina littorea. 
 
 III. POST-GLACIAL DEPOSITS. Under this head are in- 
 cluded various fluviatile deposits, such as brick-earths, low- 
 level and high-level gravels, and all those accumulations which 
 are generally understood by the terms "cave-deposits," " ossi- 
 ferous breccias," and the like. The fossils of these deposits 
 consist chiefly of the bones of Mammals, both living and 
 extinct, in many instances mixed with the bones, or, more 
 commonly, the implements of man in his earliest and rudest 
 condition. Most of the Pre-glacial Mammals which have 
 been previously enumerated, survived the Glacial period, and 
 appear in Post - glacial deposits ; but along with these are 
 other forms some extinct, some still in existence which are 
 not known to have lived in times prior to the Glacial epoch. 
 The following list is given by Mr Boyd Dawkins of the 
 Mammals which inhabited Britain during the Post-glacial 
 epoch : 
 
 LIST OF POST-GLACIAL MAMMALS. 
 
 Palaeolithic Man. 
 
 The Glutton (Gulo lusctts). 
 
 The Cave Bear (Ursus spelaus) ? 
 
 The Grizzly Bear (Ursus /mar)? 
 
 The Cave Lion (Felis leo=Felis spelira). 
 
 The Cave Hyaena (Hycena sfefoa). 
 
 The Panther (Felis par Jus). 
 
 The Musk-sheep (Ovibos moschatus). 
 
 The Tichorhine Rhinoceros (R. tic/torhinus). 
 
 The Mammoth (Elephas primigenius). 
 
 The Lemming (Afyodes lemmus). 
 
 The Cave Pika (Lagomys). 
 
 The Pouched Marmot (Spermophilus). 
 
 Spermophilus erylhrogenoides. 
 
 GEOGRAPHICAL SUCCESSION OF ORGANIC FORMS. 
 A few words may be said here on a law which may be called 
 the " law of the geographical succession of organic forms," 
 and which is illustrated more completely by the Mammalia 
 than by any other extinct animals. An examination, namely, 
 of the facts of the geological distribution of Mammals, leads to 
 the striking generalisation that " the present distribution of 
 organic forms dates back to a period anterior to the origin of
 
 GEOGRAPHICAL SUCCESSION OF ORGANIC FORMS. 561 
 
 existing species " (Lyell). In other words, though the extinct 
 Mammals of the later geological deposits of any given country 
 differ specifically from those now existing in the same country, 
 they are nevertheless referable to the same orders, and are in 
 every respect more closely allied to the present Mammalian 
 fauna than to that of any other country. A few examples will 
 render this perfectly clear. 
 
 Australia at the present day is an altogether peculiar zoolo- 
 gical province, characterised by the abundance and variety of 
 Marsupials which inhabit it. In the Post-tertiary deposits of 
 Australia, however, we are presented with proofs that Marsu- 
 pials were just as characteristic of Australia during late geolo- 
 gical epochs as they are now. In the Post-pliocene period 
 we know that Australia was occupied by Kangaroos, Kan- 
 garoo-rats, Wombats. Phalangers, and Carnivorous Marsupials, 
 in every way representing the living Marsupials in zoological 
 value, but specifically distinct, and generally of gigantic size. 
 
 In the same way, South America at the present day is espe- 
 cially characterised by a Mammalian fauna containing many 
 peculiar forms, the Edentata being especially conspicuous, and 
 having a larger representation than in any other region. 
 Similar but distinct forms, however, are found to have existed 
 in South America anterior to the creation of any existing 
 species. Thus, the modern Sloths of South America are re- 
 presented by the colossal Mylodon, Megalonyx, Scelidotherium, 
 and Megatherium. The little armour-plated Armadillos are 
 represented by the equally colossal Glyptodon. The Llamas 
 representing in South America the Camels of the Old World 
 are represented by the curious extinct genus Macrauchenia. 
 The Platyrhine Monkeys have their extinct representatives. 
 Fossil Tapirs take the place of the two existing species ; and 
 the Peccaries are represented by at least five extinct species 
 of Dicotyles. The bone-caves of Brazil have also yielded re- 
 mains of Sloths, Coatis, Kinkajous, Armadillos, Guinea-pigs, 
 Agoutis, Capybaras, Pacas, Coypus, Vampire Bats, and Cerco- 
 labes, allied to, yet distinct from, the species now inhabiting 
 South America. 
 
 Similarly, India is at present the only country in which 
 four-horned Antelopes occur; and it is in the Siwalik Hills 
 that there have been found the two gigantic four-horned An- 
 telopes, which constitute the genera Sivatherium and Brama- 
 therium. 
 
 In Europe, again, the Mammalian fauna of the later Ter- 
 tiary periods is much more closely allied to that now charac- 
 terising the Old World, than to that of the New. We have 
 
 2 N
 
 562 HISTORICAL PALEONTOLOGY. 
 
 the Lion, Bear, Wolf, Fox, and other well-known Carnirora. 
 Elephants, Rhinoceroses, and Hippopotami, then as now, are 
 characteristic Old World forms. The Ruminants are equally 
 characteristic of the eastern hemisphere, though not exclu- 
 sively confined to it, and they have numerous and varied re- 
 presentatives in later Tertiary deposits. The Giraffe is repre- 
 sented by the Helladoiherium, and the Bactrian Camel by the 
 Merycotherium of the Siberian Drift. The fossil Quadrumana, 
 too, of Europe, all belong to the Catarhine section of the 
 order. 
 
 It is unnecessary to pursue the subject further, but no law 
 is more firmly established than this : " That with extinct as 
 with existing Mammalia, particular forms were assigned to 
 particular provinces ; and that the same forms were restricted 
 to the same provinces at a former geological period as they 
 are at the present day " (Owen). It is to be borne in mind, 
 however, that the law, as just stated, holds good for the later 
 Tertiary period only, and does not apply, in any manner that 
 admits of being traced, to the earlier geological epochs.
 
 GLOSSARY. 
 
 ABDOMEN (Lat. abdo, I conceal). The posterior cavity of the body, contain- 
 ing the intestines and others of the viscera. In many Invertebrates there 
 is no separation of the body-cavity into thorax and abdomen, and it is only 
 in the higher Annulosa that a distinct abdomen can be said to exist. 
 
 ABERRANT (Lat. aberro, I wander away). Departing from the regular type. 
 
 ABNORMAL (Lat. ab, from ; norma, a rule). Irregular ; deviating from the 
 ordinary standard. 
 
 ABRANCHIATE (Gr. a, without ; bragchia, giJl). Destitute of gills or bran- 
 chiae. 
 
 ACANTHOPTERYGII (Gr. akantha, spine ; pterux, wing). A group of bony 
 fishes with spinous rays in the front part of the dorsal fin. 
 
 ACARINA (Gr. al-ari, a mite). A division of the Arachnida, of which the 
 Cheese-mite is the type. 
 
 ACEPHALOUS (Gr. a, without ; kepkale, head). Not possessing a distinct 
 head. 
 
 ACETABULA (Lat. acetabulum, a cup). The suckers with which the cephalic 
 processes of many Cephalopoda (Cuttle-fishes) are provided. 
 
 ACETABULUM. The cup-shaped socket of the hip-joint in Vertebrates. 
 
 ACRODONT (Gr. akros, high ; odous, tooth). Applied to Lizards, in which the 
 teeth are anchylosed with the summit of the jaw. 
 
 ACROGENS (Gr. akros, high ; gennao, I produce. ) Plants which increase in 
 height by additions made to the summit of the stem, by the union of the 
 bases of the leaves. 
 
 ACTINOZOA (Gr. aktin, a ray ; and zoon, an animal). That division of the 
 Ccelenterata of which the Sea-anemones may be taken as the type. 
 
 ALVEOLI (Lat. dim. of alvus, belly). Applied to the sockets of the teeth. 
 
 AMBULACRA (Lat. ambulacrum, a place for walking). The perforated spaces 
 or "avenues" through which are protruded the tube-feet, by means of 
 which locomotion is effected in the Echinodermata. 
 
 AMBULATORY (Lat. ambulo, I walk). Formed for walking. Applied to a 
 single limb, or to an entire animal. 
 
 AMMONITID^:. A family of Tetrabranchiate Cephalopods, so called from the 
 resemblance of the shell of the type-genus, Ammonites, to the horns of the 
 Egyptian God, Jupiter- Ammon. 
 
 AMCEBA (Gr. amoibos, changing). A. species of Rhizopod, so called from the 
 numerous changes of form which it undergoes. 
 
 ASKEBIFORM. Resembling an Amoeba in form. 
 
 AMORPHOZOA (Gr. a, without ; morphe, shape ; zoon, animal). A name some- 
 times used to designate the Sponges. 
 
 AMPHIBIA (Gr. ampfii, both; bios, life). The Frogs, Newts, and the like, 
 which have gills when young, but can always breathe air directly when 
 adult. 
 
 AMPHICCELOUS (Gr. amphi, at both ends ; toilot, hollow). Applied to verte- 
 brae which are concave at both ends.
 
 564 GLOSSARY. 
 
 AMPHIPODA (Gr. amphi, and pous, a foot). An order of Crustacea. 
 
 ANAL (Lat. units, the vent). Connected with the anus, or situated near the 
 
 anus. 
 ANARTHROPODA (Gr. a, without ; arthrot, a joint ; nous, foot). That division 
 
 of . 1 in, ill,,. <r animals in which there are no articulated appendages. 
 ANCHYLOSIS or ANKYLOSIS (Gr. ankulos, crooked). The union of two bones 
 
 by osseous matter, so that they become one bone, or are immovably joined 
 
 together. 
 ANOIOSPERMS (Gr. angeion, a vessel ; tperma, seed). Plants which have their 
 
 seeds enclosed in a seed-vessel. 
 ANNKLIDA (a Gallicised form of Annulata). The Ringed worms, which form 
 
 one of the divisions of the . I narthropoda. 
 ANNULATED. Composed of a succession of rings. 
 
 ANNULOIDA (Lat. annuhts, a ring ; Gr. eidot, form). The sub-kingdom com- 
 prising the Echinoderniata and the Scolecida(=Echinozoa). 
 ANNULOSA (Lat. annulux). The sub-kingdom comprising the Anarthropoda 
 
 and the Arthropoda or Articulata, in all of which the body is more or less 
 
 evidently composed of a succession of rings. 
 ANOMODONTIA (Gr. anomos, irregular; odous, tooth). An extinct order of 
 
 Reptiles, often called Dicynodontia. 
 ANOMURA (Gr. anomos, irregular ; oura, tail). A tribe of Decapod Crustacea, 
 
 of which the Hermit-crab is the type. 
 ANOPLOTH BRIDGE (Gr. anoplos, unarmed ; ther, beast). A family of Tertiary 
 
 Ungulates. 
 ANOURA (Gr. a, without ; oura, tail). The order of Amphibia comprising the 
 
 Frogs and Toads, in which the adult is destitute of a tail. Often called 
 
 Batrachia. 
 ANTENNAE (Lat. antenna, a yard-arm). The jointed horns or feelers possessed 
 
 by the majority of the Articulata. 
 ANTENNULES (dim. of Antennae). Applied to the smaller pair of antennae in 
 
 the Crustacea. 
 ANTIBRACHIUM (Gr. anti, in front of; brachion, the arm). The fore-arm of 
 
 the higher Vertebrates, composed of the radius and ulna. 
 ANTLERS. Properly the branches of the horns of the Deer tribe (Cervidce), 
 
 but generally applied to the entire horns. 
 APIOCRINID^E (Gr. avion, a pear ; krinon, lily). A family of Crinoids the 
 
 ' ' Pear-encrinites. ' 
 APLACENTALIA. The section of the Mammalia, comprising the two divisions 
 
 of the Didelphia and Monodelphia, in which the young is not furnished 
 
 with a placenta. 
 APODA (Gr. a, without ; pode*, feet). Applied to those fishes which have no 
 
 ventral fins. Also to the footless Ccecilice amongst the Amphibia. 
 APODAL. Devoid of feet. 
 APTERA (Gr. a, without ; pteron, a wing). A division of Insects, which is 
 
 characterised by the absence of wings in the adult condition. 
 APTEROUS. Devoid of wings. 
 APTERYX (Gr. a, without; pterux, a wing). A wingless bird of New Zealand, 
 
 belonging to the order Cursores. 
 ARAOHNIDA (Gr. arachne, a spider). A class of the Articulata, comprising 
 
 Spiders, Scorpions, and allied animals. 
 ARBORESCENT. Branched like a tree. 
 ARCH^OPTERYX (Gr. archaios, ancient; pterux, wing). The singular fossil 
 
 bird which alone constitutes the order of the Saunirce. 
 ARENACEOUS. Sandy, or composed of grains of sand. 
 ARTICULATA (Lat. articulut, a joint). A division of the animal kingdom, 
 
 comprising Insects, Centipedes, Spiders, and Crustaceans, characterised by 
 
 the possession of jointed bodies or jointed limbs. The term ArtJtropoda is 
 
 now more usually employed. 
 ARTIODACTYLA (Gr. artioi, even ; daktulot, a finger or toe). A division of 
 
 the hoofed quadrupeds (Unyulata) in which each foot has an even number 
 
 of toes (two or four).
 
 GLOSSARY. 565 
 
 ASCIDIOIDA (Gr. aslog, a bottle ; eidos, a form). A synonym of Tunicata, a 
 class of Molluscous animals, which have the shape, in many cases of a 
 two-necked bottle. 
 
 ASEXUAL. Applied to modes of reproduction in which the sexes are not 
 concerned. 
 
 ASIPHONATE. Not possessing a respiratory tube or siphon. (Applied to a 
 division of the Lamellibranchiate Molluscs). 
 
 ASTEROID (Gr. aster, a star ; and eidos, form). Star-shaped, or possessing 
 radiating lobes or rays like a star-fish. 
 
 ASTEROIDEA. An order of Echinodermata, comprising the Star-fishes, char- 
 acterised by their rayed form. 
 
 ASTOSIATOUS (Gr. a, without; stoma, mouth). Not possessing a mouth. 
 
 ATLAS (Gr. the God who holds up the earth). The first vertebra of the neck, 
 which articulates with and supports the skull. . 
 
 AVES (Lat. avis, a bird). The class of the Birds. 
 
 AVICULARIUM (Lat. avicula, dim. of avis, a Bird). A singular appendage, 
 often shaped like the head of a bird, found in many of the Polyzoa. 
 
 Axis (Gr. axon, a pivot). The second vertebra of the neck, upon which the 
 skull and atlas usually rotate. 
 
 AZYGOUS (Gr. a, without ; zuyon, yoke). Single ; without a fellow. 
 
 BALANID.E (Gr. balanos, an acorn). A family of sessile Cirripedes, commonly 
 called "Acorn-shells." 
 
 BALEEN (Lat. balcena, a whale). The horny plates which occupy the palate 
 of the true or " whalebone " "Whales. 
 
 BATIDES (Gr. bates, a bramble). The family of the Elasmobranchii comprising 
 the Rays. 
 
 BATRACHIA (Gr. batrachos, a frog). Often loosely applied to any of the Am- 
 phibia, but sometimes restricted to the Amphibians as a class, or to the 
 single order of the Anoura. 
 
 BELEMMTID^E (Gr. bel&nnon, a dart). An extinct group of Dibranchiate 
 Cephalopods, comprising the Belemnites and their allies. 
 
 BIFID. Cleft into two parts ; forked. 
 
 BILATERAL. Having two symmetrical sides. 
 
 BIMANA (Lat. bis, twice ; manus, a hand). The order of MammaKa compris- 
 ing man alone. 
 
 BIPEDAL (Lat. bis, twice ; pes, foot). Walking upon two legs. 
 
 BIVALVE (Lat. Ms, twice ; valvce, folding-doors). Composed of two plates or 
 valves ; applied to the shell of the Lamellibranchiata and Brachiopoda, and 
 to the carapace of certain Crustacea. 
 
 BLASTOIDBA (Gr. blastos, a bud ; and eidos, form). An extinct order of Echi- 
 nodermata, often called Pentremites. 
 
 BRACHIOPODA (Gr. brachion, an arm ; poux, the foot). A class of the Mollus- 
 coula, often called " Lamp-shells," characterised by possessing two fleshy 
 arms continued from the sides of the mouth. 
 
 BRACHIUM (Gr. brachion, arm). Applied to the upper arm of Vertebrates. 
 
 BRACHYURA (Gr. brachus, short ; oura, tail). A tribe of the Decapod Crusta- 
 ceans with short tails (i.e., the Crabs). 
 
 BRADYPODID^E (Gr. bradus, slow ; podes, feet). The family of Edentata com- 
 prising the Sloths. 
 
 BRANCH i A (Gr. bragchia, the gill of a fish). A respiratory organ adapted to 
 breathe air dissolved in water. 
 
 BRANCHIATE. Possessing gills or branchiae. 
 
 BRANCHIFERA (Gr. bragchia, gill ; and jAm>, I carry). A division of ffastero- 
 podous Molluscs, in which the respiration is aquatic, and the respiratory 
 organs are mostly in the form of distinct gills. 
 
 BRANCHIO-GASTEROPODA (= Branchifera). 
 
 BRANCHIOPODA (Gr. bragchia; and pous, foot). A legion of Crustacea, in 
 which the gills are supported by the feet. 
 
 BRANCHIOSTEGAL (Gr. bragchia, gill ; stego, I cover). Applied to a membrane 
 and rays by which the gills are protected in many fishes.
 
 566 GLOSSARY. 
 
 BRUTA (Lat. bruttu, heavy, stupid). Often used to designate the Mammalian 
 order of the Edentata. 
 
 BRYOZOA (Gr. bruon, moss : zoiin. animal). A synonym of Polyzoa. a class of 
 the Mollutcoida. 
 
 BucOAt (Lat. Lucca, mouth or cheeks). Connected with the mouth. 
 
 BURSIFORH (Lat. burta, a purse ; forma, shape). Shaped like a purse ; sub- 
 spherical. 
 
 BYSSIFEBOUS. Producing a byssus. 
 
 BYSSUS (Gr. lutsos, flax). A term applied to the silky filaments by which 
 the Pinna, the common Mussel, and certain other bivalve JJolimca, attach 
 themselves to foreign objects. 
 
 CADUCIBRANCHIATE (Lat. caducut, falling off; Gr. bragchia, gill). Applied 
 to those Amphibians iu which the gills fall off before maturity is 
 reached. 
 
 CADUCOUS. Applied to parts which fall off or are shed during the life of the 
 animal. 
 
 C.BCAL (Lat. ccecut, blind). Terminating blindly, or in a closed extremity. 
 
 CAECUM (Lat. ccecwt). A tube which terminates blindly. 
 
 C^EflPiTOSE (Lat ccespet, a turf). Tufted. 
 
 CAINOZOIC. (See Kainozoic.) 
 
 CALAMITES (Lat. calamus, a reed). Extinct plants with reed-like stems, be- 
 lieved to be gigantic representatives of the Equisetacea. 
 
 CALCAREOUS (Lat. calx, lime). Composed of carbonate of lime. 
 
 CALICE. The little cup in which the polype of a coralligenous Zoophyte 
 (ActinozoSii) is contained. 
 
 CALYCOPHORID^E (Gr. kalux, a cup ; and phero, I carry). An order of the 
 Oceanic Hydrozoa, so called from their possessing bell-shaped swimming 
 organs (nectocalyces). 
 
 CALYX (Lat. calyx, a cup). Applied to the cup-shaped body of Vorticella 
 (Protozoa), or of a Crinoid (Echinodermata). 
 
 CAMPANULARIDA (Lat. campanula, a bell). An order of Hydroid Zoophytes. 
 
 CANINE (Lat. cais, a dog). The eye-tooth of Mammals, or the tooth which 
 is placed at or close to the prsemaxillary suture in the upper jaw, and the 
 corresponding tooth in the lower jaw. 
 
 CAPITULUM (Lat. dim. ofcaput, head). Applied to the body of a Barnacle 
 (Lepadida), from its being supported upon a stalk or peduncle. 
 
 CARAPACE. A protective shield. Applied to the upper shell of Crabs, Lob- 
 sters, and many other Crustacea; also to the case with which certain of the 
 Infusoria are provided. Also the upper half of the immovable case in 
 which the body of a Chelonian is protected. 
 
 CARINAT^S (Lat. carina, a keel). Applied by Huxley to all those birds in 
 which the sternum is furnished with a median ridge or keel. 
 
 CARNIVORA (Lat. caro, flesh ; voro, I devour). An order of the Mammalia. 
 
 CARNIVOROUS (Lat. caro, flesh ; voro, I devour). Feeding upon flesh. 
 
 CARNOSE (Lat. caro). Fleshy. 
 
 CARPUS (Gr. tarpot, the wrist). The small bones which intervene between 
 the fore-arm and the metacarpus. 
 
 CATARHINA (Gr. kata, downwards ; rhinet, nostrils). A group of the Quadra.- 
 mana. 
 
 CAUDAL (Lat. cauda, the tail). Belonging to the tail. 
 
 CAVICORNIA (Lat. caviu, hollow ; cornu, a horn). The " hollow-horned " 
 Ruminants, in which the horn consists of a central bony "horn-core" sur- 
 rounded by a horny sheath. 
 
 CENTRUM (Gr. kentron, the point round which a circle is described by a pair 
 of compasses). The central portion or " body" of a vertebra. 
 
 CEPHALA8PlD.fi (Gr. kephale, head ; atpit, shield). A family of fossil fishes. 
 
 CEPHALIC (Gr. kephale, head). Belonging to the bead. 
 
 CKPHALO-BRANCHIATE (Gr. kephale ; and bragchia, gill). Carrying gills upon 
 the head. Applied to a section of the Annelida, which, like the Serpvla, 
 have tufts of external gills placed upon the head.
 
 GLOSSARY. 567 
 
 CEPHALOPHORA (Gr. kephale; and phero, I carry). Used synonymously with 
 Encephala, to designate those Alollusca which possess a distinct head. 
 
 CEPHALOPODA (Gr. kephale; antipodes, feet). A class of the Mollusca, com- 
 prising the Cuttle-fishes and their allies, in which there is a series of arms 
 ranged round the head. 
 
 CEPHALOTHORAX (Gr. kephale; and thorax, chest). The anterior division of 
 the body in many Crustacea, and Arachnida, which is composed of the 
 coalesced head and chest. 
 
 CERVICAL (Lat. cervix, neck). Connected with the region of the neck. 
 
 CESTRAPHORI (Gr. kestra, a weapon ; phero, I carry). The group of Elasmo- 
 branchii represented at the present day by the Port Jackson Shark. 
 
 CETACEA (Gr. ketos, a whale). The order of Mammals comprising the Whales 
 and Dolphins. 
 
 CHEIROPTERA (Gr. cheir, hand ; pteron, a wing). The order of Mammals com- 
 prising the Bats. 
 
 CHEL.E (Gr. chele, a claw). The prehensile claws with which some of the 
 limbs are terminated in certain Crustacea, such as the Crab, Lobster, &c. 
 
 CHELATE. Possessing chelae ; applied to a limb. 
 
 CHELICER.E (Gr. chele, a claw ; and keras, a horn). The prehensile claws of 
 the Scorpion, supposed to be homologous with antennae. 
 
