HEL 1 cHSii ^'^ : -' THE LIBRARY OF THE UNIVERSITY OF CALIFORNIA LOS ANGELES ULYSSES S. GRANT COLLECTION lie RALPH D. REED UBRAtT UNIVERSE '. ,,f tos AMGELES. CAUB-, / f 3 / Frederick Warne Gf Co's Publications THE LIBRARY OF NATURAL HISTORY ROMANCE. The Romance of Wild Flowers. A Companion to the British Flora. By Edward Step, F.L.S., author of " Favourite Flowers of Garden and Greenhouse," " Wayside and Woodland Blossoms,"- &c. In crown 8vo, cloth gilt, gilt top, price 6s. This volume (No. i) contains upwards of 200 Original Illustrations by M. E. Step, T. Carreras, and the Author, of which 32 are full-page plates, finely printed in tints from photographs taken from Nature expressly for the work. Love of the country, which steadily grows upon our ever-increasing town populations since they have taken to cycling, is largely mixed up with an interest in the animal and vegetable life of moorland, wood, and seashore. To aid irl the identification of these creatures there are numerous admirable Floras and Text-books, which give the structural details with brevity and technical precision. Unfortunately, such literature only encourages .the enthusiast, whilst it repels all others. The Library of Natural History Romance is projected, not for the enthusiastic specialist, but for the others^the readers who do not want to be told that a certain organ or creature is of such a shape, but why it is so formed. Structure will be indicated plainly, but the reason for that structure and its relation to the creature's habits and mode of life will be brought out strongly. The volumes will really aim at imparting the most interesting facts of Natural History in the most interesting manner, to which end the pencil and the camera will be freely used to assist the pen. " No one is better qualified to write a popular book on the British flora than Mr. Edward Step. He is the guide, counsellor, and friend of eveiy field club, and his knowledge, gained as it is from Nature herself rather than from the library or the class-room, is placed before the unscientific reader in just such a form as he or she can easily comprehend. Print, illustrations, and text are alike excellent, and this library should appeal to every lover of the country." Pall Mall Gazette. Chandos House, Bedford Street, Strand, London Frederick Warm & Co.'s Publications HOW TO KNOW AND WHERE TO FIND THE WILD FLOWERS. Wayside and Woodland Blossoms. First and Second Series. Pocket Guides to the British Wild Flowers for the Country Rambler. By Edward Step, author of "Favourite Flowers of Garden and Greenhouse," &c. In pocket-book form, size 6 by 4 ins., in neat art linen gilt, limp binding, round corners, price ys. 6d. each ; or in best French morocco tuck, gilt edges, with expanding Pocket for Notes, Specimens, &c., price los. 6d. each. The purpose of these volumes is to assist a very large and increasing class of persons who possess a strong love of flowers, but to whom the ordinary " Floras " are as books written in an unknown tongue. The author's aim has been to write a work that, whilst it satisfied the rambler who merely wishes to identify the flowers of his path, might also serve as a stepping-stone to the " Floras " of Hooker, Bentham, and Boswell-Syme. Each volume contains over 120 coloured plates, por- trayingabout 156 species, drawn direct from nature; among them representatives of all the best-known genera will be found. There are also several black and white plates, and upwards of 400 species are clearly described in the text. Mr. Britten, writing of the First Series in Nature Notes, said" Mr. Step has condensed the best observations into a small compass, and his little volume is greatly in advance of every previous undertaking. It will add very slightly to the bulk of the most restricted arrangement of luggage, and forms an admirable pocket companion for the lover of wild flowers. . . . In it the reader will find much to learn and very little to unlearn, and we know of no other that can be so unreservedly recommended to the tyro in British Botany." "This is just the little book which every true lover of that particular phase of natural beauty namely, wild flowers delights to find in his pocket when rambling along country lanes. The delicately-tinted illustra- tions are absolutely true to their growing counterparts." Liverpool Mercury. " It is an excellent book, which will be welcomed alike by the more learned in flower lore and by the beginner who would be more fully versed in the evolutions of woodland and wayside life." Sheffield Daily Telegraph. Ghandos House, Bedford Street, Strand, London , . . . The Library of Natural History . . . Romance SHELL LIFE i 4 i TO 7 BANDED SNAIL; 8 TO 10 WRINKLED SNAIL; n, 12 HEATH SNAIL: 13 TO 15 POINTED SNAIL. SHELL LIFE AN INTRODUCTION TO THE BRITISH MOLLUSCA EDWARD STEP, F.L.S. AUTHOR OF 'FAVOURITE FLOWERS OF GARDEN AND GREENHOUSE' "WAYSIDE AND WOODLAND BLOSSOMS" "THE ROMANCE OF WILD FLOWERS" ETC. ETC. WITH UPWARDS OF SIX HUNDRED ILLUSTRATIONS LONDON FREDERICK WARNE & CO. AND NEW YORK 1901 [All Rights Rese>-ued\ Geology Librar Q1L PREFACE rilHE object of this work is much the same as that -* which led to the writing of its companion volume The Romance of Wild Flowers to awaken an interest in, and lead to a closer study of, the creatures de- scribed. Shells and their makers, of course, necessi- tated a different kind of treatment from that accorded to the wild flowers ; but the author's plan of making his readers first acquainted with the outstanding characteristics of the prevailing types of structure as embodied in such familiar forms as the snail, the mussel, and the cuttle, will enable them to follow him throughout the further chapters. It is not pretended that this volume will enable the reader to determine the exact species of all the native mollusks that may come under his notice ; but it is hoped he may get from it an intelligent idea of the sub - kingdom so far as it is represented in these islands, and may be assisted in discriminating between most of those commonly encountered in the woods and lanes, by the pond and stream, or along the seashore. Of the seven hundred and fifty species of Mollusca in- digenous in the British Islands and the adjacent seas, no less than six hundred and fifty species have been briefly described in these pages. But it is not as a 6 6 Treface shell - collector's handbook that the volume is .sent forth ; rather to suggest the consideration of these creatures as living organisms, whose diversity of form and structure has intimate relation to their mode of life, the persecution of enemies, and other factors in the struggle for existence though some of us are at times too apt to regard such differences as being dictated by the needs of the classifying naturalist. In accordance with this intention, so far as was compatible with the necessity for pro- ducing a volume of handy size, attention has been directed to those habits and external influences that may reasonably be considered to have brought about modifications of form and colour, protective resem- blances, and so forth. A few words may be added as to the system upon which the Genera, Families, and Orders have been grouped (see Appendix). In this matter I have mainly followed the plan adopted by the Rev. A. H. Cooke, M.A., in his admirable "Molluscs" (Cambridge Natural History, vol. iii.), which is likely to long remain the standard text-book. The reader who desires to enter upon the wider and deeper study of this branch of Nature will thus experience no diffi- culty in expanding his elementary acquaintance with our local fauna into a fuller knowledge of the Mollusca of the world. CONTENTS I. INTRODUCTORY Materials for the study of Mollusks close at hand Garden Snail and its shell Swan Mussel and Common Mussel Common Sepia or Cuttle Types of three principal classes of Shell-life ...... 21 II. THE SHELL AND ITS FORMATION Shell/?sA a misnomer Some Mollusks without shells The primitive shell Importance of the conical form to shore - dwellers Form of shell determined by habit of Mollusk Comparisons between the shells of shallow and deep water, rock and sand The door of the shell The Oyster a degenerate Thin shells of pelagic species Thin- ness of fresh-water shells Land-snails Shells of Slugs and Cuttles undeveloped or absent . . . .32 III. FEEDING AND BREATHING Oyster, though headless, has a mouth Bivalves all tongueless Cuttles' bird-like beak The Snail's wonderful tooth-ribbon, and thousands of teeth Powerful gizzards Lungs and gills Air-breathers and water-breathers The molluscan heart and circulation Blood mostly colourless . 40 IV. SEEING, HEARING AND SMELLING Sense organs of Mollusks differ from those of higher animals Decentralisation of sense impressions Local brains Nerve-threads, commissures, and ganglia Eyes and eye-spots Stalked-eyes, internal eyes, and vanished eyes Evolution of the molluscan eye The Argus-eyed Scallops The Saddle-oyster's sense of hearing Otocysts and Otoliths Sense of smell more important than sight or hearing Whelk's keen scent Slug's sense of locality A strange form of nose Sense of touch acute . . .48 Contents V. NUT-SHELLS AND MUSSELS PAGE Bivalve shells Nut-shells The "foot" of a burrower in gravel How the valves are kept closed Hinges, locking- teeth, and bands of muscle Leda-shells Long siphons denote a deep burrower Microscopic food of bivalves Saddle-oysters and their attachment-plug Noah's Ark Dog-Cockle Eared Limopsis Common Mussel Its value for food and bait Gregarious Its byssus, or mooring- ropes Mussels as foreshore conservators The legend of Bicleford Bridge Horse Mussels and their crab companion . Crenellas ....... 