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 UNIVERSITY OF CALIFORNIA. 
 
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 BIOLOGY 
 
 Received 
 Accessions No. 
 
 Shelf No. 
 
INTRODUCTION AND SUCCESSION 
 
 VERTEBRATE LIFE IN AMERICA. 
 
 AIST ADDRESS 
 
 DELIVERED BEFORE THE 
 
 AMERICAN ASSOCIATION FOR THE ADVANCEMENT OF SCIENCE, 
 AT NASHVILLE, TENN., AUGUST 30, 1877, 
 
 PROFESSOR 0. C. MARSH, 
 
 i< 
 
 Vice President. 
 
 L I B R A R Y 
 UKIVEBSiTY OF 
 .CALIFORNIA. 
 
Tuttle, Morenoase A Tuylor, Printers, New f-Uven, Conn. 
 
LIBRARY 
 
 UNIVERSITY OF 
 
 CALIFORNIA. 
 
 INTRODUCTION AND SUCCESSION OF VERTEBRATE 
 LIFE IN AMERICA. 
 
 THE origin of life, and the order of succession in which its 
 various forms have appeared upon the earth, offer to science 
 its most inviting and most difficult field of research. 
 Although the primal origin of life is unknown, and may per- 
 haps never be kno.wn, yet no one has a right to say how much 
 of the mystery now surrounding it science cannot remove. 
 It is certainly within the domain of science to determine when 
 the earth was first fitted to receive life, and in what form the 
 earliest life began. To trace that life in its manifold changes 
 through past ages to the present is a more difficult task, but 
 one from which modern science does not shrink. In this wide 
 field, every earnest effort will meet some degree of success ; 
 every year will add new and important facts ; and every 
 generation will bring to light some law, in accordance with 
 which ancient life has been changed into life as we see it 
 around us to-day. That such a development has taken place, 
 no one will doubt who has carefully traced any single group 
 of animals through its past history, as recorded in the crust of 
 the earth. The evidence will be especially conclusive, if the 
 group selected belongs to the higher forms of life, which are 
 sensitive to every change in their surroundings. But I am sure 
 I need offer here no argument for evolution ; since to doubt 
 evolution to-day is to doubt science, and science is only another 
 name for truth. 
 
Taking, then, evolution as a key to the mysteries of past life 
 on the earth, I invite your attention to the subject I have 
 chosen : THE INTRODUCTION AND SUCCESSION OF VERTEBRATE 
 LIFE IN AMERICA. 
 
 In the brief hour allotted to me, I could hardly hope to give 
 more than a very incomplete sketch of what is now known on 
 this subject. I shall, therefore, pass rapidly over the lower 
 groups, and speak more particularly of the higher vertebrates, 
 which have an especial interest to us all, in so far as they 
 approach man in structure, and thus indicate his probable 
 origin. These higher vertebrates, moreover, are most important 
 witnesses of the past, since their superior organization made 
 them ready victims to slight climatic changes, which would 
 otherwise have remained unrecorded. 
 
 In considering the ancient life of America, it is important to 
 bear in mind that I can only offer you a brief record of a few 
 of the countless forms that once occupied this continent. The 
 review I can bring before you will not be like that of a great 
 army, when regiment after regiment with full ranks moves by 
 in orderly succession, until the entire host has passed. My 
 review must be more like the roll-call after a battle, when only 
 a few scarred and crippled veterans remain to answer to their 
 names. Or rather, it must resemble an array of relics, dug 
 from the field of some old Trojan combat, long after the con- 
 test, when no survivor remains to tell the tale of the strife. 
 From such an ancient battle-field, a Schliernann might unearth 
 together the bronze shield, lance-head, and gilded helmet of a 
 prehistoric leader, and learn from them with certainty his race 
 and rank. Perhaps the skull might still retain the barbaric 
 stone weapon by which his northern foe had slain him. Near 
 by, the explorer might bring to light the commingled coat of 
 mail and trappings of a horse and rider, so strangely different 
 from the equipment of the chief, as to suggest a foreign ally. 
 From these, and from the more common implements of war 
 that fill the soil, the antiquary could determine, by patient 
 study, what nations fought, and, perhaps, when, and why. 
 
By this same method of research, the more ancient strata 
 of the earth have been explored, and, in our Western wilds, 
 veritable battle-fields, strown with the fossil skeletons of the 
 slain, and guarded faithfully by savage superstition, have been 
 despoiled, yielding to science treasures more rare than bronze 
 or gold. Without such spoils, from many fields, I could not 
 have chosen the present theme for my address to-night. 
 
 According to present knowledge, no vertebrate life is known 
 to have existed on this continent in the Archaean, Cambrian, or 
 Silurian periods; yet during this time, more than half of the 
 thickness of American stratified rocks was deposited. It by 
 no means follows that vertebrate animals of some kind did not 
 exist here in those remote ages. Fishes are known from the 
 Upper Silurian of Europe, and there is every probability that 
 they will yet be discovered in our strata of the same age, if not 
 at a still lower horizon. 
 
 In the shore deposits of the early Devonian sea, known as 
 the Schoharie Grit, characteristic remains of Fishes were pre- 
 served, and in the deeper sea that followed, in which the 
 Corniferous limestone was laid down, this class was well 
 represented. During the remainder of the Devonian, Fishes 
 continue abundant in the shallower seas, and, so far as now 
 known, were the only type of vertebrate life. These fishes 
 were mainly Ganoids, a group, represented in our present 
 waters by the Gar-pike (Lepidosleus) and Sturgeon (Acipenser), 
 but, in the Devonian sea, chiefly by the Placoderms, the exact 
 affinities of which are somewhat in doubt. With these were 
 Elasmobranchs, or the Shark tribe, and among them a few 
 Chimaeroids, a peculiar type, of which one or two members still 
 survive. The Placoderms were the monarchs of the ocean. All 
 were well protected by a massive coat of armor, and some of 
 them attained huge dimensions. The American Devonian fishes 
 now known are not as numerous as those of Europe, but they 
 were larger in size, and mostly inhabitants of the open sea. 
 Some twenty genera and forty species have been described. 
 
6 
 
 The more important genera of Placoderms are, Diniclithys, 
 Aspidichthys, and Diploynathus, our largest Palaeozoic fishes. 
 Others are, Acanthaspis, Acantholepis, Coccosteus, Macropetalich- 
 thys, and Onychodus. Among the Elasmobranchs were, Clado- 
 dus, Ctenacanthus, Machcer acanthus, Rhynchodus, and Ptyctodus, 
 the last two being regarded as Chima3roids. In the Chemung 
 epoch, the great Dipterian family was introduced with Dipterus, 
 Heliodus, and possibly Ceratodus. Species of the European 
 genera, BothrioUpis and Holoptychius, have likewise been found 
 in our Devonian deposits. 
 
 With the close of the Devonian, came the almost total extinc- 
 tion of the great group of Placoderms, while the Elasmobranchs, 
 which had hitherto occupied a subordinate position, increase in 
 numbers and size, and appear to be represented by Sharks, 
 Eays, and Chimseras. Among the members of this group from 
 the Carboniferous, were numerous Cestracionts, species of 
 Cochliodus of large size, with others of the genera Deltodus, 
 Helodus, Psammodus and Sandalodus. Of the Petalodonts, 
 there were Antliodus, Chomatodus, Ctenoptychius, Petalodus and 
 Petalorhyrtckus ; and of the Hybodonts, the genera Cladodus, 
 Carcharopsis and Diplodus. These Elasmobranchs were the 
 rulers of the Carboniferous open sea, and more than one hun- 
 dred species have been found in the lower part of this forma- 
 tion alone. The Ganoids, although still abundant, were of 
 smaller size, and denizens of the more shallow and confined 
 waters. The latter group of fishes was represented by true 
 Lepidostidae, of the genera Palceoniscus, Amblypterus, Platyso- 
 mus and Eurylepis. Other genera are, Rhizodus, Megalichthys, 
 Ctenodus, JEdestus, Orodus, Cten acanthus, Gyracanthus, and C<xla- 
 canthus. Most of these genera occur also in Europe. 
 
 From the Permian rocks of America, no vertebrate remains 
 are known, although in the same formation of Europe Ganoids 
 are abundant; and with them are remains of Sharks, and some 
 other fishes, the affinities of which are doubtful. The Palaeo- 
 zoic fishes at present known from this country are quite as 
 numerous as those found in Europe. 
 
In the Mesozoic age, the Fishes of America begin to show a 
 decided approach to those of our present waters. From the 
 Triassic rocks, Ganoids only are known, and they are all more 
 or less closely related to the modern Gar-pike, or Lepidosteus. 
 They are of small size, and the number of individuals 
 preserved is very large. The characteristic genera are, Catop- 
 lerus, Ischypterus, Ptycholepis, Rhabdolepis, and Turseodus. 
 From the Jurassic deposits, no remains of fishes are known, 
 but in the Cretaceous, ichthyic life assumed many and 
 various forms ; and the first representatives of the Teleosts, 
 or bony fishes, the characteristic fishes of to-day, make 
 their appearance. In the deep open sea of this age, Elas- 
 mobranchs were the prevailing forms, Sharks and Chimseroids 
 being most numerous. In the great inland Cretaceous sea of 
 North America, true osseous fishes were most abundant, and 
 among them were some of carnivorous habits, and immense 
 size. The more sheltered bays and rivers were shared by the 
 Ganoids and Teleosts, as their remains testify. The more 
 common genera of Cretaceous Elasmobranchs were, Otodus, 
 Oxyrhina, Galeocerdo, Lamna and Ptychodus. Among the 
 osseous fishes, Beryx, Enchodus, Portheus and Saurocephalus 
 were especially common, while the most important genus of 
 Ganoids was Lepidolus. 
 
 The Tertiary fishes are nearly all of modern types, and from 
 the beginning of this period there was comparatively little 
 change. In the marine beds, Sharks, Rays and Chimasroids 
 maintained their supremacy, although Teleosts were abundant, 
 and many of them of large size. The Ganoids were compara- 
 tively few in number. In the earliest Eocene fresh-water 
 deposits, it is interesting to find that the modern Gar-pike, 
 and Amia, the Dog-fish of our western lakes, which by their 
 structure are seen to be remnants of a very early type, are 
 well represented by species so closely allied to them that only 
 an anatomist could separate the ancient from the modern. In 
 the succeeding beds, these fishes are still abundant, and with 
 them are Siluroids nearly related to the modern Cat-fish 
 
(Pimelodus). Many small fishes, allied apparently to the 
 modern herring (Cfapea), left their remains in great numbers 
 in the same deposits, and, with them has been recently found 
 a land-locked Ray (Heliobatis). 
 
 The almost total absence of remains of fishes from the Mio- 
 cene lake-basins of the West is a remarkable fact, and perhaps 
 may best be explained by the theory that these inland waters, 
 like many of the smaller lakes in the same region to-day, were 
 so impregnated with mineral matters as to render the existence 
 of vertebrate life in them impossible. No one who has tasted 
 such waters, or has attempted to ford one of the modern alkaline 
 lakes which are often met with on the present surface of the 
 same deposits, will doubt the efficiency of this cause, or the 
 easy entombment of trie higher vertebrates that ventured within 
 their borders. Tn the Pliocene lake-basins of the same region, 
 remains of fishes were not uncommon, and in some of them are 
 very numerous. These are all of modern types, and most of 
 them are Cyprinoids, related to the modern Carp. The Post- 
 pliocene fishes are essentially those of to-day. 
 
 In this brief synopsis of the past ichthyic life of this Conti- 
 nent, I have mentioned only a few of the more important facts, 
 but sufficient, I trust, to give an outline of its history. Of this 
 history, it is evident that we have as yet only a very imperfect 
 record. We have seen that the earliest remains of fishes 
 known in this country, are from the lower Devonian ; but these 
 old fishes show so great a diversity of form and structure, as 
 to clearly indicate for the class a much earlier origin. In this 
 connection, we must bear in mind that the two lowest groups 
 of existing fishes are entirely without osseous skeletons, and 
 hence, however abundant, would leave no permanent record in 
 the deposits in which remains of fishes are usually preserved. 
 It is safe to infer, from the knowledge which we now possess 
 of the simpler forms of life, that even more of the early fishes 
 were cartilaginous, or so destitute of hard parts as to leave no 
 enduring traces of their existence. Without positive knowledge 
 of such forms, and considering the great diversity of those we 
 
have, it would seern a hopeless task at present to attempt 
 to trace successfully the genealogy of this class. One line, 
 however, appears to be direct, from our modern Gar-pike, 
 through the lower Eocene Lepidosteus to the Lepidotus of the 
 Cretaceous, and perhaps on through the Triassic Isbhypterus 
 and Carboniferous Palceoniscus ; but beyond this, in our rocks, 
 it is lost. The living Chimaera of our Pacific coast has nearly 
 allied forms in the Tertiary and Cretaceous, more distant rela- 
 tives in the Carboniferous, and a possible ancestor in the 
 Devonian Rhynchodus. Our Sharks likewise can be traced 
 with some certainty back to the Palaeozoic ; and even the 
 Lepidosiren, of South America, although its immediate pre- 
 decessors are unknown, has some peculiar characters which 
 strongly point to a Devonian ancestry. These suggestive lines 
 indicate a rich field for investigation in the ancient life-history 
 of American fishes. 
 