 CHELONIA (Gr. chelone, a tortoise). The order of Reptiles comprising the 
 Tortoises and Turtles. 
 
 CHELONOBATRACHIA (Gr. chelone, a tortoise ; bafrachos, a frog). Sometimes 
 applied to the Amphibian order of the Anoura (Frogs and Toads). 
 
 CHILOGNATHA (Gr. cfieilos, a lip ; and gnathos, a jaw). An order of the My- 
 
 CHILOPODA (Gr. cheilos; and podes, feet). An order of the Myriapoda. 
 
 CHITINB (Gr. chiton, a coat). The peculiar chemical principle, nearly allied 
 to horn, which forms the exoskeleton in many Invertebrate Animals, espe- 
 cially in the Arthropoda (Crustacea, Insecta, &c.) 
 
 CIRRI (Lat. cirras, a curl). Tendril-like appendages, such as the feet of Bar- 
 nacles and Acorn-shells (Cirripedes), the lateral processes on the arms of 
 Brachiopoda, &c. 
 
 CIRRIFEROUS or CiRRiGEROUS. Carrying cirri. 
 
 CIRRIPEDIA, CIRRHIPEDIA, or CiRRHOPODA (Lat. cirrus, & curl ; and pes, a 
 foot). A sub-class of Crustacea with curled jointed feet. 
 
 CLADOCERA (Gr. klados, a branch ; keras, a horn). An order of Crustacea with 
 branched antennas. 
 
 CLAVATE (Lat. clavus, a club). Club-shaped. 
 
 CLAVICLE (Lat. clavicula, a little key). The " collar-bone," forming one of the 
 elements of the pectoral arch of Vertebrates. 
 
 CLOACA (Lat. a sink). The cavity into which the intestinal canal and the 
 ducts of the generative and urinary organs open in common, in some In- 
 vertebrates (e.g., in Insects), and also in many Vertebrate animals. 
 
 CLYPEIFORM (Lat. clypeus, a shield ; and forma, shape). Shield-shaped ; ap- 
 plied, for example, to the carapace of the King-crab. 
 
 CCELENTERATA (Gr. koilos, hollow ; enteron, the bowel). The sub-kingdom 
 which comprises the Hydrozoa and Actinozoa. Proposed by Frey and 
 Leuckhart in place of the old term Radiata, which included other animals 
 as well. 
 
 CffiNENCHYMA (Gr. koinos, common ; enchuma, tissue, literally an infusion). 
 The common calcareous tissue which unites together the various corallites 
 of a compound corallum. 
 
 CffiNCECiusi (Gr. koinos, common ; oikos, house). The entire dermal system 
 of any Polyzoon : employed in place of the terms polyzoary or polypidom. 
 
 COENOSARC (Gr. koinos, common ; sarx, flesh). The common organised me- 
 dium by which the separate polypites of a compound JJydrozoon are con- 
 nected together. 
 
 COLEOPTERA (Gr. koleos, a sheath; pteron, wing). The order of Insects 
 (Beetles) in which the anterior pair of wings are hardened, and serve as pro- 
 tective cases for the posterior pair of membranous wings.
 
 $68 GLOSSARY. 
 
 COLUBRINA (Lat. colulxr, a snake). A division of the Ophidia. 
 COLUMBACEI (Lat. columba, a dove). The division of Rasoriai birds compris- 
 ing the Doves and Pigeons. 
 COLUMELLA (Lat. dim. of cofumna, a column). In Conchology, the central 
 
 axis round which the whorls of a spiral univalve are wound. Amongst the 
 
 J ctinozoa, it is the central axis or pillar which is found in the centre of the 
 
 thecae of many corals. 
 COLUMN. Applied to the cylindrical body of a Sea-anemone (Actinia) ; also 
 
 to the jointed stem or peduncle of the stalked Orinoidt.. 
 CONCHIFKRA (Lat concha, a shell; fero, I carry). Shell-fish. Applied in a 
 
 restricted sense to the bivalve Molluscs, and used as a synonym for Lamelli- 
 
 brancldata. 
 CONDYLE (Gr. kondulos, a knuckle). The surface by which one bone articulates 
 
 with another. Applied especially to the articular surface or surfaces by 
 
 which the skull articulates with the vertebral column. 
 CONIROSTRES (Lat. conus, a cone ; rottrum, a beak). The division of Perching 
 
 Birds with conical beaks. 
 
 COPEPODA (Gr. tope, an oar ; podes, feet). An order of Crustacea. 
 CORACOID (Gr. korax, a crow ; eidos, form). One of the bones which enters 
 
 into the composition of the pectoral arch in Birds, Reptiles, and Mono- 
 
 tremes. In most Mammals it is a mere process of the scapula, having, in 
 
 man, some resemblance in shape to the beak of a crow. 
 CORALLIGENOUS. Producing a corallum. 
 CORALUTE. The corallum secreted by an Actinozoon which consists of a single 
 
 polype ; or the portion of a composite corallum which belongs to, and is 
 
 secreted by, an individual polype. 
 CORALLUM (from the Latin for Keel Coral). The hard structures deposited in, 
 
 or by, the tissues of an ActinozoSn commonly called a " coral." 
 CORIACEOUS (Lat. corium, hide). Leathery. 
 CORYNIDA (Gr. korune, a club). A group of the Hydroid Zoophytes, so called 
 
 from their sometimes possessing clubbed tentacles. 
 CosT.fi (Lat. costa, a rib). Applied amongst the Crinoidea to designate the 
 
 rows of plates which succeed the inferior or basal portion of the cup (pel- 
 vis). Amongst the Corals the " cost " are vertical ridges which occur 
 
 on the outer surface of the theca, and mark the position of the septa 
 
 within. 
 
 COSTAL (Lat. costa, a rib). Connected with the ribs. 
 CRANIUM (Gr. kranipn, the skull). The bony or cartilaginous case in which 
 
 the brain is contained. 
 
 CRINOIDEA (Gr. krinon, a lily ; eidos, form). An order of Echinodermata, com- 
 prising forms which are usually stalked, and sometimes resemble lilies in 
 
 shape. 
 
 CROCODILIA (Gr. krokodeilos, a crocodile). An order of Reptiles. 
 CROSSOPTERYOID^! (Gr. krossotos, a fringe ; pterux, a fin). A sub-order of 
 
 Ganoids in which the paired fins possess a central lobe. 
 CRUSTACEA ( Lat. crusta, a crust). A class of Articulate animal?, comprising 
 
 Crabs, Lobsters, &c., characterised by the possession of a hard shell or 
 
 crust, which they cast periodically. 
 CRYPTOGAMS (Gr. kruptos, concealed ; gamos, marriage). A division of plants 
 
 in which the organs of reproduction are obscure and there are no true 
 
 flowers. 
 CTENOID (Gr. tteit, a comb ; eidos, form). Applied to those scales of fishes, 
 
 the hinder margins of which are fringed with spines or comb-like projections. 
 CTENOPHORA (Gr. kteit, a comb ; and phero, I carry). An order of A<< 
 
 comprising oceanic creatures, which swim by means of " ctenophores," or 
 
 bands of cilia arranged in comb-like plates. 
 CURSORES (Lat. curro, I run). An order of A vex, comprising birds destitute 
 
 of the power of flight, but formed for running vigorously (e.g., the Ostrich 
 
 and Emeu). 
 
 CUSPIDATE. Furnished with small pointed eminences or "cusps." 
 CUTICLE (Lat. ciUicula, dim. of cutu, skin). The pellicle which forms the
 
 GLOSSARY. 569 
 
 outer layer of the body amongst the Infusoria. The outer layer of the 
 
 integument generally. 
 CYCLOID (Gr. kuklos, a circle ; eidos, form). Applied to those scales of fishes 
 
 which have a regularly circular or elliptical outline with an even margin. 
 CTCLOSTOMI (Gr. kuklos, and stoma, mouth). Sometimes used to designate 
 
 the Hag-fishes and Lampreys, forming the order Marsipobranchii. 
 CYST (Gr. kustis, a bladder or bag). A sac or vesicle. 
 CYSTOIDEA (Gr. kustis, a bladder; and eidos, form). An extinct order of 
 
 Echinodermata. 
 
 DECAPODA (Gr. deka, ten ; podes, feet). The division of Crustacea which have 
 ten ambulatory i'eet ; also the family of Cuttle-fishes, in which there are 
 ten arms or cephalic 
 
 DECIDUOUS (Lat. decido, I fall off). Applied to parts which fall off or are 
 
 shed during the life of the animal. 
 DECOLLATED (Lat. decollo, I behead). Applied to univalve shells, the apex of 
 
 which falls off in the course of growth. 
 
 DEINOSAUUIA (Gr. deinos, terrible ; saura, lizard). An extinct order of Rep- 
 tiles. 
 DENDRIFORM, DENDRITIC, DENDROID (Gr. dendron, a tree). Branched like a 
 
 tree, arborescent. 
 
 DERMAL (Gr. derma, skin). Belonging to the integument. 
 DESMIDLE. Minute fresh- water plants, of a green colour, without a siliceous 
 
 epidermis. 
 
 DEXTRAL (Lai. dextra, the right hand). Right-handed. Applied to the di- 
 rection of the spiral in the greater number of univalve shells. 
 DIAPHRAGM (Gr. diaphragma, a partition). The "midriff" or the muscle 
 
 which in Mammalia forms a partition between the cavities of the thorax 
 
 and abdomen. 
 DIASTEMA (Gr. dia, apart ; histemi, to place). A gap or interval, especially 
 
 between teeth. 
 DIATOMACE^; (Gr. diatemno, I sever). An order of minute plants, which are 
 
 provided with siliceous envelopes. 
 DLBRANCHIATA (Gr. dis, twice ; bragchia, gill). The order of Cephalopoda 
 
 (comprising the Cuttle-fishes, &c.) in which only two gills are present. 
 DICYNODONTIA (Gr. dis, twice ; kuon, dog ; odovs, tooth). An extinct order 
 
 of Reptiles. 
 DIDELPHIA (Gr. dis, twice ; delphus, womb). The subdivision of Mammals 
 
 comprising the Marsupials. 
 DIGIT (Lat. diyilus, a finger). A finger or toe. 
 
 DIGITIGRADA (Lat. diyitus ; gradior, I walk). A subdivision of the Camivora. 
 DIGITIGRADE. Walking upon the tips of the toes, and not upon the soles of 
 
 the feet. 
 DIMYARY (Gr. dis, twice ; muon, muscle). Applied to those bivalve Molluscs 
 
 (Lamellibranchiata) in which the shell is closed by two adductor muscles. 
 DIPHYODONT (Gr. dis, twice ; phuo, I generate ; odous, tooth). Applied to 
 
 those Mammals which have two sets of teeth. 
 DIPNOI (Gr. dis, twice ; pnoe, breath). The order of Fishes represented by 
 
 the Lepidosiren. 
 DIPTERA (Gr. dh, twice ; pteron, wing). An order of Insects characterised by 
 
 the possession of two wings. 
 DISCOID (Gr. diskos, a quoit ; eidos, form). Shaped like a round plate or 
 
 quoit. 
 DISCOPHORA (Gr. diskos, a quoit ; phero, I carry). This term is applied to the 
 
 Medusae, or Jelly-fishes, from their form ; and is sometimes used to desig- 
 nate the order of the Leeches (Hirudinea), from the suctorial discs which 
 
 these animals possess. 
 DISSEPIMENTS (Lat. dissepio, I partition off). Partitions. Used in a restricted 
 
 sense to designate certain imperfect transverse partitions, which grow from 
 
 the septa of many corals. 
 DISTAL. Applied to the quickly-growing end of the hydrosoma of a Hydro-
 
 57 GLOSSARY. 
 
 zoSn; the opposite, or "proximal," extremity growing leas rapidly, and 
 being the end by which the organism is fixed, when attached at all. 
 
 DIURNAL (Lat. dies, day). Applied to animals which are active during the 
 day. 
 
 DORSAL (Lat. dorsum, back). Connected with the back. 
 
 DORSIBRANCHIATE (Lat. dorsum, the back ; Gr. bragckia, gill). Having ex- 
 ternal gills attached to the back ; applied to certain A MMJMMand Afotltuct. 
 The term is of mongrel composition, and "notobranchiate" is more cor- 
 rectly employed. 
 
 ECHINODERMATA (Gr. echinos; and derma, skin). A class of animals com- 
 prising the Sea-urchins, Star-fishes, and others, most of which have spiny 
 skins. 
 
 ECHINOIDEA (Gr. echinos; and eidos, form). An order of Echinodermata, com- 
 prising the Sea-urchins. 
 
 ECHINULATE. Possessing spines. 
 
 ECTOCYST (Gr. ektos, outside ; kuttis, a bladder). The external investment of 
 the ccenoecium of a Polyzo&n. 
 
 ECTODERM (Gr. ektos, and derma, skin). The external integumentary layer of 
 the Coslenterata. 
 
 EDENTATA (Lat. e, without ; dens, tooth). An order of Mammalia often 
 called BnUa. 
 
 EDENTULOUS. Toothless, without any dental apparatus. Applied to the 
 mouth of any animal, or to the hinge of the bivalve Molluscs. 
 
 EDRIOPHTHALMATA (Gr. hedraios, sitting ; optuhalmos, eye). The division 
 of Crustacea in which the eyes are sessile, and are not supported upon 
 stalks. 
 
 ELASMOBRANCHII (Gr. elasma, a plate ; bragchia, gill). An order of Fishes, 
 including the Sharks and Rays. 
 
 ELYTRA (Gr. elutron, & sheath). The chitinous anterior pair of wings in 
 Beetles, which form cases for the posterior membranous wings. Also ap- 
 plied to the scales or plates on the back of the Sea-mouse (Aphrodite). 
 
 EMBRYO (Gr. en, in ; bruo, I swell). The earliest stage at which the young 
 animal is recognisable in the impregnated ovum. 
 
 ENALIOSAURIA (Gr. enalios, marine ; saura, lizard). Sometimes employed as 
 a common term to designate the extinct Reptilian orders of the Ickthyosauria 
 and Plesiosauria. 
 
 ENCEPHALOUS (Gr. en, in ; kephale, the head). Possessing a distinct head. 
 Usually applied to all the Alollutca proper, except the Lamellibranchiata. 
 
 ENDOCYST (Gr. endon, within ; kustit, a bag). The inner membrane or in- 
 tegumentary layer of a Polyzoon. In Cristatella, where there is no " ecto- 
 cyst," the endocyst constitutes the entire integument. 
 
 ENDODERM (Gr. endon ; aud derma, skin). The inner integumentary layer of 
 the Coslenterata. 
 
 ENDOPODITK (Gr. endon ; and pout, foot). The inner of the two secondary 
 joints into which the typical limb of a Crustacean is divided. 
 
 ENDOSKELETON (Gr. endon ; and skeletos, dry). The internal hard structures, 
 such as bones, which serve for the attachment of muscles, or the protec- 
 tion of organs, and which are not a mere hardening of the integument. 
 
 EusiFORM (Lat. ensis, a sword ; forma, shape). Sword-shnped. 
 
 ENTOMOPHAOA (Gr. entonta, insects ; pluiyo, I eat). A section of the Marsu- 
 pialia. 
 
 ENTOMOSTRACA (Gr. enloma, insects ; ostrakon, a shell). Literally Shelled 
 Insects, applied to a division of Crustacea. 
 
 ENTOZOA (Gr. entos, within ; zoiin, animal). Animals which are parasitic in 
 the interior of other animals. 
 
 EOCENK (Gr. tot, dawn ; kainos, new or recent). The lowest division of the 
 Tertiary Rocks, in which species of existing shells are to a small extent 
 represented. 
 
 EPIDERMIS (Gr. epi, upon ; derma, the true skin). The outer non-vascular 
 layer of the skin, often called the scarf-skin or cuticle.
 
 GLOSSARY. 571 
 
 EPIMERA (Gr. epi, upon ; meron, thigh). The lateral pieces of the dorsal arc 
 
 of the somite of a Crustacean. 
 EPIPODIA (Gr. epi, upon ; pous, the foot). Muscular lobes developed from 
 
 the lateral and upper surfaces of the " foot" of some Molluscs. 
 EPIPODITE (Gr. epi, upon; pous, foot). A process developed upon the basal 
 
 joint, or " protopodite," of some of the limbs of certain Crustacea. 
 EPISTERNA (Gr. epi, upon ; sternon, the breast-bone). The lateral pieces of 
 
 the inferior or ventral arc of the somite of a Crustacean. 
 EPISTOME (Gr. epi ; and stoma, mouth). A valve-like organ which arches 
 
 over the mouth in certain of the Polyzoa. 
 EPITHECA (Gr. epi; and theke, a sheath). A continuous layer surrounding 
 
 the thecre in some Corals externally. 
 EPIZOA (Gr. epi, upon ; zoon, animal). Animals which are parasitic upon 
 
 other animals. In a restricted sense, a division of Crustacea which are 
 
 parasitic upon fishes. 
 EQUILATERAL (Lat. cequus, equal ; latus, side). Having its sides equal. 
 
 Usually applied to the shells of the Brachiopoda. When applied to the 
 
 spiral shells of the Foraminifera, it means that all the convolutions of the 
 
 shell lie in the same plane. 
 EQUISETACEA (Lat. eyuus, horse ; seta, bristle). A group of Cryptogamous 
 
 plants, commonly known as " Horse-tails." 
 EQUIVALVE (Lat. cequus, equal; valvce, folding-doors). Applied to shells 
 
 which are composed of two equal pieces or valves. 
 ERRANTIA (Lat. erro, I wander). An order of Annelida, often called Nereidea, 
 
 distinguished by their great locomotive powers. 
 EURYPTERIDA (Gr. eurus, broad ; pteron, wing). An extinct sub-order of 
 
 Crustacea. 
 EXOPODITE (Gr. exo, outside ; pous, foot). The outer of the two secondary 
 
 joints into which the typical limb of a Crustacean is divided. 
 EXOSKELETON (Gr. exo, outside ; skeletos, dry. The external skeleton, which 
 
 is constituted by a hardening of the integument, and is often called a 
 
 " dermoskeleton." 
 
 FASCICULATED (Lat. fasciculus, a bundle). Arranged in bundles. 
 
 FAUNA (Lat. Fauni, the rural deities of the Romans). The general assem- 
 blage of the animals of any region or district. 
 
 FEMUR. The thigh-bone, intervening between the pelvis and the bones of 
 the leg proper (tibia and fibula). 
 
 FIBULA (Lat. a brooch). The outermost of the two bones of the leg in the 
 higher Vertebrata ; corresponding to the ulna of the fore-arm. 
 
 FILICES (Lat. filix, a fern). The order of Cryptogamic plants comprising the 
 Ferns. 
 
 FILIFORM (Lat. filum, a thread ; forma, shape). Thread-shaped. 
 
 FISSION (Le&.findo, I cleave). Multiplication by means of a process of self- 
 division. 
 
 FISSIPAROUS (Lat. findo ; and pario, I produce). Giving origin to fresh struc- 
 tures by a process of fission. 
 
 FLORA (Lat. Flora, the goddess of flowers). The general assemblage of the 
 plants of any region or district. 
 
 FOOT-JAWS. The limbs of Crustacea, which are modified to subserve mastica- 
 tion. 
 
 FOOT- SECRETION. The term applied by Mr Dana to the sclerobasic corallum 
 of certain A ctinozoa. 
 
 FOOT-TUBERCLES. The unarticulated appendages of the Annelida, often 
 called parapodia. 
 
 FORAMINIFERA (Lat. foramen, an aperture ; fero, I carry). An order of Pro- 
 tozoa, usually characterised by the possession of a shell perforated by 
 numerous pseudopodial apertures. 
 
 FRUGIVOROUS (L&t.fruz, fruit; voro, I devour). Living upon fruits. 
 
 FUCOIDS (Lat. fucus, sea- weed; Gr. eidos, likeness). Fossils, often of an 
 obscure nature, believed to be the remains of sea-weeds.
 
 .57 2 GLOSSARY. 
 
 FURCULUM or FURCULA. (Lat. dim. of furca, a fork). The " merry -thought " 
 of birds, or the V-ithapecl bone formed by the united clavicles. 
 
 FUSIFORM (Lat. /**, a spindle; and forma, shape). Spindle-shaped, or 
 pointed at both ends. 
 
 GALLINACEI (Lat. gallina, a fowl). Sometimes applied to the whole order of 
 the Rasorial Birds, but properly restricted to that section of the order of 
 which the common Fowl is a typical example. 
 
 GANGLION (Gr. gagglion, a knot). A mass of nervous matter containing 
 nerve-cells, and giving origin to nerve-fibres. 
 
 GANOID (Gr. ganos, splendour, brightness). Applied to those scales or plates 
 which are composed of an inferior layer of true bone covered by a superior 
 layer of polished enamel. 
 
 GANOIDEI. An order of Fishes. 
 
 GASTEROPODA (Gr. gaster, stomach ; pous, foot). The class of the Molluxa 
 comprising the ordinary univalves, in which locomotion is usually effected 
 by a muscular expansion of the under surface of the body (the " foot"). 
 
 GEMMAE (gemma, a bud). The buds produced by any animal, whether detached 
 or not. 
 
 GEMMATION. The process of producing new structures by budding. 
 
 GEMMIPAROUS (Lat. gemma, a bud ; pario, I produce). Giving origin to new 
 structures by a process of budding. 
 
 GEPHYREA (Gr. gephnra, a bridge). A class of the Anartkropoda, comprising 
 the Spoon-worms (Sipunculus) and their allies. 
 
 GIZZARD. A muscular division of the stomach in Birds, Insects, &c. 
 
 GLADIUS (Lat. a sword). Applied to the horny eudoskeleton or "pen" of 
 certain Cuttle-fishes. 
 
 GLENOID (Gr. glene, a cavity ; eidos, form). A shallow cavity ; applied espe- 
 cially to the shallow articular cavity in the shoulder-blade to which the 
 head of the humerus is jointed. 
 
 GRALLATORES (Lat. orallce, stilts). The order of the long-legged Wading 
 Birds. 
 
 GRAPTOLITIDJE (Gr. grapho, I write ; lithos, stone). An extinct sub-class of 
 the Hydrozoa. 
 
 GREOARINIDA (Lat. gregarius, occurring in numbers together). A class of the 
 Protozoa. 
 
 GUARD. The cylindrical fibrous sheath with which the internal chambered 
 shell (phragmacone) of a Belemnite is protected. 
 
 GYMNOLJEMATA (Gr. gumnot, naked ; laimos, the throat). An order of the 
 Polyzoa in which the mouth is devoid of the valvular structure known as 
 the " epistome." 
 
 GYMNOPHIONA (Gr. gumnoi, naked ; ophi*, a snake). The order of the Am- 
 phibia comprising the snake-like Ceecilive. 
 
 GYMNOPHTHALMATA (Gr. gvmnos ; and ophthalmos, the eye). Applied by Ed- 
 ward Forbes to those Medusa in which the eye-specks at the margin of the 
 disc are unprotected. The division is now abandoned. 
 
 GYMNOSOMATA (Gr. gumnos ; and toma, the body). The order of PUropoda 
 in which the body 'is not protected by a shell. 
 