54 VI. OYSTERS AND SCALLOPS Fan Mussels and Pea-crab The Oyster : its personality The parent of millions Their infantile activity and later laziness " Natives " and " Green Oysters "Enemies of the Oyster Scallops Their flight through the sea- Purpose of the ribs and " ears " The Quiii as butterfly of the sea File- shells , . . . . .75 VII. HEART-COCKLE AND FRESH-WATER COCKLES Astarte-shells Hinge-teeth and their relation to habit of Mollusk Another reason for ribs Burrowing feet Iceland Cyprina Heart - Cockle Lucina and Hatchet- shells Double-tooth Urchin-shell A strange attachment Kelly-shells Shell-collecting from fish stomachs : a big haul Coin -shells and Crustaceans A bivalve scavenger The Weasel's-eye : its strange use of shell Fresh-water Cockles and their climbing ropes Pea-shells Fresh-water Mussels: their probable origin British pearls and pearl fishery Swan Mussels The Zebra Mussel and its strange history . . . . . . . .92 VIII. WEDGE-SHELLS, VENUS-SHELLS, AND COCKLES Tellins Mud burrowers Furrow-shells Wedge-shells with milled edges Trough-shells Circe and Artemis- Smooth Venus, our most massive native Toothed edges Contents 9 PAGE not requisite The Clam Food and money Carpet-shells The Pullet Kock Venus Rock-borers Red Nose A molluscan hedgehog Various Cockles Common Cockle . 118 IX. GAPERS, PIDDOCKS, AND SHIPWORMS Shells that will not shut Sunset-shells Old Maid, a mud dweller Its remarkable siphons, always extended Basket-shells Otter-shells or " Clumps "Eaten in Herm Razors of sorts Why the hinge is not central Razors not so sharp as mussels Saxicava Flask-shell Piddocks How rocks are broken up Multivalve shells Paper Piddocks -Wood Piddock Ship-worms How wreckage is disposed of Pandora Lantern-shells Skye Gaper . 144 X. TUSK-SHELLS, MAIL-SHELLS, AND LIMPETS Elephant's - tusk A connecting link Mail-shells A shell of plates Tortoiseshell Limpets Other Limpets- Common Limpet and its stronghold How it adheres Its excavating powers Its homing habit Blue-rayed Limpet : its two forms Slit-limpets and Keyhole-limpets Ormer or Sea Ear Its perforated shell . . . .178 XI. TOP-SHELLS AND PHEASANT-SHELL Dolphin -shells Umbilicus and operculum Top-shells Pheasant-shell A tiny gem Fresh- water Nerite Prob- able origin from a marine form . . . 199 XII. NECKLACE-SHELLS AND WINKLES Violet Sea-snail and its egg-raft Eyeless derelicts Wentletraps or Staircase-shells A forty-guinea shell Aclis-shells Necklace-shells and their strange egg-bands How shells are reduced Marsenia : a snail that is seen through Protective resemblance Velvet-shell Bonnet Limpets Hungarian Cap Cup - and - Saucer Limpet A quaint interior Winkles Dwarf Winkle and its resemblance to bladders of Fucus Rough Winkle Is it becoming a land-snail ? An object-lesson in evolution Periwinkle Chink-shells 210 i o Contents XIII. SPIRE-SHELLS AND MARSH-SNAILS PAGE Round-mouthed Snail A sea-snail that has left the sea Evidences of its origin Its shell door Its enemy, Drilus Point-shell Spire-shells Rissoas and Hydrobias Small and numerous Fresh-water Winkles Sentinel-shells Belted shell Marsh Snails or River Snails Viviparous Valve-shells ... . 228 XIV. COWRY AND PYRAMID-SHELLS Small Needle-whelk " Shillifillies "Horn-shells The Reversed Horn Obelisk-shell Screw-shell or Auger A snail that deliberately breaks its shell Strange history of the Blind-shell Pelican's-foot Cowries Another object- lesson in s 1 .. ell-evolution Margin - shell Poached Egg Protective ornamentation European Cowry Atlanta . 238 XV. WHELKS AND CONELETS Some toothless sea-snails Polished Eulima Of para- sitic descent Urchin Snail A strange habitat Pyramid- shells by the score The teeth of the Whelk family Spindle-shells Why a siphon is needed Sting-winkles Varices or growth lines : what they indicate Why oysters are scarce The Purple and its dye How it clings to wave- washed rocks Its stony shell How the Star-fish eats it out of house and home Its singular egg-capsules Dog- whelks Despoilers of bait Spindle-shells Red Whelk or Buckie White Whelk Common Whelk Varieties and monsters Egg capsules Keen scent Money value of a Whelk " fishery "Least Whelk Conelets . . .248 XVI. SEA-SLUGS Darwin's mistake about Sea-slugs How shells have been discarded Actajon and Bubble-shells Snail crushers Canoe - shells Blind burrowers Shells hidden and thinned Lobe - shell Sea Hare A reputed depilatory- Its colour changes Its purple clouds The true Sea-slugs Pleurobranchus How enemies are discouraged The origin of foot-lobes Crowned Runcina Cerata and their functions Sea Lemons Resemblance to sponges Sense- Contents 1 1 organs and gill - leaves Venus Slug mimics anemone Crested Slug Declined by fishes Homberg's Triton Devoted to Deadman's Fingers Gulf- weed Slug Carrying one's liver outside Bushy - backed Slug Disguise a necessity Crowned Sea-nymph Marbled Slug Plumed ^Eolis Mimics Sagartia Alder's ^Eolis Green ^Eolis Despised /Eolis : a spectral slug Embleton's ^Eolis A variety that has taken to fresh water Other ^Eolids Crowned yEolis : an anemone eater Hermans, Crimson and Green Food and .shelter combined Alder's Slug Green Elysia Falmouth Slug Pteropods .... 267 XVII. POND-SNAILS Lung breathers Stalked -eyes and sessile eyes Herma- phrodites Herald-shell Mouse-eared Alexia Little Ear- shell Fresh-water Limpets Great Pond-snail A general feeder Its development affected by size of pond Marsh Limnaa Dwarfed Linuuca : a wet - nurse for the Liver Fluke The evolution of Sheep Rot Tennyson and Nature Smooth Pond-snail Ear Pond-snail Wandering Pond- snail Glutinous Snail Involute Snail Flat - coils or Trumpet-snails The Ram's-horn A small snail in a large house Twisted Trumpet - snail Other Trumpet-snails An American visitor Bladder-snails Moss Bladder-snail . 306 XVIII. LAND-SLUGS AND GLASS-SNAILS Unpopular subjects Not all Slugs are harmful Slugs with shells and without Carnivorous Slug A foe to earth- worms Great Grey Slug Its liking for sculleries and dairies A taste for cream and lamb A taster of books Tree Slug Yellow Slug Field Slug A destroyer of seed- lings and (reputed) consumption cure Smooth Slug Keeled Slug Small Black Slug Glass-snail Simroth's theory of Slug origins Draparnaud's Snail Cellar Snail Garlic Snail Other Glass-snails Love darts . . 328 XIX. LAND-SNAILS More Slugs Large Black Slug Fondness for fruit A very mixed feeder Dusky Slug Garden Slug Spotted Kerry Slug Twenty-five Helices Dwarf Snail The 1 2 Contents reward of patient seeking Rock Snail Hounded Snail Stone- turning and leaf-sifting Beautiful Snail Prickly Snail A climber of trees and a parachutist Plated Snail Cheese Snail A relic of the ancient forests Lapidary Snail Bristly Snail Ruddy Snail A weakness for strawberries Silky Snail Green Hairy Snail Dusky Snail Kentish Snail Carthusian Snail Copse Snail Kne\v the way to the tap Sandhill Snail A probable alien Banded Snail Snail - showers The flavour of Down mutton Sheep- snails Heath Snail Wrinkled Snail Theorising on a false basis Pointed Snail Brown - lipped Snail Its wonderful variation White-lipped Snail Common Garden Snail Comes home to roost Apple Snail or Roman Snail A reputed alien, biit more probable autochthon Apples or pot-lids Its winter sleep Its egg-laying A chalky egg- shellThe Apple-snail's first meal The Good Samaritan of Shell-life Bulins Molluscan Dirty Dicks Chrysalis- shells Numerous but minute Barred doors Tree Snail Door-shells Mimicry of beech-buds How the ridges are worn away Slippery Moss-snail Agate Snail A blind, subterrranean ghoul Amber Snails and more flukes A remarkable seashore slug . ... . . 343 XX. CUTTLES The most highly-organised mollusks Suckers and Ink- bags How colour-changes are effected The Common Octopus The Curled Octopus Eight-armed Cuttles and ten-armed Cuttles Spirula Fragile shells that cross the Atlantic -Common Cuttle" Cuttle-bone " Hectocotylus- arm Derivation of word Cuttle Eggs in bunches Pen- and-ink mollusks Little Cuttle Ross' Cuttle Common Squid First-class bait How to catch a Squid Absence of Squid ' ' pens " on shore Egg-mops Marbled Squid Flying Squids Architeuthis, a monstrous Squid Oceanic Cuttles Evolution of the Cuttles' shells 383 APPENDIX A Classified List of British Mollusks . . . 4U1 Index to Popular Names ..... 413 LIST OF ILLUSTRATIONS PAGE PLATES Laiul Snails (Helix) Front Dog Cockle, \ ispiece Top-shells and) . PhLant-shell/^'^ 6204 Green Crenella, \Facingpage 63 Necklace-shells and) 223 etc. Winkles / ' Great Scallop and Quin ,, 78 Periwinkle and) 226 Scallops, ) 84 Chink-shells J Astarte-shells, etc. J : Coneletsandj 238 Iceland Cyprina and) 94 Dog-whelks J Heart-Cockle / ' Sea-slugs . . . ,, 287 Zebra Mussel, ) 99 Sea-slugs . . . ,, 294 Montagu-shells, etc. ) ' Sea-slugs . . . ,, 302 Orb-shells and) 106 Fresh-water Snails . ,, 319 Pea-shells / Land-slugs (Limax) . ,, 334 Tellins and \ 190 Slug-shells and) 340 Furrow-shells/ l^U Glass-snails / Wedge-shells and) 127 Land-slugs (Arion) . ,, 345 Trough-shells / ' Land-snails (Helix) . ,, 351 Venus-shells and) 130 Brown-lipped Snail . ,, 363 Carpet-shells / AVhite-lipped Snail . ,, 364 Cockles . . . ., 139 Common Garden Snail ) Of*/ Sunset-shells and\ 142 and Apple Snail J " obo Piddock / ' Chrysalis Snails and\ 374 Mail-shells and \ 182 Door-shells J ' Limpets J Cuttles . . . ,, 383 Ormer and ^ 1 ft*} Cuttles . . . ,, 398 Blue-rayed Limpet) iy*> \* The above full - page plates depict about 300 figures of Mollusks, the individual names of which will be found at the foot of each plate. List of Illustrations TEXT ENGRAVINGS INTRODUCTORY . PAGE 21 Hinge-teeth . PAGE 56 Shell of Garden Snail . 22 Shining Nut-shell . 57 Swan Mussel . 26 Beaked Leda . 58 Edible Mussel 27 Dwarf Leda . 58 Soft parts of Swan Mussel Interior of Beaked Leda- (Anodonta) . 28 shell .... 58 Young of Swan Mussel . 29 Saddle-oyster, under-side 59 Sepia . 30 Side view of Saddle- oyster, showing mode THE SHELL AND ITS of attachment 60 FORMATION 32 Right side of Anomia, Limpet .... 34 with shell removed 61 Common Top . 34 Prickly variety of the Painted Top . 35 Saddle-oyster 61 Netted Dog-whelk . 35 Noah's Ark . 62 Wentletrap . 36 Milky Ark, interior 63 Sting-winkle . 36 Common Mussel ( My t il us Pelican's-foot . 36 edulis), closed and attached by the byssus 66 FEEDING AND BREATHING 40 Common Mussel, opened Beak of a Cuttle-fish to show the various (Sepia) 41 organs. 67 Portions of the tongue of Common Horse Mussel . 68 a Whelk, with a row Part of epidermis . 69 of teeth 42 Tulip Horse Mussel Teeth of raduhe of Lim- Bean Horse Mussel nica stagnates, Anci/lus Cross-cut Crenella . 1 Jluvifttilis,&nd.Sitccinea Marbled Crenella . ' 2 putris .... 43 Green Crenella, interior. 3 Under surface of Limpet 45 Black Crenella 3 SEEING, HEARING, AND OYSTERS AND SCALLOPS . 5 SMELLING . 48 Fan Mussel 6 Interior of Fan Mussel, NUT-SHELLS AND MUSSELS 54 right valve . 7 Common Nut-shell 55 Oyster, with right valve Interior of Nut-shell 55 removed 8 List of Illustrations Hunchback Scallop PAGE 82 PAGE River Pea-shell . . 