 The Amphibians, the next higher class of vertebrates, are so 
 closely related to the fishes in structure, that some peculiar 
 forms of the latter have been considered by anatomists as 
 belonging to this group. The earliest evidence of Amphibian 
 existence, on this continent, is in the Sub-Carboniferous, where 
 foot-prints have been found which were probably made by 
 Labyrinthodonts, the most ancient representatives of the class. 
 Well preserved remains are abundant in the Coal Measures, 
 and show that the Labyrinthodonts differed in important par- 
 ticulars from all modern Amphibians, the group which includes 
 our frogs and salamanders. Some of these ancient animals 
 resembled a salamander in shape, while others were serpent-like 
 in form. None of those yet discovered were frog-like, or without 
 a tail, although the restored Labyrinthodont of the text books 
 is thus represented. All were protected by large pectoral 
 bony plates, and an armor of small scutes on the ventral surface 
 of the body. The walls of their teeth were more or less folded 
 whence* the name Labyrinthodont. The American Amphib- 
 ians known from osseous remains are all of moderate size, 
 but the foot-prints attributed to this group indicate animals 
 2 
 
10 
 
 larger than any of the class yet found in the old world. The 
 Carboniferous Amphibians were abundant in the swampy trop- 
 ical forests of that period, and their remains have been found 
 imbedded in the coal then deposited, as well as in hollow 
 stumps of the trees left standing. 
 
 The principal genera of this group from American Car- 
 boniferous rocks, are, Sauropus, known only from footprints, 
 Baphetes, Dendrerpeton, Hylonomus, Hylerpeton, Raniceps, Pelion, 
 Leptophradus, Molgophis, Plyonius, Amphibamus, Cocytinus, and 
 Ceraterpeton. The last genus occurs also in Europe. Certain of 
 these genera have been considered by some writers to be more 
 nearly related to the Lizards, among true reptiles. Some other 
 genera known from fragmentary remains or footprints in this 
 formation have likewise been referred to the true reptiles, but 
 this question can perhaps be settled only by future discoveries. 
 
 ~$o Amphibia are known from American Permian strata, but 
 in the Triassic, a few characteristic remains have been found. 
 The three genera, Dictyocephalus, Dispelor and Pariostegus, have 
 been described, but, although apparently all Labyrintho- 
 donts, the remains preserved are not sufficient to add much to 
 our knowledge of the group. The Triassic foot-prints which 
 have been attributed to Amphibians are still more unsatis- 
 factory, and at present no important conclusions in regard to 
 this class can be based upon them. From the Jurassic and 
 Cretaceous beds of this Continent, no remains of Amphibians 
 are known. A few only have been found in the Tertiary, 
 and these are all of modern types. 
 
 The Amphibia are so nearly allied to the Ganoid fishes, that 
 we can hardly doubt their descent from some member of that 
 group. With our present limited knowledge of the extinct 
 forms, however, it would be unprofitable to attempt to trace in 
 detail their probable genealogy. 
 
 The authors to whom especial credit is due for our knowl- 
 edge of American fossil Fishes and Amphibians, are New- 
 berry, Leidy, Cope, Dawson, Agassiz, St. John, Gibbes, Wy- 
 man, Kedfield, and Emmons, and the principal literature of the 
 subject will be found in their publications. 
 
11 
 
 Reptiles and Birds form the next great division of ver- 
 tebrates, the Sauropsida, and of these the Reptiles are the older 
 type, and may be first considered. While it may be stated 
 with certainty that there is at present no evidence of the exist- 
 ence of this group in American rocks older than the Car- 
 boniferous, there is some doubt in regard to their appearance 
 even in this period. Various foot-prints which strongly resem- 
 ble those made by Lizards ; a few well preserved remains similar 
 to the corresponding bones in that group; and a few charac- 
 teristic specimens, nearly identical with those from another 
 order of this class, are known from American Coal Measures. 
 These facts, and some others which point in the same direction, 
 render it probable that we may soon have conclusive evidence of 
 the presence of true Reptiles in this formation, and in our over- 
 lying Permian, which is essentially a part of the same series. 
 In the Permian rocks of Europe, true Reptiles have been 
 found. 
 
 The Mesozoic Period has been called the Age of Reptiles, 
 and during its continuance some of the strangest forms of rep- 
 tilian life made their appearance, and became extinct. Near 
 its commencement, while trie Triassic shales and sandstones 
 were being deposited, true reptiles were abundant. Among 
 the most characteristic remains discovered are those of the 
 genus Belodon, which is well known also in the Trias of 
 Europe. It belongs to the Thecodont division of Reptiles, 
 which have teeth in distinct sockets, and its nearest affinities 
 are with the Crocodilia, of which order it may be considered 
 the oldest known representative. In the same strata in which 
 the Belodonts occur, remains of Dinosaurs are found, and it is 
 a most interesting fact that these highest of reptiles should make 
 their appearance, even in a generalized form, at this stage of 
 the earth's history. The Dinosaurs, although true reptiles in 
 all their more important characters, show certain well marked 
 points of resemblance to existing birds of the order RatilcK, a 
 group which includes the Ostriches ; and it is not improbable 
 that they were the parent stock from which birds originated. 
 
12 
 
 During Triassic time, the Dinosaurs attained in America an 
 enormous development both in variet} T of forms and in size. 
 Although comparatively few of their bones have as yet 
 been discovered in the rocks of this country, they have left 
 unmistakable evidence of their presence in the foot-prints and 
 other impressions upon the shores of the waters which they 
 frequented. The Triassic sandstone of the Connecticut Valley 
 has long been famous for its fossil foot-prints, especially the 
 so-called "bird-tracks," which are generally supposed to have 
 been made by birds, the tracks of which many of them closely 
 resemble. A careful investigation, however, of nearly all the 
 specimens yet discovered, has convinced me that there is not a 
 particle of evidence that any of these fossil impressions were 
 made by birds. Most of these three-toed tracks were certainly 
 not made by birds ; but by quadrupeds, which usually walked 
 upon their hind feet alone, and only occasionally put to the 
 ground their smaller anterior extremities. I have myself 
 detected the impressions of these anterior limbs in connection 
 with the posterior foot-prints of nearly all of the supposed 
 " bird-tracks" described, and have little doubt that they will 
 eventually be found with all. These double impressions -are 
 precisely the kind which Dinosaurian reptiles would make, 
 and as the only characteristic bones yet found in the same 
 rocks belong to animals of this group, it is but fair to attribute 
 ail these foot-prints to Dinosaurs, even where no impressions 
 of fore-feet have been detected, until some evidence appears 
 that they were made by Birds. I have no doubt that 
 Birds existed at this time, although at present the proof is 
 wanting. 
 
 The principal genera of Triassic Reptiles known from osseous 
 remains in this country are, Amphisaurus (Meyadactylus), 
 from the Connecticut Valley, Bathygnathus, from Prince Ed- 
 ward's Island, Belodon and Clepsysaurus. Other generic names 
 which have been applied to foot-prints and to fragmentary 
 remains, need not be here enumerated, A few remains of 
 Reptiles have been found in undoubted Jurassic rocks of 
 
13 
 
 America, but they are not sufficiently well determined to be 
 of service in this connection. Others have been reported from 
 supposed Jurassic strata, which are now known to be Creta- 
 ceous. It will thus be seen that, although reptilian life was 
 especially abundant during the Triassic and Jurassic periods, 
 bat few bones have been found. This is owing in part to the 
 character of most of the rocks then formed, which were not 
 well fitted for preserving such remains, although admirably 
 adapted to retain foot-prints. 
 
 During the Cretaceous Period, Reptilian life in America 
 attained its greatest development, and the sediments laid down 
 in the open seas and estuaries were usually most favorable for 
 the preservation of a faithful record of its various phases. With- 
 out such a perfect matrix as some of these deposits afford, many 
 of the most interesting vertebrates recently brought to light 
 from this formation would probably have remained unknown. 
 The vast extent of these beds ensures, moreover, many future 
 discoveries of interest. 
 
 In the lowest Cretaceous strata of the Rocky Mountain 
 region, the Dakota group, part of which at least represents 
 the Wealden of Europe, remains of Chelonia, or Turtles, Croc- 
 odiles, and Dinosaurs occur, the last being especially abun- 
 dant. The Chelonia, although known from the Jurassic of 
 Europe, here appear for the first time in American rocks. 
 Some of the earliest forms are allied to the modern genus 
 Trionyx. In the higher Cretaceous beds, some Chelonians of 
 enormous size have been found. They belong to the genus 
 Atlantochelys, which has the ribs separate, as in the existing 
 Spharyis, and presents other embryonic characters. A few 
 genera appear to be related to the modern genus Chelone. The 
 remaining Cretaceous species were mostly of the Emydoid 
 type ; and others were related to Chelydra. The more important 
 genera of Cretaceous Chelonians known from characteristic speci- 
 mens are, Allan tochelys (Protostega), Adocus, Sothremys, Coinpse- 
 mys, Plastomenus, Osteopygis, Propleura, Lytoloma, and Taphros- 
 phys. Most of these genera were represented by several species, 
 
14 
 
 and the individuals were numerous. No land Tortoises have as 
 yet been found in this formation. In American Tertiary depos- 
 its, Ohelonians are abundant, especially in the fresh-water beds. 
 They all show near affinities with modern types, and most of 
 them can be referred to existing genera. In the Tertiary lake- 
 basins of the West, land Tortoises are very numerous, and 
 with them are many fresh-water forms of Trionyx and allied 
 genera. 
 
 A striking feature of the American Cretaceous fauna, as con- 
 trasted with that of Europe, is the almost entire absence in our 
 strata of species of Ichthyosaurus and Plesiosaurus, which 
 abound in many other regions, but here seem to be replaced by 
 the Mosasaurs. A few fragmentary remains have indeed been 
 referred to these genera, but the determination may fairly be 
 questioned. This is more than true of the proposed new order 
 Streptosauria, which was founded wholly on error. The order 
 Plesiosauria, however, is well represented, but mainly by forms 
 more nearly related to the genus Pliosaurus than to the type 
 of the group. These were marine reptiles, all of large size, 
 while some of them attained vast dimensions. So far as at 
 present identified, they may be referred to the genera, Cimalio- 
 saurus, Discosaurus (Elasmosaurus), and Pliosaurus. The num- 
 ber of species is comparatively few, and none are known above 
 the Cretaceous. The important suggestion of Gegenbaur, that 
 the Halisauria, which include the Plesiosaurs, branched off 
 from the Fishes before the Amphibians, finds some support in 
 American specimens recently discovered. 
 
 The Reptiles most characteristic of our American Cretaceous 
 strata are the Mosasauria, a group with very few representatives 
 in other parts of the world. In our Cretaceous seas, they ruled 
 supreme, as their numbers, size, and carnivorous habits, enabled 
 them to easily vanquish all rivals. Some were at least sixty 
 feet in length, and the smallest ten or twelve. In the inland 
 Cretaceous sea from which the Rocky Mountains were begin- 
 ning to emerge, these ancient " Sea Serpents" abounded; and 
 many were entombed in its muddy bottom. On one occasion, 
 
15 
 
 as I rode through a valley washed out of this old ocean bed, I 
 saw no less than seven different skeletons of these monsters in 
 sight at once. The Mosasaurs were essentially swimming Liz- 
 ards, with four well developed paddles, and they had little affin- 
 ity with modern serpents, to which they have been compared. 
 The species are quite numerous, but they belong to compara- 
 tively few genera, of which Mosasaurus, Tylosaurus, Lestosaurus 
 and Edestosaurus, have alone been identified with certainty. The 
 genus Mosasaurus was first found in Europe. All the known 
 species of the group are Cretaceous. 
 
 The Crocodilia are abundant in rocks of Cretaceous age in 
 America, and two distinct types are represented. The older 
 type, which is foreshadowed by Belodon of the Trias, has bicon- 
 cave vertebrae, and shows marked affinities with the genus 
 Teleosaurus, from the Jura of Europe. The best known 
 genus is Hyposaurus, of which there are several species, all 
 more or less resembling in form the modern Gavial of the 
 Ganges. A peculiar intermediate form is seen in Diplosaurus, 
 from the Wealden of the Rocky Mountains. The second type, 
 which now makes its appearance for the first time, has pro- 
 ccelian vertebrae, and in other respects resembles existing Croc- 
 odiles. The genera described are Bottosaurus, Holops and Tho- 
 racosaurus, none of which, so far as known, pass above the 
 Cretaceous. Of Crocodilia with opisthoccelous vertebras, Amer- 
 ica, so far as we know, has none. Specimens similar to those 
 so termed in Europe, are not uncommon here, but they per- 
 tain to Dinosaurs. 
 
 In the Eocene fresh-water beds of the West, Crocodilians 
 are especially abundant, and all, with the exception of Limno- 
 saurus, belong apparently to the genus Crocodilus, although 
 some species show certain points of resemblance to existing 
 Alligators. The Miocene lake-basins of the same region 
 contain no remains of Crocodiles, so far as known, and the 
 Pliocene deposits have afforded only a single species. The 
 Tertiary marine beds of the Atlantic Coast contain com- 
 paratively few Crocodilian remains, and all are of modern 
 
. 16 
 
 types ; the genus Oavialis having one Eocene species, and the 
 Alligator being represented only in the latest deposits. 
 
 It is worthy of special mention in this connection, that no 
 true Lacertilia, or Lizards, and no Ophidia, or Serpents, have 
 yet been detected in American Cretaceous beds ; although their 
 remains, if present, would hardly have escaped observation in 
 the regions explored. The former will doubtless be found, as 
 several species occur in the Mesozoic of Europe ; and perhaps 
 the latter, although the Ophidians are apparently a more mod- 
 ern type. In the Eocene lake-basins of Western America, re- 
 mains of Lizards are very numerous, and indicate species much 
 larger than any existing to-day. Some of these, the Glyptosau- 
 ridan, were protected by a highly ornamented bony coat of mail, 
 and others were covered with scales, like recent Lizards. A 
 few resembled, in their more important characters, the modern 
 Iguana. The genera best represented in the Eocene, are, Gtyp- 
 tosaurus, Iguanavus, Oreosaurus, Thinosaurus, Tinosaurus and 
 Saniva. Some of these genera appear to have continued into the 
 Miocene, but here, as well as in the Pliocene, few remains of 
 this group have been found. It is not improbable that some 
 of our extinct Eeptiles may prove to belong to Rynchocephala, 
 but at present this is uncertain. The genus Notosaurus, from 
 Brazil, has biconcave vertebras, and some other characters 
 which point to that group. No Dicynodonts or Theriodonts 
 have as yet been found in this country. 
 