 HALLUX (Lat. alltx, the thumb or great toe). The innermost of the five 
 
 digits which normally compose the kind foot of a Vertebrate animal. In 
 
 man, the great toe. 
 HEMIPTERA (Gr. hemi; and pteron, wing). An order of Insects in which the 
 
 anterior wings are sometimes " hemelytra." 
 HERMAPHRODITE (Gr. Jlermes, Mercury ; Aphrodite, Venus). Possessing the 
 
 characters of both sexes combined. 
 HETEROCERCAL (Gr. heiei-os, diverse; lerl-ot, tail.) Applied to the tail of 
 
 Fishes when it is unsymmetrical, or composed of two unequal lobes. 
 HKTEROPODA (Gr. heterot, diverse ; podes, feet). An aberrant group of the 
 
 Gasteropoda, in which the foot is modified so as to form a swimming 
 
 organ.
 
 GLOSSARY. 573 
 
 HIRUDINEA (Lat. hirudo, a horse-leech). The order of A nnelida comprising 
 
 the Leeches. 
 HISTOLOGY (Gr. histos, a web ; logos, a discourse). The study of the tissues, 
 
 more especially of the minuter elements of the body. 
 HOLOCEPHALI (Gr. holes, whole ; kephale, head). A sub-order of the Elasmo- 
 
 branchii comprising 1 the Chimcerce. 
 HOLOSTOMATA (Gr. holos, whole ; stoma, mouth). A division of Gasteropodous 
 
 Molluscs, in which the aperture of the shell is rounded, or " entire." 
 HOLOTHUROIDEA (Gr. holothourion ; and eidos, form). An order of Echinoder- 
 
 mata comprising the Trepangs. 
 HOMOCERCAL (Gr. homos, same ; kerkos, tail). Applied to the tail of Fishes 
 
 when it is symmetrical, or composed of two equal lobes. 
 HOMOLOGOUS (Gr. homos ; and logos, a discourse). Applied to parts which 
 
 are constructed upon the same fundamental plan. 
 HUMERUS. The bone of the upper arm (Irachium) in the Vertebrates. 
 HYALINE (Gr. hualos, crystal). Crystalline or glassy. 
 HYBODONTS (Gr. hubos, curved ; odous, tooth). A group of Fishes of which 
 
 Hylodus is the type-genus. 
 HYDROIDA (Gr. hudra; and eidos, form). The sub-class of the Hydrozoa, 
 
 which comprises the animals most nearly allied to the Hydra. 
 HYDROTHECA (Gr. hudra; and tJieke, a case). The little cbitinous cups in 
 
 which the polypites of the Serlularida and Campanularida are protected. 
 HYDROZOA (Gr. hudra; and zob'n, animal). The class of the Coelenterata 
 
 which comprises animals constructed after the type of the Hydra. 
 HYMENOPTERA (Gr. humen, a membrane ; pteron, a wing). An order of In- 
 sects (comprising Bees, Auts, &c.) characterised by the possession of four 
 
 membranous wings. 
 
 HYOID (Gr. U ; eidos, form). The bone which supports the tongue in Ver- 
 tebrates, and derives its name from its resemblance in man to the Greek 
 
 letter U. 
 HYPOSTOME (Gr. hupo, under ; stoma, mouth). The upper lip, or "labrum," 
 
 of certain Crustacea (e.g., Trilobites). 
 HYRACOIDEA (Gr. kurax, a shrew ; eidos, form). An order of the Mammalia 
 
 constituted for the reception of the single genus Hyrax. 
 
 ICHTHYODORULITE (Gr. ichthus, fish ; dorus, spear ; lithos, stone). The fossil 
 fin-spines of Fishes. 
 
 ICHTHYOMORPHA (Gr. ichthus ; morphe, shape). An order of Amphibians, 
 often called Urodela, comprising the fish-like Newts, &c. 
 
 ICHTHYOPHTHIRA (Gr. ichthus ; phtheir, a louse). An order of Crustacea com- 
 prising animals which are parasitic upon Fishes. 
 
 ICHTHYOPSIDA (Gr. ichthus ; opsis, appearance). The primary division of 
 Vertebrata, comprising the Fishes and Amphibia. Often spoken of as the 
 Branchiate Vertebrata. 
 
 ICHTHYOPTEUYGIA (Gr. ichthus ; plerux, wing). An extinct order of Reptiles. 
 
 ICHTHYOSAURIA (Gr. ichthus ; saura, lizard). Synonymous with Ichtliyopterygia. 
 
 ILIUM. The haunch-bone, one of the bones of the pelvic arch in the higher 
 Vertebrates. 
 
 IMAGO (Lat. an image or apparition). The perfect insect, after it has under- 
 gone its metamorphoses. 
 
 IMBRICATED. Applied to scales or plates which overlap one another like tiles. 
 
 INCISOR (Lat. incido, I cut). The cutting teeth fixed in the intermaxillary 
 bones of the Mammalia, and the corresponding teeth in the lower jaw. 
 
 INEQUILATERAL. Having the two sides unequal, as in the case of the shells 
 of the ordinary bivalves (Lamellibranchiata) . When applied to the shells 
 of the Foramiuifera, it implies that the convolutions of the shell do not lie 
 in the same plane, but are obliquely wound round an axis. 
 
 INEQUIVALVE. Composed of two unequal pieces or valves. 
 
 INFUNDIBULUM (Lat. for funnel). The tube formed by the coalescence or 
 apposition of the epipodia in the Cephalopoda. Commonly termed the 
 "funnel," or "siphon."
 
 574 GLOSSARY. 
 
 INFUSORIA (Lat. infittum, an infusion). A class of Protozoa, BO called bo- 
 cause they are often developed in organic infusions. 
 
 INOPBRCULATA (Lat in, without; operculum, a lid). The division of pul- 
 monate Gasteropoda in which there is no shelly or horny plate (operculum) 
 by which the shell is closed when the animal is withdrawn within it. 
 
 I NSIVTA (Lat. in*' i-, I cut into). The class of articulate animals commonly 
 known as Insects. 
 
 INSECTIVORA (Lat. insectum, an insect; voro, I devour). An order of 
 Mammals. 
 
 INSECTIVOROUS. Living upon Insects. 
 
 INSESSORES (Lat. insedeo, I sit upon). The order of the Perching Birds, often 
 called Passeres. 
 
 INTERAMBULAORA. The rows of plates in an Echinodtrm, which are not per- 
 forated for the emission of the "tube-feet." 
 
 INTERMAXILL.S, or PR^MAXILL*. The two bones which are situated between 
 the two superior maxillae in Vertebrata. In man, and some monkeys, the 
 prsemaxillae anchylose with the maxillae, so as to be irrecognisable in the 
 adult. 
 
 INVERTEBRATA (Lat. in, without ; vertebra, a bone of the back). Animals 
 without a spinal column or backbone. 
 
 ISCHIUM (Gr. ischion, the hip). One of the bones of the pelvic arch in Verte- 
 brates. 
 
 ISOPODA (Gr. isos, equal ; podes, feet). An order of Ci ustacea in which the 
 feet are like one another and equal. 
 
 JUOULAK (Lat. ivgulum, the throat). Connected with, or placed upon, the 
 throat. Applied to the ventral fins of fishes when they are placed beneath 
 or in advance of the pectorals. 
 
 KAINOZOIC (Gr. kainos, recent ; zoe, life). The Tertiary period in Geology, 
 
 comprising those formations in which the organic remains approximate 
 
 more or less closely to the existing fauna and flora. 
 KERATODE (Gr. keras, horn ; eidos, form). The horny substance of which the 
 
 skeleton of many sponges is made up. 
 KERATOSA. The division of Sponges in which the skeleton is composed of 
 
 keratode. 
 
 LABIUM (Lat for lip). Restricted to the lower lip of Articulate animals. 
 LABRUM (Lat. for lip). Restricted to the upper lip of Articulate animals. 
 LABYRINTHODONTIA (Gr. laburinthos, a labyrinth ; odous, tooth). An extinct 
 
 order of Amphibia, so called from the complex microscopic structure of 
 
 the teeth. 
 LACERTILIA (Lat. lacerta, a lizard). An order of Reptilia comprising the 
 
 Lizards and Slow-worms. 
 
 L.f.MODiroDA (Gr. laimos, throat ; dis, twice ; podes, feet). An order of Crus- 
 tacea, so called because they have two feet placed far forwards, as it were, 
 
 under the throat 
 LAMBLLIBRANCHIATA (Lat. lamella, a plate ; Gr. bragchia, pill). The class of 
 
 Mollusca, comprising the ordinary bivalves, characterised by the possession 
 
 of lamellar gills. 
 
 LAMELLIROSTRES (Lat. lamella, a plate ; rostrum, beak). The flat-billed Swim- 
 ming Birds (Natatores), such as Ducks, Geese, Swans, &c. 
 LARVA (Lat. a mask). The insect in its first stage after its emergence from 
 
 the egg, when it is usually very different from the adult. 
 LARYNX. The upper part of the windpipe, forming a cavity with appropriate 
 
 muscles and cartilages, situated beneath the hyoid bone, and concerned in 
 
 Mammals in the production of vocal sounds. 
 LENTICULAR (Lat. lens, a bean). Shaped like a biconvex lens. 
 LKi'iDODENDRON (Gr. lepis, & scale ; dendi-on, a tree). A genus of extinct 
 
 plants, so named from the scale-like scars upon the stem left by the falling 
 
 off of the leaves.
 
 GLOSSARY. 575 
 
 LEPIDOPTERA (Gr. lepis, a scale ; pteron, a wing). An order of Insects, com- 
 prising Butterflies and Moths, characterised by possessing four wings which 
 are usually covered with minute scales. 
 
 LEPIDOTA (Gr. lepis, a'scale). Formerly applied to the order Dipnoi, con- 
 taining the Mud-fishes (Lepidosiren). 
 
 LEPTOCARDIA (Gr. lepto*, slender, small ; cardia, heart). The name given by 
 Muller to the order of Fishes comprising the Lancelot, now called PJiaryn- 
 gobranckii. 
 
 LOPHOPHORE (Gr. lophos, a crest ; and phero, I carry). The disc or stage 
 upon which the tentacles of the Polyzoa are borne. 
 
 LOPHYROPODA (Gr. lophouros, having stiff hairs ; and podes, feet). A section 
 of Crustacea. 
 
 LORICATA (Lat. lorica, a cuirass). The division of Reptiles comprising the 
 Chelonia and Crocodilia, in which bony plates are developed in the skin 
 (derma). 
 
 LUCERNARIDA (Lat. lucerna, a lamp). An order of the Hydrozoa. 
 
 LUMBAR (Lat. lumbus, loin). Connected with the loins. 
 
 LUNATE (Lat. luna, moon). Crescentic in shape. 
 
 LYCOPODIACE.E (Gr. lupos, a wolf ; pous, foot). The group of Cryptogamic 
 plants generally known as " Club-mosses." 
 
 MACRURA (Gr. macros, long ; oura, tail). A tribe of Decapod Crustaceans with 
 long tails (e.g., the Lobster, Shrimp, &c.) 
 
 MADREPORIFORM. Perforated with small holes, like a coral ; applied to the 
 tubercle by which the ambulacra! system of the Echinoderms mostly com- 
 municates with the exterior. 
 
 MALACOSTRACA (Gr. malakos, soft ; ostrakon, shell). A division of Crustacea. 
 Originally applied by Aristotle to the entire class Crustacea, because their 
 shells were softer than those of the Mollusca. 
 
 MAMMALIA (Lat. mamma, the breast). The class of Vertebrate animals which 
 suckle their young. 
 
 MANDIBLE (Lat. mandibulum, a jaw). The upper pair of jaws in Insects ; 
 also applied to one of the pairs of jaws in Crustacea and Spiders, to the beak 
 of Cephalopods, the lower jaw of Vertebrates, &c. 
 
 MANTLE. The external integument of most of the Mollusca, which is _T 
 developed, and forms a cloak in which the viscera are protected, 
 cally called the "pallium." 
 
 MANUS (Lat. the hand). The hand of the higher Vertebrates. 
 
 MARSIPOBRANCHII (Gr. marsipos, a pouch ; bragchia, gill). The order of 
 Fishes comprising the Hag-fishes and Lampreys, with pouch-like gills. 
 
 MARSUPIALIA (Lat. marsupium, a pouch). An order of Mammals in which the 
 females mostly have an abdominal pouch in which the young are carried. 
 
 MASTICATORY (Lat. mastico, I chew). Applied to parts adapted for chewing. 
 
 MAXILL.E (Lat. jaws). The inferior pair or pairs of jaws in the Arthropoda 
 (Insects, Crustacea, &c.) The upper jaw-bones of Vertebrates. 
 
 MAXILLIPEDES (Lat. maxillae, jaws ; pes, the foot). The limbs in Crustacea 
 and Myriapoda which are converted into masticatory organs, and are com- 
 monly called "foot-jaws." 
 
 MEDULLA (Lat. marrow). Applied to the marrow of bones ; or to the spinal 
 cord, with or without the adjective " spinalis." 
 
 MEDUSA. An order of Hydrozoa, commonly known as Jelly-fishes (Disco- 
 phora, or Acalephce), so called because of the resemblance of their tentacles 
 to the snaky hair of the Medusa. Many Medusce are now known to be 
 merely the gonophores of Hydrozoa. 
 
 MEROSTOMATA (Gr. meron, thigh ; stoma, mouth). An order of Crustacea in 
 which the appendages which are placed round the mouth, and which offi- 
 ciate as jaws, have their free extremities developed into walking or pre- 
 hensile organs. 
 
 MESENTERIES (Gr. mesos, intermediate ; enteron, intestine). In a restricted 
 sense, the vertical plates which divide the somatic cavity of a Sea-anemone 
 (Actinia) into chambers.
 
 576 GLOSSARY. 
 
 MESOPODIUM (Or. metot, middle ; pout, foot). The middle portion of the 
 "foot "of Molluscs. 
 
 MESOSTERNUM (Or. mesos, intermediate ; sternon, the breast-bone). The 
 middle portion of the sternum, intervening between* the attachment of the 
 second pair of ribs and the xiphoid cartilage (xiphitternum). 
 
 MESOTHOHAX (Gr. mesos; and thorax, the chest). The middle ring of the 
 thorax in Insects. 
 
 MKSOZOIC (Gr. mesox; and zoe, life). The Secondary period in Geology. 
 
 METACARPUS (Gr. meta, after ; karpos, the wrist). The bones which form the 
 " root of the hand," and intervene between the wrist and the fingers. 
 
 METAMORPHOSIS (Gr. met a, implying change ; morplte, shape). The changes 
 of form which certain animals undergo in passing from their younger to 
 their fully-grown condition. 
 
 METAPODIUM (Gr. meta, after ; pous, the foot). The posterior lobe of the foot 
 in Mollufca ; often called the " operculigerous lobe," because it develops 
 the operculum when this structure is present. 
 
 METASTOMA (Gr. meta, after ; stoma, mouth). The plate which closes the 
 mouth posteriorly in the Crustacea. 
 
 METATARSUS (Gr. meta, after ; tarsot, the instep). The bones which inter- 
 vene between the bones of the ankle (tarsus) and the digits in the hind-foot 
 of the higher Vertebrates. 
 
 METATHORAX (Gr. meta, after ; t/iorax, the chest). The posterior ring of the 
 thorax in Insects. 
 
 MIMETIC (Gr. mimetikos, imitative). Applied to organs or animals which re- 
 semble each other in external appearance, but not in essential structure. 
 
 MOLARS (Lat. mo/a, a mill). The "grinders" in man, or the teeth in diphyo- 
 dont Mammals which are not preceded by milk-teeth. 
 
 MoLLOSCA (Lat. mollis, soft). The sub-kingdom which includes the Shell- 
 fish proper, the Polyzoa, the Tunicata, and the Lamp-shells; so called from 
 the generally soft nature of their bodies. 
 
 MOLLUSCOIDA (Mollusca; Gr. eidos, form). The lower division of the Molliuca, 
 comprising the Polyzoa, Tunicata, and Brachiopoda. 
 
 MONODELPHIA (Gr. monos, single; delphus, womb). The division of Mammalia 
 in which the uterus is single. 
 
 MONOMYARY (Gr. mono*, single ; muon, muscle). Applied to those bivalves 
 (Lamelliliranchiata) in which the shell is closed by a single adductor muscle. 
 
 MONOPHYODOXT (Gr. monos ; phuo, I generate ; odous, tooth). Applied to 
 those Mammals in which only a single set of teeth is ever developed. 
 
 MONOTHALAMOUS (Gr. moiios ; and tkalamos, chamber). Possessing only * 
 single chamber. Applied to the shells of Foraminifera and Mollusca. 
 
 MONOTREMATA (Gr. monos ; trema, aperture). The order of Mammals com- 
 prising the Duck-mole and Echidna, in which the intestinal canal opens 
 into a " cloaca" common to the ducts of the urinary and generative organs. 
 
 MOLTILOCULAR (Lat. multus, many; loculns, a little purse). Divided into 
 many chambers. 
 
 MuLTl VALVE. Applied to shells which are composed of many pieces. 
 
 MULTDXOULA (Lat. multus, many ; ungula, hoof). The division of Perisso- 
 dactyle Ungulates, in which each fool has more than a single hoof. 
 
 MYRIAPODA or MYRIOPODA (Gr. mvriot, ten thousand ; podes, feet). A class 
 of Arthropoda comprising the Centipedes and their allies, characterised by 
 their numerous feet. 
 
 NACREOUS (Fr. nacre, mother-of-pearl, originally Oriental.) Pearly; of the 
 
 texture of mother-of-pearl. 
 
 NATATORES (Lat. nare, to swim). The order of the Swimming Birds. 
 NATATORY (Lat. nare, to swim). Formed for swimming. 
 NAUTILOID. Resembling the shell of the Xautilus in shape. 
 NERVURES (Lat. ncrvus, a sinew). The ribs which support the membranous 
 
 wings of insects. 
 
 NEURAL (Gr. neuron, a nerve). Connected with the nervous system. 
 NKURAPOPHY8IS (Gr. neuron, a nerve ; apophtuit, a projecting part). The
 
 GLOSSARY. 577 
 
 " spinous process " of a vertebra, or the process formed at the point of 
 junction of the neural arches. 
 
 NEUROPTERA (Gr. neuron ; and pteron, a wing). An order of Insects charac- 
 terised by four membranous wings with numerous reticulated nervures 
 (e. g., Dragon-flies). 
 
 NOCTURNAL (Lat. nox, night). Applied to animals which are active by night. 
 
 NORMAL (Lat. norma, a rule). Conforming to the ordinary standard. 
 
 NOTOBRANCHIATA (Gr. notos, the back ; and bragchia, gill). Carrying the 
 gills upon the back ; applied to a division of the Annelida. 
 
 NOTOCHORD (Gr. notos, back ; chorde, string). A cellular rod which is devel- 
 oped in the embryo of Vertebrates immediately beneath the spinal cord, 
 and which is usually replaced in the adult by the vertebral column. Often 
 it is spoken of as the " chorda dorsalis." 
 
 NUDIBRANCHIATA (Lat. nudus, naked ; and Gr. Iragchia, gill). An order of 
 the Gasteropoda in which the gills are naked. 
 
 NUMMULITES (Lat. nummux, a coin). A large coin-shaped Foraminifer of the 
 Eocene period. 
 
 OCCIPITAL. Connected with the occiput, or the back part of the head. 
 
 OCEANIC. Applied to animals which inhabit the open ocean ( = pelagic). 
 
 OCELLI (Lat. diminutive of oculus, eye). The simple eyes of many Echino- 
 derms, Spiders, Crustaceans, Molluscs, &c. 
 
 OCTOPODA (Gr. octo, eight ; nous, foot). The tribe of Cuttle-fishes with eight 
 arms attached to the head. 
 
 ODONTOCETI (Gr. odous, tooth; Mos, whale). The "toothed" Whales, in 
 contradistinction to the " whalebone " Whales. 
 
 ODONTOID (Gr. odous ; eidos, form). The "odontoid process " is the centrum 
 or body of the first cervical vertebra (atlas). It is detached from the atlas, 
 and is usually anchylosed with the second cervical vertebra (axis), and it 
 forms the pivot upon which the head rotates. 
 
 ODONTOPHORE (Gr. odout, tooth; phero, I carry). The so-called "tongue," 
 or masticatory apparatus of Gasteropoda, Pteropoda, and Cephalopoda. 
 
 OESOPHAGUS. The gullet or tube leading from the mouth to the stomach. 
 
 OLIGOCH^TA (Gr. oligos, few ; chaite, hair). An order of Annelida, compris- 
 ing the Earth-worms, in which there are few bristles. 
 
 OMNIVOROUS (Lat. omnia, everything ; voro, I devour). Feeding indiscrimin- 
 ately upon all sorts of food. 
 
 OPERCULATA (Lat. operculum, a lid). A division of pulmonate Gasteropoda, 
 in which the shell is closed by an operculum. 
 
 OPERCULUM. A horny or shelly plate developed in certain Moliusca upon the 
 hinder part of the foot, and serving to close the aperture of the shell when 
 the animal is retracted within it ; also the lid of the shell of a Balanus or 
 Acorn- shell ; also the chain of flat bones which cover the gills in many 
 fishes. 
 
 OPHIDIA (Gr. ophis, a serpent). The order of Reptiles comprising the Snakes. 
 
 OPHIDOBATHACHIA (Gr. ophif ; batrachos, a frog). Sometimes applied to the 
 order of Snake-like Amphibians comprising the Ccecilice. 
 
 OPHIOMORPHA (Gr. ophis ; morphe, shape). The order of Amphibia compris- 
 ing the Ccecilice. 
 
 OPHIUROIDEA (Gr. ophis, snake ; oura, tail ; eidos, form). An order of Echino- 
 dermata, comprising the Brittle-stars and Sand-stars. 
 
 OPISTHOBRANCHIATA (Gr. opisthen, behind ; bragchia, gill). A division of 
 Gasteropoda in which the gills are placed on the posterior part of the body. 
 
 OPISTHOCOELOUS (Gr. opisthen, behind ; koilos, hollow). Applied to vertebrae, 
 the bodies of which are hollow or concave behind. 
 
 ORAL (Lat. os, mouth). Connected with the mouth. 
 
 ORNITHODELPHIA v Gr. ornis, a bird ; delphus, womb). The primary division 
 of Mammals comprising the Monotremata. 
 
 ORNITHOSCELIDA (Gr. ornis, bird ; skelos, leg). Applied by Huxley to the 
 Deinosaurian Reptiles, together with the genus Compsognathus, on account 
 of the bird-like character of their hind-limbs. 
 2 O
 
 5/8 GLOSSARY. 
 
 ORTHOCERATID* (Gr. orthos, straight ; kerat, horn). A family of the Nav.- 
 
 tilidce, in which the shell is straight, or nearly BO. 
 ORTHOPTEKA (Gr. ortho*, straight ; pteron, wing). An order of Insects. 
 OSSICULA (Lat. diminutive of ot, bone). Literally small bones. Often used 
 
 to designate any hard structures of small size, such as the calcareous plates 
 
 in the integument of the Star-fishes. 
 OSTRAOODA (Gr. ostrakon, a shell). An order of small Crustaceans which are 
 
 enclosed in bivalve shells. 
 OTOLITHS (Gr. out, ear ; and lithos, stone). The calcareous bodies connected 
 
 with the sense of hearing, even in its most rudimentary form. 
 OVARIAN VESICLES or CAPSULES. The generative buds of the Sertularida. 
 