109 Variegated Scallop 83 Painter's Mussel . .111 Quin or Queen 84 Pearl Mussels, showing Seven-rayed Scallop 85 pearl within the shell, Tiger Scallop . 85 and detached pearls . 113 Mottled Scallop, shell Swan Mussel, end view . 114 and animal . 86 Duck Mussel . . .115 Gaping File-shell . 88 Zebra Mussel. . .116 Heart File-shell . 88 Fragile File-shell . 89 WEDGE - SHELLS, VENUS - Gaping File-shell . 89 SHELLS AND COCKLES 118 File-shell in its nest 90 Tellin, with foot and Gaping File - shell, in- siphons extended . 119 terior .... 91 Blunt Tellin . . .120 Baltic Tellin . . .120 HEART - COCKLE AND Thin Tellin . . .120 FRESH-WATER COCKLE 92 Hough Tellin, interior . 121 Furrowed Astarte . 93 White Furrow-shell . 123 Furrowed Astarte, in- Peppery Furrow-shell . 123 terior .... 93 Hinge-plate of Peppery Flat Astarte . 94 Furrow-shell . .123 Iceland Cyprina 95 Banded Wedge-shell . 125 Interior of Cyprina 95 Polished Wedge-shell . 125 Heart-Cockle . 96 Elliptical Trough-shell . 126 Beaks of Heart-Cockle . 96 Cut Trough-shell . . 127 Interior of Heart-Cockle 97 Rayed Trough-shell . 127 Northern Lucina . 97 Smooth Venus . .128 Globose Kelly-shell, sus- Little Circe - shell, ex- pended by byssus 101 terior . . . .129 Interiorof Globose Kelly- Little Circe - shell, in- shell . 102" terior . . . .129 Minute Kelly-shell 102 Enlarged plan of hinge Scaly Coin-shell 103 of Little Circe-shell . 129 Shining Coin-shell and Rayed Artemis . .129 enlarged hinge . 105 InteriorofRayedArtemis 129 Convex Coin-shell . 105 Smooth Artemis . . 130 Turton's Weasel-eye, Smooth Venus . . 130 open and closed . 106 Interior of Smooth Venus 131 Hinge-teeth, Sphccrium . 107 Banded Venus . .132 Horny Orb- shell 108 Warty Venus . . .132 Nut Orb- shell 108 Warty Venus, interior . 133 Lake Orb-shell 109 Striped Venus . . 133 2 i6 List of Illustrations PAGE Wavy Venus, exterior Wrinkled Rock-borer PAOK 161 and interior . .134 Arctic Rock-borer . 162 Golden Carpet-shell . 135 Flask-shell, front view . 162 Banded Carpet-shell . 135 Flask-shell, side view 162 Banded Carpet-shell, in- Flask-shell . 163 terior . . . .136 Case of Flask-shell . 163 Pullet Carpet-shell . . 136 Pholas in its burrow 164 Cross-cut Carpet-shell . 137 Right valve of Common Rock Venus . . .137 Piddock . 165 Rock -borer (Petricola Portion of hinge-plate . 165 lithophaga) . . .138 Dorsal shields. 166 Rough Cockle . . 140 Common Piddock in its Little Cockle . . .140 cell . 166 Banded Cockle . . 141 White Piddock 167 Common Cockle, interior 141 Little Piddock 167 Paper Piddock 168 GAPERS, PIDDOCKS, AND Wood Piddock 169 SHIP-WORMS . . 144 Ship-worm 170 Blunt Gaper . . .145 Norwegian Ship-worm . 172 Hinge - teeth of Psam- Pandora-shell . 173 mobia .... 145 Left valve of Pandora . 173 Tellin-like Sunset-shell . 146 Thin Lantern-shell . 175 Faroe Sunset-shell . . 147 Papery Lantern-shell 176 Hinge and cartilage pro- cess of Gapers . .148 TUSK-SHELLS, MAIL-SHELLS ( Old Maid . . .149 AND LIMPETS 178 Blunt Gaper . . .150 Elephant's Tusk-shell . 179 Basket-shell . . .151 Grooved Tusk-shell 180 Interior of Basket-shell, Mail-shells . 181 showing hinge-teeth . 151 Under-side of Chiton and Pointed Basket-shell . 151 profile of head 182 Sipl'.ons of Necera . . 151 Bristly Mail-shell . 183 Oblong Otter-shell . . 153 Bordered Mail-shell 185 Common Otter-shell . 154 Smooth Mail-shell . 185 Short Razor . . . 155 Marbled Mail-shell 186 Smooth Short Razor . 155 Tortoiseshell Limpet 186 Egg-shell Razor . . 156 Common Limpet . 188 Pod Razor . . .157 Blue-rayed Limpet 193 Pod Razor, interior of Blue-rayed Limpet, older left valve . . .158 specimen 193 Sword Razor . . .160 Keyhole Limpet 194 Wrinkled Rock- borer . 161 Punctured Limpet . 194 List of Illustrations PAGE Punctured Limpet, from above . . . .195 Common Slit-limpet . 195 Rosy Slit-limpet . . 195 Ormer . . . .196 TOP-SHELLS AND PHEAS- ANT-SHELL . . .199 Head of Grey-top . . 201 Operculum . . .201 Common Top-shell . . 201 Grey Top-shell . . 205 Painted Top . . .205 Pheasant-shell . . 207 Head of Phasianclla . 208 Fresh-water Nerite . 208 NECKLACE -SHELLS AND WINKLES . . .210 Violet Sea-snail with its float . . . .211 Violet -snail and float, side view . . . 212 Head of Wentletrap . 213 Common Wentletrap . 213 Glossy Aclis-shell . . 214 Egg -band of Natica alcleri . . . .215 Large Necklace-shell . 216 Life aspect of N. catena . 216 Common Necklace-shell . 217 Velvet-shell . . .219 Hungarian Cap . . 221 Cup-and-Saucer Limpet, interior . . .221 Single roAV of teetli from theradulaof Periwinkle 222 Animal of male Peri- winkle, with the shell removed . . .223 Periwinkle . . .224 Eggs of Periwinkle . 225 PAGE Banded Chink-shell, . 226 Banded Chink-shell, en- larged . . . .226 Pallid Chink-shell . . 227 Eggs and young of Pallid Chink-shell . . .227 SPIRE-SHELLS AND MARSH- SNAILS. . . .228 Round-mouthed Snail . 229 Latticed Spire-shell . 231 Thick-lipped Spire-shell . 231 Laver Spire-shell . . 232 Common Bithynia . . 233 Dun Sentinel . . .233 Dun Sentinel . . .234 White Belted-shell . . 234 River Snails . . .235 Common River Snail . 236 Lister's River Snail . 236 Common Valve-shell . 237 COWRY AND PYRAMID- SHELLS. . . .238 Small Needle-whelk . 239 Auger-shell . . .240 Blind-shell . . .240 Pelican's foot . . .241 Pelican's foot, from below 242 Margin-shell, from above and below . . . 243 Margin-shell and animal 243 Poached Egg . . .244 Poached Egg-shell . . 244 Young shell of Cowry . 245 European Cowry, from above and below . . 245 European Cowry . . 245 Atlanta peroni . . 246 WHELKS AND CONELETS . 248 Polished Eulima , . 249 i8 List of Illustrations PAGE TAGK Conical Pyramid-shell . 250 Gulf-weed Slug . . 287 Staircase Pyramid . . 251 Bushy-backed Slug . . 288 Sting-winkle . . .252 Plumed .Eolis . . 291 Ribbed Spindle-shell . 252 Dotted vEolis . . .297 Purple or Dog-winkle . 255 Green Elysia . . . 301 Egg-capsules of the Black Limapontia . . 302 Purple. . . .257 Clione . . . .303 Netted Dog-whelk . .257 Shell of Limacina . . 304 Netted Dog-whelk . . 258 Clio pymmidata . . 305 Slender Spindle-shell . 260 Common Whelk . . 262 POND-SNAILS . . .306 Row of teeth of Common Least Herald-shell . . 307 Whelk . . .263 Mouse- eared Alexia . 308 Opercula of Whelk, nor- Fresh-water Limpet . 309 mal form and double . 263 Part of a row of teeth Cluster of Egg-capsules . 263 from the radula of Least Whelk . . .265 Fresh-water Limpet . 310 Seven -ribbed Conelet . 265 Portion of row of teeth Teeth of Bela . . .265 from radula of Great Red Conelet . . .266 Pond-snail . . .311 Turreted Conelet . . 266 Great Pond-snail . . 312 Great Pond-snail . . 313 SEA-SLUGS . . . .267 Marsh Limnrca . .314 Actaeon-shell . . .271 Dwarfed Limna>a . . 314 Blunt Bubble-shell . . 271 Smooth Pond-snail . . 316 Canoe-shell . . . 272 Ear Pond-snail . . 317 Cylindrical Bubble-shell 272 Wandering Pond-snail . 317 Cylindrical Bubble-shell 273 Ram's- horn Snail . . 320 Southern Bubble-shell . 273 Ram's-horn . . .321 Soft Bubble-shell . . 274 Whirlpool Trumpet . 322 Gizzard -plates of Accra . 275 Margined Trumpet . 323 Soft Bubble-shell . . 275 Shining Trumpet . . 325 Lobe-shell . . .275 Fountain Bladder-snail . 325 Lobe-shell . . .276 Shell of Fountain Sea Hare. . . . 276 Bladder-snail . . 325 Shell of Sea Hare . . 276 Moss Bladder-snail . 326 Spawn of Doris . . 282 Young of Doris, with LAND-SLUGS AND GLASS- shell . . . .282 SHELLS . . .328 Red Doris . . . 282 Shell-bearingSlug(Testo- Hairy Sea Lemon . . 283 cclla haliotidea) . . 330 Crested Slug . . .286 Great Slug . . .332 List of Illustrations Shell of Great Slug- PAGE 333 Pellucid Glass-snail and shell . 338 Cellar-snail 340 Tawny Glass-snail . 342 LAND-SNAILS . 343 Black Slug . 344 Lapidary Snail 353 Kentish Snail 356 Carthusian Snail . 357 Sandhill Snail 358 Pointed Snail . 362 Brown-lipped Snail 363 Mountain Bulin 370 Lesser Bulin . 370 Large Chrysalis-snail 371 Pupa an tivertigo 373 Tree Snail 373 Plaited Door-shell . 374 PAGE Two-lipped Door-shell . 376 Slippery Moss-snail . 378 Three - toothed Moss- snail . . . .379 Agate Snail . . .379 Amber Snail . . .380 Row of teeth of radula of Succinea putris . 380 Large Amber Snail . 381 Graceful Amber Snail . 381 CUTTLES . . . .383 Suckers of Cuttle . . 385 Spirula peronii . . 389 Common Cuttle . . 389 Shell of Sepia . . . 390 Pen of Little Cuttle . 391 Little Cuttle, upper-side 392 Common Squid . . 394 Pen of Common Squid . 394 HE materials for beginning an acquaintance with the shell- bearing animals lie almost at every back door. Should there be an untidy corner of the ^' ( garden where empty flower-pots are stored, a water-butt, or old wood is stood there, without search, you may surely find a few examples of the dingy and too common Garden Snail. Much as we may object to the presence of this Snail where there are choice or tender plants, we shall find it a very handy example if we desire to obtain knowledge respecting the class to which it belongs. All the Mollusca, it is true, do not agree in structure with the Snail, any more than they agree in external appearance, but we may well adopt it as one of the few general types of structure under which all the species may be classed. A description of a species that is accessible to all, and at least familiar by sight, should prove more generally acceptable than an illustration drawn from 22 Shell Life the sea, which to the mass of Britons is not always get-at-able : therefore we search slightly among the trailing ivy in the back-garden and pick up a rather shabby-looking shell. This is the portable house wherein is lodged the common Garden Snail, and when the shell has been washed by contact with the dripping leaves after a heavy summer shower, one may get an idea of its true colours. It has a yellowish ground, thickly overlaid with spots and bands of dark warm brown broken by irregular lines of lighter tint. The shell is packed with a solid jelly of greenish hue the living creature that formed the hard shell by excretion from its outer surfaces, but at present it is without form, a mere jelly in a jelly -mould. Let us put this specimen into a saucer with a little tepid water, and see what effect it will have upon him. Here are just those conditions he likes best, warmth and moisture, and he immediately begins to emerge from his shell and