 The first American Serpents, so far as now known, appear 
 in the Eocene, which contains also the oldest European species. 
 On the Atlantic border, the genus Titanophis (Dinophis) is 
 represented by several species of large size, one at least thirty 
 feet in length, and all doubtless inhabitants of the sea. In the 
 fresh-water Western Eocene, remains of snakes are abundant, 
 but all are of moderate size. The largest of these were related 
 to the modern Boa Constrictors. The genera described are 
 Soavus, Liihophis and Limnophis. The Miocene and Pliocene 
 Snakes from the same region are known only from a few frag- 
 mentary remains. 
 
17 
 
 The Pterosauria, or flying Lizards, are among the most 
 interesting Reptiles of Mesozoic time, and many of them left 
 their remains in the soft sediments of our inland Cretaceous 
 sea. These were veritable Dragons, having a spread of wings 
 of from ten to twenty-five feet. They differed essentially from 
 the smaller Pterodactyls found in the old world, in the entire 
 absence of teeth, showing in this respect a resemblance to 
 modern birds ; and they possess other distinctive characters. 
 They have therefore been placed in a new order, Pteranodontia, 
 from the typical genus Pteranodon, of which five species are 
 known. The only other genus is Nyctosaurus, represented by a 
 single species. All the specimens yet found are from essen- 
 tially the same horizon, in the Chalk of Kansas. The reported 
 discovery of remains of this order from older formations in this 
 country is without foundation. 
 
 The strange Reptiles known as Dinosauria, which, as we 
 have seen, were numerous during the deposition of our Triassic 
 shales and sandstones, have not yet been found in American 
 Jurassic, but were well represented here throughout the Cre- 
 taceous, and at its close became extinct. These animals possess 
 a peculiar interest to the anatomist, since, although reptilian 
 in all their main characters, they show clear affinities with 
 the Birds, and have some features which may point to Mammals. 
 The Cretaceous Dinosaurs were all of large size, and most of 
 them walked on the hind feet alone, like modern Struthious 
 birds. Two well marked types may be distinguished among 
 the remains discovere:! in deposits of this age : the herbiv- 
 orous forms, represented mainly by Hadrosaurus, a near ally of 
 the Iguanodon of Europe ; and their carnivorous enemies, of 
 Which Dryptosaurus (Lcelaps) may be considered typical in this 
 country, and Megalosaurus in Europe. Near the base of our 
 Cretaceous formation, in beds which I regard as the equivalent 
 of the European Wealden, the most gigantic forms of this 
 order yet discovered have recently been brought to light. One 
 of these monsters (Titanosaurus montanus), from Colorado, is 
 by far the largest land animal yet discovered; its dimensions 
 3 
 
18 
 
 being greater than was supposed possible, in an animal that 
 lived and moved upon the land. It was some fifty or sixty 
 feet in length, and, when erect, at least thirty feet in height. 
 It doubtless fed upon the foliage of the mountain forests, 
 portions of which are preserved with its remains. With Titan- 
 osaurus, the bones of smaller Dinosaurs, one (Nanosaurus) not 
 larger than a Cat, as well as those of Crocodiles and Turtles, 
 are not uncommon. The recent discovery of these interesting 
 remains, many and various, in strata that had long been pro- 
 nounced by professional explorers barren of vertebrate fossils, 
 should teach caution to those who decline to accept the imper- 
 fection of our knowledge to-day as a fair plea for the supposed 
 absence of intermediate forms. 
 
 In the marine Cretaceous beds of the West, only a single 
 Dinosaur {Hadrosaurus agilis), has been found, but in the higher 
 fresh-water beds, which mark the close of this formation, their 
 remains are numerous, and indicate several well marked species, 
 if not genera. In the marine beds on the Atlantic Coast, the 
 bones of Dinosaurs are frequently met with, and in the Upper 
 Cretaceous Green sand of New Jersey, the type specimens of 
 Hadrosaurus and Dryptosaurus were found. In Cretaceous 
 fresh-water deposits on the coast of Brazil, remains of this order 
 occur, but the specimens hitherto discovered are not sufficiently 
 characteristic for accurate determination. This is unfortunately 
 true of many Dinosaurian fossils from North America, but the 
 great number of these Eeptiles which lived here during the 
 Cretaceous Period promises many future discoveries, and sub- 
 stantial additions to our present knowledge of the group. 
 
 The first appearance of Birds in America, according to our 
 present knowledge, was during the Cretaceous Period, although 
 many announcements have been made of their existence in 
 preceding epochs. The evidence of their presence in the Trias, 
 based on footprints and other impressions, is, at present, as we 
 have seen, without value; although we may confidently await 
 their discovery there, if not in older formations. Archwopteryx, 
 from the European Jura, the oldest bird known, and now 
 
19 
 
 fortunately represented by more than a single specimen, 
 clearly indicates a much higher antiquity for the class. The 
 earliest American forms, at present known, are the Odontornithes, 
 or Birds with teeth, which have been exhumed within the last 
 few years, from the Chalk of Kansas. The two genera, Hes- 
 perornis and Ichthyornis, are types of distinct orders, and differ 
 from each other and from Archceopteryx much more than do 
 any existing birds among themselves ; thus showing that Birds 
 are now a closed type, and that the key to the history of the 
 class must be sought for in the distant past. 
 
 In Hesperornis, we have a large aquatic bird, nearly six feet 
 in length, with a strange combination of characters. The jaws 
 are provided with teeth, set in grooves ; the wings were rudi- 
 mentary, and useless ; while the legs were very similar to those 
 of modern diving birds. This last feature was merely an adap- 
 tation, as the more important characters are Struthious, showing 
 that Hesperornis was essentially a carnivorous swimming Ostrich. 
 Ichthyornis, a small flying bird, was stranger still, as the teeth 
 were in sockets; and the vertebrae biconcave, as in Fishes, 
 and a few Reptiles. Apatornis and other allied forms occur 
 in the same beds, and probably all were provided with teeth. 
 It is strange that the companions of these ancient toothed 
 Birds should have been Pterodactyls without teeth. In the 
 later Cretaceous beds of the Atlantic Coast, various remains 
 of aquatic Birds have been found, but all are apparently dis- 
 tinct from those of the West. The known genera of Ameri- 
 can Cretaceous birds are, Apatornis, Baptornis, Graculavus, 
 Hesperornis, Ichthyornis, Laornis, Lesiornis, Palceotringa and 
 Telmatornis. These are represented by some twenty species. 
 In Europe, but two species of Cretaceous birds are known, 
 and both are based upon fragmentary specimens. 
 
 During the Tertiary period, Birds were numerous in this 
 country, and all yet discovered appear to have belonged to 
 modern types. The Eocene species described are mostly wading 
 birds, but here, and in the later Tertiary deposits, some charac- 
 teristic American forms make their appearance, strongly fore- 
 
20 
 
 shadowing oar present aviari fauna. The extinct genera are the 
 Eocene Uintornis, related to the Woodpeckers, and Aletornis, 
 which includes several species of Waders. Among the existing 
 genera found in our Tertiary beds are, A guild. Bubo, Meleagris, 
 Grus, Graculus, Pujfinus, and Catarractes. The Great Auk 
 (Alca impennis), which was once very abundant on our North- 
 east Coast, has become extinct within a few years. 
 
 In this brief summary of the past life of Eeptiles and Birds 
 in America, I have endeavored to exclude doubtful forms, and 
 those very imperfectly known, preferring to present the conclu- 
 sions reached by careful study, incomplete though they be, rather 
 than weary you with a descriptive catalogue of all the fossils 
 to which names have been applied. Even this condensed 
 review can hardly fail to give you some conception of the 
 wealth of our continent in the extinct forms of these groups, 
 and thus to suggest what its actual life must have been. 
 
 Although the Trias offers at present the first unquestioned 
 evidence of true Reptiles, we certainly should not be justified 
 in supposing for a moment that older forms did not exist. So 
 too in considering the different groups of Reptiles, which seem 
 to make their first appearance at certain horizons, flourish- for 
 a time, and then decline, or disappear, every day brings evidence 
 to show that they are but fragments of the unraveled strands 
 which converge in the past to form the mystic cord uniting all 
 life. If the attempt is made to follow back any single thread, 
 and thus trace the lineage of a group, we are met by difficulties 
 which the science of to-day can only partially remove. And yet 
 the anatomist constantly sees in the fragments which he studios 
 hints of relationship which are to him sure prophecies of future 
 discoveries. 
 
 The genealogy of the Chelonia is at present unknown, and 
 our American extinct forms, so far as we now have them, 
 throw little light on their ancestry. This is essentially true, 
 also, of our Plesiosauria, Lacertilia and Ophidia, although sug- 
 gestive facts are not wanting to indicate possible lines of 
 descent. With the Crocodilia, however, the case seems to be 
 
21 
 
 different, and Huxley has clearly pointed out the path for 
 investigation. It is probable that material already exists in 
 our museums for tracing the group through several important 
 steps in its development. We have already seen that the 
 modern procoelian type of this order goes back only to the 
 Upper Cretaceous, while the Belodonts, of our Triassic rocks, 
 with their biconcave vertebras, are the oldest known Croco- 
 dilians. Our Jurassic, unfortunately, throws but little light on 
 the intermediate forms, but we know that the line was con- 
 tinued, as it was in the old world through Tekosaurus. The 
 beds of the Rocky Mountain Wealden have just furnished us 
 with a genuine "missing link," a saurian (Diplosaurus) with 
 essentially the skull and teeth of a modern Crocodile, and the 
 vertebras of its predecessor from the Trias. This peculiar rep- 
 tile clearly represents an important stage in the progressive 
 series, and evidently one soon after the separation of the Croc- 
 odile branch from the main stem. The modern Gavial type 
 appears to have been developed about the same time, as the form 
 was well established in the Upper Cretaceous genus, Thoraco- 
 saurus. The Teleosaurian group, with biconcave vertebrae, 
 evidently the parent stock of Crocodilians, became extinct with 
 Hyposaurus of the same horizon, leaving the Crocodile and 
 Gavial, with their more perfect procoelian vertebrae, to contend 
 for the supremacy. In the early Eocene, both of these types 
 were abundant, but some of the Crocodiles possessed characters 
 pointing towards the Alligators, which do not appear to have 
 been completely differentiated until later. 
 
 Nothing is really known to-day of the earlier genealogy of 
 the Pterosauria, but our American forms, without teeth, are 
 clearly the last stage in their development before this peculiar 
 group became extinct. The oldest European form, Dimorphodon, 
 from the Lower Lias, had the entire jaws armed with teeth, and 
 was provided with a long tail. The later genus Pterodactylus 
 retained the teeth, but had essentially lost the tail ; while 
 Ramphorhynchus had retained the elongated tail, but had lost 
 the teeth from the fore part of both jaws. In the genus Pterano- 
 
22 
 
 don from the American Cretaceous, the teeth are entirely absent, 
 and the tail is a mere rudiment. In the gradual loss of the 
 teeth and tail, these reptiles followed the same path as Birds, and 
 might thus seem to approach them, as many have supposed. 
 This resemblance, however, is only a superficial one, as a study 
 of the more important characters of the Pterodactyls shows 
 that they are an aberrant type of Reptiles, totally oft' the line 
 through which the Birds were developed. The announcement 
 made not long since in Europe, and accepted by some American 
 authors, that the Plerosauria, in consequence of certain points 
 in their structure, were essentially Birds, is directly disproved 
 by American specimens, far more perfect than those on which 
 the conclusion was based. 
 
 It is now generally admitted by biologists who have made 
 a study of the vertebrates, that Birds have come down to us 
 through the Dinosaurs, and the close affinity of the latter 
 with recent Struthious Birds will hardly be questioned. The 
 case amounts almost to a demonstration, if we compare, with 
 Dinosaurs, their contemporaries, the Mesozoic Birds. The 
 classes of Birds and Reptiles, as now living, are separated by a 
 gulf so profound that a few years since it was cited by the 
 opponents of evolution as the most important break in the 
 animal series, and one which that doctrine could not bridge 
 over. Since then, as Huxley has clearly shown, this gap 
 has been virtually filled by the discovery of bird-like Reptiles 
 and reptilian Birds. Compsognathus and Archceopteryx of the 
 Old World, and Ichihyornis and Hesperornis of the New, are 
 the stepping stones by which the evolutionist of to-day leads 
 the doubting brother across the shallow remnant of the gulf, 
 once thought impassable. 
 
 It remains now to consider the highest group of the Animal 
 Kingdom, the class Mammalia, which includes Man. Of the 
 existence of this class before the Trias we have no evidence, 
 either in this country or in the Old World, and it is a significant 
 fact that at essentially the same horizon in each hemisphere, sim- 
 
23 
 
 ilar low forms of Mammals make their appearance. Although 
 only a few incomplete specimens have been discovered, they 
 are characteristic and well preserved, and all are apparently 
 Marsupials, the lowest Mammalian group which we know in 
 this country, living or fossil. The American Triassic Mam- 
 mals are known at present only from two small lower jaws, on 
 which is based the genus Dromotherium, supposed to be related 
 to the insect-eating Myrmecobius, now living in Australia. 
 