 PACHYDERMATA (Gr. pachus, thick ; derma, skin). An old Mammalian order 
 constituted by Cuvier for the reception of the Rhinoceros, Hippopotamus, 
 Elephant, &c. 
 
 PALEONTOLOGY (Gr. palaios, ancient ; and logos, discourse). The science of 
 fossil remains or of extinct organised beings. 
 
 PAL.OTHKRin.E (Gr. palaios, ancient; ther, beast). A group of Tertiary 
 Ungulates. 
 
 PALEOZOIC (Gr. palaios, ancient ; and zoe, life). Applied to the oldest of the 
 great geological epochs. 
 
 PALUOBRANCHIATA (Lat. pallium; and Gr. braychia, gill). An old name for 
 the Brachiopoda, founded upon the belief that the system of tubes in the 
 mantle constituted the gills. 
 
 PALLIUM (Lat. pallium, a cloak). The mantle of the Mollusca. Pallial : 
 relating to the mantle. Pallial line or im/tre&sion : the line left in the dead 
 shell by the muscular margin of the mantle. Pallial shell ; a shell which is 
 secreted by, or contained within, the mantle, such as the " bone " of the 
 Cuttle-fishes. 
 
 PALPI (Lat. palpo, I touch). Processes supposed to be organs of touch, 
 developed from certain of the oral appendages in Insects, Spiders, and Crus- 
 tacea, and from the sides of the mouth in the Acephalous Molluscs. 
 
 PAPILLA (Lat. for nipple). A minute soft prominence. 
 
 PARAPODIA (Gr. para, beside ; podes, feet). The unarticulated lateral loco- 
 motive processes or " foot-tubercles " of many of the Annelida. 
 
 PARIETAL (Lat. paries, a wall). Connected with the walls of a cavity or of 
 the body. 
 
 PATAGIUM (Lat. the border of a dress). Applied to the expansion of the in- 
 tegument by which Bats, Flying Squirrels, and other animals support them- 
 selves in the air. 
 
 PATELLA. The knee-cap or knee-pan. A sesamoid bone developed in the 
 tendon of insertion of the great extensor muscles of the thigh. 
 
 PECTINATE (Lat. pecten, a comb). Comb-like ; applied to the gills of certain 
 Gasteropods, hence called Pectinibranekiata. 
 
 PECTORAL (Lat. pectus, chest). Connected with, or placed upon, the chest. 
 
 PEDAL (Lat. pes, the foot). Connected with the foot of Molluxa. 
 
 PEDICELLARI^E (Lat. pedicellus, a louse). Certain singular appendages found 
 in many Echi/wderms, attached to the surface of the body, and resembling 
 a little beak or forceps supported on a stalk. 
 
 PEDICLE (Lat. dim. of pes, the foot). A little stem. 
 
 PEDIPALPI (Lat. pet, foot ; eaidpalpo, I feel). An order of Arachnida com- 
 prising the Scorpions, &o. 
 
 PEDUNCLE (Lat. pedunculiu, a stem or stalk). In a restricted sense applied 
 to the muscular process by which certain Rrachiopods are attached, and 
 to the stem which bears the body (capitulum) in Barnacles. 
 
 PEDUNCULATE. Possessing a peduncle. 
 
 PELAOIC (Gr. pelagos, sea). Inhabiting the open ocean. 
 
 PELVIS (Lat. for basin). Applied, from analogy, to the basal portion of the 
 cup (calyx) of Crinoids. The bony arch with which the hind-limbs are 
 connected in Vertebrates. 
 
 PEHENSIBRANCHIATA (Lat perennit, perpetual ; Gr. bragchia, gill). Applied to
 
 GLOSSARY. 579 
 
 those Amphibia in which the gills are permanently retained throughout 
 
 life. 
 
 PERGAMENTACEOUS (Lat. pergamena, parchment). Of the texture of parchment. 
 PERIOSTRACUM (Gr.peri, around ; and ostrakon, shell). The layer of epidermis 
 
 which covers the shell in most of the Mollusca. 
 
 PERISOME (Gr. peri; and soma, body). The coriaceous or calcareous integu- 
 ment of the Echinodermata. 
 PERISSODACTYLA (Gr. perissos, uneven ; daklulos, finger). Applied to those 
 
 Hoofed Quadrupeds (Ungulata) in which the feet have an uneven number 
 
 of toes. 
 
 PETALOID. Shaped like the petal of a flower. 
 PHALANGES (Gr. phalanx, a row). The small bones composing the digits of 
 
 the higher Vertebrata. Normally each digit has three phalanges. 
 PHANEROGAMS (Gr. phaneros, visible ; gamos, marriage). Plants which have 
 
 the organs of reproduction conspicuous, and which bear true flowers. 
 PHARYNUOBRANCHII (Gr. pharugx, pharynx ; bragchia, gill). The order of 
 
 Fishes comprising only the Lancelot. 
 PHARYNX. The dilated commencement of the gullet. 
 PHRAGMACONE (Gr. phrayma, a partition ; and konos, a cone). The chambered 
 
 portion of the internal shell of a Belemnite. 
 PHYLACTOL^EMATA (Gr. phulasso, I guard ; and laimos, throat). The division 
 
 of Polyzoa in which the mouth is provided with the arched valvular process 
 
 known as the " epistome." 
 
 PHYLLOPODA (Gr. phullon, leaf ; and nous, foot). An order of Crustacea. 
 PHYSOPHORID.E (Gr. phusa, air-bladder ; and phero, I carry). An order of 
 
 Oceanic Hydrozoa. 
 
 PHYTOID (Gr. phuton, a plant ; and eidos, form). Plant-like. 
 PHYTOPHAGOUS (Gr. phuton, a plant ; and phago, I eat). Plant-eating, or 
 
 herbivorous. 
 PINNATE (Lat. pinna, a feather). Feather-shaped ; or possessing lateral pro- 
 
 PINNIGRADA (Lat. pinna, a feather ; gradior, I walk). The group of Carni- 
 
 vora, comprising the Seals and Walruses, adapted for an aquatic life. Often 
 
 called Pinnipedia. 
 
 PINNULE (Lat. dim. of pinna). The lateral processes of the arms of Crinoids. 
 PISCES (Lat. piscis, a fish). The class of Vertebrates comprising the Fishes. 
 PLACENTA (Lat. a cake). The " after-birth," or the organ by which a vascu- 
 lar connection is established in the higher Mammalia between the mother 
 
 and the foetus. 
 
 PLACENTAL. Possessing a placenta ; or connected with the placenta. 
 PLACOID (Gr. plax, a plate ; eidos, form). Applied to the irregular bony 
 
 plates, grains, or spines which are found in the skin of various fishes 
 
 (Elasmobranchii). 
 PLAGIOSTOMI (Gr. plagios, transverse ; stoma, mouth). The Sharks and Rays, 
 
 in which the mouth is transverse, and is placed on the under surface of the 
 
 head. 
 PLANTIGRADE (Lat. planta, the sole of the foot ; gradior, I walk). Applying 
 
 the sole of the foot to the ground in walking. 
 
 PLASTRON. The lower or ventral portion of the bony case of the Chelonians. 
 PLATYRHINA (Gr. plains, broad ; rhines, nostrils). A group of the Qvadrumana. 
 PLEURODONT (Gr. pleuron, rib, side ; odous, tooth). Having the teeth anchy- 
 
 losed with the inner side of the jaws. 
 
 PLEURON (Gr. pleuron, a rib). The lateral extensions of the shell of Crustacea. 
 PNEUMATIC (Gr. pneuma, air). Filled with air. 
 PODOPHTHALMATA (Gr. pous, foot ; and ophthalmos, eye). The division of 
 
 Crustacea in which the eyes are borne at the end of long footstalks. 
 POLLEX (Lat. the thumb). The innermost of the five normal digits of the 
 
 anterior limb of the higher Vertebrates. In man, the thumb. 
 POLYCYSTINA (Gr. polus, many ; and kustis, & cyst). An order of Protozoa, 
 
 with foraminatea siliceous shells. 
 POLTPART. The hard chitinous covering secreted by many of the Hydrozoa.
 
 5 8o 
 
 GLOSSARY. 
 
 POLYPE (Gr. point, many ; pout, foot). Restricted to the single individual of 
 a simple Actinozoiin, such as a Sea-anemone, or to the separate zoouls <>f it 
 compound A ctinozoon. Often applied indiscriminately to any of the C'oefen- 
 terata, or even to the Polysoa. 
 
 POLYPIDE. The separate zooid of a Polyzoon. 
 
 POLYPIDOM. The dermal system of a colony of a Hydrozotin, or Polyzoiin. 
 
 POLYPITE. The separate zooid of a Ifydrozoiin. 
 
 POLYTHALAMOUS (Gr. polut ; and thalamox, chamber). Having many cham- 
 bers ; applied to the shells of Foraminifera and Cephalopoda. 
 
 POLYZOA (Gr. polut ; and zoiin, animal). A division of the Molluscoida com- 
 prising compound animals such as the Sea-mat sometimes called Bryozoa. 
 
 POLYZOARIUM. The dermal system of the colony of a Polyzoon (= Polypidom). 
 
 POKCKLLANOUS. Of the texture of porcelain. 
 
 PORIFERA (Lat. porus, a pore ; and/ero, I carry). Sometimes used to desig- 
 nate the Foraminijera, or the Sponget. 
 
 POST- ANAL. Situated behind the anus. 
 
 POST-OBSOPHAGEAL. Situated behind the gullet. 
 
 POST-ORAL. Situated behind the mouth. 
 
 PR^EMAXIULE see Intermaxillse. 
 
 PR^MOLARS( Lat. prce, before; molares, the grinders). The molar teeth of 
 Mammals which succeed the molars of the milk-set of teeth. In man, the 
 bicuspid teeth. 
 
 PR^E-OSSOPHAGEAL. Situated in front of the gullet. 
 
 PR^E-STERNUM. The anterior portion of the breast-bone, corresponding with 
 the manubrium tterni of human anatomy, and extending as far as the point 
 of articulation of the second rib. 
 
 PROBOSCIDEA (Lat. proboscis, the snout). The order of Mammals comprising 
 the Elephants. 
 
 PROCCELOUS (Gr. pro, before ; loilos, hollow). Applied to vertebrae, the bodies 
 of which are hollow or concave in front. 
 
 PROPODIUM (Gr. pro, before ; poos, foot). The anterior part of the foot in 
 Molluscs. 
 
 PROSOBRANCHIATA (Gr. proton, in advance of; braychia, a gill). A division 
 of Gasteropodous Molluscs in which the gills are situated in advance of the 
 heart. 
 
 PROSOMA (Gr. pro, before ; soma, body). The anterior part of the body. 
 
 PROTHORAX (Gr. pro ; and thorax, chest). The anterior ring ot the thorax of 
 insects. 
 
 PROTOPHYTA (Gr. protot ; and phuton, plant). The lowest division of plants. 
 
 PROTOPLASM (Gr. protot; and plasto, I mould). The elementary basis of or- 
 ganised tissues. Sometimes used synonymously for the "sarcode" of the 
 Protozoa. 
 
 PROTOPODITE (Gr. prolot, first ; and pout, foot). The basal segment of the 
 typical limb of a Crustacean. 
 
 PROTOZOA (Gr. protot ; and zoon, animal). The lowest division of the animal 
 kingdom. 
 
 PROXIMAL (Lat. proximo, next). The slowly-growing, comparatively-fixed 
 extremity of a limb or of an organism. 
 
 PSKUDOPODIA (Gr. pseudos, falsity ; and pout, foot). The extensions of the 
 body-substance which are put forth by the Rhizopoda at will, and which 
 serve for locomotion and prehension. 
 
 PTEROPODA (Gr. pteron, wing ; and pout, foot). A class of the Mollusca which 
 swim by means of fins attached near the head. 
 
 PTKROSAURIA (Gr. pteron, wing ; mum, lizard). An extinct order of Reptiles. 
 
 PUBIS (Lat. pubet, hair). The share-bone ; one of the bones which enter into 
 the composition of the pelvic arch of Vertebrates. 
 
 PULMOGASTKROPODA (=Pulmonifera). 
 
 PULMONARIA. A division of Arachnida which breathe by means of pulmo- 
 nary sacs. 
 
 PULMONIFERA (Lat. pulmo, a lung ; and /wo, I carry). The division of Mol- 
 lutca which breathe by means of a pulmonary chamber.
 
 GLOSSARY. 581 
 
 RULMONATE. Possessing lungs. 
 
 PYRIFORM (Lat. pyrus, a pear ; and forma, form). Pear-shaped. 
 
 QUADRUMANA (Lat. ouatuor, four; manus, hand). The order of Mammals 
 comprising the Apes, Monkeys, Baboons, Lemurs, &c. 
 
 RADIATA (Lat. radius, a ray). Formerly applied to a large number of animals 
 which are now placed in separate sub-kingdoms (e.g., the Ccelenterata, the 
 Echinodermata, the Infusoria, &c.) 
 
 RADIOLARIA (Lat. radius, a ray). A division of Protozoa. 
 
 RADIUS (Lat. a spoke or ray). The innermost of the two bones of the fore- 
 arm of the higher Vertebrates. It carries the thumb, when present, and 
 corresponds with the tibia of the hind-limb. 
 
 RAMUS (Lat. a branch). Applied to each half or branch of the lower jaw, or 
 mandible, of Vertebrates. 
 
 RAPTORES (Lat. rapto, I plunder). The order of the Birds of Prey. 
 
 RASORES (Lat. rado, I scratch). The order of the Scratching Birds (Fowls, 
 Pigeons, &c.) 
 
 RATIT.E (Lat. rates, a raft). Applied by Huxley to the Cursorial Birds, which 
 do not fly, and have therefore a raft-like sternum without any median 
 keel. 
 
 RECTUM (Lat. rectus, straight). The terminal portion of the intestinal canal, 
 opening at the surface of the body at the anus. 
 
 REPTILIA (Lat. repto, I crawl). The class of the Vertebrata comprising the 
 Tortoises, Snakes, Lizards, Crocodiles, &c. 
 
 REVERSED. Applied to spiral univalves, in which the direction of the spiral 
 is the reverse of the normal i.e., sinistral. 
 
 RHIZOPHAQA (Gr. rhiza, root ; phago, I eat). A group of the Marsupials. 
 
 RHIZOPODA (Gr. rhiza, a root ; and pous, foot). The division of Protozoa com- 
 prising all those which are capable of emitting pseudopodia. 
 
 RHYNCHOLITES (Gr. rhunckos, beak ; and lithos, stone). Beak-shaped fossils 
 consisting of the mandibles of Cephalopoda. 
 
 RODENTIA (Lat. rodo, I gnaw). An order of the Mammals; often called Glires 
 (Lat. glit t a dormouse). 
 
 RUGOSA (Lat. rugosus, wrinkled). An order of Corals. 
 
 RUMINANTIA (Lat. ruminor, I chew the cud). The group of Hoofed Quadru- 
 peds (Unjulata) which " ruminate " or chew the cud. 
 
 SACRUM. The vertebrae (usually anchylosed) which unite with the haunch- 
 bones (ilia) to form the pelvis.- 
 
 SAND-CANAL (= STONE-CANAL). The tube by which water is conveyed from 
 the exterior to the ambulacral system of the Echinodermata. 
 
 SARCODE (Gr. sarx, flesh ; eidos, form). The jelly-like substance of which 
 the bodies of the Protozoa are composed. It is an albuminous body contain- 
 ing oil-granules, and is sometimes called " animal protoplasm." 
 
 SARCOiDS(Gr. sarx; and eidos, form). The separate amcebiform particles 
 which in the aggregate make up the " flesh " of a Sponge. 
 
 SAURIA (Gr. saura, a lizard). Any lizard-like Reptile is often spoken of as a 
 " Saurian ; " but the term is sometimes restricted to the Crocodiles alone, 
 or to the Crocodiles and Lacertilians. 
 
 SAUROBATRACHIA (Gr. saura; latrachos, frog). Sometimes applied to the 
 order of the tailed Amphibians ( Urodeld). 
 
 SAUROPSIDA (Gr. saura; and opsis, appearance). The name given by Huxley 
 to the two classes of the Birds and Reptiles collectively. 
 
 SAUROPTERYGIA (Gr. saura; pterux, wing). An extinct order of Reptiles, 
 called by Huxley Plesiosauria, from the typical genus Plesiosaurus. 
 
 SAURUR^: (Gr. saura; oura, tail). The extinct order of Birds comprising 
 only the Archaeopteryx. 
 
 SCANSORES (Lat. scando, I climb). The order of the Climbing Birds (Parrots, 
 Woodpeckers, &c.) 
 
 SCAPULA (Lat. for shoulder-blade). The shoulder-blade of the pectoral arch
 
 $82 GLOSSARY. 
 
 of Vertebrates ; in a restricted sense, the row of plates in the cup of 
 Crinoids, which give origin to the arms, and are usually called the " axil- 
 lary radials." 
 
 SCLERENCHYMA (Gr. tkleros, hard; and enchuma, tissue). The calcareous 
 tissue of which a coral is composed. 
 
 SCLEROBASIO (Gr. skleros, hard ; basis, pedestal). The coral which is pro- 
 duced by the outer surface of the integument in certain Actinozoa (e.g., 
 Red Coral), and forms a solid axis which is invested by the soft parts of the 
 animal. It is called " foot-secretion " by Mr Dana. 
 
 SCLERODERMIC (Gr. skleros ; and derma, skin). Applied to the corallum which 
 is deposited within the tissues of certain Actinozoa, and is called "tissue- 
 secretion" by Mr Dana. 
 
 SCLEROTIC (Gr. skleros, hard). The outer dense fibrous coat of the eye. 
 
 SCOLECIDA (Gr. skolex, worm). A division of the Annuloida. 
 
 SCUTA (Lat. scutum, a shield). Applied to any shield-like plates; especially 
 to those which are developed in the integument of many Reptiles. 
 
 SELACHIA or SELACHII (Gr. selachos, a cartilaginous fish, probably a shark). 
 The sub-order of Elasmobranchii comprising the Sharks and Dog-fishes. 
 
 SEPIOSTAIRE. The internal shell of the Sepia, commonly known as the 
 " cuttle- bone." 
 
 SEPTA. Partitions. 
 
 SERPENTIFORM. Resembling a serpent in shape. 
 
 SERTULARIDA (Lat. sertum, a wreath). An order of Hydrozoa, 
 
 SESSILE (Lat. sedo, I sit). Not supported upon a stalk or peduncle ; attached 
 by a base. 
 
 SET. (Lat. bristles). Bristles or long stiff hairs. 
 
 SETIFEROUS. Supporting bristles. 
 
 SETIGEROUS (=Setiferous). 
 
 SETOSE. Bristly. 
 
 SiGiLLARioiDS (Lat. sigilla, little images). A group of extinct plants of which 
 Sigillaria is the type, so called from the seal-like markings on the bark. 
 
 SILICEOUS (Lat. silex, flint). Composed of flint. 
 
 SINISTRAL (Lat. sinittra, the left hand). Left-handed ; applied to the direc- 
 tion of the spiral in certain shells, which are said to be " reversed." 
 
 SIPHON (Gr. siphon, a tube). Applied to the respiratory tubes in the Mol- 
 lusca ; also to other tubes of different functions. 
 
 SIPHONOPHORA (Gr. siphon ; and^ro, I carry). A division of the Hydrozoa 
 comprising the Oceanic forms (Calycophoridce and Physopfioridce). 
 
 SIPHONOSTOMATA (Gr. siphon ; and stoma, mouth). The division of Gasterv- 
 podous Molluscs, in which the aperture of the shell is not " entire," but 
 possesses a notch or tube for the emission of the respiratory siphon. 
 
 SIPHUNCLE (Lat. siphiincuhm, a little tube). The tube which connect* to- 
 gether the various chambers of the shell of certain Cephalopoda (e.g., the 
 Pearly Nautilus). 
 
 SIPUNOULOIDEA (Lat. siphunculus, a little siphon). A class of Anarthropoda 
 (Annulosa). 
 
 SIRENIA (Gr. leiren,, a mermaid). The order of Mammalia comprising the 
 Dugongs and Manatees. 
 
 SOLIDUNGDLA (Lai. solidus, solid ; ungula, a hoof). The group of Hoofed 
 Quadrupeds comprising the Horse. Ass, and Zebra, in which each foot has 
 only a single solid hoof. Often called Soliptdia. 
 
 SOMATIC (Gr. soma, body). Connected with the body. 
 
 SOMITE (Gr. toma). A single segment in the body of an Articulate animal. 
 
 SPERMATOZOA (Gr. tperma, seed ; and zoon, animal). The microscopic fila- 
 ments which form the essential generative element of the male. 
 
 SPICULA (Lat. tpiculum, a point). Pointed needle-shaped bodies. 
 
 SPIRACLES (Lat. tpiro, I breathe). The breathing-pores, or apertures of the 
 breathing-tubes (tracheae) of Insects. Also the single nostril of the Hag- 
 fishes, the " blow-hole " of Cetaceans, &c. 
 
 SPLANCHNOBKELETON (Gr. splagchna, viscera ; skeletos, dry). The hard struc- 
 tures occasionally developed in connection with the internal organs or viscera.
 
 GLOSSARY. 5 83 
 
 SPONGE-PARTICLES see Sarcoids. 
 
 SPONGIDA (Gr. spoggos, a sponge). The division of Protozoa commonly known 
 
 as sponges. 
 SQUAMATA (Lat. squama, a scale). The division of Eeptiles comprising the 
 
 Ophidia and Lacerlilia, in which the integument develops horny scales, but 
 
 there are no dermal ossifications. 
 STELLERIDA (Lat. stella, star). Sometimes employed to designate the order of 
 
 the Star-fishes. 
 STELLIFORM. Star-shaped. 
 STERNUM (Gr. stemon). The breast-bone. 
 STOLON (Gr. slolos, a sending forth). Offshoots. The connecting processes 
 
 of sarcode, in Foraminifera ; the connecting tube in the social Ascidians; 
 
 the processes sent out by the coenosarc of certain Actinozoa. 
 STOMAPODA (Gr. stoma, mouth ; pous, foot). An order of Crustacea. 
 STOMATODE (Gr. stoma). Possessing a mouth. The Infusoria are thus often 
 
 called the Stomatode Protozoa. 
 STREPSIPTERA (Gr. strepha, I twist ; and pteron, wing). An order of Insects 
 
 in which the anterior wings are represented by twisted rudiments. 
 STREPSIRHINA (Gr. strepho, I twist ; rkines, nostrils). A group of the Quad- 
 
 rumana, often spoken of as Prosimice. 
 STYLIFORM (Lat. stylus, a pointed instrument; forma, form). Pointed in 
 
 shape. 
 
 SUB-CALCAREOUS. Somewhat calcareous. 
 SUB-CENTRAL. Nearly central, but not quite. 
 SUB-PEDUNCULATE. Supported upon a very short stem. 
 SUB-SESSILE. Nearly sessile, or without a stalk. 
 SUTURE (Lat. suo, 1 sew). The line of junction of two parts which are 
 
 immovably connected together. Applied to the line where the whorls 
 
 of a univalve shell join one another ; also to the lines made upon the 
 
 exterior of the shell of a chambered Cephalopod by the margins of the 
 
 septa. 
 