assume a definite shape. His body is elongated, with a flat base and a rounded upper side, the front ending in a sort of head dis- tinguished by two pairs of what children designate "horns." These tentacles, instead of having the character of horns, are exceedingly soft and mobile, readily shortened to escape injury, or even completely withdrawn into the head. The lower of these appendages are short, and curved towards the ground ; the upper ones are much longer and carry the eyes Introductory 2 3 at their extremities they take an upward direction and are waved backwards and forwards for the purpose of receiving impressions. The shell is supported near the middle of this elongated body, and appears to be rather small for the accommodation of so large an inmate, though we have not yet seen the whole of the Snail. What we can now see extended is generally known as the foot the locomotive organ of the Snail. Within the shell is a good deal more the " visceral hump " con- taining most of the internal organs. By a series of muscular contractions the Snail glides along upon the sole of its foot, slime being poured out for the necessary lubrication of its path the glistening silvery trail that often enables the irate gardener swiftly to avenge the loss of his choicest seedlings. The mouth of the creature, as will have been seen, is situated just below the smaller pair of tentacles, and is bounded by lips. Behind the upper lip is the horny, arched, and ribbed jaw which bites off and breaks down the food, which is then passed over a ribbon-like tongue, set in regular order with thousands of hook-like teeth, which rasp it into minute frag- ments. It then, of course, finds its way to the crop and the stomach by way of the gullet, for, in spite of the Snail's jelly-like, structureless appearance, it can boast of heart, liver, kidney, reproductive organs, and both nervous and muscular systems. With these items we have no immediate concern, for in this volume I do not propose to enter deeply into the anatomy of my subjects; but there is one point to which I must call attention. If we look at the mouth of the shell when the Snail is extended, we shall see 24 Shell Life that it is closely lined with a very soft material called the mantle. The name suggests that this organ invests the whole body of the Snail when it is with- drawn into the shell; it does this and more the mantle is the immediate producer of the shell. The porcelain of our Snail's shell is composed mainly of carbonate of lime, and a microscopical section reveals the fact that it is made up of three distinct layers, each formed separately by different portions of the mantle. The material is obtained from the tissues of the plants upon which the Snail feeds, and has been absorbed from the soil by the roots. It appears to be separated from the Snail's blood as this circulates through the mantle, which has the power to pour it in a fluid state upon its outer surface. By exposure to the atmosphere the fluid lime mixed with animal matter hardens into shell. This animal matter is conchiolin, a substance not differing greatly from chitin, of which the hard parts of insects are con- structed. The calcareous particles appear to be held together by the animal matter, and the whole sets into a hard stony formation. When a portion of shell is soaked in a weak acid, the carbonate of lime is dis- solved and a very delicate gelatinous film is left. A similar result is obtained in the case of Whelk and Top-shells to which certain sea-anemones attach them- selves. The base of the anemone appears to pour out some acid which dissolves the lime and leaves only a soft papery shell-form behind. When the mollusk is dead and the empty shell is left exposed to the atmo- sphere, the animal matter soon perishes and leaves the shell without gloss and exceedingly brittle. All parts of the mantle have power to excrete one Introductory 2 5 or other layers of this shell, as is proved by the repair of breakages. Many an adult shell bears signs of earlier accidents, the fractures being always evident from the fact that the colour patterns of the original are not reproduced. It is only the edge of the mantle that can produce the colour and pattern, and this is the part that first makes all the additions to a grow- ing shell to allow room for the growth of the animal, whilst the other parts of the mantle merely strengthen this first layer by backing and thickening it. The upper layer therefore carries the pattern and colour, whilst the lowest layer is usually white and highly polished. Outside all there is a kind of animal varnish, protecting the shell from many injuries, and this is known sometimes as the epidermis, but more correctly as the periostracum. Sometimes the shelly matter assumes the crystalline condition, the carbonate of lime having taken the form of calcite or aragonite. The statement made above that the fluid shell-matter is poured out and moulded upon the external surface of the mantle is the modern view generally held, but some authorities agree with the late Dr. W. B. Carpenter, who held that it was secreted in the cells and interstices of the outer membrane of the mantle, which was afterwards separated. The Snail breathes air, but its " lung " is merely a cavity opening directly on the surface of the animal and closed at will, in a manner corresponding to the opening and closing of our lips. Its inner walls are lined with a fine network of vessels through which the blood courses, absorbing oxygen from the moist air and giving off carbon. This simple form of lung is referred to as the Pulmonary Sac, and its external 26 Shell Life opening may be watched for just below the lip of the shell on the right-hand side. Each individual Garden Snail combines the func- tions of both sexes. When one reflects that every one of those Snails clustering under the ivy will probably produce numerous eggs, he ceases to wonder at the enormous number that contrives to survive in spite of the depredations of birds and gardeners. One hundred may be taken as the average number of its eggs, and these are deposited in cup-shaped hollows among herbage, and covered with a little loose earth. The young come forth with the same shape as their parents, carrying a tiny, glassy shell on their backs, and differ- ing only in size. They become adult in about a year, and live until about five years old. Late in autumn they retire in companies to dry nooks and corners, there to spend the winter, many of them attaching their shells to those of their neighbours, all closed by tough films which keep in some degree of warmth. The Snail is not the stupid senseless creature he is commonly thought to be. His entire body is very sensi- tive, and even when deprived of his eyes he can distinguish between light and darkness. His sense of locality is of a high order, for he has his favourite roosting place and invariably returns to it for his day's rest after a night's wanderings in search of food. As an example of a second class of shells and shell- makers, let us take either of the large Swan Mussels Introductory 27 that live in fresh-water ponds and lakes, or the Edible Mussel of our seashores. These are so much alike in general structure, that either will serve our present purpose. Here the shell is a bivalve that is, it is formed in two pieces (valves) which are hinged together by their upper edges. Having ., . j. i ., Edible Mussel seen that the shell of the Snail was produced by the mantle, we shall not be surprised to find that the Swan Mussel's mantle is in two parts corresponding with the valves of the shell. Within the two lobes of the mantle there are four plates or leaves of very delicate tissue the gills in two pairs. Between these again lie the foot, the visceral mass, and the lips of the mouth. This creature, though it has a mouth, has no head, and it does not wander about in search of food, but lies partly embedded in the mud with the shell gaping slightly, and waits for its food to come to it. The gill-plates are covered with delicate filaments (cilia) like the gossamer of small spiders, and, appar- ently by the constant rhythmical movement of these, currents of water are drawn in, passed over and between the gills, where the blood circulating through their tissues absorbs the oxygen, whilst the microscopic forms of animal and plant life with which the waters abound are filtered out and passed to the lips. This being the method of their feeding, the bivalves lack the horny jaws and the tooth-studded ribbon such as we found in the Garden Snail. Occasionally examples of the Swan Mussel are found combining the functions 28 Shell Life of both sexes, but as a rule in bivalves the sexes are in separate individuals. We have here several points of difference in struc- ture and habit be- tween the Garden Snail and the Swan Mussel ; there is also a want of uniformity in the length of their lives, for our pres- ent subject attains a respectable old age varying from twenty to thirty years, and does not begin to pro- duce young until it is five years old. This difference of age may be at ,/*' f j least partly ac- Soft parts of Swan Mussel (Anodonta) COUnted for by the foot; b, mouth; c, lips; d, c, gills; /, vent; quiet Sedentary g, mantle; h, siphon ,. .. , , .