 Although the Jura of Europe has yielded other similar 
 Mammals, we have as yet none of this class from that forma- 
 tion ; while, from rocks of Cretaceous age, no Mammals are 
 known in any part of the world. This is especially to be 
 regretted, as it is evidently to the Cretaceous that we must 
 look for the first representatives of many of our present groups 
 of Mammals, as well as for indications of their more ancient 
 lineage. That some discovery of this nature from the Creta- 
 ceous is near at hand, I cannot doubt, when I consider what the 
 last few years have brought to light in the Eocene. 
 
 In the lowest Tertiary beds of this country, a rich Mam- 
 malian fauna suddenly makes its appearance, and from that 
 time through the Age of Mammals to the present, America 
 has been constantly occupied by this type of life in the greatest 
 diversity of form. Fortunately, a nearly continuous record of 
 this life, as preserved, is now accessible to us, and ensures great 
 additions to our knowledge of the genealogy of Mammals, and 
 perhaps the solution of more profound problems. Before pro- 
 ceeding to discuss in detail American fossil Mammalia, it is 
 important to define the divisions of time indicated in our 
 Tertiary and Post-Tertiary deposits, as these in many cases 
 mark successive stages in the development of the mammals. 
 
 The boundary line between the Cretaceous and Tertiary in 
 the region of the Eocky Mountains has been much in dispute 
 during the last few years, mainly in consequence of the uncer- 
 tain geological bearings of the fossil plants found near this hori- 
 zon. The accompanying invertebrate fossils have thrown little 
 light on the question, which is essentially, whether the great 
 
24 
 
 Lignite series of the West is uppermost Cretaceous, or lowest 
 Eocene. The evidence of the numerous vertebrate remains is, 
 in my judgment, decisive, and in favor of the former view. 
 
 This brings up an important point in Palaeontology, one to 
 which my attention was drawn several years since, namely : 
 the comparative value of different groups of fossils in marking 
 geological time. In examining the subject with some care, I 
 found that, for this purpose, plants, as their nature indicates, 
 are most unsatisfactory witnesses; that invertebrate animals 
 are much better ; and that vertebrates afford the most reliable 
 evidence of climatic and other geological changes. The sub- 
 divisions of the latter group, moreover, and in fact all forms 
 of animal life, are of value in this respect, mainly according 
 to the perfection of their organization, or zoological rank. 
 Fishes, for example, are but slightly affected by changes that 
 would destroy Reptiles or Birds, and the higher Mammals 
 succumb under influences that the lower forms pass through 
 in safety. The more special applications of this general law, 
 and its value in geology, will readily suggest themselves. 
 
 The evidence offered by fossil remains is, in the light of this 
 law, conclusive, that the line, if line there be, separating .our 
 Cretaceous from the Tertiary, must at present be drawn where 
 the Dinosaurs and other Mesozoic vertebrates disappear, and 
 are replaced by the Mammals, henceforth the dominant type. 
 
 The Tertiary of Western America comprises the most exten- 
 sive series of deposits of this age known to geologists, and 
 important breaks in both the rocks and the fossils separate it 
 into three well-marked divisions. These natural divisions are 
 not the exact equivalents of the Eocene, Miocene, and Pliocene 
 of Europe, although usually so considered, and known by the 
 same names ; but, in general, the fauna of each appears to be 
 older than that of its corresponding representative in the other 
 hemisphere; an important fact, not hitherto recognized. This 
 partial resemblance of our extinct faunas to others in regions 
 widely separated, where the formations are doubtless somewhat 
 different in geological age, is precisely what we might expect, 
 
25 
 
 if, as was probable, the main migrations took place from this 
 Continent. It is better at once to recognize this principle, 
 rather than attempt to bring into exact parallelism, formations 
 that were not strictly contemporaneous. 
 
 The freshwater Eocene deposits of our Western Territories, 
 which are in the same region at least two miles in vertical 
 thickness, may be separated into three distinct subdivisions. 
 The lowest of these, resting unconformably on the Cretaceous, 
 has been termed the Vermilion Creek, or Wahsatch, Group. It 
 contains a well-marked mammalian fauna, the largest and most 
 characteristic genus of which is the ungulate Coryphodort, and 
 hence I have called these deposits the Coryphodon Beds. The 
 middle Eocene strata, which have been termed the Green 
 River arid Bridger Series, may be designated as the Dinoceras 
 Beds, as the gigantic animals of this order are only found here. 
 The uppermost Eocene, or the Uintah Group, is especially 
 well characterized by large mammals of the genus Diplacodon, 
 and hence may be termed the Diplacodon Beds. The fauna of 
 each of these three subdivisions was essentially distinct, and the 
 fossil remains of each were entombed in different and successive 
 ancient lakes. It is important to remember that these Eocene 
 lake-basins all lie between the Eocky Mountains on the east 
 and the Wahsatch Range on the west, or along the high 
 central plateau of the Continent. As these mountain chains 
 were elevated, the enclosed Cretaceous sea, cut off from the 
 ocean, gradually freshened, and formed these extensive lakes, 
 while the surrounding land was covered with a luxuriant trop- 
 ical vegetation, and with many strange forms of animal life. 
 As the upward movement of this region continued, these lake- 
 basins, which for ages had been filling up, preserving in their 
 sediments a faithful record of Eocene life-history, were slowly 
 drained by the constant deepening of the outflowing rivers, and 
 they have since remained essentially dry land. 
 
 The Miocene lake-basins are on the flanks of this region, 
 where only land had been since the close of the Cretaceous. 
 These basins contain three faunas, nearly or quite distinct. The 
 4 
 
26 
 
 lowest Miocene, which is only found east of the Eocky Moun- 
 tains, alone contains the peculiar mammals known as the Bron- 
 totheridce, and these deposits may be called the Brontotherium 
 Beds. The strata next above, which represent the middle Mio- 
 cene, have as their most characteristic fossil the genus Oreodon, 
 and are known as the Oreodou Beds. The upper Miocene, which 
 occurs in Oregon, is of great thickness, and from one of its most 
 important fossils, Miohippus, may be designated as the Miohip- 
 pus Series. The climate here during this period was warm 
 temperate. 
 
 Above the Miocene, east of the Eocky Mountains and on the 
 Pacific Coast, the Pliocene is well developed, and is rich in 
 vertebrate remains. The strata rest uncon form ably on the 
 Miocene, and there is a well marked faunal change at this 
 point, modern types now first making their appearance. For 
 these reasons, we are justified in separating the Miocene from 
 the Pliocene at this break; although in Europe where no 
 marked break exists, the line seems to have been drawn at a 
 somewhat higher horizon. Our Pliocene forms essentially a 
 continuous series, although the upper beds may be distin- 
 guished from the lower by the presence of a true Equus, and 
 some other existing genera. The Pliocene climate was similar to 
 that of the Miocene. The Post-Pliocene beds contain many ex- 
 tinct mammals, and may thus be separated from recent deposits. 
 
 Eeturning now to our subject from this geological digression, 
 which will hardly be deemed unprofitable, since I have given 
 you in few words the results of a great deal of hard mountain 
 work, let us consider the Tertiary mammals, as we know 
 them from the remains already discovered, and attempt to 
 trace the history of each order down to the present time. We 
 have seen that a single small Marsupial, from the Trias, is 
 the only mammal found in all the American rocks below the 
 Eocene; and yet in beds of this age, immediately over the 
 Chalk, fossil mammals of many different kinds' abound. 
 
 The Marsupials, strange to say, are here few in number, and 
 diminutive in size; and have as yet been identified only by frag- 
 
27 
 
 mentary specimens, and most of them too imperfect for accurate 
 description. In the higher Eocene deposits, this group is more 
 abundant, but still represented by small animals, most of them 
 insectivorous, or carnivorous in habit, like the existing Opos- 
 sum. From the Miocene and Pliocene, no remains of Marsupials 
 have been described. From the Post-Tertiary, only specimens 
 nearly allied to those now living are known, and most of these 
 were found in the caves of South America. 
 
 The Edentate Mammals are evidently an American type, 
 and on this Continent attained a great development in numbers 
 and size. No Eocene Edentates have been found here, and 
 although their discovery in this formation has been announced, 
 the identification proves to have been erroneous. In the Mio- 
 cene of the Pacific Coast, a few fossils have been discovered 
 which belong to animals of this group, and to the genus Moropus. 
 There are two species, one about as large as a Tapir, and the 
 other nearly twice that size. This genus is the type of a dis- 
 tinct family, the Moropodidce. In the lower Pliocene above, 
 well preserved remains of Edentates of very large size have 
 been found at several widely separated localities in Idaho and 
 California. These belong to the genus Morotherium, of which 
 two species are known. East of the Eocky Mountains, in the 
 lower Pliocene of Nebraska, a large species apparently of the 
 genus Moropus has been discovered. The horizon of these 
 later fossils corresponds nearly with beds in Europe that have 
 been called Miocene. In the Post-Pliocene of North America, 
 gigantic Edentates were very numerous and widely distributed, 
 but all disappeared with the close of that period. These forms 
 were essentially huge Sloths, and the more important genera 
 were Megatherium, Mylodon and Megalonyx. The genera 
 Megalocnus and Myomorphus have been found only in Cuba. 
 
 In South America during the Pliocene or Post-Pliocene, 
 enormous Edentates were still more abundant, and their 
 remains are usually in such perfect preservation as to suggest 
 a very recent period for their extinction. The Sloth tribe 
 is represented by the huge Mylodon, Megatherium, Megalonyx, 
 
28 
 
 Coelodon, Ochotheriutn, Gnathopis, Lestodon, Scelidotherium, and 
 SphcBnodon ; and among the Armadilloes were Chlainydotherium, 
 Eurydon, Glyptodon, fleterodon, Pachytherium and Schistopleurum. 
 Glossotherium, another extinct gen as, is supposed to be allied 
 to the Ant-eaters. 
 
 It is frequently asserted, and very generally believed, that the 
 large number of huge Edentata which lived in North America 
 during the Post-Pliocene, were the results of an extensive 
 migration from South America soon after the elevation of 
 the Isthmus of Panama, near the close of the Tertiary. No 
 conclusive proof of such migration has been offered, and 
 the evidence, it seems to me, so far as we now have it, is 
 directly opposed to this view. No undoubted Tertiary Edentates 
 have _yet been discovered in South America, while we have at 
 least two species in our Miocene, and during the deposition of 
 our lower Pliocene, large individuals of this group were not 
 uncommon as far north as the forty-third parallel of latitude, 
 on both sides of the Rocky Mountains. In view of these facts, 
 and others which I shall lay before you, it seems more natural 
 to conclude from our present knowledge, that the migration, 
 which no doubt took place, was from north to south. The 
 Edentates finding thus in South America a congenial home 
 flourished greatly for a time, and although the larger forms are 
 now all extinct, diminutive representatives of the group still 
 inhabit the same region. 
 
 The Cetacea first appear in the Eocene, as in Europe, and 
 are comparatively abundant in deposits of this age on the 
 Atlantic Coast. The most interesting remains of this order, yet 
 found, belong to the Zeuglodontidw, which are carnivorous 
 whales, and the only animals of the order with teeth implanted 
 by two roots. The principal genera of this family are Zeuglodon 
 and Squalodon, the former genus being represented by gigantic 
 forms, some of which were seventy feet in length. The genus 
 Saurocetes, which includes some small animals of this group, has 
 been found in South America. The Dolphin family (Delphini- 
 dce) are well .represented in the Miocene, both on the Atlantic 
 
29 
 
 and Pacific Coast, The best known genus is Priscodelphinus, of 
 which several species have been described. Several other 
 generic names which have been applied to fragments need not 
 here be enumerated. In none of the Tertiary species of this 
 family were the cervical vertebrae ankylosed. The Sperm 
 Whales (Catodontidce) were also abundant throughout the Ter- 
 tiary, and with them in the earlier beds, various Ziphioid forms 
 have been found. The toothless Bakenidce are only known 
 with certainty as fossils from the later Tertiary and more 
 recent deposits. 
 
 The Sirenians, which appear first in the Eocene of the 
 Old World, occur in the Miocene of our. Eastern Coast, and 
 throughout the later Tertiary. The specimens described have 
 ail been referred to the genus Manatus, and seem closely 
 related to our living species. In the Tertiary of Jamaica, a 
 skull has been found which indicates a new genus, Prorastomus, 
 also allied to the existing Manatee. The genus Rhytina, once 
 abundant on our Northwest Coast, has recently become extinct. 
 
 The Ungulates are the most abundant Mammals in the Ter- 
 tiary, and the most important; since they include a great 
 variety of types, some of which we can trace through their 
 various changes down to the modified forms that represent 
 them to-day. Of the various divisions in this comprehensive 
 group, the Perissodactyle, or odd-toed Ungulates, are evidently 
 the oldest, and throughout the Eocene are the prevailing forms. 
 Although all of the Perissodactyles of the earlier Tertiary are 
 more or less generalized, they are still quite distinct from the 
 Artiodactyles, even at the base of the Eocene. One 
 family, however, the CoryphodontidoB, which is well represented 
 at this horizon, both in America and Europe, although essen- 
 tially Periseodactyle, possesses some characters which point to a 
 primitive Ungulate type from which the present orders have 
 been evolved. Among these characters are the diminutive 
 brain, which in size and form approaches that of the Reptiles, 
 and also the five-toed feet from which all the various forms of 
 the mammalian foot have been derived. Of this family, only 
 
30 
 
 a single genus, Ooryphodon (Bathmodori), is known, but there 
 were several distinct species. They were the largest mammals 
 of the lower Eocene, some exceeding in size the existing Tapirs. 
 