 SWIMMERETS. The limbs of Crustacea, which are adapted for swimming. 
 SYMPHTSIS (Gr. sumphusis, a growing together). Union of two bones in 
 
 which there is no motion or but a very limited amount. 
 STNAPTICUL^! (Gr. sunapto, I fasten together). Transverse props sometimes 
 
 found in Corals, extending across the loculi like the bars of a grate. 
 
 TABULA (Lat. tabula, a tablet). Horizontal plates or floors found in some 
 
 Corals, extending across the cavity of the " theca " from side to side. 
 TACTILE (Lat. tango, I touch). Connected with the sense of touch. 
 TARSO-METATARSUS. The single bone in the leg of Birds produced by the 
 
 union and anchylosis of the lower or distal portion of the tarsus with the 
 
 whole of the metatarsus. 
 TARSUS (Gr. tarsos, the flat of the foot). The small bones which form the 
 
 ankle (or "instep" of man), and which correspond with the wrist (carpus) 
 
 of the anterior limb. 
 TECTIBRANCHIATA (Lat. tectus, covered ; and Gr. bragchia, gills). A division 
 
 of Opistkobranchiate Gasteropoda in which the gills are protected by the 
 
 mantle. 
 
 TEGUMENTARY (Lat. tegumentum, a covering). Connected with the integu- 
 ment or skin. 
 
 TELEOSTEI (Gr. teleios, perfect; osteon, bone). The order of the "Bony Fishes." 
 TELSON (Gr. telson, a limit). The last joint in the abdomen of Crustacea; 
 
 variously regarded as a segment without appendages, or as an azygous 
 
 appendage. 
 
 TERGUM (Lat. for back). The dorsal arc of the somite of an Arthropod. 
 TERRICOLA (Lat. terra, earth ; and colo, I inhabit). Employed occasionally 
 
 to designate the Earth-worms (Lumbricidue). 
 TEST (Lat. testa, shell). The shell of Mollusca, which are for this reason 
 
 sometimes called " Testacea ;" also, the calcareous case of Echinoderms; 
 
 also, the thick, leathery, outer tunic in the Tunicata.
 
 584 GLOSSARY. 
 
 TESTACEOUS. Provided with a shell or hard covering 
 
 T ETRABRANCHIATA (Gr. tetra, four ; bragchia, gill). The order of Cephalopoda, 
 characterised by the possession of four gills. 
 
 TUALASSICOLLIDA (Gr. thalatsa, sea ; kolla, glue). A division of Protozoa. 
 
 THECA (Gr. theke, a sheath). A sheath or receptacle. 
 
 THECOSOMATA (Gr. thete ; and soma, body). A. division of Pteropodout 
 Molluscs, in which the body is protected by an external shell. 
 
 THERIOMORPHA (Gr. Uw, beast ; morphe, shape). Applied by Owen to tbo 
 order of the Tail-less Amphibians (Anoura). 
 
 THORAX (Gr. a breastplate). The chest 
 
 TIBIA (Lat. a flute). The shin-bone, being the innermost of the two bones of 
 the leg, and corresponding with the radius in the anterior extremity. 
 
 TOTIPALMAT.E (Lat. Mvs, whole ; palma, the palm of the hand). A group 
 of Wading Birds in which the hallux is united to the other toes by mem- 
 brane, so that the feet are completely webbed. 
 
 TRACHEA (Gr trachda, the rough windpipe). The tube which conveys air 
 to the lungs in the air-breathing Vertebrates. 
 
 TRACHEAE. The breathing-tubes of Insects and other articulate animals. 
 
 TBACHEARIA. The division of Arachnida which breathe by means of tra- 
 cheae. 
 
 TRILOBITA (Gr. treis, three ; lobos, a lobe). An extinct order of Crustacean*. 
 
 TROCHANTER (Gr. trecho,l turn). A process of the upper part of the thigh- 
 bone (femur) to which are attached the muscles which rotate the limb. 
 There may be two, or even three, trochanters present. 
 
 THOCHOID (Gr. trocfios, a wheel ; and eidos, form). Conical with a flat base ; 
 applied to the shells of Foraminifera and Univalve Molluscs. 
 
 TROPHI (Gr. trophos, a nourisher). The parts of the mouth in insects which 
 are concerned in the acquisition and preparation of food. Often called 
 ' ' instruments cibaria. " 
 
 TROPHOSOME (Gr. trepho, I nourish ; and soma, body). Applied collectively 
 to the assemblage of the nutritive zooids of any UydrozoSn. 
 
 TRUNCATKD (Lat. trunco, I shorten). Abruptly cut off; applied to univalve 
 shells, the apex of which breaks off. so that the shell becomes " decol- 
 lated." 
 
 TUBICOLA (Lat. tula, a tube ; and colo, I inhabit). The order of Annelida 
 which construct a tubular case in which they protect themselves. 
 
 TUBICOLOUS. Inhabiting a tube. 
 
 TUNICATA (Lat. tunica, a cloak). A class of Molluscoida which are enveloped 
 in a tough leathery case or "test." 
 
 TURBINATED (Lat. turbo, a top). Top-shaped ; conical with a round base. 
 
 ULNA (Gr. olene, the elbow). The outermost of the two bones of the fore- 
 arm, corresponding with the fibula of the hind-limb. 
 
 UMBELLATE (Lat. umbtlla, a parasol). Forming an umbel i.e., a number of 
 nearly equal radii all proceeding from one point. 
 
 UMBILICUS (Lat. for navel). The aperture seen at the base of the axis of 
 certain univalve shells, which are then said to be "perforated" or " um- 
 bilicated." 
 
 UMBO (Lat. the boss of a shield). The beak of a bivalve shell. 
 
 UMBRELLA. The contractile disc of one of the Lttcernarida. 
 
 UNCINATE (Lat. uncinus, a hook). Provided with hooks or bent spines. 
 
 UNOUICULATE (Lat. unguit, nail). Furnished with claws. 
 
 UNGULATA ( Lat ungula, hoof). The order of Mammals comprising the Hoofed 
 Quadrupeds. 
 
 UNGULATE. Furnished with expanded nails constituting hoofs. 
 
 UNILOCULAR (Lat. unus, one ; and loculus, a little purse). Possessing a single 
 cavity or chamber. Applied to the shells of Foraminifera and Mollutca. 
 
 UNIVALVE (Lat. uniu, one ; valvce, folding-doors). A shell composed of a 
 single piece or valve. 
 
 URODELA (Gr. oura, tail ; delot, visible). The order of the Tailed Amphi- 
 bians (Newts, &c.)
 
 GLOSSARY. 585 
 
 VARICES (Lat. varix, a dilated vein). The ridges or spinose lines which mark 
 
 the former position of the mouth in certain univalve shells. 
 VASCULAR (Lat. vas, a vessel). Connected with the circulatory system. 
 VENTRAL (Lat. venter, the stomach). Kelating to the inferior surface of the 
 
 body. 
 VERMES (Lat. verm-is, a worm). Sometimes employed at the present day in 
 
 the same, or very nearly the same, sense as Annuloida, or as Annuloida 
 
 plus the A narthropoda. 
 
 VERMIFORM (Lat. vermis, worm ; and/orwa, form). Worm-like. 
 VERTEBRA (Lat. verto, I turn). One of the bony segments of the vertebral 
 
 column or backbone. 
 VERTEBRATA (Lat. vertebra, a bone of the back, from vertere, to turn). The 
 
 division of the Animal Kingdom roughly characterised by the possession 
 
 of a backbone. 
 
 VESICLE (Lat. vesica, a bladder). A little sac or cyst. 
 VIBRACULA (Lat. vibro, I shake). Long filamentous appendages found in 
 
 many Polyzoa. 
 
 VIPERINA (Lat. vipera, a viper). A group of the Snakes. 
 VIVIPAROUS (Lat. vivus, alive ; and pario, I bring forth). Bringing forth 
 
 young alive. 
 
 WHORL. The spiral turn of a univalve shell. 
 
 XIPHISTERNUM (Gr. xiphos, sword ; sternon, breast- bone). The inferior or 
 posterior segment of the sternum, corresponding with the " xiphoid carti- 
 lage" of human anatomy. 
 
 XIPHOSURA (Gr. xiphos, & sword ; and oura, tail). An order of Criistacea, 
 comprising the Limuli or King-Crabs, characterised by their long sword- 
 like tails. 
 
 ZEUGLODONTID^; (Gr. zeugle, a yoke ; odous, a tooth). An extinct family of 
 Cetaceans, in which the molar teeth are two-fanged and look as if com- 
 posed of two parts united by a neck. 
 
 ZOOID (Gr. 20071, animal ; and eidos, like). The more or less completely in- 
 dependent organisms produced by gemmation or fission, whether these 
 remain attached to one another or are detached and set free. 
 
 ZOOPHYTE (Gr. zoon, animal ; phuton, plant). Loosely applied to many 
 plant-like animals, such as Sponges, Corals, Sea-anemones, Sea- mats, &c.
 
 INDEX. 
 
 Absence of certain animals in fossiliferous 
 
 deposits, how accounted for, 27-39. 
 Aeanthocladia, 196, 529. 
 Acanthodes, 830. 
 Acanthodidce, 322-330. 
 Aeanthopteri, 318. 
 Acanthotrpongia, 68. 
 Acanthotehon, 177. 
 Acanthoteuthis, 295. 
 Acarida, 182. 
 Acasta, 152. 
 Acaste, 170. 
 Acer, 502. 
 
 Acerotherium, 425, 426. 
 ^IcAatina, 266. 
 ^cicuto, 268. 
 Aciculidce, 268. 
 Acidaspidas, 171. 
 ^cidapis, 171. 
 Acipenser, 322, 333. 
 Acmata, 259. 
 Acorn-shells, 150. 
 Acrodont Lizards, 362. 
 Acrodus, 335, 337, 339, 340, 410. 
 Acrogens, 473 ; age of, 476. 
 Aerotepis, 530. 
 Acrosalenia, 110. 
 Acrostiehites, 497, 533. 
 ylcroura, 117. 
 Acteonella, 261. 
 
 6, 87. 
 
 Actinocrinus, 121, 126. 
 Actinogpongia, 637. 
 ^ictinozoa, 73; characters, 85; distribu- 
 
 tion in time, 86. 
 Adductor muscles of Lamellibranchiata, 
 
 218. 
 
 jEchmodvs, 324. 
 J'Mina, 169. 
 Jfpiorni*, 390, 394. 
 , T4. 
 
 Age of Acrogens, 476; of Oymnosperms, 
 476; of Angiosperms, 476. 
 
 tM, 162, 163, 167, 168. 
 Alceg, 435. 
 
 Alcyonaria, 73; characters of, 101; dis- 
 tribution of, in time, 101. 
 Alcyonium, 101. 
 Alethopteris. 482, 486, 494. 
 Alqas, 473, 477. 
 Alligator, 366, 36T. 
 
 Alnus, 500. 
 
 Alum-schists, of Sweden, 510. 
 
 Amber, insects preserved in, 186. 
 
 Amblypterus, 323, 534. 
 
 Amblyrhynchug, 365. 
 
 Ambonychia, 223, 224. 
 
 Ambulacral ossiclesof Star-nshes, 112, 113. 
 
 Amia, 323. 
 
 Amiadas, 322, 323, 327. 
 
 Ammonites, 289; sections of, 290. 
 
 Ammonitidce, 279, 280, 281; characters 
 
 of, 286; shell of, 279, 286. 
 Amcebea, 59. 
 Amphibia, 305; characters of, 346 ; orders 
 
 of, 347 ; distribution of, iu time, 347. 
 Arnphitcelia (Crocodilia), 366,367. 
 Amphicyon, 450. 
 Amphidetus, 109. 
 Amphihelia, 96. 
 Amphileites, 405, 410. 
 Amphion, 170. 
 Amphipoda. 176. 
 Amphusbcena, 361. 
 Amphigponqia, 69. 
 Amphistegtna, 63. 
 ^mp/uUeriww, 405, 410, 411. 
 Ainphitrag-ulus, 434. 
 
 , 526. 
 
 Ampullaria, 245, 255. 
 , 167, 169. 
 . 537. 
 
 Ananchytes, 109. 
 Ananchytidce, 109. 
 ^TiartAropodo, 136. 
 -dnattfa, 153, 155. 
 ^Tiatma, 888,98ft. 
 ^?iatinuto, 218, 238. 
 /1/ic/iitAerium, 428 
 Aneyloeerat, 291. 292. 
 
 t, 268. 
 , 347, 348. 
 Angelina, 161, 167, 169. 
 Angiosperms 473. 
 ^,j7i>,361. 
 
 Animal Kingdom, divisions of, 44-52. 
 Anisopus, 533. 
 Annelida, 136 : characters of, 136 ; distri- 
 
 bution of, in time, 137. 
 Annvlaria, 478, 482, 483, 494. 
 Annuloida, 103. 
 Annulftsa, 29, 47 ; characters of, 136 ; dis- 
 
 tribution of, in time, 136.
 
 INDEX. 
 
 587 
 
 Anodon, 229, 230. 
 Anaema, 458. 
 A nogens, 473. 
 Anomia, 221. 
 Anomodontia, 373. 
 Anomopteris, 497. 
 Anomura, 179, 180. 
 Anoplotheridce, 430, 431. 
 Anoplotherium, 430. 
 ^noura, 340, 347, 349. 
 Ant-eaters, 413. 
 Antedon, 123. 
 Antholithes, 474, 484, 494. 
 Anthracopalcemon, 178. 
 Anthracosia, 234, 236. 
 Anthracosaunis, 352. 
 Anthracotherium, 430. 
 Antilocapra, 437. 
 Antilocapridce, 438, 439. 
 jiniiZope, 437, 439. 
 Antilopidce, 437, 438. 
 Antipathes, 88. 
 Antwerp Crag, 556. 
 ^pafeon, 352. 
 Aphragmites, 286. 
 Apiocrinidce, 127, 128. 
 Apiocrinus, 118, 128. 
 Apiocystites, 130, 133. 
 
 Aplysiadce, 261. 
 
 ^i>orosa, 96 ; distribution of, in time, 97. 
 
 Aporrhais, 252. 
 
 Apteryx, 393, 394. 
 
 Aptornis, 390. 
 
 Aptychus, 154. 
 
 ^4pws, 159, 165, 166. 
 
 Aralo-Caspian beds, 556. 
 
 Arachnida, characters of, 181 ; orders of, 
 
 182; distribution of, in time, 182. 
 Araneida, 182, 183. 
 Araucaria, 497, 500. 
 Ara/iicarioxylon, 475, 493. 
 ^Irca, 226, 227. 
 Arcades, 216, 218, 226. 
 Archceocidaris, 108, 110. 
 Archceocyathus, 68. 
 Archceoniscus, 177. 
 Arehceopteryx, 383, 386, 390, 396. 
 Archagaricon, 475. 
 Arehegosauria, 352. 
 Archegosaurus, 352. 
 Archimedipora, 196. 
 Archimulacris, 186. 
 Archiulidce, 184. 
 Archiulus, 184. 
 Arctocyon, 451, 460. 
 Arctomys, 460. 
 
 Arenicolites, 142. 
 
 Arethusina, 171. 
 
 Argonauta, 274, 275, 294. 
 
 Argonautidce, 275, 294. 
 
 Armadillos, 413, 416. 
 
 Arms of Star-lishes, 111, 113; of Ophiu- 
 roids, 116; of Crinoids, 119; of Cys- 
 tideans, 130; of Blastoidea, 134; of 
 Brachiopoda, 201. 
 
 Aroides, 499. 
 
 Artemia, 159. 
 
 Arthraster, 115. 
 
 Arthrophycus, 479. 
 
 Arthropoda, 143, 144. 
 
 Arthropterus, 342. 
 
 ^ rticulata (Brachiopoda), 202 ; (Crinoi- 
 
 dea), 128. 
 
 Artiodactyla, 423, 428. 
 xlrOT'coZa, 459. 
 Asaphidce, 167. 
 ^sapAw, 164, 165, 166, 167. 
 Ascidian Molluscs, 187. 
 -4scoceras, 283, 285, 286. 
 Asiphonida, 218, 219. 
 Aspergillum, 239. 
 Aspidiaria, 491. 
 Aspidocaris, 159. 
 Aspidorhynchus, 538. 
 Aspidura, 117, 533. 
 ^IsiacMs, 179. 
 Astarte, 234, 235. 
 Asteroidea, characters of, 110 ; distribu- 
 
 tion of, in time, 114. 
 Asterolepis, 520. 
 Asterophyllites, 482, 483, 484, 489, 494. 
 
 Astrceidce, 97, 100. 
 ^reeoppra, 96. 
 Astrangia, 96. 
 Astrogonium, 115. 
 Astropecten, 111, 114. " 
 Astropyga, 110. 
 Astylospongia, 68, 69. 
 Athyris, 206. 
 Atlantic Ooze, 23. 
 Atlantidce, 262, 263. 
 Atrypa, 206. 
 Auchenaspis, 331. 
 Auchenia, 433, 434. 
 Aulacopleura, 171. 
 
 , 97, 100. 
 
 ^UtricMZMfoe, 268. 
 Aurochs, 439. 
 ^Ives, 381. 
 Avicula, 223, 224. 
 Avicula contorta beds, 531. 
 Avicularia, 194. 
 Aviculidce, 219, 223. 
 Aviculopecten, 222, 223. 
 Axinus, 229, 530. 
 
 Bactrites, 276, 287, 288. 
 
 Baculites, 276, 287, 293. 
 
 Bagshot series, 549. 
 
 Bairdia, 156, 157. 
 
 Bakewellia, 530. 
 
 Bala beds, 516. 
 
 Balcena, 419. 
 
 Balcenidce, 419, 420. 
 
 Balcenodon, 422. 
 
 Balanidce, 150, 152. 
 
 Balanophyllia, 96. 
 
 Balanus, 151, 152. 
 
 Balistidce, 318. 
 
 Banksia, 499, 502. 
 
 Baphetes, 352, 353. 
 
 Baptosaurus, 365. 
 
 Barnacles, 152. 
 
 Barramunda, 314, 343, 344, 345. 
 
 Barrandia, 169. 
 
 .Battdes, 337, 341. 
 
 Batrachia, 349. 
 
 Belemnitella, 290. 
 
 Belemnites, 297; sections of, 298. 
 
 Belemnitidce, 275, 277, 294, 296.
 
 588 
 
 INDEX. 
 
 /:. : m m '-- 
 
 MM .- 
 
 Brltmnottvthii, 898. 
 Belrmnoziphiiu, 421. 
 ll.-l,n,,nu, 175. 
 
 245. 263. 
 
 /. :' ... ' M 
 
 Beloteuthii. 295. 
 IHnbridjce bed*, 549. 
 eryx. 318. 818. 
 Bft/richia, 1M, 167. 
 Biduutopom. 197. 
 Bimana, 466. 
 Bimeria, 75. 
 
 Birds.' characters of, 881 ; distribution of, 
 
 In time, 388 ; orders of, 3U 1-396. 
 Bivalve Molluscs, 214. 
 fftirfllillci. characters of, 133 ; distribu- 
 
 tion of, in time, 135. 
 nirnniittae, 318. 
 Bopyridv, 178. 
 Bat, 489, 440. 
 fiourjftttticrinus, 128. 
 Bovey Tracy lignites, 502. 
 Bovida, 437, 439, 440. 
 Brachiupoda, characters of, 198 ; shell of, 
 
 199 ; families of, 203 ; distribution of, 
 
 in time, 202, 203. 
 Brachymetopiis, 167. 
 Brachytira, 180. 
 Bi-adyjxididtr, 413, 414. 
 Bradypux. 898. 
 Bramatheriuin, 438, 439. 
 Bronchi fern (Gasteropoda), 241, 244, 246. 
 Bronteidce, 171. 
 Bronteut, 163, 167, 171. 
 Brontozoum, 633. 
 llruta, 413. 
 
 Bryozoa (see Polyzoa). 
 Bueeinidce, 248. 
 Hiicrinuin. 248. 
 
 i*. 266. 
 
 261. 
 
 r. 261. 
 
 Bunter Sandstein, 530, 531. 
 Burrows of Annelides, 141, 142. 
 Btithograpxvt, 78. 
 Buthotrephu, (77, 479. 
 
 Cadncibranchiate Amphibians, 34C. 
 
 Ccecilict, 347, 355. 
 
 Calamaries, 295. 
 
 Catomi/e*, 474, 475, 480, 487, 488, 489, 494, 
 
 Calamodrndran, 482, 483. 
 Calathium, 68. 
 Calcalre grosaier, 649. 
 
 Calciferous Sand-rock, 513. 
 CWMnnyte, 67, 68. 
 Callithrve. 466. 
 CaUoeyrt.te., 130, 18J, 133. 
 
 iynMiiii. 78, 79. 
 
 Calyeirphorida, 73. 74 
 OifalllU. 183. 167, 170. 
 CaJynwnuto, 170. 
 
 Calyptraida, 269. 
 
 Calyx of Crinoids, 119; of Cystoidea, 129; 
 
 Camarophoria?2()8, 530. 
 
 Cambrian period, rocks of, 512 ; life of, 
 
 618 ; flora of, 477. 
 Camelidce, 433. 
 Camelopardalidce, 433, 436. 
 Cttmtlopardalu, 436. 
 Camelus, 433. 
 Campanularida, 76. 
 Canceltaria, 247. 
 Cancr, 180. 
 Condona, 156, 167. 
 Canute, 449, 454. 
 Canw, 454. 
 
 Capitulum of Lepadoids, 152, 153. 
 Capra, 439. 
 Caprina, 233. 
 Caprotina, 232. 
 
 Caradoc beds, 513. 
 
 Carboniferous period, rocks of, 524 ; life 
 
 of, 526 ; flora of, 485. 
 Carboniferous Slates, 534. 
 Carcharodon, 335, 340. 
 Cardiadce, 218, 233. 
 Cardinia, 236. 
 
 Cardiocarpum, 474, 482, 484, 494. 
 Cardiola, 224. 
 Cardiomorpha, 527. 
 Cardita, 234, 235. 
 Cardium, 233. 
 Carmaria, 245, 262, 263. 
 Carnivora, characters of, 447, 448 ; Pinni- 
 
 grade, 449; Plantigrade, 450; Digiti- 
 
 grade, 452 ; distribution of, in time, 449. 
 Carpenteria, 64. 
 Carriage - spring apparatus of Brachio- 
 
 pods, 201. 
 Caryocarig, 159. 
 Caryocrinus, 130. 
 
 Cassidulida, 109. 
 
 Ccwsw, 242, 248, 249. 
 
 Castor, 458, 459. 
 
 Castorida, 458. 
 
 Castoroiden, 459. 
 
 CajfuaritM, 394. 
 
 Cntarhine Monkeys, 465, 466. 
 
 Catodontidte, 419. 
 
 Catopygtu, 544. 
 
 Co/ur, 545. 
 
 Coufoptem, 474, 482, 485. 
 
 Cave Bear, 451. 
 
 Cave Hyaena, 453. 
 
 Cave Lion, 465. 
 
 Cave Pika, 560. 
 
 Cavicornia, 433, 437. 
 
 Caeuto, 468. 
 
 Cebw, 466. 
 
 CeUepora, 198. 
 