* lire lived by the Swan Mussel, which has also probably brought about a condition of degeneration from a primitive form ; whilst the active Snail has no doubt advanced from that primitive condition. The evidences of this degeneration are to be found in the loss of head, eyes, masticatory apparatus, and reduced means of locomotion. One other dissimilarity between these two types Introductory 29 must be noted. We have seen that the Snail lays eggs, and that when the young escape from these they resemble their parents in all respects other than size. The Swan Mussel retains its eggs until they hatch, but the little creatures that emerge in no wise resemble the parent. They appear to represent an early ancestral condition of the species. They have a temporary two-valved shell with hooked tips, with which they cling to the fins and tails of fishes, leading a kind of parasitical existence for a time ; and then they drop to the mud where a new and permanent shell grows within the valves of their cradle. This part of the Swan Mussel's history may be dealt with more fully later. Our third type of structure must be sought in the sea, for it has neither land nor fresh- water repre- sentative. It is the Common Sepia, one of the Cuttles. Here there is no sign of an external shell, and the shape is altogether different from either of those we have already considered. The Sepia is quite symmetrical in form, with a distinct head surmounted by a crown of eight arms and two long clubbed tentacles. In the centre of this crown is the mouth, armed with a pair of horny jaws not greatly unlike the beak of a parrot, which they resemble in their action. Within the mouth there is a tooth- ribbon like that of the Snail, but it is comparatively small, because the principal work of disintegration of food is done by the jaws, and the Sepia's digestive powers are of a superior order. The eyes are large Shell Life and prominent, placed on the sides of the head below the arms. There is no external shell, but in the mantle there is the one familiarly known as " C u 1 1 1 e - bo n e," more especially to bird fanciers. This consists of a thin hard shield, filled with thin soft plates of porous lime. The Sepia can walk head downwards by the aid of its arms, whose inner surfaces are covered with powerful suckers ; it can also swim rapidly backwards by violently ejecting water from the gill-chamber through a tube called the funnel. The opening by which water is admitted to the pair of gills is in front below the arms. The sexes are distinct, and the young are produced from eggs attached in great clusters to seaweeds. These three creatures the Garden Snail, the Swan Mussel, and the Sepia stand as types of the three principal classes of mollusks with which we have to deal in the following pages ; and we have so introduced them on the principle of pro- ceeding from the most generally known to the less known. Regarded from the point of view of the systematic naturalist, the Sepia, as the highest Sepia Introductory 3 1 type, should stand first, the Snail next, and the Swan Mussel last, its structure being more primi- tive than that of the others, but reversing this order we propose to deal first with the more simple forms. For the natural sequence of the British species, proceeding from the most highly organised to the lowest groups, the reader is referred to the Appendix. HE great group of animals briefly considered in the fol- lowing pages has been singu- larly unfortunate in the names that have been bestowed upon it. The majority of the creatures comprised in it have been described as Shell -fisli by the non - scientific person, and as such associated with forms so dissimilar as crabs and lobsters, which resemble oysters and whelks only in the fact that they are not fishes. On the other hand, when the great Cuvier was seeking a name for the entire class in which cuttles, snails, bivalves, and slugs are included, and wishing to indicate the soft, boneless character of their bodies, he selected the word Mollusca, derived from the Latin mollis, soft. But it is not a very distinctive name, for there are many soft boneless creatures not included in the group, and moreover the Romans used the name for a kind of nut with a soft shell. 32 The Shell and its Formation 3 3 We are, therefore, in the position of having no well- known name that will apply with anything approach- ing accuracy or distinctness, in the way, for example, that we denote beasts, birds, reptiles, and fishes ; and there does not appear to be any prospect of getting what we want. The naturalist is so used to the term mollusk that he is not likely to seek or adopt another, and the layman is too conservative to give up so well-known and so inaccurate a name as Shell- fish. The reader will understand why the word " Shells " occupies a more important position in the title of this volume than the makers and wearers of those shells, and will not regard it as being due to sympathy with the early collectors and writers who regarded the shell as of chief importance, and the animal that secreted and lived in it as quite a secondary matter. In such a case accuracy is out of the question, for many of the creatures described in these pages have no apparent shell ; a greater number have absolutely none when full-grown, though some of them begin life with a rudimentary shell which does not develop. But though the shell is not everything, it is so characteristic of the Mollusca as a class, that we are justified in giving some consideration to it at the start. There is every reason for supposing that the primitive molluscan shell was not much unlike that which covers the Limpets to-day. Such a form gives great strength with but a small expenditure of material, and it is susceptible of modification in many directions. A number of species whose anatomy shows they are not intimately related, have retained this form of shell to the present day. In proof of this 34 Shell Life we need only refer to the native species of Acmcca, Haliotis, Calyptrcea, and Ancylus. For creatures living in shallow water along the seashores, exposed to frequent hammer- ing by the waves, such a form would be highly protective, as may be proved by watching the Limpets (Patella) on the rocks. Adhering tightly with the base of their bodies to the rock, and drawing down the edges of the shell by muscular contraction, the wave breaks upon the shell without harming or shifting it. In the case of the Limpet the shell is enlarged equally all round its edge, so that it fits accurately to the spot of rock the Limpet has chosen for a permanent resting-place. Even where the simple uncoiled form of shell has been departed from, there has in innumerable in- stances been a retention of the general external shape, that the minimum of resistance shall be offered to the waves. Take either of the common species of Top-shells that frequent the same situations as the Limpets : although the cone is here coiled several times upon an axis, the external shape is still that of a cone with an almost flat All our univalve shells will be found to be modifications of this type, in some making a low pyramid, in others drawn out to a proportionately great length. This diversity of form is, no doubt, determined by the habit of the mollusk and the situation it inhabits. For example, those T'he Shell and its Formation 35 species that adhere to rocks in shallow water (Top, Purple, Winkle, Limpet), and are therefore subject to the rushing of water and the heavy beating of breakers, have their shells broad, smooth, and free from sculpturing that might catch the water and so result in the mollusk being swept from its hold. Closely related species that live on sandy or gravelly bottoms appear in many cases to find an advantage in angles and knobs ; probably because, their foothold being precarious, when they are detached by waves their irregular surface prevents their being swept far from the spot. This difference is well illustrated lay comparing the Common Top with a closely allied species, the Painted Top, which occurs on Painted Top Sand > and haS Netted Dog-whelk the surface of the shell broken up into a series of little knobs. The Netted Dog-whelk lives on sandy shores, and its shell has a similar surface, whilst the upper surface of the animal is dotted with dark spots that closely resemble grains of sand. The Common Wentletrap has a great number of flat plates standing out edgewise from each coil of the long shell. The very rugged character of the Sting Winkle's house is obviously determined by similar reasons for utility ; and, though much less rugged, the strong sculpturing of the Pelican's-foot is clearly of the same order. How the character of the shell is modified by Shell Life changed habits in the creature that makes it, may be seen clearly in the case of the Blue-rayed Limpet (Helcion). In its young condition it should be sought on the broad fronds of the large tangles and oar - weed. The form of the thin shell well suits it for this situation, the frond float- sting Winkle Wentletrap ing i 11 currents and the shell offering little opposition to the flow of the water. As the frond waves iridescent gleams play upon its purple-brown, and in order that the Blue-rayed Limpet may not be readily seen it bears upon its clear brown shell from three to six fine lines of bright blue radiating from the apex and giving an effect similar to that seen on the tangles. As it gets older this Limpet climbs down the stalk, where there is no iridescence, and finally is to be found among the root-like suckers by which the weed is attached to the rock. In such a situation there is more risk to the shell from the rush of stones, etc., at the lower level. The shell, in con- sequence, becomes much thickened, the edges are modified to fit it for adhering to the cylindrical stem instead of the plane surface of the frond, and as the blue lines would be an attraction rather than a disguise they are gradually obscured. The shell ^The Shell and its Formation 37 has assumed the form known as the Smooth Limpet. Exotic species of Patella that live entirely upon floating seaweeds have their transparent shells like those of Helcion, but those that live upon rocks require thick shells to withstand the breakers. All the species to which we have just referred with the exception of the Limpets have the mouth of the shell accurately closed by a thin plate of shell or chitin. It is seen closing the orifice of the Wentletrap figured opposite, and on the end of the foot of the Sting Winkle beside it. It is known as the opercidum, or cover, and at one time was con- sidered to be the other valve, bringing the univalves into close agreement with the bivalves. But a little consideration serves to show that the operculum is not part of the true shell, for it is not a product of the mantle, but of the foot. And this brings us to the consideration of the enormous difference between the shells of, say, the Oyster and the Whelk. In spite of the very high value, commercial and epicurean, that is set upon the Oyster, present-day knowledge all seems to point to the probability that he is a degenerate from the form of the ancestral mollusk, which almost certainly had a head and something approaching a masticatory apparatus. Whilst some of its de- scendants in