 In the middle Eocene, West of the Kocky Mountains, a 
 remarkable group of ungulates makes its appearance. These 
 animals nearly equaled the Elephant in size, but had shorter 
 limbs. The skull was armed with two or three pairs of horn- 
 cores, and with enormous canine tusks. The brain was propor- 
 tionally smaller than in any other land mammal. The feet had 
 five toes, and resembled in their general structure those of Co- 
 ryphodon, thus indicating some affinity with that genus. These 
 mammals resemble in some respects the Perissodactyles, and in 
 others the Proboscidians, yet differ so widely from any known 
 Ungulates, recent or fossil, that they must be regarded as form- 
 ing a distinct order, the Dinocerata. Only three genera are 
 known, Dinoceras, Tinoceras and Umtatherium, but quite a num- 
 ber of species have been described. During the later part of the 
 middle Eocene, these animals were very abundant for a short 
 time, and then became extinct, leaving apparently no succes- 
 sors, unless possibly we have in the Proboscidians their much 
 modified descendants. Their genetic connection with the 
 Coryphodonts is much more probable, in view of what we 
 now know of the two groups. 
 
 Besides these peculiar Mammals, which are extinct, and 
 mainly of interest to the Biologist, there were others in the 
 early Tertiary which remind us of those at present living 
 around us. When a student in Germany some twelve years 
 ago, I heard a world-renowned Professor of Zoology gravely 
 inform his pupils that the Horse was a gift of the Old World 
 to the New, and was entirely unknown in America until 
 introduced by the Spaniards. After the lecture, I asked him 
 whether no earlier remains of horses had been found on 
 this Continent, and was told in reply that the reports to that 
 effect were too unsatisfactory to be presented as facts in science. 
 This remark led me, on my return, to examine the subject 
 myself, and I have since unearthed, with my own hands, not less 
 
31 
 
 than thirty distinct species of the horse tribe, in the Tertiary 
 deposits of the West alone ; and it is now, I think generally 
 admitted that America is, after all, the true home of the Horse. 
 
 I can offer you no better illustration than this of the advance 
 vertebrate palaeontology has made during the last decade, or of 
 the important contributions to this progress which our Rocky 
 Mountain region has supplied. 
 
 The oldest representative of the horse, at present known, is 
 the diminutive Eohippus from the lower Eocene. Several spe- 
 cies have been found, all about the size of a fox. Like most 
 of the early mammals, these Ungulates had forty-four teeth, 
 the molars with short crowns, and quite distinct in form from 
 the premolars. The ulna and the fibula were entire and dis- 
 tinct, and there were four well developed toes and a rudiment 
 of another on the fore feet, and three toes behind. In the 
 structure of the feet, and in the teeth, the Eohippus indicates 
 unmistakably that the direct ancestral line to the modern horse 
 has already separated from the other Perissodactyles. In the 
 next higher division of the Eocene, another genus (Orohippus) 
 makes its appearance, replacing Eohippus, and showing a 
 greater, although still distant, resemblance to the Equine type. 
 The rudimentary first digit of the fore foot has disappeared, 
 and the last premolar has gone over to the molar series. Oro- 
 hippus was but little larger than Eohippus, and in most other 
 respects very similar. Several species have been found in the 
 same horizon with Dinoceras, and others lived during the upper 
 Eocene with Diplacodon, but none later. 
 
 Near the base of the Miocene, in the Brontotherium beds, 
 we find a third closely allied genus, Mesoliippus, which is about 
 as large as a sheep, and one stage nearer the horse. There are 
 only three toes and a rudimentary splint bone on the fore feet, 
 and three toes behind. Two of the premolar teeth are quite 
 like the molars. The ulna is no longer distinct, or the fibula 
 entire, and other characters show clearly that the transition is 
 advancing. In the upper Miocene, Mesohippus is not found, 
 but in its place a fourth form, Miohippus, continues the line. 
 
32 
 
 This genus is near the Anchitherium of Europe, but presents 
 several important differences. The three toes in each foot are 
 more nearly of a size, and a rudiment of the fifth metacarpal 
 bone is retained. All the known species of this genus are larger 
 than those of Mesohippus, and none pass above the Miocene. 
 
 The genus Protohippus of the lower Pliocene, is yet more 
 equine, and some of its species equaled the ass in size. There 
 are still three toes on each foot, but only the middle one, cor : 
 responding to the single toe of the horse, comes to the ground. 
 This genus resembles most nearly the Hipparion of Europe. 
 In the Pliocene, we have the last stage of the series before 
 reaching the horse, in the genus Pliohippus, which has lost the 
 small hooflets, and in other respects is very equine. Only in 
 the upper Pliocene, does the true Equus appear, and complete 
 the genealogy of the Horse, which in the Post-Tertiary roamed 
 over the whole of North and South America, and soon after 
 became extinct. This occurred long before the discovery of 
 the Continent by Europeans, and no satisfactory reason for the 
 extinction has yet been given. Besides the characters I have 
 mentioned, there are many others, in the skeleton, skull, teeth, 
 and brain of the forty or more intermediate species, .which 
 show that the transition from the Eocene Eoliippus to the 
 modern Equus, has taken place in the order indicated, and I 
 believe the specimens now at New Haven will demonstrate 
 the fact to any anatomist. They certainly carried prompt 
 conviction to the first of anatomists, who was the honored guest 
 of the Association a year ago, whose genius had already indi- 
 cated the later genealogy of the horse in Europe, and whose 
 own researches so well qualified him to appreciate the evidence 
 here laid before him. Did time permit, I might give you at 
 least a probable explanation of this marvellous change, but 
 justice to the comrades of the horse in his long struggle for 
 existence demands that some notice of their efforts should be 
 placed on record. 
 
 Beside the Horse and his congeners, the only existing Peris- 
 sodactyles are the Rhinoceros and the Tapir. The last is the 
 
33 
 
 oldest type, but the Rhinoceros bad near allies throughout the 
 Tertiary ; and, in view of the continuity of the equine line, it is 
 well worth while to attempt to trace his pedigree. At the 
 bottom of the Eocene, in our Western lake-basins, the tapiroid 
 genus Helaletes is found, represented by numerous small mam- 
 mals hardly larger than the diminutive horses of that day. In 
 the following epoch of the Eocene, the closely allied Ilyracliyus 
 was one of the most abundant animals. This genus was nearly 
 related to the Lophiodon of Europe, and in its teeth and skele- 
 ton strongly resembled the living Tapir ; whose ancestry, to 
 this point, seems to coincide with that of the Rhinoceros we 
 are considering. Strangely enough, the Rhinoceros line, before 
 it becomes distinct, separates into two branches. In the upper 
 part of the Dinoceras Beds, we have the genus Colonoceras, 
 which is really a Hyrachyus with a transverse pair of very 
 rudimentary horn-cores on the nasal bones. In the lower 
 Miocene west of the Rocky Mountains, this line seems to pass 
 on through the genus Dicer atfierium, and in the higher Miocene 
 this genus is well represented. Some of the species nearly 
 equaled in size the existing Rhinoceros, which Diceraikerium 
 strongly resembled. The main difference between them is a 
 most interesting one. The rudimentary horn-cores on the 
 nasals, seen in Colonoceras, are in Diceratherium developed into 
 strong bony supports for horns, which were placed transversely, 
 as in the Ruminants, and not on the median line, as in all 
 existing forms of Rhinoceros. In the Pliocene of the Pacific 
 Coast, a large Rhinoceros has been discovered, which may 
 be a descendant of Diceratherium, but as the nasal bones have 
 not been found, we must wait for further evidence on this 
 point. Returning now to the other branch of the Rhinoceros 
 group, which left their remains mainly East of the Rocky 
 Mountains, we find that all the known forms are hornless. 
 The upper Eocene genus Amynodon is the oldest known 
 Rhinoceros, and by far the most generalized of the family. 
 The premolars are all unlike the molars, the four canines are 
 of large size, but the inner incisor in each jaw is lost in the 
 5 
 
34 
 
 fully adult animal. The nasals were without horns. There 
 were four toes in front, and three behind. The genus Hyrac- 
 odon, of the Miocene, which is essentially a Rhinoceros, has 
 a full set of incisor and canine teeth; and the molars are so 
 nearly like those of its predecessor Hyrachyus, that no one will 
 question the transformation of the older into the newer type. 
 Hyracodon, however, appears to be off the true line, for it has 
 but three toes in front. In the higher Miocene beds, arid 
 possibly with Hyracodon, occurs a larger Rhinoceros, which 
 has been referred to the genus Aceratherium. This form has 
 lost the canine and one incisor above, and two incisors below. 
 In the Pliocene are several species closely related, and of large 
 size. Above the Pliocene in America, no vestiges of the 
 Rhinoceros have been found, and our American forms doubt- 
 less became extinct at the close of this period. 
 
 The Tapir is clearly an old American type, and we have 
 seen that, in the Eocene, the genera Helaletes and Hyrachyus 
 were so strongly tapiroid in their principal characters, that the 
 main line of descent probably passed through them. It is 
 remarkable that the Miocene of the West, so greatly developed as 
 it is on both sides of the Rocky Mountains, should have-yielded 
 but a few fragments of tapiroid mammals, and the same is true 
 of the Pliocene of that region. In the Miocene of the Atlantic 
 Coast, too, only a few imperfect specimens have been found. 
 These forms all apparently belong to the genus Tapiravus, 
 although most of them have been referred to Lophiodon, a lower 
 Eocene type. In the Post-Tertiary, a true Tapirus was abun- 
 dant, and its remains have been found in various parts of North 
 America. The line of descent, although indistinct through 
 the middle and upper Tertiary, was doubtless continuous in 
 America, and several species exist at present, from Mexico 
 southward. It is worthy of notice that the species North of 
 the Isthmus of Panama appear all to be generically distinct 
 from those of South America. 
 
 In addition to these three Perissodactyle types which, as 
 the fittest, have alone survived, and whose lineage I have 
 
35 
 
 endeavored to trace, there were many others in earl}' Tertiary 
 times. Some of these disappeared with the close of the 
 Eocene, while others continued, and assumed strange special- 
 ized shapes in the Miocene, before their decline and extinction. 
 One series of the latter deserves especial mention, as it includes 
 one of the most interesting families of our extinct animals. 
 Among the large mammals in the lower Eocene is Limnohyus, 
 a true Perissodactyle, but only known here from fragments of 
 the skeleton. In the next higher beds, this genus is well 
 represented, and with it is found a nearly allied form, Palceo- 
 syops. In the upper Eocene, both have left the field, and the 
 genus Diplacodon, a very near relative, holds the supremacy. 
 The line seems clear through these three genera, but on 
 crossing the break' into the Miocene, we have, apparently as 
 next of kin, the huge Brontotheridce. These strange beasts show 
 in their dentition and some other characters the same transition 
 steps beyond Diplacodon, which that genus had made beyond 
 Palceosyops. The Brontotheridce were nearly as large as the 
 Elephant, but had much shoTter limbs. The skull was elon- 
 gated, and had a transverse pair of large horn-cores on the 
 rnaxillaries, in front of the orbits, like the middle pair in 
 Dinoeeras. There were four toes in front, and three behind, 
 and the feet were similar to those of the Rhinoceros. There 
 are four genera in this group, Brontotherium ; Diconodon; Afeno- 
 dus (Titanotherium) ; and Megacerops, which have been found 
 only in the lowest Miocene, east of the Rocky Mountains. 
 
 In the higher Miocene beds of Oregon, an allied genus, 
 Chalicotherium, makes its appearance. It is one stage further 
 on in the transition, and perhaps a descendant of the Bronto- 
 theridce ; but here, so far as now known, the line disappears. 
 It is a suo-gestive fact, that this genus has now been found in 
 
 CO O 
 
 Western America, China, India, Greece, Germany and France, 
 indicating thus, as I believe, the path by which many of our 
 ancient mammals helped to people the so-called Old World. 
 
 The Artiodactyles, or even-toed Ungulates, are the most 
 abundant of the larger mammals now living; and the group 
 
36 
 
 dates back at least to the lowest Eocene. Of the two well 
 marked divisions of this order, the Bunodonts and the Seleno- 
 donts, as happily defined by Kowalevsky, the former is the 
 older type, which must have separated from the Perissodactyle 
 line after the latter had become differentiated from the prim- 
 itive Ungulate. In the Coryphodon Beds of New Mexico, 
 occurs the oldest Artiodactyle yet found, but it is at present 
 known only from fragmentary specimens. These remains are 
 clearly Suilline in character, and belong to the genus EoJiyus. 
 In the beds above, and possibly even in the same horizon, 
 the genus Helohyus is not uncommon, and several species are 
 known. The molar teeth of this genus are very similar to 
 those of the Eocene Hyracotherium, of Europe, which is sup- 
 posed to be a Perissodactyle, while Helohyus certainly is not, 
 but apparently a true lineal ancestor of the existing pigs. 
 In every vigorous primitive type which was destined to survive 
 many geological changes, there seems to have been a tendency 
 to throw off lateral branches, which became highly specialized 
 and soon died out, because they are unable to adapt themselves 
 to new conditions. The narrow path of the persistent Suilline 
 type, throughout the whole Tertiary, is strown with the remains 
 of such ambitious offshoots, while the typical pig, with an 
 obstinacy never lost, has held on in spite of Catastrophes and 
 Evolution, and still lives in America to-day. In the lower 
 Eocene, we have in the genus Parahyus apparently one of these 
 short-lived, specialized branches. It attained a much larger 
 size than the true lineal forms, and the number of its teeth 
 was reduced. In the Dinoceras Beds, or middle Eocene, we 
 have still, on or near the true line, Hdohyus, which is the 
 last of the series known from the American Eocene. All 
 these early Suillines, with the possible exception of Parahyus, 
 appear to have had at least four toes, all of usable size. 
 