 Cellules of Graptolites, 7, 81. 
 
 Centemodon, 364. 
 
 Centipedes, 183. 
 
 Centrodus, 338, 339. 
 
 Ctphalcupida!, 322, 331. 
 
 Cephalatpis, 331. 
 
 Cephalopoda, characters of, 272; distri- 
 
 bution of. in time, 276 ; Tetrabranchiate, 
 
 277 ; Dibranchiate, 293.
 
 INDEX. 
 
 589 
 
 Ceratioearis, 159, 160. 
 
 Ceratites, 276, 2ST, 288, 289, 534. 
 
 Ceratodus, 327, 339, 342, 343, 344. 345. 
 
 Cerithiadce, 252. 
 
 Cerithium, 252. 
 
 Cercolabes, 450. 
 
 Cercoleptes, 451. 
 
 Cercopithecus, 466. 
 
 Cervidce, 433, 434. 
 
 Cervus, 435, 436. 
 
 Cegtracion, 337, 339, 340, 335. 
 
 Cestraciontidtz, 337. 
 
 Cestraphori, 335, 336, 337, 338, 339, 34". 
 
 Cetacea, characters of, 418; distribution 
 of, in time, 419. 
 
 Cetiosaunis, 368, 378, 379. 
 
 Cetotolites, 420. 
 
 Chceropotamus, 430. 
 
 Chcetodontidce, 318. 
 
 Chalicomys, 459. 
 
 Chalicotherium, 431. 
 
 Chalk, 540 ; compared with the Atlantic 
 Ooze, 23. 
 
 Chama, 230. 
 
 Chamcerops, 501. 
 
 Chamidce, 218, 230. 
 
 Champsodelphis, 420. 
 
 Chasmops, 170. 
 
 CheUostomata, 193, 194, 195. 
 
 Cheirolepis, 323, 327. 
 
 Cheiroptera, characters of, 460 ; distribu- 
 tion of, in time, 461. 
 
 Cheirotherium, 350, 351. 
 
 Cheiruridce, 167, 169. 
 
 Cheirurus, 163, 167, 170. 
 
 Chelichnus, 359. 
 
 Chelone, 359. 
 
 Chelonia, characters of, 356; distribution 
 of, in time, 359. 
 
 Ckeloniidce, 358, 359. 
 
 Chemnitzia, 251, 253. 
 
 Chemung period, 522. 
 
 Chenendopora, 537. 
 
 Chilognatha, 183, 184. 
 
 Chilopoda, 183. 
 
 Chimceridce, 336. 
 
 Chirotes, 361. 
 
 C/ii<on, 260. 
 
 Chitonidce, 260, 
 
 Chcetetes, 526. 
 
 Chondrites, 479. 
 
 Chondrosteus, 333. 
 
 Chonetes, 210, 211. 
 
 Choneziphius, 421. 
 
 Cidaridce, 109. 
 
 Cidaris, 106, 109. 
 
 CrnioZomw, 392. 
 
 Cinnamomum, 500, 502. 
 
 Cinulia, 261. 
 
 Circus, 396. 
 
 Cirri of Brachiopods, 201. 
 
 Cirripedia, characters of, 149 ; orders of, 
 150 ; distribution of, in time, 152 ; Ses- 
 sile, 150 ; Pedunculated, 152. 
 
 Cladocera, 155. 
 
 Cladodus, 338, 339. 
 
 Claiborne beds, 550. 
 
 Claii#ili<i, 266, 267. 
 
 Clavagella, 239, 240. 
 
 Cleavage, 89. 
 
 Cleodora, 269, 270. 
 
 Clepsysaurus, 364. 
 
 Climacograpsus, 84, 85. 
 
 Climactichnites, 167. 
 
 Climatius, 330. 
 
 CZiona, 71. 
 
 Clupeidce, 316. 
 
 Clymenia, 281, 282, 283. 
 
 Clypeaster, 109. 
 
 Clypeasteridce, 109. 
 
 Clypeus, 109. 
 
 Coal, structure of, 485. 
 
 Coal-measures, 525. 
 
 Coccosteus, 331, 332, 520. 
 
 Cochliodus, 339. 
 
 Caelacanthini, 327, 329. 
 
 Ccdacanthus, 327, 329, 530. 
 
 Caelenterata, characters of, 73 ; divisions 
 
 of, 73 ; distribution of, in time, 73, 74. 
 Coelogenys, 458. 
 Cffinenchyma, 89. 
 Ccencecium, 192. 
 Ccenopithecits, 466. 
 Coleoptera, 185, 186, 187. 
 Collyrites, 109. 
 Collyritidce, 109. 
 Colobus, 465. 
 Colonies, 26. 
 Colossochelys, 359. 
 Colubrine Snakes, 360. 
 Columbacei, 394. 
 Columella of Corals, 91 ; of the shell of 
 
 Gasteropods, 242. 
 Column of Crinoids, 118, 123. 
 Colymbidce, 390. 
 Comarocystites, 131. 
 Comatula, 122, 123, 127, 128. 
 Common canal of Graptolites, 80. 
 Compsognatha, 380. 
 Compsognathus, 377, 380. 
 Conchicolites, 138, 139. 
 C'jnchifera (see Lamettibranchiata). 
 Conchiosaurus, 372. 
 Conchodus, 338. 
 
 Conclusions to be drawnfrom Fossils, 40-44. 
 Conidce, 249. 
 Coniopteris, 498. 
 Coniosaurus, 364. 
 Coniston series, 516. 
 Conocardium, 233, 234. 
 Conocoryphe, 167, 169. 
 Conodonts, 314. 
 Conosmilia, 100. 
 Constricting Snakes, 361. 
 Contemporaneity of strata, 14-20. 
 Continuity, Geological, 20-26. 
 Conularia, 270, 271. 
 Cvnulus, 266. 
 Conus, 249. 
 Copepoda, 155. 
 Coralline Crag, 555. 
 Corallium, 102. 
 Coral-reefs, ancient, 95, 96. 
 Corals, gemmation and fission of, 93-95. 
 Corals, simple and compound, 88, 89, 90, 
 
 91, 92, 93. 
 Coral-Rag, 536. 
 Coraa;, 340. 
 Corbis, 234. 
 Corbula, 238. 
 Cordaites, 474, 480. 
 Cornbrash, 536. 
 Corniferous period, 519. 
 Cornulites, 138.
 
 590 
 
 INDEX. 
 
 CWynMfa, 74.75, 78. 
 
 , . 
 Crag. Antweq), 556 ; Coralline 555 ; Nor- 
 
 wich, 0>.; Rd, .; White, 16. 
 CVama. 203, 211, 212. 
 OnMiMto, 202, 211. 
 Crauattlla, 234. 235. 
 CrmatopUrit, 497. 
 Ovpid Ja, 269. 
 Cretaceous period, rocks of, 640; life of, 
 
 645 ; flora of, 499. 
 CribfUa. 111. 
 Cribrotponffia, 537. 
 CriMdu, 459. 
 Crieodtu, 326. 
 Cnnouiea. characters of, 118 ; distribution 
 
 of, in time, 126. 
 Criuoidal limestone, 126. 
 Criixrrai, 291. 
 CritttUaria, 537, 543. 
 CrovxlUia, 365-368. 
 Croeodiltu, 366. 
 Cromer Forest-bed, 558. 
 Crottopodia, 142, 143. 
 Crouopterygid*. 321, 322, 326, 327. 
 OrMHMBtU, 497. 
 Crotalocriniu, 126. 
 Crustacea, characters of, 144 ; orders of, 
 
 149 ; distribution of, in time, 148. 
 Cryphffus, 170. 
 Cmttoguu, 473. 
 Ctf.naeanthut, 338, 520. 
 Ctenodipteri, 327, 328. 
 Ctenodutctit, 111, 114. 
 Ctfttodonta, 226, 227. 
 CUnodut, 338. 
 Cttnoidei, 307, 815. 
 Ctenoid scales of fishes, 307. 
 Ctenophora. 73, 85. 
 CUnoptychitu, 338, 339. 
 Cttnnttomata, 101, 194. 
 Cueulidte, 395. 
 Cucullcea, 226, 227. 
 CuUeUus, 237. 
 
 , 500. 
 
 Cuttle-Hshes, 203. 
 Cuvieria, 269. 270. 
 Cyathatpii, 832. 
 CyoMoonta, 90. 
 CwafAnaronid^, 99, 101. 
 Cyathina. 543. 
 Cya/Aorrtniw, 12. 
 
 T, 99. 101. 
 
 , 473, 476, 494, 49, 497. 
 , 498. 
 , 499. 
 
 , 288. 
 
 tomata, 193, 194, 195. 
 omidtn, 28. 
 rites, 261. 
 yperiteg, 482, 483, 492. 
 haspidce, 171. 
 
 , 250.' ' 
 
 .;.;, I, r, 250. 
 
 tridella, 167. 
 yridina, 156, 157, 623. 
 wina, 234. 
 
 wrinida, 218, 234, 31. 
 *, 156, 157. 
 
 234. 
 
 (,"206, 534. 
 
 eras, 276, 283, 284, 291, 534. 
 ta, 226-228. 
 . 245, 263, 264. 
 idae, 99, 101. 
 . r.wn, 99. 
 Cyntoidea, characters of, 129; distribution 
 
 of, in time, 132. 
 Cythere, 156, 157. 
 Ct/therea, 236. 
 Cytherella, 156, 157. 
 
 Dactylarea, 537. 
 
 Dadoxylon, 474, 475, 482, 493, 494. 
 
 Dakosaurug, 367. 
 
 Dalmania, 170. 
 
 Dapedidas, 324. 
 
 Dapedius, 324. 
 
 Dasypodidat, 413. 
 
 Daiyput, 416. 
 
 Dagyprocta, 458. 
 
 Dasyurus. 408. 
 
 DavidsoHia, 208. 
 
 Decapoda (Crustacea), 177 ; (Cephalo- 
 poda), 295. 
 
 Deep-sea corals, 95. 
 
 Defrancia, 197. 
 
 Deinosauria, characters of, 376 ; distribu- 
 tion of, in time, 377. 
 
 Deinotherium, 418, 442, 443, 447. 
 
 Deiphon, 170. 
 
 Delphinidce, 419, 420. 
 
 Detphinus, 420. 
 
 Dendrarea, 537. 
 
 Deivirerpeton, 352. 
 
 Dendrodug, 326. 
 
 Dendrograpgug, 77-79. 
 
 Dendrophytlia, 96. 
 
 Dendropupa, 267. 
 
 flentalidce, 260. / 
 
 Dent'alina, 537. 
 
 7>n<aiium, 137, 138, 242, 260. 
 
 Derivative rocks, 8. 
 
 DcmopfcyHum, 96. 
 
 Devonian period, rocks of, 520 ; life of, 
 621 ; flora of, 480. 
 
 Diadema, 110. 
 
 Diademadte, 110. 
 
 Ditutopora., 197. 
 
 Dibrancbiate Cephalopoda, characters of, 
 293; families of, 275; distribution of, in 
 time, 294. 
 
 Dicernt, 230. 
 
 Dfefto6un, 431. 
 
 Dichograpsut, 83. 
 
 Dicotyledons, 473.
 
 INDEX. 
 
 591 
 
 Dicranograpsus, 85. 
 
 Dictuolites, 479. 
 
 Dictyonema, 77-79. 
 
 Dicynodon, 373, 374. 
 
 Didelphidce, 408. 
 
 Didelphys, 407, 411. 
 
 Didus, 394. 
 
 Didyrnograpsus, 82, 83. 
 
 Digitigrada (Carnivora), 448. 
 
 Dikelocephalus, 164, 167, 169. 
 
 Di'inorphodon, 376. 
 
 Dimyary Bivalves, 218. 
 
 Dimylus, 463. 
 
 Dinophis, 361. 
 
 Dinornis, 390, 394. 
 
 Dinosauria (see Deinosauria}. 
 
 Dionide, 169. 
 
 Diplacanthus, 330. 
 
 Diplograpsus, 82, 84, 85. 
 
 Diploplerus, 326. 
 
 Dipnoi, characters of, 343; distribution of. 
 
 in time, 314, 343, 345. 
 Dipodida-., 459. 
 
 Diprionidian Graptolites, 82, 84. 
 Diprotodon, 412. 
 Diptera, 186, 187. 
 Dipterus, 327, 328, 345. 
 Dipws, 460. 
 Dixcina, 203, 212. 
 Discinidce, 202, 212. 
 Discinocaris, 159, 160. 
 Discoidea, 107. 
 Discorbina, 60, 62. 
 Dissepiments (Corals), 93. 
 Dithyrocaris, 159. 
 DUrupa, 138, 149. 
 Dolichosaurus, 364. 
 Donax, 237. 
 Dorcatherium, 434. 
 Dremotherium, 434. 
 Dromaius, 394. 
 Dromatherium, 409, 532. 
 Dromia, 180. 
 Dromilites, 180. 
 Dryandra, 499. 
 Dryopithecus, 466. 
 Dysaster, 109. 
 Dysasteridce, 109. 
 
 Ebalia, 180. 
 
 Eeculiomphahis, 263, 265. 
 
 Echidna, 406, 407. 
 
 Echinidce, 110. 
 
 Echinoconidce, 109. 
 
 Echinoconus, 109. 
 
 Echinocyamus, 109. 
 
 Echinodermata, characters of, 102; orders 
 of, 103 ; distribution of, in time, 103. 
 
 Echinodon, 364. 
 
 Echinoencrinug, 133. 
 
 Echinoidea, characters of, 103 ; distribu- 
 tion of, in time, 108; families of, 109. 
 
 Echinoneida, 109. 
 
 Echinoneus, 109. 
 
 Echinosphcerites, 123. 
 
 Echinus, 110, 112. 
 
 Edaphodus, 336. 
 
 Edentata, characters of, 413 ; distribution 
 of, in time, 414. 
 
 Edestes, 338. 
 
 Edestosaurus, 365. 
 
 Edmondia, 527. 
 
 Edrwphthalmata, 175, 176. 
 
 Elasmobranchii, characters of, 334 ; fam- 
 ilies of, 335; distribution of, in time, 
 335. 
 
 Elasmodus, 336. 
 
 Elephas, 442-446. 
 
 Elk, 435 ; Irish, 435, 436. 
 
 Ellipsocephalus, 167, 169. 
 
 Emarainula, 258. 
 
 Emydidce, 358, 359. 
 
 J?mj/, 357, 359. 
 
 Enaliosauria, 369. 
 
 Encrinurus, 167, 170. 
 
 Encrinus, 127, 533. 
 
 Endoceras, 284. 
 
 Endogens, 473. 
 
 Enoploelytia, 179. 
 
 Enoploteuthis, 295. 
 
 Entalophora, 197. 
 
 Entomig, 156. 
 
 Entomostraca, 155. 
 
 Entrochal Marble, 126. 
 
 Eocene period, rocks of, 546; life of, 550 ; 
 flora of, 500. 
 
 Eocystites, 132. 
 
 Eophyton, 474, 477, 478. 
 
 Eosauruf, 356, 369, 370. 
 
 Eoscorpiug, 183. 
 
 Eozoon, 63. 
 
 Ephemeridce, 185. 
 
 Epitheca (Corals), 92. 
 
 Equidai, 427. 
 
 Equisetacece, 473, 474, 480, 487. 
 
 Equisetii.es, 476, 489, 494. 
 
 Equus, 428. 
 
 Erichthys, 177. 
 
 Erinaceidas, 463. 
 
 ErirMcevs, 463. 
 
 Errantia, 137, 141, 142. 
 
 JJri/on, 178, 179. 
 
 Eschara, 197, 198. 
 
 Escharidce, 197. 
 
 Escharina, 193. 
 
 Esocidce, 316. 
 
 Estheria, 157, 158, 159, 224, 533. 
 
 Eulima, 251. 
 
 Eunomia, 533. 
 
 Euomphalug, 255, 256, 264, 265, 534. 
 
 Eupatagus, 109. 
 
 Euphoberia, 184. 
 
 EupsammidcB, 100. 
 
 Eurypterida, 145, 148, 171, 172, 173. 
 
 Eurypterus, 173. 
 
 Eurysternum, 539. 
 
 Euskelesaurus, 377. 
 
 Exogens, 473. 
 
 Exogyra, 220. 
 
 Extracrinus, 123, 127. 
 
 Facial suture of Trilobites, 162. 
 
 Fagus, 500. 
 
 Faluns, 553. 
 
 Fascicularia, 198. 
 
 Fasciolaria, 247. 
 
 Favorites, 523. 
 
 Favositidce, 97, 100. 
 
 Favospongia, 69. 
 
 Favularia, 491, 493. 
 
 FeiMfoe, 449, 453, 454, 455, 456. 
 
 .Fefo, 455. 
 
 Fenestella, 195, 196, 529.
 
 592 
 
 INDEX. 
 
 FtntHeUida, 105. 
 Fie*,, 499. 
 Filiett, 476. 485. 
 Firolider, 862. 
 Fission of Corals, 04. 
 
 tOKh 
 
 Flabellum, VO. 
 
 FlinU, origin of, 60. 
 
 Flora of the Cambrian period, 477; of the 
 Silurian period, 478 ; of the Devonian 
 period, 480 ; of the Carboniferous, 485 ; 
 
 of the Permian period, 494 ; of the Trins, 
 406 ; of the Jurassic period, 497; of the 
 Cretaceous period, 499 ; of the Eocene, 
 600 ; of the Miocene, 501 ; of the Plio- 
 
 ,.....-, 
 
 Foramintfera, characters of, 60; test of, 
 
 Globulut, 251. 
 Glossodtu, 339. 
 
 *, 126. 
 
 , , 132. 133. 
 Glyptodipterini, 326, 327, 328. 
 ,416. 
 
 nut, 326, 327, 328. 
 toUpit, 326. 
 
 Gomphocerat, 283, 285. 
 Gmnpholepis, 520. 
 Gonfaster, 111, 112, 114, 115. 
 Goniatitet, 276, 287, 288, 289, 534. 
 Gonweerat, 284. 
 Goniodixnw, 111, 114, 115. 
 Ganiopholis, 367. 
 Goniophyllum, 99. 
 
 01, 02 ; uisinuuuou 01, iii ume, o*-oo. 
 Forest Marble, 536 
 
 Gargonidai, 101. 
 
 Formation, definition of, 7. 
 
 Graculavus, 390. 
 
 Fossil, definition of. 2. 
 
 Grallatoret, 392. 
 
 Fossilisation, 34. 
 Frondicularia, 537. 
 
 Grantia, 69. 
 Graphularia, 101. 
 
 Fucoidal Sandstone of Sweden, 477, 514. 
 Fncoids, 477, 479, 474. 
 Fuiica, 392. 
 Fuller's-Earth, 536. 
 
 Grapsus, 180. 
 GrapMUes, 80, 81, 82. 
 GraptolUidee, characters of, 79; distri- 
 bution of, in time, 79, 82. 
 
 Fvngidtr, 97, 100. 
 
 Great Oolite, 536. 
 
 
 Greensand, Lower, 540 ; Upper, 542. 
 
 Ftuut, 243, 247, 248. 
 
 Grevillia, 499, 502. 
 Grijfithides, 167, 171. 
 
 Gadida, 318. 
 
 Gru, 392. 
 
 Gabrcyniu, 454. 
 Galatea, 178. 
 Galeocerdo, 886, 840. 
 
 Grypfuea, 220, 221. 
 Guard of Belemnite, 297. 
 Guettardia, 543. 
 
 GaUriUt, 104, 109. 
 
 Gulo, 452. 
 
 Galettet, 406. 411. 
 Gallinacei, 394. 
 
 Guynia, 99. 
 Gymnodontidce, 318. 
 
 Gammaru*, 176. 
 
 Gynimolamiata (Polyzoa), 192. 
 
 Ganiptom/x, 176, 177. 
 
 Gymtwsomata (Pteropoda), 269. 
 
 danocrphala, 352. 
 Ganodiu. 336. 
 
 Gymnosperms, 473. 
 Gypseous Series of Montmartre, 549. 
 
 Ganoidfi, characters of, 320 ; sub-orders 
 
 Gyracanthus, 338. 
 
 of, S22 ; distribution of, in time, 322. 
 
 Gyroeerat, 283, 286, 291. 
 
 Ganoid scales, 807. 
 GatUropoda, characters of, 240 ; shell of, 
 242 ; families of, 244 ; distribution of, in 
 
 Gyroptychiut, 326. 
 Gyroprittis, 530. 
 
 time, 245. 
 
 Hadrotaunu, 377. 
 
 Gattornu, 390, 394. 
 
 Halcyornis, 390, 395. 
 
 <. UMMLM 
 Gattroeluenidee, 218, 239. 
 
 Ilalicarc, 418. 
 Haliomma, 66. 
 
 Ganlt, 540. 
 
 <..'.:... ' 
 
 Haliotidce, 256, 264. 
 Haliotig, 266, 257. 
 
 Gemmation of Corals, 03-95. 
 
 Halisaurus, 365. 
 
 General succession of organic types, 52-55. 
 Geological continuity, 20-26 
 Geological record, imperfection of, 82. 
 
 Halitheriwn, 418. 
 Hamilton period, 522. 
 Ilamites, 876, 288, 292. 
 
 GmpAtftu, 184. 
 
 Hamster, 459. 
 
 
 Haploerinvf, 126. 
 
 Qeotrjfput, 463. 
 
 Uaplophlebium, 185, 186. 
 
 **Ki a> j!^ m 
 
 Hapl<,phyU\a, 99. 
 Harlech Grits, 612. 
 
 Giraffe. 436, 437.' 
 
 Harpedidtr, 171. 
 
 Glabrlla of Trilobites, 161. 
 
 ll-irt- ~. 163, 171. 
 
 Glacial deposlU, 550. 
 Glarial hells, 550. 
 
 Hatteria. 363. 
 Headon Series, 549. 
 
 MMMSMM, lot. 
 GUdUttAia, 60S. 
 
 Heart-urchins, 109. 
 Helderberg series, Lower, 517; Upper, 
 
 
 622. 
 
 Gfc*Vtrma, 60, 62, 65. 
 
 lleliattraea, 96.
 
 INDEX. 
 
 593 
 
 HeUcidce, 266. 
 
 Helicoceras, 292. 
 
 Ht-.liopora, 96. 
 
 Helix, 266. 
 
 Helladotherium, 437. 
 
 Ilelminthites, 143. 
 
 Helminthocltiton, 260. 
 
 Hemiaspix, 174. 
 
 Hemicidaridce, 110. 
 
 Hemicidaris, 104, 106, 110. 
 
 Hemicosmites, 129, 133. 
 
 Hemipnevstes, 544. 
 
 Hemiptera, 186, 187. 
 
 Hemitrochuicus, 529. 
 
 Hermit Crabs, 180. 
 
 Hesperornidce, 390. 
 
 Hetsperornis, 390. 
 
 Heterocercal, tail of Fishes, 312, 313. 
 
 Heteropoda, characters of, 262 ; families 
 
 of, 262; distribution of, in time, 245, 
 
 262. 
 