successive generations went on im- proving the simple tent-like form of their shells, by twisting them into spirals, and developing their organs to fit them for lives of varied activity ; others, finding that the sea was well provided with food, appeared to think that activity involved an unnecessary strain upon the organism. These simply 38 Shell Life attached themselves to rocks or weeds, or burrowed slightly in sand or mud, and lay with their mouths open to receive such good things as might chance to fall in. They lay over on one side, the mantle became divided into two lobes, and consequently the shell moulded upon its surface was in two valves hinged together, the head was lost, though the toothless, tongueless mouth remained, hidden by the lobes of the mantle. That the general tendency of development was in the direction of improving upon the simple ancestral form is indicated by the fact that of the enormous number of distinct species known in a fossil or recent condition, only one-fifth are bi- valves, whilst three-fourths have a single shell. To get back to the adaptation of the shell to the conditions of life : pelagic or floating species have the shell reduced to a thin glassy consistency, serv- ing the double purpose of rendering them light and transparent, the transparency preventing their easy detection by enemies who are likely to regard them instead as part of the jelly-fishes upon which such pelagic mollusks largely subsist. Some species that dwell in deep water out of the reach of surface convulsions have very thin shells also. At the other extreme some deep-water forms that have evidently been much sought after by the larger fishes for their food secrete very thick and solid shells that may be proof against the equally hard and stony palate-teeth of the fishes. In all the fresh- water forms it is evident there can be little need for thick and heavy shells, and as a matter of fact they are light and thin. Especially is this The Shell and its Formation 39 the case with the pond-snails, who probably find carbonate of lime not very plentiful in their little world, neither is it greatly needed as a protection. A strong shell is required by those land-snails whose habitat exposes them to the attacks of birds like the thrush, but it is essential that the shell should not be heavy. The carbonate of lime is in this case obtained from the plants upon which the snails feed, and it is therefore only to be expected that on chalky soils the snails should be exceedingly abundant, whilst in sandy districts they are rare or entirely absent. But it does not follow that on chalky soil the shells will be necessarily thick, Clausilia laminata, for example, plentiful in beech woods on the chalk, having a thin semi-transparent shell, apparently with little chalk in it. In the slugs of our gardens and hedgerows the shell has been reduced to a little shield covering the breathing organ, or to a few granules of lime beneath the mantle ; whilst many of the Sea-slugs have found it an advantage not to develop the shell at all, though they are born with the nucleus of a shell like all other mollusks. A somewhat similar case to that of the terrestrial slugs, so far that is as the shell is concerned, will be found among the Cephalopods : the Sepia produces beneath its mantle the familiar " cuttle-bone," in the Squid this is reduced to the long transparent " pen " of animal matter only, whilst in the Octopus the shell is represented by two little stylets in the substance of the mantle. LTHOUGH it is not a part of my purpose to enter upon the anatomy and physiology of the Mollusca beyond what is necessary for an understanding of the differences in form and habit of the various groups, there are certain points which are so char- acteristic of the class, or which distinguish the several orders, that some elementary reference to them is essential. But the reader whose interest at present extends only to external forms and coverings may, an it please him, for the present skip this chapter and return to it later. Though, as we have seen, the bivalves have probably retrograded so far from the prevailing type as to have lost their heads, these presumed degenerates have retained a mouth and a digestive system as being necessary to their continued existence. But though the mouth remains in these bivalves, it is little more than an opening to the Feeding and Breathing 41 gullet and the stomach ; there are neither jaws, teeth, nor tongue. The absence or presence of a tongue has been found to be an important item in classification, and we find that some authors have divided the Mollusca into two unequal groups, the Tongue-bearers (Glossophorct) and the Tongue- less (Afflosaay, the Tongue-bearers including the Cuttles and the Univalves, the Bivalves constituting the Tongueless. It is in the Cuttles that we find the highest development of jaws for the purpose of biting off portions of food. These are composed of chitin, formed much like the beak of a parrot, and working much in the same fashion except that in the case of the Cuttle Uppe ' , (a > an . d ' w ^ <';> P. rt j1'. of the beak of a Cuttle-fish (Sepia) the upper jaw works within the lower. The more ordinary type of jaws may be observed by watching any of our common snails feeding. The Land-snails (Helix) have the jaw only in one portion, and this is placed behind the upper lip ; but in the Pond-snails (Limncea) there is an accessory plate on either side of the mouth, and these act with the upper plate. If a pond- snail be watched as it glides up the glass of an aquarium and cleans off the minute vegetation, the mechanism of the jaws will be understood better than from a description. The food having been cut off by the jaws is not yet in a condition to be readily digested; it has first to be masticated. This work is performed 42 Shell Life by a very remarkable organ peculiar to the Mollusca. It is an almost transparent ribbon of chitin, whose upper surface bears a large number of minute teeth, of varying forms, number, and arrangement, set in transverse rows, and each row symmetrically divided into central, lateral, and marginal teeth. The organ is variously known as the tongue, the radula, the lingual ribbon, or the odontophore. Only a small portion is brought into action, the remainder xX <^^"^ being coiled away at the back of the ^^ mouth, ready for use when the teeth Portions of the tongue J of a wheik, with on the torepart shall have been worn a row of teeth ^ These teeth as a rule are few (greatly enlarged) . and large in those species ot car- nivorous habit, whilst those of herbivorous tendency have them small and numerous. Many of the carnivorous mollusks make their tongues serve a double office, for they have no jaws, and the whole of the cutting and breaking up of their food has to be done by the teeth; this, no doubt, explains their larger size. The number of these teeth to one tongue or radula varies to a remarkable extent : thus, one of the Sea- slugs (jEolis coronata) of our own coasts has only about 17, whilst the large brown Sprinkled-snail (Helix aspersa) of our gardens and hedges has 105 teeth in each transverse row, and no less than 135 rows that is, a total of 14,175 teeth in one mouth. There are, of course, many species with numbers intermediate between JZolis and Helix; the large Pond-snail (Limncea stagnalis), whose teeth are shown in the figure a below, has 111 such teeth in Feeding and Breathing 43 a row and about 110 rows = 12,210; the little Fresh- water Limpet (Ancylus fluviatilis) I has 120 rows of 75 = 9000; and the Amber Shell (Succinea putris) c of our watersides has 50 rows of 65 teeth = 3250. A Mexican species of Helix is said to have 40,000 teeth, whilst Umbrella, a Mediterranean mollusk, has so many it is impossible to count them, but they have been estimated to number somewhere about 750,000 ! Every one of these minute teeth has Teeth of radula of a, Limncea stagnalis; 6, Ancylus fluviatilis; c, Sttccinea putris (greatly magnified) muscular attachment to the radula, and can be erected or depressed at the will of the mollusk. These remarkable organs extracted from the mouth of any of the common mollusks of our hedges or seashores, make beautiful objects for the microscope ; but their preparation requires a good deal of care and nice manipulation. They are first boiled in caustic potash to get rid of the animal matter, and after washing in clean water are mounted in glycerine jelly. Most of the mollusks that bear these radulae are also provided with salivary glands, and in some of the species that habitually bore through the shells 44 Shell Life of others in order to feed upon the occupant, the saliva is found to contain an appreciable proportion of free sulphuric acid, which evidently softens the spot of shell upon which the radula is then brought to bear. The molluscan stomach, with which we have not space to deal, varies with the habit and food of the mollusk. Some species have it lined with knife-like plates, or with knobs and teeth. The Canoe-shell (Scaphander lignarius) has a gizzard in which the Tusk-shell (Dentalium), its favourite food, is crushed up prior to digestion. Having glanced at the mechanism by which the mollusks prepare their food for assimilation, let us take a similarly brief and superficial view of the means whereby the blood is aerated in the principal groups. It is evident that one system of respiration will not serve for the whole of the Mollusca, seeing that whilst some spend their lives submerged in fresh or salt water, others live as constantly surrounded by the atmosphere. Many of the fresh- water species, however, breathe air only, and cannot therefore venture far from the surface, their air-chamber requiring to be frequently recharged. On the other hand, marine species like the Limpet and Periwinkle, provided with gills for breathing water, have to spend hours on the dry rocks, and can only do so by storing sufficient moisture to keep their gills damp. It is probable that the ancestral mollusk had no special organs for respiration, but simply absorbed oxygen through his surface tissues, beneath which the blood flowed and took up the vital gas. Then Feeding and Breathing 45 probably the production of a shell closely covered so much of the surface that a simple