 In the lower Miocene, we find the genus Perchoerus, seem- 
 ingly a true Suilline, and with it remains of a larger form, 
 Elotherium, are abundant. The latter genus occurs in Europe 
 in nearly., the same horizon, and the specimens known from 
 
37 
 
 each Continent agree closely in general characters. The name 
 Pelonax has been applied erroneously to some of the American 
 forms ; but the specimens on which it was based clearly belong 
 to Elotherium. This genus affords another example of the 
 aberrant Suilline offshoots, already mentioned. Some of the 
 species were nearly as large as a Rhinoceros, and in all there were 
 but two serviceable toes; the outer digits, seen in living ani- 
 mals of this group, being represented only by small rudiments 
 concealed beneath the skin. In the upper Miocene of Oregon, 
 Suillines are abundant, and almost all belong to the genus 
 Thinohyus, a near ally of the modern Peccary (Dicotyles), but 
 having a greater number of teeth, and a few other distinguish- 
 ing features. In the Pliocene, Suillines are still numerous, and 
 all the American forms yet discovered are closely related to 
 Dicotyles. The genus Platygonus is represented by several 
 species, one of which was very abundant in the Post-Tertiary 
 of North America, and is apparently the last example of a side 
 branch, before the American Suillines culminate in existing 
 Peccaries. The feet in this' species are more specialized than 
 in the living forms, and approach some of the peculiar features 
 of the ruminants ; as for example a strong tendency to coales- 
 cence in the meta podia! bones. The genus Platygonus became 
 extinct in the Post- Tertiary, and the later and existing species 
 are all true Peccaries. No authenticated remains of the genera 
 Sus, Porous, Phacochcerus, or the allied Hippopotamus, the Old 
 World Suillines, have been found in America, although several 
 announcements to that effect have been made. 
 
 In the series of generic forms between the lower Eocene 
 Eohyus and the existing Dicotyles. which I have very briefly 
 discussed, we have apparently the ancestral line ending in the 
 typical American Suillines. Although the demonstration is 
 not yet as complete as in the lineage of the Horse, this is not 
 owing to want of material, but rather to the fact that the 
 actual changes which transformed the early Tertiary pig into 
 the modern Peccary were comparatively slight, so far as they 
 are indicated in the skeletons preserved, while the lateral 
 
38 
 
 branches were so numerous as to confuse the line. It is clear, 
 however, that from the close of the Cretaceous to the Post- 
 Tertiary, the Bunodont Artiodactyles were especially abun- 
 dant on this Continent, and only recently have approached 
 extinction. 
 
 The Selenodont division of the Artiodactyles is a more 
 interesting group and, so far as we now know, makes its first 
 appearance in the upper Eocene of the West, although forms, - 
 apparently transitional, between it and the Bunodonts occur in 
 the Dinoceras Beds, or middle Eocene. These belong to the 
 genus Homacodon, which is very nearly allied to Ilelohyus and 
 but a single step away from this genus toward the Selenodonts. 
 By a fortunate discovery, a nearly complete skeleton of this 
 rare intermediate form has been brought to light, and we are 
 thus enabled to define its characters. Several species of 
 Homacodon are known, all of small size. This primitive 
 Selenodont had forty-four teeth, which formed a nearly con- 
 tinuous series. 
 
 The molar teeth are very similar to those of ffelohyus, but 
 the cones on the crowns have become partially triangular in 
 outline, so that when worn, the Selenodont pattern is clearly 
 recognizable. The first and second upper molars, moreover, 
 have three distinct posterior cusps, and two in front; a peculiar 
 feature, which is seen also in the European genera Dichobune 
 and Cainotherium. There were four toes on each foot, and the 
 metapodial bones were distinct. The type species of this genus 
 was about as large as a cat. With Helohyus, this genus forms 
 a well marked family, the Helohyidw. 
 
 In the Diplacodon horizon of the upper Eocene, the Seleno- 
 dont dentition is no longer doubtful, as it is seen in most of 
 the Artiodactyla yet found in these beds. These animals are 
 all small, and belong to at least three distinct genera. One of 
 these, Eomeryx, closely resembles Homacodon in most of its 
 skeleton, and has four toes, but its teeth show well marked 
 crescents, and a partial transition to the teeth of Hyopolamus, 
 from the Eocene of Europe. With this genus, is another 
 
39 
 
 (Parameryx), also closely allied to Homacodon, but apparently a 
 straggler from the true line, as it has but three toes behind. 
 The most pronounced Selenodont in the upper Eocene is the 
 Oromeryx, which genus -appears to be allied to the existing 
 Deer family, or Cervidce, and if so is the oldest known repre- 
 sentative of the group. These facts are important, as it has 
 been supposed, until very recently, that our Eocene contained 
 no even-hoofed mammals. 
 
 In -the lowest Miocene of the West, no true crescent-toothed 
 Arliodactyla have as yet been identified, with the exception 
 of a single species of Hyopoiamus ; but in the overlying beds 
 of the middle Miocene, remains of the Oreodoniidw occur in 
 such vast numbers as to indicate that these animals must 
 have lived in large herds around the borders of the lake-basins 
 in which their remains have been entombed. These basins are 
 now the denuded deserts so well termed Mauvaises Terres by 
 the early French trappers. The least specialized, and apparently 
 the oldest, genus of this group is Agriochcerus, which so nearly 
 resembles the older Plyopotdmus, and the still more ancient 
 Eomeryx, that we can hardly doubt that they all belonged to 
 the same ancestral line. The typical Oreodonts are the genera 
 Oreodon and Eporeodon, which have been aptly termed by 
 Leidy, ruminating hogs. They had forty-four teeth, and four 
 well developed toes on each foot. The true Oreodons, which 
 were most numerous east of the Rocky Mountains, were about 
 as large as the existing Peccary, while Eporeodon, which was 
 nearly twice this size, was very abundant in the Miocene of 
 the Pacific slope. 
 
 In the succeeding Pliocene formation, on each side of the 
 Rocky Mountains, the genus Merychyus is one of the prevailing 
 forms, and continues the line on from the Miocene, where the 
 true Oreodons became extinct. Beyond this, we have the genus 
 Merychochmrus, which is so nearly allied to the last, that they 
 would be united by many naturalists. With the close of the 
 Pliocene, this series of peculiar ruminants abruptly terminates, 
 no member surviving until the Post-Tertiary, so far as known. 
 
40 
 
 A most interesting line, that leading to the Camels and Lla- 
 mas, separates from the primitive Selenodont branch in the 
 Eocene, probably through the genus Parameryx. In the Mio- 
 cene, we find in Poebrotherium and some nearly allied forms 
 unmistakable indications that the Cameloid type of ruminant 
 had already become partially specialized, although there is a 
 complete series of incisor teeth, and the metapodial bones are 
 distinct. In the Pliocene, the Camel tribe was, next to the 
 Horses, the most abundant of the larger mammals. The line is 
 continued through the genus Procamelus, and perhaps others, 
 and in this formation the incisors first begin to diminish, and 
 the metapodials to unite. In the Post-Tertiary we have a true 
 Auchenia, represented by several species, and others in South 
 America, where the Alpacas and Llamas still survive. From 
 the Eocene almost to the present time, North America has been 
 the home of vast numbers of the Camelidce, and there can be 
 little doubt that they originated here, and migrated to the Old 
 World. 
 
 Returning once more to the upper Eocene, we find another 
 line of descent starting from Oromeryx, which, as we have 
 seen, had apparently then just become differentiated from the 
 older Bunodont type. Throughout the middle and upper 
 Miocene, this line is carried forward by the genus Leptomeryx 
 and its near allies, which resemble so strongly the Pliocene 
 Cervidce that they may fairly be regarded as their probable 
 progenitors. Possibly some of these forms may be related to 
 the Tragulidce, but at present the evidence is against it. 
 
 The Deer family has representatives in the upper Miocene of 
 Europe, which contains fossils strongly resembling the fauna of 
 our lower Pliocene, a fact always to be borne in mind in com- 
 paring the horizon of any group in the two continents. Several 
 species of Cervidce, belonging to the genus Cosoryx, are known 
 from the lower Pliocene of the West, and all have very small 
 antlers, divided into a single pair of tynes. The statement 
 recently published, that most of these antlers had been broken 
 during the. -life of the animals, is unsupported by any evidence, 
 
41 
 
 and is erroneous. These primitive Deer do not have the orbit 
 closed behind, and they have all the four metapodial bones 
 entire, although the second and fifth are very slender. In the 
 uppei' Pliocene, a true C&rvus of large size has been discovered. 
 In the Post-Tertiary, Cervus, Akes, and Tarandus have been met 
 with, the latter far south of its present range. In the caves of 
 South America, remains of Cervus have been found, and also two 
 species of Antelopes, one referred to a new genus, Leptothei ium. 
 
 The Hollow-horned Ruminants, in this country, appear to 
 date back no further than to the lower Pliocene, and here only 
 two species of Bid n have as yet been discovered. In the Post- 
 Tertiary this geniis was represented by numerous individuals 
 and several species, some of large size. The Mask Ox (Ouibos) 
 was not uncommon during some parts of this epoch, and 
 its remains are widely distributed. 
 
 No authentic fossil remains of true Sheep, Goats, or Giraffes 
 have as yet been found on this continent. 
 
 The Proboscideans, which are now separated from the typi- 
 cal Ungulates as a distinct order, make their first appearance in 
 North America in the lower Pliocene, where several species of 
 Mastodon have been found. This genus occurs, also, in the 
 upper Pliocene, and in the Post-Tertiary; although some of 
 the remains attributed to the latter are undoubtedly older. 
 The Pliocene species all have a band of enamel on the tusks, 
 and some other peculiarities observed in the oldest Mastodons 
 of Europe, which are from essentially the same horizon. Two 
 species of this genus have been found in South America, in 
 connection with the remains of extinct Llamas and Horses. 
 The genus Elephas is a later form, and has not yet been iden- 
 tified in this country below the upper Pliocene, where one 
 gigantic species was abundant. In the Post-Pliocene, remains 
 of this genus are numerous. The hairy Mammoth of the Old 
 World (Elephas primigenius) was once abundant in Alaska, and 
 great numbers of its bones are now preserved in the frozen 
 cliffs of that region. This species does not appear to have 
 extended east of the Rocky Mountains, or south of the Colum- 
 6 
 
42 
 
 bia River, but was replaced there by the American Elephant, 
 which preferred a milder climate. Remains of the latter have 
 been met with in Canada, throughout the United States, and in 
 Mexico. The last of the American Mastodons and Elephants 
 became extinct in the Post-Tertiary. 
 
 The order Toxodontia includes two very peculiar genera, 
 Toxodon and Nesodon, which have been found in the Post-Ter- 
 tiary deposits of South America. These animals were of huge- 
 size, and possessed such mixed characters that their affinities 
 are a matter of considerable doubt. They are thought to be 
 related to the Ungulates, Rodents, and Edentates, but as the 
 feet are unknown, this cannot at present be decided. 
 
 Macrauchenia and Homalodontotherium are two other peculiar 
 genera from South America, now extinct, the exact affinities 
 of which are uncertain. AnoplotJierium and Palceolherium, so 
 abundant in Europe, have not been found in our North 
 American Tertiary deposits, although reported from South 
 America. 
 
 Perhaps the most remarkable mammals yet found in Amer- 
 ica are the Tillodontia, which are comparatively abundant in 
 the lower and middle Eocene. These animals seem to. com- 
 bine the characters of several different groups, viz : the Car- 
 nivores, Ungulates, and Rodents. In the genus Tillotherium, 
 the type of the order, and of the family Tillotheridce, the skull 
 resembles that of the Bears ; the molar teeth are of the 
 ungulate type; while the large incisors are very similar to those 
 of Rodents. The skeleton resembles that of the Carnivores, 
 but the scaphoid and lunar bones are distinct, and there is a 
 third trochanter on the femur. The feet are plantigrade, and 
 each had five digits, all with long pointed claws. In the 
 allied genus Stylinodon, which belongs to a distinct family, the 
 StylinodoniidcK, all the teeth were rootless. Some of these 
 animals were as large as a Tapir. The genus Dryptodon has 
 been found only in the Coryphodon beds of New Mexico, while 
 Tillotherium and Stylinodon occur in the middle Eocene of 
 Wyoming. Anchippodus probably belongs to this group, which 
 
43 
 
 may perhaps include some other forms that have been named 
 from fragmentary specimens. 
 
 The Rodents are an ancient type, and their remains are not 
 unfrequeutly disinterred in the strata of our lowest fresh-water 
 Eocene. The earliest known forms are apparently all related 
 to the Squirrels, and the most common genus is Sciwravus, 
 which continued throughout the Eocene. A nearly allied form, 
 which may prove to be the same, is Paramys, the species of 
 which are larger than those of the older type. In the Dino- 
 ceras beds, the genus Colonomys is found, and the specimens 
 preserved point to the Muridce, as the nearest living allies. A 
 peculiar genus, Apaiemys, which also occurs in the middle 
 Eocene, has gliriform incisors, but the molars resemble those of 
 Insectivores. All the Eocene Rodents are of small size, the 
 largest being about as large as a rabbit. 
 
 In the middle and upper Miocene lake-basins of the West, 
 Rodents abound, but all are of moderate size. The Hares first 
 appear in the Oreodon beds, and continue in considerable num- 
 bers through the rest of the Tertiary and Post-Tertiary to the 
 present day. In these beds, the most common forms belong to 
 the Leporidw, and mainly to the genus Palocolagus. The Squirrel 
 family is represented by Ischyromys, the Muridce by the genus 
 Eumys, and the Beavers by Palceocastor. In the upper Miocene 
 of Oregon, most of the same genera are found, and with them 
 some peculiar forms, very unlike anything now living. One of 
 these is the genus Allomys* possibly related to the flying 
 Squirrels, but having molar teeth somewhat like those of the 
 Ungulates. In the Pliocene, east and west of the Rocky Moun- 
 tains, Rodents continue abundant, but most of them belong to 
 existing genera. Among these are Castor, Hystrioc, Cynomys, 
 Geomys, Lepus and Hesperomys, In the Post-Tertiary, the 
 gigantic beaver, Castoroides, was abundant throughout most of 
 North America. Hydrochcerus has been found in South Caro- 
 lina. In the caves of the island of Anguilla, in the West 
 Indies, remains of large extinct Rodents belonging to the Chin- 
 cliillidce have been discovered. 
 