 Hexaprotodon, 429, 430. 
 Hipparwn, 428. 
 Hippocampidce, 319. 
 Hippopodium, 234, 236. 
 Hippopotamidce, 429. 
 Hippopotamus, 429. 
 Hippurite Limestone, 231. 
 Hippurites. 232. 
 Hippuritidce, 218, 219, 231, 232. 
 Histioderma, 142. 
 Holcodus, 365. 
 Holectypus, 109. 
 Holocephali, 335, 336. 
 Holocystis, 97, 99. 
 Holopea, 258. 
 Holoptychius, 326, 328. 
 Holostomata (Gasteropoda), 244, 245, 250. 
 Holothuroidea, 135. 
 Holtenia, 70. 
 Homacanthus, 338. 
 Homalonotm, 161, 164, 167, 170. 
 Homocercal, tail of Fishes, 312, 313. 
 Homotaxeous deposits, 17. 
 Homothetus, 185. 
 Hoploparia, 179. 
 Horse, 427, 428. 
 Hudson River period, 516. 
 Huronia, 284. 
 
 Huronian period, rocks of, 511. 
 Hyaena, 453. 
 Hycenictis, 452. 
 Hycenidce, 449, 452, 453. 
 Hycenodon, 453. 
 Hyalea, 270. 
 Hyaleidce, 269. 
 Hybodonts, 339. 
 Hyboduy, 335, 337, 339, 534. 
 Hydrida, 74. 
 Hydrochceruis, 453. 
 Hydroida,, 73. 
 Hydrozoa, characters of, 73 ; divisions 
 
 of, 73 ; distribution of, in time, 74. 
 Hylceosaurus, 377. 
 Hylerpeton, 352. 
 Hylobates, 466. 
 Hylonomus, 352, 356. 
 Hymenocaris, 159, 160. 
 Ilyme-nophyllites, 486, 487, 
 Hymenoptera, 186, 187. 
 
 Hyolitheg, 270. 
 Hyopotamus, 430. 
 Hyperodapedon, 362, 363. 
 Hypostome, of Trilobites, 165. 
 Hypsilophodon, 377. 
 Hypsiprymnopsis, 409. 
 Hypsiprymmu, 408, 413. 
 Hyracoidea, 441. 
 Hyracotherium, 441, 466. 
 Hyrax, 441. 
 Hystricidce, 458. 
 Hystrix, 458. 
 
 lacchus, 465. 
 
 Janthina, 258. 
 
 Ibis, 392. 
 
 Ichthyerpeton, 352. 
 
 Ichthyocrinus, 126. 
 
 Ichthyodorulites, 317, 335, 336, 337. 
 
 Ichthyomorpha, 347. 
 
 Ichthyopterygia, 368, 369, 370. 
 
 Ichthyosauria, 368. 
 
 Ichthyosaurus, 369, 370. 
 
 Jctitherium, 452. 
 
 Idiochelys, 539. 
 
 Idmonea, 197, 198. 
 
 Iguanodon, 377, 378. 
 
 Illcenus, 161, 162, 163, 164, 169. 
 
 Imperfection of the Palaeontological 
 
 Record, 27-39. 
 
 Inarticulata (Brachwpoda), 202. 
 Inferior Oolite, 
 Infusoria, 28, 59. 
 Infusorial Earth, 67. 
 Ink-bag, of Cuttle-fishes, 273. 
 Inoceramus, 223, 224, 225. 
 Insecta, characters of, 185 ; orders of, 
 
 187 ; distribution of, in time, 185, 186. 
 Insectivora, characters of, 462 ; families 
 
 of, 463 : distribution of, in time, 462. 
 Insessores, 395. 
 Integropallialia (LamellibrancMata), 
 
 Involutina, 537. 
 
 Irish Elk, 435, 436. 
 
 Irregular Echinoids, 107. 
 
 Isastrcea, 537. 
 
 Ischadites, 72. 
 
 Ischwdus, 336. 
 
 Isocardia, 234, 235. 
 
 Isopoda, characters of, 176; distribution 
 
 of, in time, 176, 177. 
 Ju/ws, 184. 
 
 Jackson beds, 550. 
 Jelly-fishes, 74. 
 Jerboa, 460. 
 Juglans, 499. 
 
 Jurassic period, rocks of, 535; life of, 
 537 ; flora of, 497. 
 
 Kaidacarpum, 499. 
 Kangaroo, 408, 412. 
 Kangaroo-rat, 408, 411, 413. 
 Keratosa (Spongida), 67. 
 Keuper, 531. 
 Kimmcridge Clay, 536. 
 King Crabs, 174. 
 Knorria, 491. 
 Koninckia, 206, 534.
 
 594 
 
 INDEX. 
 
 beds, 681, 632. 
 
 i^SluA^l^, 81 cha'rarteni of, 860; 
 
 llhhllllllllll of, In time, 862. 
 Uce-corals, 195. 
 Ltuntida, 364. 
 
 LactrtUia, 350 ; characters of, 361 ; dis- 
 tribution of, in time, 362. 
 
 Lamodipoda, 176. 
 
 &VMW, 467, 458. 
 
 Lamellibranehiata. characters of, 214; 
 shell of, 216 ; divisions of, 218 ; dis- 
 tribution of, in time, 219; families 
 of, 210 240. 
 0. 
 
 ,32. 
 390, 392. 
 <K,602. 
 Laarentian period, rocks of, 510 ; life of, 
 
 Leaia, 158, 159. 
 
 Leda, 226, 228. 
 
 Leowninotitet, 500. 
 
 Z3o*m, 865. 
 
 Lemming, 459. 
 
 Lemuridce, 464, 466. 
 
 Ltpadidas, 150 ; shell of, 152, 153. 
 
 Lepadocrinitet, 189, 180, 133. 
 
 Lepat, 163, 154, 165. 
 
 Leptrditia, 156, 167. 
 
 Lepidcuter, 111, 116. 
 
 Lepidodendroids, 475, 489. 
 
 Lepidodendron, 474, 475, 480, 483, 490, 
 
 491, 494, 629. 
 LepidoganoLi., 322. 
 
 Ltpidnphloiot, 474. 480, 480, 491. 
 Lfpidoptera, 180, 187. 
 Lepidotirtn, 342, 343, 345. 
 LepidoiUidce. 322, 323. 
 LepidntUui, 320, 823. 
 Lepidottrobu*, 491. 
 Lepidotida, 324, 326. 
 pufotu., 325. 
 
 K, S38. 
 
 s, 210. 
 
 Ltptotntthu, 295. 
 7, 468. 
 
 Lias, 635 
 
 Lielmda', 170. 
 
 LieAoa. 171. 
 
 LicrvpHyc^, 479. 
 
 Lpunent, of Bivalve Molluacs, 215. 
 
 Limnadia 169 
 
 b . H I ;'-.. MT, 
 
 ^^f'^lJl' ir *> 17 . 175. 
 
 Lingvlida, 202, 208, 213. 
 Au/u.Vfaj/iiar, 503. 
 Liriodendnm, 500. 601, 603. 
 it/intomui. 185. 
 Lithodomiu, 225, 228. 
 LUhorni*, 390, 395. 
 Litogtuter, 178. 
 Littorina, 254. 
 Littorinida, 264. 
 Lituites, 281, 232, 286. 
 Lituola, 643. 
 Lizards, 361. 
 Llanberis Slates, 512. 
 Llandeilo Bocks, 516. 
 Llandovery Bocks, 516. 
 Lo&oeewua, 537. 
 Loganograpmu, 514. 
 London Clay, 548. 
 
 Lophobranchii, 318, 321. 
 Lophohelia, 96. 
 Lvphopea, 194. 
 Loricata (Reptilia), 355. 
 Loricula, 152, 154, 155. 
 Lower Cretaceous Bocks, 541. 
 Lower Oolites, 535. 
 Loxonema, 251,253, 534. 
 LMcernarida, 73, 74, 
 Z,ucma, 234. 
 Lucinidae, 218, 234. 
 Ludlow Bocks, 516. 
 Z/Midia, 111, 114. 
 Lutra, 452. 
 Lutraria, 236. 
 
 Lycopodiatece, 474, 480, 482, 490. 
 Lycopodites, 474, 480. 
 iycosa, 183. 
 
 Jfacactwt, 466. 
 
 Macellodon, 364. 
 
 Machairodus, 456. 
 
 Maclurea, 245, 263. 264. 
 
 Macrauchenia, 433, 434. 
 
 MacrocheiHis, 251. 
 
 Macropodidas, 408, 413. 
 
 Macropoma, 327. 
 
 Macrospondyhis, 367. 
 
 Macrotherium, 414. 
 
 Macrura, 178, 179. 
 
 ^fac^ra, 236. 
 
 Mactridce, 218, 236. 
 
 Madrepora, 96. 
 
 Madreporidor, 97, 100. 
 
 Madreporiform tubercle, 106. 
 
 Mn-stricht beds, 540. 
 
 Malacodermata (Zoantharia), 86. 
 
 Malacopteri, 315. 
 
 Malacostraca, 175. 
 
 Malocystitts, 133. 
 
 Mammalia, characters of, 397; skeleton 
 of, 398 ; dentition of, 403 ; distribution 
 of, in time, 405 ; orders Cf, 406. 
 
 Mammoth, 443, 444, 445. 
 
 Manatid<e, 418. 
 
 Mandibles, of Cephalopoda, 273. 
 
 .V.i,,/,-. 413, 414. 
 
 JTimen. 643. 
 
 ManteUia, 497, 498. 
 
 Marxipobranchii, 314. 
 
 Marsupial bones, 408.
 
 INDEX. 
 
 595 
 
 Marsupialia, characters of, 407 ; distribu- 
 tion of, in time, 408. 
 
 Marmpites, 127, 128. 
 
 Mastodon, 442, 446, 447. 
 
 Mastodonsaimis, 353. 
 
 Meandrina, 95, 96. 
 
 Meandropora, 198. 
 
 Medusidce, 73, 74. 
 
 Megaceros, 435, 436. 
 
 Megachirus, 179 
 
 Megalichthys, 326, 327. 
 
 Megalodon, 234, 236, 534. 
 
 Merjalonyx, 414, 416. 
 
 Megalosaurus, 377, 380. 
 
 Megatherium, 414, 415. 
 
 Melania, 253. 
 
 Melaniadce, 253. 
 
 .Mefes, 452. 
 
 JfefiaflB, 451. 
 
 Melocrinus, 126. 
 
 Membranipora, 544. 
 
 Menopoma, 347, 349. 
 
 Merostomata, characters of, 171 ; sub- 
 orders of, 171. 
 
 Merycotherium, 433. 
 
 Mesopithecus, 466. 
 
 Metamorphism, 39. 
 
 Metoptoma, 259, 260. 
 
 Metriophyllum, 100. 
 
 Jfyr, 179. 
 
 Michelinia, 90. 
 
 Micrabacia, 543. 
 
 Micraster, 109. 
 
 Microconchm, 140. 
 
 Microdiscus, 162. 
 
 3/<crokses, 405, 409, 531. 
 
 Middle Oolites, 536. 
 
 Migrations, 16. 
 
 Milu,la, 60. 
 
 Millepara, 96. 
 
 Milleporidce, 97, 100. 
 
 Millstone Grit, 524, 525. 
 
 Miocene period, rocks of, 552; life of, 
 553; flora of ,501. 
 
 JWttra, 249, 250. 
 
 Modiola, 225, 226. 
 
 Modiolopsis, 225, 226. 
 
 Molasse, 553. 
 
 Mole, 463. 
 
 Mottusca, characters of, 187 ; shell of, 187- 
 189; distribution of, in time, 189. 
 
 Mollusca Proper, characters of, 190 ; divi- 
 sions of, 190. 
 
 Mollutcoida, characters of, 190 ; divisions 
 of, 190. 
 
 Monera, 28, 59. 
 
 Monitors, 362. 
 
 Monocotyledons, 473. 
 
 Monomyary Bivalves, 218. 
 
 Monoprionidian Graptolites, 82. 
 
 Mouotis, 534. 
 
 Monotremata, characters of, 406. 
 
 Montlivaltia, 92, 93, 533. 
 
 Mopsea, 101. 
 
 Mosasauroids, 364, 365. 
 
 Mosasaurus, 364, 365. 
 
 Moschidce, 433, 434. 
 
 Moschiis, 434, 
 
 Mountain Limestone, 524. 
 
 Mugilidce. 318. 
 
 Muntjak, 433, 435. 
 
 Murcenidce, 316. 
 
 Murchisonia, 257, 258, 534. 
 
 Murex, 247. 
 
 Muricidte, 247. 
 
 Muridas, 459, 463. 
 
 Muschelkalk, 531. 
 
 Musk-ox, 440. 
 
 Mustela, 452. 
 
 Mustelidce, 449, 452. 
 
 Mutilata, 417. 
 
 Mya, 237, 238. 
 
 Myacidce, 218, 238. 
 
 Myacites, 238, 239. 
 
 Myceteg, 4*5, 466. 
 
 Mygale, 463. 
 
 Myliobatis, 342. 
 
 Mylodon, 414, 415, 416. 
 
 Myodts, 459. 
 
 Myophoria, 228, 229, 534. 
 
 JUyopotamus, 459. 
 
 Myoxidce, 460, 463. 
 
 Myoxus, 460. 
 
 Myrianites, 142. 
 
 Myriapoda, characters of, 183 ; distribu- 
 
 tion of, in time, 184. 
 Myrmecobius, 405, 408, 409. 
 Mysarachne, 463. 
 -Jfysi*, 177. 
 Mytilidce, 218, 225. 
 Mytilus, 225, 530. 
 
 Nacreous Shells, 188. 
 
 JVassa, 248. 
 
 Xasua, 451. 
 
 Satatores, 391. 
 
 A'afica, 250. 
 
 Saticelta, 251. 
 
 Naticidce, 250. 
 
 Naticopsis, 251. 
 
 SautilidcR, characters of, 281 ; shell of, 
 
 279, 281 ; distribution of, in time, 281. 
 Nautiloid Foraminifera, 62. 
 Nautilus, Pearly, 277 ; Paper, 294. 
 Nautilus. 274, 276, 277, 278, 280, 281, 282. 
 
 Necrogammarus, 176. 
 
 Neolimulus, 174. 
 
 Nereites, 143. 
 
 Nerinea, 252, 534. 
 
 Nerita, 255. 
 
 Neritidce, 255. 
 
 Neritina, 255. 
 
 Neuroptera, 185, 186, 187. 
 
 Neuropteris, 475, 482, 486, 495, 497, 538. 
 
 Nipadites, 500, 501. 
 
 Nodosaria, 60, 62. 
 
 Nceggerathia, 475, 494, 495. 
 
 Norwich Crag, 555. 
 
 Nothosaurus, 372. 
 
 Notidanus, 335, 340. 
 
 A'ototherium, 412. 
 
 Nucleobranchiata (see Ileteropoda), 262. 
 
 Nucleolites, 537. 
 
 Kucula 226, 227. 
 
 A'udibranchiata, 245. 
 
 Numenius, 392. 
 
 Nummulites, 62, 64, 65, 549. 
 
 Nunnnulitic Limestone, 65. 
 
 Nuthetes, 364. 
 
 Nyssa, 503. 
 
 Obolella, 213, 214. 
 , 213.
 
 596 
 
 INDKX. 
 
 74. 
 '6,291. 
 97. 100 
 
 , 498, 499. 
 
 Old Red Sandstone. 620, 621. 
 
 N . /'. U r. U - 
 OUnut, 107, 108. 
 OliffocluHa, 136. 
 Ottro. 248, 249. 
 . 249. 
 
 OrxAui, 335, 337. 
 Oni'jrtM, 181, 170. 
 
 Oolitic period, rocks of, 635; life of, 537; 
 flow of. 497. 
 
 <> . . \-: . .1 
 
 owrnilum. of Cirripedes, 150; of Euryp- 
 terids, 173; of Limnlus, 174; of Gas- 
 teropoda, 241; of Maclurea, 2(33: of 
 TA^a. 270. 
 
 Ophuirrjxlon, 852. 
 
 <>l>l,i,a. characters of, 360; distribution 
 of, in time, 860. 
 
 Ophileta, 260, 804. 
 
 Ophiofoma. 117. 
 
 Ophioderma, 117. 
 
 OpUobpU, 117. 
 
 npliiimuirplia, 347. 
 
 0/>Aiura. 116. 
 
 (jjihiuroidra, rliaractere of, 115; distribu- 
 tion of, in time. 117. 
 
 Opitthobranchiata, 245. 
 
 Oputhoccelui (Crvcodilia), 366, 36S. 
 
 Opossum, 411. 
 
 Oracanthut, 838. 
 
 Orbitoidft, 62. 
 
 Orbitoliies, 62, 72. 
 
 Or'.nt,,,.,, 61. 
 
 Orrhritia, 176. 
 
 OretuUr, 114, 115. 
 
 or^.u.i. IM^H, succesaion of, 52-54. 
 
 Oriskany Sumlstonc, 622. 
 
 Ortnojri//on, 474, 482. 
 
 Onnthnrtniiichii*. 40C, 407. 
 
 OmttJttMMtdO, 377, 3SO. 
 
 Ornithntattria, 875. 
 
 OrtAw. 208, 209. 
 Orthirina, 208, 209. 
 OrfA.wm, S76. 283, 284, 634. 
 OrtAflerra/wJn-, 27, 283. 
 Ortkonata. 225, 220. 
 Or1lu,j>tfra, 185, 186. 187. 
 Orion*. .',18. 
 Osborne aerie*, 649. 
 
 OWraoodo.charmcter* of. 156; distribution 
 of. In time, 156, 157, 638. 
 
 SSXS 
 
 
 Ovarian capsules of Graptolltes, 81. 
 
 Ovarian pyramid of Cystideans, 181. 
 
 Ovibot, 440. 
 
 Ovicell, 193. 
 
 0*UA. 487, 4S9, 441. 
 
 On*, 439. 
 
 Oxford Clay, 636. 
 
 Oxyrhina, 340, 341. 
 
 Pachydtrmata, 423. 
 
 Pachypteris, 498. 
 
 J>ach;/ri*ina, 234, 236. 
 
 Pachyseris, 96. 
 
 J'aehiitheca, 474, 480. 
 
 Padillcllsh, 333. 
 
 Paffuridce, 180. 
 
 Patiunm, 180. 
 
 Paicearea. 22S. 
 
 Palanster, 111, 114, 115. 
 
 Pala-chinwt, 108, 110. 
 
 I'alvga, 177. 
 
 Palaichthyes, 845. 
 
 Palteinachus, 180. 
 
 Palaoehorda, 142. 
 
 Palceocoma, 114, 115. 
 
 Palatocoritne, 75. 
 
 PaUtocrinnidx, 123, 126. 
 
 Paltfoeyehu, 97. 
 
 PaUroci/on, 454. 
 
 Paiaoditew, 114, 115. 
 
 Paleolithic Man, 468. 
 
 Palceomarwn, 68. 
 
 Palaonucus, 323, 530, 534. 
 
 Paheonyctis, 452. 
 
 Palivontological Record, imperfection of, 
 
 27-39. 
 
 Paleontology, definition of, 1. 
 Paltrophis, 361. 
 Palceophycus, 477, 479. 
 PaUeopteris, 4S5. 
 Paleeopyge, 167. 
 
 Palamsiren, 347. 
 Paltfospalax, 468. 
 Pala-osponffia, 68. 
 Palaeothertdce, 427. 
 Palceotheriwn, 427. 
 Palcentringa, 390, 392. 
 Paltruxjilon, 493. 
 J'alaptcriix, 30, 394. 
 ]"ata*teri'na. 114, 115. 
 Pali (Corals), 92. 
 Palinurus, 179. 
 
 Pallial line, of Bivalve shells, 216. 
 Pallial sinus, 217. 
 Palmacites, 494. 
 Pahidicellea. 194. 
 J'altuHna, 245, 255. 
 I'almtinida, 255. 
 Pandanea, 499. 
 
 * 
 
 Paper Nautilus, 204. 
 Paradvxidas, 168 
 j;ir,t,l..jri,l?. 167, 168, 169. 
 J'aramtiricfa, 99. 
 
 , 
 
 Parktria, 66. 
 Panxfrcs. 895. 
 /*f#/fa, 242. 259. 
 Patellid^, 259.
 
 INDEX. 
 
 597 
 
 Pauropus, 184. 
 
 Pearly Nautilus, 274, 277, 278. 
 
 Peccary, 430 
 
 Pecopteris, 475, 482, 486, 495, 497, 498, 533. 
 
 Pecten, 221, 222. 
 
 Pectinaria, 137. 
 
 Pectinated rhombs of Cystideans, 132. 
 
 Pectunculus, 226, 227. 
 
 Pedicellariae, H4. 
 
 Pedicellinece, 194. 
 
 Pedipalpi, 182. 
 
 Pedunculated Cirripedes, 150, 152. 
 
 Peltoearig, 159, 160. 
 
 Pen, of Cuttle-fishes, 294. 
 
 Penarth beds, 531. 
 
 Pennatulidce, 101. 
 
 Pentacrinus, 123, 124, 127, 128. 
 
 Pentatnerus, 207, 208. 
 
 Pentremites. 133, 134. 
 
 Percidce, 318. 
 
 Perdicidte, 394. 
 
 PerennibrancMata (Amphibia), 346. 
 
 Perforata, 96 ; distribution of, in time, 97. 
 
 Peridinium, 59. 
 
 Periechocrirms, 126. 
 
 Perischoechmidce, 108, 110. 
 
 Perispongia, 537. 
 
 Perissodactyla, 423, 424. 
 
 Permian period, rocks of, 52S ; life of, 
 
 529 ; flora of, 495. 
 Perna, 223, 224. 
 Petalodus, 339. 
 Petraia, 89. 
 Petraster, 114, 115. 
 Petrodiifi, 339. 
 Petrospongiadce, 69. 
 Pezophaps, 391. 
 Phacopidce, 167, 170. 
 Phacops, 162, 167, 170. 
 Phalangidce, 182. 
 Phalangistidce, 408, 413. 
 Phanerogams, 473. 
 Phaneropleurini, 327, 329. ' 
 Phaneropleuron, 327, 329. 
 Pharyngobranchii, 314. 
 Phascolomys, 408. 
 Phascolotheriurn, 405, 410. 
 Phasianidce, 394. 
 Phillipsastrcea, 95. 
 Phillipsia, 167, 171. 
 Phlebopteris, 498. 
 Phocidce, 449, 450. 
 Pholadidce, 218, 239. 
 Pholadomya, 239. 
 PAoZas, 240. 
 Pholidogaster, 352. 
 Pholidophorus, 324. 
 Phorus, 254. 
 Phragmacone, of Spirilla, 296; of Belem- 
 
 nite, 297. 
 
 Phragmoceras, 283, 285. 
 Phylactolcemata, 194. 
 Phyllograpsus, 85. 
 Phyllopoda, characters of, 159 ; distribu- 
 
 tion of, in time, 159. 
 Phyllostomidce, 461. 
 Phyllostoma, 462. 
 
 Physeter, 420. 
 Physophoridce, 73, 74, 84. 
 Physostomata, 315. 
 Phytopsis, 479. 
 
 Pileolus, 255. ' 
 
 Pileopsis, 259. 
 
 Pinites, 493. 
 
 Pinna, 223, 224. 
 
 Pinnigrada, 448. 
 
 Pinnipedia, 447, 448. 
 
 Pinnularia, 477, 478, 482, 483. 
 
 Pisania, 247. 
 