comb-like organ was developed to carry on this function constantly. Such an organ exists in what we may regard as little different from the primitive form in certain species of Mail-shells (Chiton). Into this comb-like organ (ctenidium) the blood flows, and through the tissues of the branches absorbs the oxygen from the surrounding waters. In other species these simple ctenidia have degenerated until no longer functional, and their place is taken more efficiently by a series of plate - like gills encircling the body Such a form of res- piratory apparatus may be seen in the Limpet, of which a figure is here given. Here the letters c c c show the position of the encircling series of gill-plates, whilst the true but aborted ctenidia must be sought in a pair of very small yellow bodies situated on the sides of the neck. External branchiae a, foot; 6, are also developed in many of the Sea-slugs, taking the form of cerata, whip- like, plume-like, or foliage-like processes from the back, face of Limpet antle ; c, gills ; d, mouth ; e, tentacles 46 Shell Life through which the blood flows and takes up oxygen through their tissues. In the bivalves, as will be more fully described later, the gills vary greatly in the degree of complexity. They are usually placed on either side of the body between it and the mantle which thus form the branchial cavity. In most cases a couple of tubes or siphons lead to this chamber from the exterior, one admitting fresh supplies of water, the other carrying off that which has passed over the gills and been robbed of its oxygen. In the land and fresh-water snails (excepting the few whose shells are closed by an operculum) respira- tion is effected in a " lung-chamber," though there is no lung in the sense of a spongy mass of tubes as we know it in the higher animals. The chamber, which opens on the right side of the snail, more or less towards the front part, is lined with a network of branching vessels through which the blood circulates. Air is taken into this cavity frequently when the mollusk is active, and then the opening is closed until all the oxygen has been taken up by the blood, when the chamber is refilled and again closed. The Pond-snails (Limncea) when living in shallow water frequently come to the surface to recharge this cavity with fresh air, but when living at considerable depths they appear to absorb the oxygen from the water, whether by filling this lung-chamber or through the general skin-surface is not quite clear. In intimate relation with the varied forms of gills or lungs there is, of course, a heart ; and where there is only a single gill there will only be one auricle and one ventricle to the heart, but there may be two or four auricles if there are as many gills. From the Feeding and Breathing 47 gills the oxygenated blood flows to the heart, whence by way of the aorta it is distributed throughout the body, and returning by veins it is again passed through the gills. It must not be supposed, however, that the circulation is as rigidly confined in definite tubular vessels as in the higher animals. Much of the blood appears to flow indefinitely in irregular spaces of the body called lacunce and sinuses, getting reinforced by that which has passed through the gills and heart, but perhaps not all of it finding its way back to these organs. The vital fluid is in most mollusks colourless, but a few of the more active species possess the red colouring matter (hcemoglobin) which distinguishes the blood of vertebrates. S we have just learned in the cases of respiration and circulation, we must not expect to find in the Mollusca organs of sense similar to those of the higher animals. The whole of the body being so soft is no doubt highly sensitive ; nevertheless there are special organs for special senses, and these organs are well furnished with nerves to convey their im- pressions to the local brain. For there is no grand centre of the nervous system as furnished by our brain. Instead of one great trunk-line of nerves and nerve-bundles, as in the vertebrates, we find in the mollusks a system of large and small nerve-threads traversing the length and breadth of the animal, connected here and there by loops (commissures), and from certain knots (local brains or ganglia) sending off a number of short branches. All these local brains are connected by other nerves, and the chief of them are known as the cerebral, the pedal, and Seeing, Hearing, and Smelling 49 the visceral ganglia. In those mollusks that possess a distinct head nerves go off from the cerebral ganglion to the tentacles, the eyes, and are connected with a pair of small ganglia (the buccal ganglia) that command all the mouth parts, the pedal ganglia supplies the foot, the visceral or pleural ganglia send nerves to the mantle, the heart, the gills, the stomach, and the other internal organs. The eyes of the Mollusca are alike different from those of higher animals, and from one another. The highest development of the molluscan eye is found among the Cuttle-fishes and their allies, but a pair of well-developed eyes is the possession of nearly all the mollusks that are furnished with heads. Yet the presence of a head is not absolutely essential for the acquirement of eyes, for some of the bivalves, such as the Scallops and Ark-shells, have eyes on the fringes of the mantle, and some foreign species of Mail-shells (Chiton) have been found to have certain parts of their shell-plates closely studded with minute pigmented dots which serve the office of eyes. In the land-snails the eyes are carried at the top of the longer pair of tentacles, a position which allows the snail to see in all directions ; in the water-snails the eyes are at the base of the tentacles. Species that live underground have the eyes more or less aborted. Our own little Needle-shell (Ccccilianella acicula), which lives an entirely subterranean life, has lost them altogether ; so also have several of our marine- snails that are always seeking their food under the sand. Others of similar habit have eyes, but they are covered by thick skin that can allow very little impression of light to reach them. So Shell Life From a consideration of a series of molluscan eyes it is not Difficult to surmise the developmental history of the most perfect among them. Thus, in the Limpet to which we have already referred as being probably much like the ancestral mollusk there is little more than a fold of the skin forming a depres- sion lined with rod-shaped cells containing pigment and forming a retina, which is connected \vith the optic nerve. In the Tops (Troclms) the depression of the epidermis is greater, so that it encloses a spherical space lined with retinal cells and filled with fluid (vitreous humour), but open in front so that the face of the eye is bathed in water. In the Sting Winkles (Murex) there is an advance upon this form, for the opening of the eye has become quite closed and there is a lens before the vitreous humour. Now the eyes of these three species present a very close resemblance to three stages in the development of the eye in the embryo of the Squid (Loligo), which shows an advance upon Murex by producing an iris round the fore-part of the lens, an optical chamber in front of the lens, and a transparent cornea before that again. It must be apparent that eyes are of the greatest value to the most active species of Mollusca the Cuttles. These have, consequently, developed their eyes to a greater degree of efficiency than other orders. The inactive, often fixed, bivalves have been found in many cases to have a pair of eyes on what may be regarded as the head during their larval condition, thus indicating that in the early history of the Pelecypoda they had eyes in the adult state. Those bivalves that lead a more active life, such as Seeing, Hearing, and Smelling 5 i the Scallops (Pecten), have a considerable develop- ment of eyes upon the fringes of the mantle, and it has been reasonably surmised that these eyes enable them to guide themselves in their vigorous zigzag flights through the waters. But it may be regarded as tolerably certain that these eye-substitutes, or pigment spots, that are crowded upon certain parts of the mantle in many bivalves are merely sensitive to varying qualities of light and are useless for observation. The casting of a shadow upon such species affects these pigment spots, and from them the intelligence is conveyed along the nerves to the various ganglia, with the result that as a precaution- ary measure, the foot and siphons are withdrawn and the valves are shut with a snap. The Land- snails (Helix) being crepuscular or nocturnal in their habits can see farther in twilight than at midday, but their visual powers are very limited at the best, and extend only to a distance of about six millimetres. The Round - mouthed Snail (Cyclo- stoma elegans), however, whose eyes are not mounted on tentacles, can see to a distance of about a foot. The sense of hearing has not been very extensively investigated, at least little but negative results have been obtained from experiments made with a view to testing its extent. One experiment of the kind made by Mr. W. Bateson in the Plymouth Laboratory of the Marine Biological Association, a few years ago, showed that a Saddle-oyster (Anomia) sus- pended in the water to be free from any chance of jarring of the solidly -framed tank, closed its valves on Mr. Bateson making a creaking sound 52 Shell Life of a particular pitch by rubbing his finger along the glass. The seat of hearing resides in a pair of closed cells called otocysts filled with a clear fluid in which are suspended one or more grains of chalky material called otolitks, and lined with cilia. These otoliths may be very numerous, and they are agitated by sounds in the immediate neighbourhood of the animal. These vibrations act upon the cilia which convey impressions by the acoustic nerve to the cerebral or the pedal ganglia. The most important of the senses to the Mollusca is apparently that of smell. It is quite certain that it is much farther-reaching than either vision or hearing, and more constantly in use. Great numbers of carnivorous mollusks, such as whelks, dog-whelks, and naticas, are found in lobster-pots baited with " high " fish which they have smelled