44 
 
 The early Tertiary Rodents known from South America are 
 the genera Megamys, Theridromys, and a large species referred 
 to Arvicola. In Brazil, the Pliocene Rodents found are referred 
 to the existing genera Cavia, Kerodon, Lagostomus, Ctenomys, 
 Hesperomys, Oxymycterus, Arvicola and Lepus. A new genus, 
 Cardiodus, described from this horizon, is a true Rodent, but 
 the peculiar Typotherium, which has been referred to this order 
 by some authorities, has perhaps other affinities. In the' 
 Post-Tertiary, the Rodents were very abundant in South 
 America, as they are at present. The species are in most 
 instances distinct from those now living, but the genera are 
 nearly the same. The Caviidae were especially numerous. 
 Cercolabes, Myopolamus, and Lagostomus are also found, and two 
 extinct genera, Phyllomys and Lonchophorus, 
 
 The Cheiroptera, or Bats, have not been found in this country 
 below the middle Eocene, where two extinct genera, Nyctilestes 
 and Nyclitherium, are each represented by numerous remains. 
 These fossils all belong to small animals, and, so far as they 
 have been investigated, show no characters of more than generic 
 importance to distinguish them from the Bats of to-day. No 
 other members of this group are known from our Tertiary. 
 In the Post-Tertiary, no extinct species of Bats have been 
 found in North America, but from the caves of Brazil quite 
 a number have been reported. These all belong to genera 
 still living in South America, and most of them to the family 
 Phyllostomidcz. 
 
 The Insectivores date back, in this country, at least to the 
 middle Eocene. Here numerous remains occur, which have 
 been described as belonging to this order, although it is pos- 
 sible that some of them were insect-eating Marsupials. The 
 best known genera are, Hemiaeodon, Centetodon, Talpavus, and 
 Entomacodon ; all represented by animals of small size. In 
 the Miocene, the bones of Insectivores are comparatively abun- 
 dant, and the genera best determined are Ictops and Leptictis. 
 A few specimens only have been found in the Pliocene and 
 Post-Plioeene, most of them related to the Moles. No extinct 
 
Insectivores are known from South America, and no member 
 of the group exists there at present. 
 
 The Carnivora, or true flesh-eating animals, are an old type, 
 well represented in the Eocene, and, as might be expected, 
 these early forms are much less specialized than the living 
 species. In the Coryphodon beds, the genus Limnocyon, 
 allied to the Pterodon of the European Eocene, is abundant. 
 Another genus, apparently distinct, is Prototomus, and several 
 others have been named from fragmentary fossils. In the 
 middle Eocene, Carnivores were still more numerous, and many 
 genera have been discovered. One of these, Limnofelis, was 
 nearly as large as a lion, and apparently allied to the cats, 
 although the typical Felidce seem not yet to have been differen- 
 tiated. Another Carnivore of nearly equal size was Orocyon, 
 which had short massive jaws and broad teeth. Dromocyon and 
 Mesonyx were large animals, allied to Hycenodon. The teeth 
 were narrow, and the jaws long and slender. Among the 
 smaller Carnivores were, Vulpavus, Viverravus, Sinopa, Thino- 
 cyon, and Ziphacodon. 
 
 In our Western Miocene, Carnivores are abundant, and 
 make an approach to modern types. The Felidce, are well rep- 
 resented, the most interesting genus being Afachairodus, which 
 is not uncommon in the Oreodon beds on both sides of the 
 Rocky Mountains. An allied genus is Diniclis, and several 
 smaller Cats are known from about the same horizon. The 
 Canidce are represented by Ampliicyon, a European genus, and 
 by several species of Cants, or a very nearly allied form. The 
 peculiar genus Hycenodon, found also in Europe, and the type of 
 a distinct family, is abundant in the Miocene east of the Rocky 
 Mountains, but has not yet been found on the Pacific Coast. 
 In the Pliocene of both regions, the Canidce are numerous, 
 and all apparently belong to the existing genus Cains. The 
 genus Machairodus is still the dominant form of the Cats, which 
 are abundant, and for the most part belong to the genus Felis. 
 The extinct Leptarctus is supposed to belong to the Ursidce, 
 and if so, is the oldest American representative of this family. 
 
46 
 
 In the Post-Pliocene, the extinct Felidw include species nearly 
 as large as a lion, and smaller forms very similar to those still 
 living. Bears, Kaccoons and Weasels have also been found. 
 
 In the Pliocene of South America, Machairodus represents 
 the Felidte, while the genera Ar cloth erium and Hycenarctus 
 belong to the Bear family. Species of Mustela and Canis have 
 also been found. In the caves of Brazil, the fauna of which 
 is regarded as Post-Pliocene, one species of Machairodus is 
 known, and one of Syncdurus. Canis and Iclicyon, still living 
 in Brazil, and the extinct genus Speoihos, represent the Canidce. 
 Mephitis and Galictis, among the Weasels, were also present, 
 and with them species of Nasua and Arctotheriuin. 
 
 We come now to the highest group of Mammals, the Pri- 
 mates, which includes the Lemurs, the Apes, and Man. This 
 order has a great antiquity, and even at the base of the Eocene 
 we find it represented by several genera belonging to the lower 
 forms of the group. In considering these interesting fossils, it is 
 important to have in mind that the Lemurs, which are usually 
 regarded as Primates, although at the bottom of the scale, are 
 only found at the present day in Madagascar and the adjacent 
 regions of the globe. All the American Monkeys, moreover, 
 belong to one group, much above the Lemurs, while the Old 
 World Apes are higher still, and most nearly approach Man. 
 
 In the lower Eocene of New Mexico, we find a few repre- 
 sentatives of the earliest known Primates, and among them are 
 the genera Lemuravus and Limnotherium, each the type of a 
 distinct" family. These genera became very abundant in the 
 middle Eocene of the West, and with them are found many 
 others, all however, included in the two families, Lemuravidce 
 and Limnotheridce. Lemuravus appears to have been most 
 nearly allied to the Lemurs, and is the most generalized form 
 of the Primates yet discovered. It had forty-four teeth, form- 
 ing a continuous series above and below. The brain was 
 nearly smooth, and of moderate size. The skeleton most 
 resembles that of the Lemurs. A nearly allied genus, belong- 
 ing to the same family, is Hyopsodus. Limnotherium (Tomithe- 
 
47 
 
 ram) also is nearly related to the Lemurs, but shows some affin- 
 ities with the South American Marmosets. This genus had 
 forty teeth. The brain was nearly smooth, and the cerebellum 
 large, and placed mainly behind the cerebrum. The orbits are 
 open behind, and the lachrymal foramen is outside the orbit. 
 Other genera belonging to the Limnotheridce, are, Nolharctos, 
 Hipposyus, Microsyops, Pahmcodon, TJmwlesles and Telmatolestes. 
 Besides these, Antiacodon (Anaptomorphus), Bathrodon and Mes- 
 acodon should probably be placed in the same group. In the 
 Diplacodon Beds, or Upper Eocene, no remains of Primates have 
 yet been detected, although they will doubtless be found there. 
 All the Eocene Primates known from American strata are low 
 generalized forms, with characters in the teeth, skeleton and 
 feet that suggest relationships with the Carnivores, and even 
 with the Ungulates. These resemblances have led paleontolo- 
 gists to refer some imperfect specimens to both these orders. 
 
 In the Miocene lake basins of the West, only a single spe- 
 cies of the Primates has been identified with certainty. This 
 was found in the Oreodon Beds of Nebraska, and belongs to 
 the genus Laopilhecus, apparently related both to the Limno- 
 theridce and to some existing South American Monkeys. In 
 the Pliocene and Post-Pliocene of North America, no remains 
 of Primates have yet been found. 
 
 In the Post-Pliocene deposits of the Brazilian caves, remains 
 of Monkeys are numerous, and mainly belong to extinct spe- 
 cies of Callithrix, Cebus and Jacchus, all living South American 
 genera. Only one extinct genus, Protopiihecus, which embraced 
 animals of large size, has been found in this peculiar fauna. 
 
 It is a noteworthy fact, that no traces of any Anthropoid 
 Apes, or indeed of any Old World Monkeys have yet been 
 detected in America. Man, however, the highest of the Pri- 
 mates, has left his bones and his works from the Arctic Circle 
 to Patagonia. Most of these specimens are clearly Post-Ter- 
 tiary, although there is considerable evidence pointing to the 
 existence of Man in our Pliocene. All the remains yet dis- 
 covered belong to the well-marked genus Homo, and apparently 
 
48 
 
 to a single species, at present represented by the American 
 Indian. 
 
 In tli is rapid review of Mammalian life in America, from its 
 first known appearance in the Trias down to the present time, I 
 have endeavored to state briefly the introduction and succes- 
 sion of the principal forms in each natural group. If time per- 
 mitted, I might attempt the more difficult task of trying to 
 indicate what relations these various groups may possibly bear 
 to each other ; what connection the ancient Mammals of this 
 continent have with the corresponding forms of the Old World; 
 and, most important of all, what real progress Mammalian life 
 has here made since the beginning of the Eocene. As it is, I 
 can only say in summing up, that the Marsupials are clearly 
 the remnants of a very ancient fauna, which occupied this 
 continent millions of years ago, and from which the other 
 Mammals were doubtless all derived, although the direct evi- 
 dence of the transformation is wanting. 
 
 Although the Marsupials are nearly related to the still 
 lower Monotremes, now living in the Australian Region, we 
 have as yet no hint of the path by which these two groups 
 became separated fr.om the inferior vertebrates. Neither have 
 we to-day much ifght as to the genetic connection existing 
 between Marsupials and the placental Mammalia, although it is 
 possible that the different orders of the latter had their origin 
 each from a separate group of the Marsupials. 
 
 The presence, however, of undoubted Marsupials in our 
 lower and middle Eocene, some of them related to the genus 
 DidelpJiys, although remotely, is important evidence as to the 
 introduction of these animals into America. Against this, their 
 supposed absence in our Miocene and Pliocene can have but 
 limited weight, when taken in connection with the fact that 
 they flourished in the Post-Tertiary, and are still abundant. 
 The evidence we now have is quite as strongly in favor of a 
 migration of Marsupials from America to the Old World, as the 
 reverse, which has been supposed by some naturalists. Possi- 
 bly, as Huxley has suggested, both countries were peopled with 
 these low mammals from a continent now submerged. 
 
The Edentate mammals have long been a puzzle to Zoolo- 
 gists, and up to the present time no clew to their affinities with 
 other groups seems to have been detected. A comparison of 
 the peculiar Eocene Mammals which I have called the Tillo- 
 donlia, with the least specialized Edentates, brings to light 
 many curious resemblances in the skull, teeth, skeleton and 
 feet. These suggest relationship, at least, and possibly we 
 may yet find here the key to the Edentate genealogy. At 
 present, the Tillodonts are all from the lower and middle 
 Eocene, while Maropus, the oldest edentate genus, is found in 
 the middle Miocene, and one species in the lower Pliocene. 
 
 The Edentates have been usually regarded as an American 
 type, but the few living forms in Africa, and the Tertiary 
 species in Europe, the oldest known, have made the land 
 of their nativity uncertain. I have already given you some 
 reasons for believing that the Edentates had their first home 
 in North America, and migrated thence to the southern 
 portion of the continent. This movement could not have 
 taken place in the Miocene period, as the Isthmus of Darien 
 was then submerged ; but near the close of the Tertiary, 
 the elevation of this region left a much broader strip of land 
 than now exists there, and over this, the Edentates and other 
 mammals made their way, perhaps urged on by the increasing 
 cold of the glacial winters. The evidence to-day is strongly in 
 favor of such a southern migration. This, however, leaves the 
 Old World Edentates, fossil and recent, unaccounted for; but I 
 believe the solution of this problem is essentially the same, 
 namely : a migration from North America. The Miocene rep- 
 resentatives of this group, which I have recently obtained in 
 Oregon, are older than any known in Europe, and, strangely 
 enough, are more like the latter and the existing African types 
 than like any of our living species. If, now, we bear in mind 
 that an elevation of only 180 feet would, as Dana has said, 
 close Behring's Straits, and give a road thirty miles wide from 
 America to Asia, we can easily see how this migration might 
 have taken place. That such a Tertiary bridge did exist, we 
 7 
 
50 
 
 have much independent testimony, and the known facts all 
 point to extensive migrations of animals over it. 
 
 The Cetacea are connected with the marine Carnivores through 
 the genus Zeuglodon, as Huxley has shown, and the points of 
 resemblance are so marked that the affinity cannot be doubted. 
 That the connection was a direct one, however, is hardly prob- 
 able, since the diminutive brain, large number of simple teeth, 
 and reduced limbs in the Whales, all indicate them to be an- 
 old type, which doubtless branched off from the more primi- 
 tive stock leading to the Carnivores. Our American extinct 
 Cetaceans, when carefully investigated, promise to throw much 
 light upon the pedigree of these strange mammals. As most 
 of the known forms were probably marine, their distribution is 
 of little service in determining their origin. 
 