 Pisces, characters of, 306; orders of, 315; 
 
 distribution of, in time, 313. 
 Pisidium, 234. 
 Pistosaurus, 372. 
 Placodus, 326, 372. 
 Placoganoids, 322. 
 Placoidei, 307. 
 Placoid scales, 307. 
 Placunopsis, 221 
 Plagiaulax, 406, 411. 
 Plagiostoma, 222. 
 Plagiostomi, 335, 336. 
 Planorbis, 242, 268. 
 Plantigrada, 448. 
 Platanus, 500, 502. 
 Ptatoa;, 318, 319. 
 Platephemera, 185. 
 Platyceras, 258, 259. 
 Platycrinus, 120, 123, 126. 
 Platygnathus, 326. 
 Platyrhina, 465. 
 Platysomidce, 325. 
 Platysomus, 325, 530. 
 Platystoma, 53-t. 
 Pleetognathi, 318, 321. 
 Plectrodus, 338. 
 Plesiosauria, 370. 
 Plesiosuurus, 371, 372. 
 Plesiosorex, 463. 
 Pleuracanthus, 335, 338, 342. 
 Pleuraster, 115. 
 Pleurobranchidce, 261. 
 Pleurocysiites, 130. 
 Pleurodictyum, 97. 
 Pleurodont Lizards, 362. 
 Pleuronectidce, 317, 318. 
 Pleurotoma, 249. 
 Pleurotomaria, 257, 264. 
 Plicatula, 222, 223. 
 Pliocene period, rocks of, 554 ; life of, 557. 
 
 flora of, 503. 
 Pliopithecus, 466. 
 Pliosaurus, 372. 
 Plmnaster, 111. 
 Podocarya, 499. 
 Podophthalmata, 176, 177. 
 Podozamites, 476, 497, 533. 
 Poikilopleuron, 377. 
 Pollicipes, 154. 
 Polycoe.Ha, 100, 529. 
 Polycystina, 66, 67. 
 Polypodites, 498. 
 Polypothecia, 543. 
 Polypterini, 326. 
 Polypterus, 321, 322, 326, 327. 
 Polytrema, 64. 
 Polyzoa, characters of, 190 ; orders of, 
 
 194 ; distribution of, in time, 195. 
 Polyzoarium, 190. 
 Populus, 500. 
 Porambonit.es, 208. 
 P&rcellana, 180. 
 Porcellia, 245. 263. 265. 
 Porites, 96.
 
 59 8 
 
 INDI.X. 
 
 Pti Mia. 7, 100. 
 
 Porotponoia, 637. 
 
 Pterotauria, characters of, 374; distribu- 
 tion of, in time, 376. 
 
 Portland Stone 636 
 
 Pterotheca, 270. 
 
 Porttoiiomya. *, 224. 
 
 Pterygotu*, 172, 173. 
 
 
 Ptilodietya, 196. 
 
 Post-GUctml Mammal's, 660. 
 
 I'-'!' ,.;;.-- 
 
 Post-Pliocene Mammals, 667. 
 
 / ..... . -' 
 Poteriocrinui. 126. 
 
 PtUograpmt, 78, 79. 
 Ptilomatter, 116. 
 Ptilopora, 196. 
 Pt,/chocercu>, 276, 288, 293 
 PtuoAodMC, 339, 340. 
 
 /' ' . : . 
 
 J',',h,itmi.fera, 241. 245, 265. 
 
 Potsdam Sandstone, 613, 614. 
 Prtr^retuntt, 177. 
 
 Pwpa, 246, 267, 267. 
 Purbeck beds, 536. 
 
 Prv-Ulai-Ul deport*. 658. 
 Pne-Glacial Mammals, 658. 
 Prrdwickia. 176. 
 
 Purpura, 248. 
 Purpiirina, 248. 
 Pttrjmroides, 638. 
 
 Primitia, 156, 157. 
 
 Pycnodontidce, 325. 
 
 Pritnnna 99 
 
 riiyaxter, Io9. 
 
 Primordial Zone. 167, 168, 513, 614. 
 
 Pygcndvx, 109. 
 
 lYiVmarfnra. 537. 
 Pri*trodon;s64. 
 
 Pygidium, 161, 164. 
 Pitgocephalm, 177. 
 
 ProboKidta, characters of, 442 ; distribu- 
 
 I'Wpterus, 530. 
 
 tion of, in time, 443. 
 
 Pwjurus. 109. 
 
 Proboscis, of Crinoids, 119, 121. 
 
 Pijramidellidce, 251. 
 
 Proccelia (CrocodUia), 366, 367. 
 
 J't/ryia, 97. 
 
 Proction, 451. 
 Prtxiucta. 21", 211, 530. 
 
 Pyrqama, 152. 
 Ptfrina, 109. 
 
 ProductiAr, 202, 210. 
 
 1'iirula, 247. 
 
 Prottida, 171. 
 
 Pi/</ion, 355, 360. 
 
 Prtxttu, 171. 
 
 
 Prongbuck, 437. 438, 439. 
 Pro-ostracurn, 297. 
 
 Quadrumana, characters of, 464; sections 
 of, 464 ; distribution of, in time, 464-466. 
 
 Prraobranchiata, 245. 
 
 Quebec group, 613, 614. 
 
 Protoponitcm, 177, 529. 
 
 Quercwi, 499, 600. 
 
 Protarea, 97. 
 
 
 Protattrr, 116, 117. 
 ProUacete, 499, 5j2. 
 
 Radiata, 73. 
 Ratliolaria, characters of, 66 ; distribu- 
 
 Prvtichnitet, 167. 
 Prvtolytoia, 182. 
 
 tion of, in time, 66. 
 Radiolites, 232. 
 
 Prot,yUhectu, 465. 
 
 /fi, 341. 
 
 Protupteri, 342. 
 
 Ralhu, 392. 
 
 Protopterit. 482. 
 
 / .. . M 
 
 Rawphorhi/nehut, 374, 376. 
 ./tana, 849. 
 
 Prutorvtaunu, 356, 362, 530. 
 
 Raiiflla, 247. 
 
 Pntoteris, 537. 
 
 Raniceps, 352. 
 
 Prototaxitet, 474, 482. 
 
 RaphioMvnts, 864. 
 
 Protopiryularia, 101. 
 
 Raptores, S95. 
 
 .PHltouil. characters of, 59; divisions of, 
 
 Rasoreg, 294. 
 
 69 ; diKtritmtion of, in time, 59, 60. 
 PntnotvttUtt, 133. 
 ftnwwMs, 237. 
 
 Rastriteg, 80, 84. 
 Jiatitff, 893. 
 Rays, 341, 342. 
 
 /Minifiocfiu. 338. 339. 
 /Vnruniiu, 474, 475, 482, 485, 495. 
 Ptevdoerinvt, 130, 133. 
 Pitvdonevroptera, 186. 
 
 Recent period, 54 8, 558. 
 Recfptafitlitc*. 71, 72 
 Red Coral, 102. 
 Red Crag, 555. 
 
 I'tfudoiiifcut, 174. 
 
 Reef-building Corals, S5, 96. 
 
 
 Regular Kcliinoids, 107. 
 Rein-deer, 436. 
 
 PiU'ipnyton, 474, 480-482. 
 
 Reptilia, characters of, 353 ; orders of, 
 
 I'folut. 185'. 
 PHratpit, 331. 332. 337. 
 
 355 ; distribution of, in time, 356. 
 Requienia, 230. 
 Retepora, 196. 
 
 I'tfnrhthyi, 331-333. 
 Pttrinea, SI4. 
 
 Reticulipora, 544. 
 
 MMWMML MA. S47. 
 
 ftAoMopfeura, 80, 194. 
 
 PUndactulut. 374, 375. 
 PttruphytluM, 476, 494, 497. 633. 
 
 Rh:i-tir l>edfl, 531. 
 Rhampha*tid<e, 395. 
 
 Ptfropoda, characters of, 269 ; shell of, 
 
 Rhea, 394, 
 Rhitiocerida, 424. 
 
 ; orders of, J69; distribution of, in 
 
 Rhinoceros 424-426. 
 
 
 Rhinolophida, 461.
 
 INDEX. 
 
 599 
 
 Rhinolophus, 462. 
 
 Rhizocrinus, 118, 128. 
 
 JRhizodus, 326, 328, 329. 
 
 Rhizopoda, 59, 60. 
 
 Rhizostornidce, 74. 
 
 Rhodocrinv*, 126. 
 
 Rhombus, 317, 318. 
 
 Rhus, 503. 
 
 Jthynchoceti, 419, 420. 
 
 Rhyncholites, 273. 
 
 Rhynchonella, 199, 203, 207. 
 
 Rhynchonellidce, 201-203, 207. 
 
 Rhynchosaurus, 362-364, 373, 374. 
 
 Rhynchoteuthis, 273, 274. 
 
 Rhytidolepis, 491, 493. 
 
 Rimula, 258. 
 
 Rissoa, 254. 
 
 Robinia, 503. 
 
 Robulina, 62. 
 
 Rodentia, characters of, 456 ; distribution 
 
 of, in time, 457. 
 Roebuck, 436. 
 Rostellaria, 247, 252. 
 Rotalia, 62, 64. 
 Rudistes, 231. 
 Rugosa, 97 ; distribution of, in time, 99 ; 
 
 families of, 101. 
 Ruminantia, characters of, 431 ; families 
 
 of, 433. 
 
 SABAL, 501. 
 Sabella, 137. 
 Sabellaria, 137. 
 Saccosoma, 122, 127. 
 Sagenaria, 480, 491. 
 Salamander, 347. 
 Salenia, 107, 110. 
 Saleniadce, 111). 
 
 Salmonidce, 316. 
 Sao, 169. 
 Sassafras, 500. 
 Satwia, 362. 
 Saurichthys, 534. 
 Saurillus, 364. 
 Saurocetes, 4'22. 
 Saurodipterini, 326, 327. 
 Sauroid Fishes, 327. 
 Sauropsida, 353. 
 Sauropterygia, 370-372. 
 Saurosternon, 364. 
 Saururce, 390, 396. 
 Saxicava, 238. 
 Scalaria, 243, 253.' 
 Scales of Fishes, 307. 
 Scalpellum, 154. 
 Scansores, 394. 
 Scaphaspis, 332. 
 Scaphites, 288, 292. 
 Schizodus, 229, 530. 
 Scissurella, 256, 257. - 
 Seiuridce, 460. 
 Sciurus, 460. 
 Sclerenchyma, 96. 
 Sclerobasica (Zoantharia), 87. 
 Sclerobasic Corals, 87. 
 Sclerodermata (Zoantharia), 88. 
 Sclerodermic Corals, 88. 
 Sclerogenidce, 318. 
 Scolecida, 102. 
 Scoliostoma, 534. 
 Scolites, 142. 
 
 Scolithus, 142. 
 
 Scolopax, 392, 546. 
 
 Scomberidce, 318. 
 
 Scorpion, 181-183. 
 
 Scorpionidce, 182. 
 
 Scutella, 104, 109. 
 
 Scyphia, 537. 
 
 Sea-anemones, 80, 81. 
 
 Sea-cucumbers, 135. 
 
 Seals, 449, 450. 
 
 Sea-Mosses, 187. 
 
 Sea-Urchins, 103. 
 
 Sedimentary Rocks, origin of, 6. 
 
 Selachii, 337, 340. 
 
 Semionotus, 324. 
 
 Semnopithecus, 466. 
 
 Sepia, 275, 295. 
 
 Sepiadce, 275, 294, 295. 
 
 Septa, of corals, 91, 92; of the shell of 
 Tetrabranchiate Cephalopods, 279, 280. 
 
 Sequoia, 502. 
 
 Seraphs, 247. 
 
 Seriatoporida;, 97, 100. 
 
 Serpula, 137, 138, 140. 
 
 Serpulites, 139. 
 
 Sertularida, characters of, 76 ; distribu- 
 tion of, in time, 77. 
 
 Sessile Cirripedes, 150-152. 
 
 Sharks, 336, 340. 
 
 Shell, of Balanoids, 150; of Lepadoids, 
 152; of MoUvsca, 187; of Brachiopoda, 
 199 ; of Lamellibranchiata, 214 ; of 
 Gasteropoda, 242 ; of Pteropoda, 269 ; 
 of Tetrabranchiate Cephalopods, 279. 
 
 Shrew-mice, 463. 
 
 Sieboldia, 349. 
 
 Sigillaria, 474, 482, 491-494. 
 
 Sigillarioids.474,475, 480, 482, 491-494, 529. 
 
 Silicispongia, 67, 68. 
 
 Silurian period, rocks of, 515; life of, 
 517 ; flora of, 478. 
 
 Siluridce, 316, 317. 
 
 Simosaurus, 372. 
 
 Sinupallialia (Lamellibranchiata), 218, 
 236. 
 
 Siphonia, 66, 70. 
 
 Siphonida (Lamellibranchiata}, 218, 219. 
 
 Siphonostomata (Gasteropoda], 244-246. 
 
 Siphonotreta, 212, 213. 
 
 Siren, 347. 
 
 Sirenia, characters of, 417; distribution of, 
 in time, 418. 
 
 Sivatherium, 438, 439. 
 
 Skiddaw Slates, 512, 514. 
 
 Slimonia, 173. 
 
 Sloths, 413, 414. 
 
 Smito, 502. 
 
 Snakes, 360. 
 
 Solarium, 254. 
 
 Solaster, 111. 114. 
 
 Solecurtus, 237. 
 
 SoZen, 237. 
 
 Solenastrcea, 96. 
 
 Solenidce, 218, 237. 
 
 Solid axis, of Graptolites, 80. 
 
 Solidungula, 423, 427. 
 Solipedia, 423. . - 
 
 Sore*, 463. 
 
 Soricidce, 463. 
 Spalacodon, 462. 
 SpalacotheriuM, 411. 
 Sparsispongia, 69.
 
 6oo 
 
 INDEX. 
 
 170. 
 
 478. 
 
 129.133. 
 
 Mm ' j -,:-..:. 
 
 i *enodo*, 363. 
 
 Spiral/ton, 474, 479. 
 i >irorbu. 137. 138. 139. 
 i rirula. 274, 275, 294 
 
 , 475, 483. 483, 436. 495, 499. 
 
 
 
 if, 67 ; distribution 
 "of. in time. 67, 68. 
 fyongiUa. 69. 
 fiponyUloptit, 69. 
 S/,i,i/-.,/.,,i. 421, 422. 
 iloraia, 342. 
 
 i(foptttia),365. 
 I. 340. 
 
 . . ,356,367. 
 
 .ftaiiria. ', 
 Stauridte, 99. 101. 
 f-tattroerphalwi, 170. 
 
 .v < Ml g !:-.' 1 
 
 lu, 115. 
 
 Stetuuter, 114, 115. 
 SfencoMtunur. 
 
 367. 
 
 /.a. 543. 
 . 420. 
 
 >u, 405. 410. 
 1,482,483.489,491. 
 . 474. 482, 493. 
 Stimapoda, chknctera of, 177 ; distribu- 
 
 tion of. in time, 177. 
 StoflMfleld Slat 
 
 I Slate, 536 ; Mammals of, 410. 
 Strate. eopUmponneity of, 14. 
 
 98. 
 530. 
 
 Strofltoduf, 
 
 s. : . 
 
 SfnpAoMn*d. 80S, 203, 8. 
 
 * 
 
 MMta.sn.us 
 
 iRrtJnctlonofiurineanimals,38.30. 
 
 Tabulata, 96 ; distribution of, in time, 
 
 97. 
 
 Tcenituter, 117. 
 Tceniopteri*, 498. 
 Talitnu, 176. 
 Taipa, 463. 
 Jalpida. 463. 
 Tapiridce, 426. 
 Tapinw, 426. 
 Taxocrinut, 126. 
 !Ta)d<m. 500, 501, 503. 
 Tectibranchiata. 244. 
 7Vfeoaurtw, 367. 
 Teleortei, characters of, 315; distribution 
 
 of, in time, 315 ; sub-orders of, 315-319. 
 Telerpeton, 356, 362, 363. 
 Tellina. 237. 
 Tellinidce, 218, 237. 
 Te/nafornw, 890, 392. 
 Temnocidaris, 100. 
 Temnopleurus, 110. 
 Tentaeulites, 139, 270, 271, 272. 
 Terebella, 137. 
 Terebra, 248. 
 Terebratella, 200, 204. 
 Terebratula, 198, 201, 203. 
 Terebratulidce, 202-204. 
 Terebratulitia, 203. 
 TVredo, 240. 
 
 Tertiary Rocks, classification of, 547. 
 TVswJafa (Crinoidea), 128. 
 Test, of Foramintfera, 61 ; of Echinoidea, 
 
 103 ; of Cirripedio, 250. 
 TentaeeUa, 267. 
 r<u<Knia>, 358, 359. 
 TetrabranfhMa, characters of, 277 ; shell 
 
 of, 279 ; distribution of, in time, 280. 
 Tetraeeroi, 439. 
 Tetradecapoda, 176. 
 Tetragonolepi*, 324. 
 Tetragrapsus, 82, 83. . 
 
 Tetraonida, 394. 
 Tetraprotodnn, 429. 
 Teudopsu, 295. 
 Teu/Aida-, 275, 277, 294, 298. 
 Textularia, 64, 65. 
 Thallogtns, 473. 
 Thamnaistrafa, 537. 
 Thamnograpnu, 78. 
 Thanct Sands, 648. 
 7%ca, 270. 
 Thetaphora, 74, 76. 
 Theeidcr, 97, 100. 
 Thecididce, 204. 
 Thffidium. 204. 205, 534. 
 Thecodontia, 367. 
 
 , 637. 
 
 Thecotamata (Pteropoda], 269. 
 Thtlodii*, 335, 337, 338. 
 TAeti*. 238. 
 
 Thinning out of beds, 36-88. 
 Thoracic* (Cirripedia), 150.
 
 INDEX. 
 
 60 1 
 
 Thylacinus, 408. 
 
 Thylacoleo, 412, 418. 
 
 Thysanura, 187. 
 
 Tornatella, 261. 
 
 Tornatellidce, 261. 
 
 Tortoises, 358, 359. 
 
 Toucan, 395. 
 
 Toxoceras, 291. 
 
 Trachydenna, 139. 
 
 Trachynemidce, 74. 
 
 Tracks, of Annelides, 141, 142. 
 
 Tremadoc Slates, 512, 515. 
 
 Trematis, 212. 
 
 Trenton period, 508, 516. 
 
 Triassic period, rocks of, 530; life of, 533; 
 
 flora of, 496. 
 Trichecidce, 450. 
 Trichites, 225. 
 Trichotropis, 247. 
 Triconodon, 406, 411 
 Tridacna, 232. 
 Tridacnidce, 218, 232. 
 Trigonia, 228, 229. 
 ?s, 287. 
 
 B, 218, 228, 530. 
 ....irpurn, 482, 484, 492,494. 
 bita, characters of, 160 ; distribution 
 of, in time, 167; families of, 167-171. 
 Trimerocephalus, 170. 
 Trinucleidce, 167, 169. 
 Trinucleus, 162, 167, 169. 
 Trionycid<z, 358, 359. 
 
 Trionyx, 359. 
 
 Tristichopterus, 327. 
 
 Triton, 247. 
 
 Trochoceras, 281, 283, 292. 
 
 Trochocyathus, 537, 543. 
 
 Trochocystites, 132. 
 
 Trochoseris, 96. 
 
 Trochovmilia, 543. 
 
 Trochus, 256. 
 
 Trogonidce, 395. 
 
 Trogontherium, 459. 
 
 Tropidaster, 537. 
 
 Tubicola, characters of, 137 ; distribution 
 of, in time, 138. 
 
 Tubiporidce, 101. 
 
 Tubularia, 74. 
 
 Tubulipora, 198. 
 
 Tubulosa, 96 ; distribution of, in time, 97. 
 
 Tunicata, 187. 
 
 Turbinaria, 96. 
 
 Turbinella, 247. 
 
 Turbinidw, 255, 264. 
 
 Turbinolia, 92. 
 
 Turbinolidce, 97, 100. 
 
 Twrfto, 255, 256. 
 
 Turrilepas, 152, 153, 154, 155. 
 
 Turrilites, 276, 288, 292. 
 
 Turritella, 253 
 
 TurriteUidce, 253. 
 
 Turtles, 358, 359. 
 
 Unionidce, 218, 229. 
 
 Univalve Shells, 240, 241. 
 
 Unrepresented time, 32-36. 
 
 Upper Cretaceous Rocks, 540. 
 
 Upper Oolitic Rocks, 536. 
 
 Uraster, 111, 113, 114, 115. 
 
 Urocondylus, 352. 
 
 Urodela, characters of, 347 ; distribution 
 
 of, in time, 347, 349. 
 Ursidce, 449, 450. 
 J7r*t, 451. 
 frtw, 439, 400. 
 
 Fofoata, 245, 555. 
 
 Valvular pyramid, of Cystideans, 131. 
 
 Varanidce, 362. 
 
 Vegetable kingdom, divisions of 473 
 
 Veneridce, 218, 219, 236. 
 
 Ventrieulites, 67, 70. 
 
 Fentw, 236. 
 
 Vermetus, 137, 138, 242, 253. 
 
 Verruca, 152. 
 
 Ferrweufoe, 150, 152. 
 
 Vertebrata, characters of, 299; skeleton 
 
 of, 300 ; distribution of, in time 306 
 Vespertilio, 461, 462. 
 Vespertilionidce, 461. 
 Vibracnla, 194. 
 Vincularia, 544. 
 Viperine Snakes, 360. 
 Virg\daria, 101. 
 Viverra, 452. 
 Viverridce, 449, 452, 453. 
 Voltzia, 476, 497, 533. 
 Valuta, 249, 250. 
 Volutidce, 249. 
 Fw/pe*, 454. 
 
 Walchia, 495, 496, 529. 
 Waldheimia, 204. 
 Wealden, 540. 
 
 Wellingtonia, 502. 
 
 Wenlock series, 516. 
 
 Whalebone Whales, 419. 
 
 White Crag, 555. 
 
 Williamsonia, 497. 
 
 Woolwich and Reading Series, 548. 
 
 Xanthidia, 69. 
 
 Xantholites, 180. 
 
 Xanthopsis, 180. 
 
 Xenoneura, 185. 
 
 Xiphodon, 431. 
 
 Xiphosura, characters of, 174; distribu- 
 
 tion of, in time, 174, 175. 
 Xiphoteuthis, 299. 
 Xylobius, 184. 
 
 (Tllmania, 475, 496, 529. 
 
 Umbrella, 262. 
 
 Uncites, 206. 
 
 Uneonfonnability, of strata, 33. 
 
 Undina, 327. 
 
 Ungulata, characters of, 423 ; divisions of, 
 
 423. 
 Unio, 229. 
 
 , 496. 
 Zamites, 497. 
 Zaphrentis, 89. 
 Zechstein, 529. 
 Zeuglodon, 421. 
 Zeuglodontidce, 419, 421. 
 Ziphioid Whales, 419, 420. 
 Ziphius, 421. 
 
 Zoantharia, 73,S6;Malacodermata,85,S6; 
 Sclerobasica, 87 ; Sclerodermata, 88-97. 
 Zonites, 246, 266. 
 Zoocapsa, 152. 
 Zygosaurus, 353.
 
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