 That the Sirenians are allied to the Ungulates, is now gen- 
 erally admitted by anatomists, and the separation of the exist- 
 ing species in distant localities suggests that they are the rem- 
 nants of an extensive group, once widely distributed. The 
 large number of teeth in some forms, the reduced limbs and 
 other characters, point back to an ancestry near that of the 
 earliest ungulates. The gradual loss of teeth in the specialized 
 members of this group, and in the Cetaceans, is quite parallel 
 with the same change in Edentates, as well as in Pterodactyls 
 and Birds. 
 
 The Ungulates are so distinct from other groups that they 
 must be one of the oldest natural divisions of mammals, and 
 they probably originated from some herbivorous marsupial. 
 Their large size, and great numbers during Tertiary and Post- 
 tertiary time, render them most valuable in tracing migrations 
 induced by climate, as well as in showing the changes of 
 structure which such a contest for existence may produce. 
 
 In the review of the extinct Ungulates, I have endeavored 
 to show that quite a number of genera usually supposed to 
 belong originally to the Old World are in reality true Amer- 
 ican types. Among these were the Horse, Rhinoceros, and 
 Tapir, all ,the existing odd-toed Ungulates, and besides these 
 
51 
 
 the Camel, Pig, and Deer. All these I believe, and many 
 others, went to Asia from our North West Coast. It must, for 
 the present, remain an open question whether we may not 
 fairly claim the Bovidce, and even the Proboscidea, since both 
 occur in our strata at about the same horizon as on the other 
 continent. On this point there is some confusion, at least in 
 names. The Himalayan deposits called Upper Miocene, and 
 so rich in Proboscideans, indicate in their entire fauna that 
 they are more recent than our Niobrara River beds, which, for 
 apparently good reasons, we regard as Lower Pliocene. The 
 latter appear to be about the same horizon as the Pikermi 
 deposits in Greece, also regarded as Miocene. Believing, how- 
 ever, that we have here a more complete Tertiary series, and a 
 better standard for comparison of faunas, I have preferred to 
 retain the names already applied to our divisions, until the 
 strata of the two continents are more satisfactorily coordinated. 
 
 The extinct Eodents, Bats, and Insect! vores of America, 
 although offering many suggestive hints as to their relation- 
 ship with other groups, and their various migrations, cannot 
 now be fully discussed. There is little doubt, however, that 
 the Rodents are a New World type, and, according to present 
 evidence, they probably had their origin in North America. 
 The resemblance in so many respects of this order to the 
 Proboscideans is a striking fact, not yet explained by the im- 
 perfectly known genealogy of either group. 
 
 The Carnivores, too, I must pass by, except to call attention 
 to a few special forms which accompanied the migrations of 
 other groups. One of these is Maclmirodus, the saber-toothed 
 Tiger, which flourished in our Miocene and Pliocene, and 
 followed the huge Edentates to South America, and the Ungu- 
 lates across Asia to Europe. With this genus went Hycenodon, 
 and some typical Wolves and Cats, but the Bears came the 
 other way with the Antelopes. That the Gazelle, Giraffe, Hip- 
 popotamus, Hyaena and other African types, once abundant in 
 Asia, did not come, is doubtless because the Miocene bridge 
 was submerged before they reached it. 
 
52 
 
 The Edentates, in their southern migration, were probably 
 accompanied by the Horse, Tapir and Rhinoceros, although no 
 remains of the last have yet been found south of Mexico. The 
 Mastodon, Elephant, Llama, Deer, Peccary, and other mam- 
 mals, followed the same path. Why the Mastodon, Elephant, 
 Ehinoceros, and especially the Horse, should have been selected 
 with the huge Edentates for extinction, and the other Un- 
 gulates left, is at present a mystery, which their somewhat 
 larger size hardly explains. 
 
 The relations of the American Primates, extinct and recent, 
 to those of the other hemisphere, offer an inviting topic, but it 
 is not in my present province to discuss them in their most 
 suggestive phases. As we have here the oldest and most 
 generalized members of the group, so far as now known, we 
 may justly claim America for the birth-place of the order. 
 That the development did not continue here until it culmi- 
 nated in Man, was due to causes which at present we can only 
 surmise, although the genealogy of other. surviving groups 
 gives some data towards a solution. Why the old world Apes, 
 when differentiated, did not come to the land of their earlier 
 ancestry, is readily explained by the then intervening oceans, 
 which likewise were a barrier to the return of the Horse and 
 Rhinoceros. 
 
 Man, however, came ; doubtless first across Behring's 
 Straits ; and at his advent became part of our fauna, as a 
 mammal and primate. In these relations alone, it is my pur- 
 pose here to treat him. The evidence, as it stands to-day, 
 although not conclusive, seems to place the first appearance of 
 Man in this country in the Pliocene, and the best proof of 
 this has been found on the Pacific coast. During several 
 visits to that region, many facts were brought to my knowl- 
 edge which render this more than probable. Man at this time 
 was a savage, and was doubtless forced by the great volcanic 
 outbreaks to continue his migration. This was at first to the 
 south, since mountain chains were barriers on the east. As 
 the native Horses of America were now all extinct, and as the 
 
53 
 
 early man did not bring the old world animal with him, his 
 migrations were slow. I believe, moreover, that his slow pro- 
 gress towards civilization was in no small degree due to this 
 same cause, the absence of the Horse. 
 
 It is far from my intention to add to the many theories ex- 
 tant in regard to the early civilizations in this country, and 
 their connections with the primitive inhabitants, or the later 
 Indians, but two or three facts have recently come to my 
 knowledge which I think worth mentioning in this connection. 
 On the Columbia River, I have found evidence of the former 
 existence of inhabitants much superior to the Indians at pres- 
 ent there, and of which no tradition remains. Among many 
 stone carvings which I saw there, were a number of heads 
 which so strongly resemble those of Apes, that the likeness at 
 once suggests itself. Whence came these sculptures, and by 
 whom were they made? Another fact that has interested me 
 very much is the strong resemblance between the skulls of the 
 typical Mound-builders of the Mississippi Valley and those of 
 the Pueblo Indians. I had long been familiar with the former, 
 and when I recently saw the latter, it required the positive 
 assurance of a friend who had himself collected them in New 
 Mexico, to convince me that they were not from the mounds. 
 A third fact, and I leave Man to the Archaeologists, on whose 
 province I am even now trenching. In a large collection of 
 Mound-builders' pottery, over a thousand specimens, which 
 I have recently examined with some care, I found many 
 pieces of elaborate workmanship so nearly like the ancient 
 water-jars from Peru, that no one could fairly doubt that some 
 intercourse had taken place between the widely separated peo- 
 ple that made them. 
 
 The oldest known remains of Man on this continent differ 
 in no important characters from the bones of the typical 
 Indian, although in some minor details they indicate a much 
 more primitive race. These early remains, some of which are 
 true fossils, resemble much more closely the corresponding 
 parts of the highest Old World Apes, than do the latter our 
 
54 
 
 Tertiary Primates, or even the recent American Monkeys. 
 Various living and fossil forms of old world Primates fill up 
 essentially the latter gap. The lesser gap between the prim- 
 itive Man of America and the Anthropoid Apes is partially 
 closed by still lower forms of men, and doubtless also by higher 
 Apes, now extinct. Analogy, and many facts as well, indicate 
 that this gap was smaller in the past. It certainly is becoming 
 wider now with every generation, for the lowest races of men 
 will soon become extinct, like the Tasmanians, and the highest 
 Apes cannot long survive. Hence the intermediate forms of 
 the past, if any there were, become of still greater importance. 
 For such missing links, we must look to the caves and later 
 Tertiary of Africa, which I regard as now the most promising 
 field for exploration in the Old World. America, even in the 
 Tropics, can promise no such inducements to ambitious ex- 
 plorers. We have, however, an equally important field, if 
 less attractive, in the Cretaceous Mammals, which must have 
 left their remains somewhere on this continent. In these two 
 directions, as I believe, lie the most important future discov- 
 eries in Paleontology. 
 
 As a cause for many changes of structure in mammals 
 during the Tertiary and Post-Tertiary, I regard, as the most 
 potent, Natural Selection, in the broad sense in which that term 
 is now used by American evolutionists. Under this head, I 
 include not merely a Malthusian struggle for life among the 
 animals themselves, but the equally important contest with the 
 elements, and all surrounding nature. By changes in the envi- 
 ronment, migrations are enforced, slowly in some cases, rapidly 
 in others, and with change of locality must come adaptation to 
 new conditions, or extinction. The life-history of Tertiary 
 mammals illustrates this principle at every stage, and no other 
 explanation meets the facts. 
 
 The real progress of mammalian life in America, from the 
 beginning of the Tertiary to the present, is well illustrated by 
 the Brain-growth, in which we have the key to many other 
 changes. /The earliest known Tertiary mammals all had very 
 
55 
 
 small brains, and in some forms this organ was proportionally 
 less than in certain Reptiles. There was a gradual increase in 
 the size of the brain during this period, and it is interesting to 
 find that this growth was mainly confined to the cerebral 
 hemispheres, or higher portion of the brain. In most groups 
 of mammals, the brain has gradually become more convoluted, 
 and thus increased in quality, as well as quantity. In some, 
 also, the cerebellum, and olfactory lobes, the lower parts of the 
 brain, have even diminished in size. In the long struggle for 
 existence during Tertiary time, the big brains won, then as 
 now ; and the increasing power thus gained rendered useless 
 many structures inherited from primitive ancestors, but no 
 longer adapted to new conditions. 
 
 Another of the interesting changes in mammals during Ter- 
 tiary time was in the teeth, which were gradually modified 
 with other parts of the structure. The primitive form of tooth 
 was clearly a cone, and all others are derived from this. All 
 classes of vertebrates below mammals, namely, Fishes, Amphi- 
 bians, Reptiles, and Birds, have conical teeth, if any, or some 
 simple modification of this form. The Edentates and Ceta- 
 ceans with teeth retain this type, except the Zeuglodonts, which 
 approach the dentition of aquatic Carnivores. In the higher 
 mammals, the incisors and canines retain the conical shape, and 
 the premolars have only in part been transformed. The latter 
 gradually change to the more complicated molar pattern, and 
 hence are not reduced molars, bat transition forms from 
 the cone to more complex types. Most of the early Tertiary 
 mammals had forty-four teeth, and in the oldest forms the 
 premolars were all unlike the molars ; while the crowns were 
 short, covered with enamel, and without cement. Each stage 
 of progress in the differentiation of the animal was, as a rule, 
 marked by a change in the teeth ; one of the most common 
 being the transfer, in form at least, of a premolar to the molar 
 series, and a gradual lengthening of the crown. Hence, it is 
 often easy to decide from a fragment of a jaw, to what horizon 
 of the Tertiary it belongs. The fossil Horses of this period, 
 
56 
 
 for example, gained a grinding tooth, for each toe they lost, 
 one in each epoch. In the single-toed existing horses, all the 
 premolars are like the molars, arid the process is at an end. 
 Other dental transformations are of equal interest, but this 
 illustration must suffice. 
 
 The changes in the limbs and feet of mammals during the 
 same period were quite as marked. The foot of the primitive 
 mammal was doubtless plantigrade, and certainly five-toed. 
 Many of the early Tertiary forms show this feature, which is 
 still seen in some existing forms. This generalized foot became 
 modified by a gradual loss of the outer toes, and increase in 
 size of the central ones ; the reduction proceeding according to 
 systematic methods, differing in each group. Corresponding 
 changes took place in the limb bones. One result was a great 
 increase in speed, as the power was applied so as to act 
 only in the plane of motion. The best effect of this speciali- 
 zation is seen to-day in the Horse and Antelope, each repre- 
 senting a distinct group of Ungulates, with five-toed ancestors. 
 
 If the history of American Mammals as I have briefly 
 sketched it, seems as a whole incomplete, and unsatisfactory, 
 we must remember that the genealogical tree of this class has its 
 trunk and larger limbs concealed beneath the debris of Meso- 
 zoic time, while its roots doubtless strike so deeply into the 
 Paleozoic that for the present they are lost. A decade or two 
 hence, we shall probably know something of the mammalian 
 fauna of the Cretaceous, and the earlier lineage of our existing 
 mammals can then be traced with more certainty. 
 
 The results I have presented to you are mainly derived 
 from personal observation ; and since a large part of the higher 
 vertebrate remains found in this country have passed through 
 my hands, I am willing to assume full responsibility for my 
 presentation of the subject. 
 
 For our present knowledge of the .extinct Mammals, Birds 
 and Reptiles of North America, science is especially indebted 
 to Leidy, whose careful, conscientious work has laid a secure 
 
57 
 
 foundation for our vertebrate palaeontology. The energy of 
 Cope has brought to notice many strange forms, and greatly 
 enlarged our literature. Agassiz, Owen, Wyman, Baird, 
 Hitchcock, Deane, Emmons, Lea, Allen, Gibbes, Jefferson, 
 DeKay, and Harlan, deserve honorable mention in the history 
 of this branch of science. The South American extinct verte- 
 brates have been described by Lund, Owen, Burmeister, Ger- 
 vais, Huxley, Flower, Desmarest, Aymard, Pictet, and Nodot. 
 Darwin and Wallace have likewise contributed valuable infor- 
 mation on this subject, as they have on nearly all forms of life. 
 
 In this long history of ancient life I have said nothing of 
 what Life itself really is. And for the best of reasons, because 
 I know nothing. Here at present our ignorance is dense, and 
 yet we need not despair. Light, Heat, Electricity, and Magnet- 
 ism, Chemical Affinity and Motion, are now considered different 
 forms of .the same force; and the opinion is rapidly gaining 
 ground that Life, or vital force, is only another phase of the 
 same power. Possibly the great mystery of Life may thus be 
 solved, but whether it be or not, a true faith in Science knows 
 no limit to its search for Truth. 
 
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