through the waters. Slugs appear to be highly endowed with this sense. Apples and bean-pods dropped in the centre of a road will draw slugs from the hedges on either side. As soon as certain species of Agaric come up in the woods slugs bear down upon them and commence feeding upon them. They are also able to locate a dish of milk in a dairy and proceed to drink from it. Of course, this sense is more highly developed in the active univalves than in the more or less sedentary bivalves, but the agile Pea-shells (Pisidium) are not deficient in it, as shown by the numbers that swarm over any dead animal that has been thrown into a ditch or pond inhabited by them. Some of the Sea-slugs have a special pair of antennae furnished with projecting plates which are believed Seeing, Hearing, and Smelling 5 3 to collect sensations of smell from the surrounding- waters. They are therefore known as rhinophwes or nose-bearers. The sense of touch is acute, as must be obvious to anyone who has handled almost any species of mollusk. Creatures of such soft substance must necessarily be very sensitive in this direction or they would meet with many injuries. To touch a snail, however lightly, is to cause it to shrink into its shell at once. A slug has no shell that it can crawl into on being molested, but it instantly draws in its eyes and antennae and hunches the body up into a thick, short heap that exposes the minimum, of surface to attack. In many of the shelled species the margin of the mantle is cut up into lobes and filaments which are all very sensitive to touch, and in some there is in addition a pair of protruding palps near the mouth that serve as tactile organs. These palps are also present in the bivalves but there, except in special cases, most of the tactile work is performed by the foot and the siphons. ANY different systems have been adopted at various times for the intelligent and orderly arrangement of the bivalve mollusks (Pelecy- poda). That followed in these pages is based upon the character of the breathing organs, and, all things considered, this appears to afford the most natural basis. In the sketch of the Swan Mussel in the opening chapter the position and structure of these organs were briefly indicated, but in that species the gills have reached a high stage of development. Starting from the simplest form of such organs we find examples in the little Nut-shells that burrow in the mud and sand of our seashores. The most plentiful of these is the Common Nut- shell (Nucula nucleus), whose empty shells may be found along our beaches washed in from deeper 3\ut-shells and Mussels 5 5 water, its living range being between 3 and 145 fathoms of water. The shell, as shown in the figure, is bluntly triangular in shape, coloured outside with yellowish green marked with darker growth-lines running parallel with the lower margin, whilst many very fine grooves radiate from the rather prominent beak to the lower margin. The little creature that produces this shell is cream coloured ; its mantle has plain margins, and its oval foot is toothed all round the edge. The mouth and lips are small, but the lips have long appendages which are protruded from the shell at the same time as the foot, and used as sense-organs in the search for food. The small brown gills are simple and plume-like. The maker of the Nut-shell burrows among sand and gravel, the '' foot " being extended to its utmost length and worked between the fragments ; each tip of the tooth-like edges then catches hold of a particle of gravel, the foot as a whole is shortened, and so the shell is hauled along by the contraction of the foot. At the same time the appendages of the lips feel about for food. When the dredge has scraped up one of these little mollusks from the bottom there is no foot visible ; it has been withdrawn into the shell, and the valves now fit closely together. Only the insertion of a knife to sever the muscles, or to break them by leverage, can effect the opening of the shell. The examination of an odd empty valve, picked up on the shore, or of the accom- panying figure, will help us to understand how this firm closure is maintained. It is a left-hand valve, 56 Shell Life so that the figure shows it in its natural position, with the concave side towards us. In the com- plete shell the upper margin of this valve is connected with its fellow by a kind of hinge (ligament), resembling those primitive leather hinges by which boys attach lids to boxes and doors to rabbit-hutches. This shell hinge, however, is more horny than leathery, and is, so to speak, fixed on the stretch, and this explains why when a bivalve mollusk dies its shell gapes open : the hinge-ligament exerts a pulling action which tends to separate the lower edges. Just beneath the beak inside each valve there is a little spoon-shaped projection containing a bulging bit of elastic cartilage, which also serves the purpose of forcing the valves apart. On either side of this cartilage is a row of low Hinge-teeth ridges like the teeth of a comb, and into (enlarged) the spaces between similar teeth on the right valve fit; the lower margin of each valve is also faintly marked in a like manner. The number of the hinge-teeth varies in different species ; in the present one there are about 15 teeth in front of the beak and about 25 behind it. The object of all these interlocking teeth is to ensure the accurate closing of the valves when they are brought together, and to prevent any lateral movement that would enable an enemy to destroy the hinge. But the mechanism by which the two valves are closed and held tightly together, in spite of the opening action of the hinge- ligament, consists of a couple of bands of muscle, one towards each end of the shell. On the pearly inner surface of the valve we can see slight oval impres- S^ut-shells and Mussels 57 sions of the ends of these muscles; these are the points to which they were attached. The hinge- teeth on the valves of the Nut-shells are simple in character, but we shall find in other species that they gradually became more complex. There are three other native species of Nut-shells whose peculiarities may be briefly noted in contrast with those of the common species. The Furrowed Nut-shell (N. sulcata) has a larger, more triangular shell, with five ridges parallel with the lower margin ; dull olive. Found locally in from 3 to 50 fathoms where the bottom is of sandy mud or clay. The Shining Nut-shell (N. nitida) is more acutely tri- angular, yellowish brown, and very glossy; mantle fringed. Sand and gravel from extreme low water to 86 fathoms, but not very common. The Thin Nut-shell (N. tenuis), though still triangular, has a tendency to roundness of outline, but flattened from side to side; brownish yellow, thin, and glossy. Found locally, in sand and mud from 25 to 100 fathoms, chiefly along the Scottish coasts, the north- east of England, and east and south of Ireland. The external colours given above are those of the living epidermis or periostracum, which invests and protects the shell from the action of gases dissolved in the water. Beneath this covering the actual surface of the shell may be entirely different in hue, but where the epidermis is permanent it will be more convenient to indicate its colour rather than that of the shell. Closely allied to the Nut-shells are the four native species of Leda, but they are readily distinguished by several differences in form and structure. One 58 Shell Life important advance in development consists in the production of the hinder part of the mantle into two long tubes or siphons, which are thrust out beyond the shell and reach up to the water above the rnud and sand in which the creature burrows. The purpose of these DwJfLeda siphons is to enable the Leda to remain safely buried whilst it gets a constant fresh current of water over its gills, and to bring microscopic food to its mouth. Through the lower of these tubes the fresh supplies pour in, whilst the vitiated current carrying off waste passes out through the upper tube. With a view to the better protection of these siphons the shell has been elon- gated backwards. In the Dwarf Leda (L. pygmcea) the siphons are not very long, and they are united throughout their length, showing that though the mollusk affects deep water (20 to 86 fathoms) it does not burrow much below the surface of the mud, or indeed remain entirely covered by it. Its tubes may be entirely withdrawn into the shell, which closes all round as do the Nut-shells. The shell is scarcely a quarter of an inch long. The Beaked Leda (L. minuta) is a much larger species, and the great change in the shape of the shell shows that the creature is given to burrowing more deeply and to remain buried. The siphons, which are united only for half their length, have become much interior of Beaked Ueda-stiell longer in order to reach the water above, and the shell has become greatly lengthened behind for their partial protection, there being and Mussels 59 insufficient room in a shell shaped like that of L. pygmcva to withdraw the whole of the long siphons. The valves at this point do not fit closely. There is a slight gape, and this indicates that owing to the constant protrusion of the siphons the mantle is never able to extend the edges of the shell so that they will meet. In some other bivalves we shall see that the foot also is kept so constantly distended that the shell gapes at the front end also. The hinge-teeth are in this species less simple in their shapes, as will be seen in the figure of the interior of a left valve. It is found in muddy gravel and sand between 20 and 100 fathoms deep, on our northern coasts. The two genera Nucula and Leda constitute the sole British representatives of the order Pro- tobranchiata, the bivalves in which the branchia3 or respiratory organs have the simplest character. They consist of parallel, unbranched, independent filaments arranged in two rows on each side of the central body-mass. In the next lowest group, the order Filibranchiata, the filaments have become so long that they are folded back upon them- selves and show signs of lateral adhesion. The order includes the Saddle- oysters (Anomioi), the Ark-shells (Area), and the TIT i / ~MT i *7 \ Saddle-oyster under Mussels (Mytilus). The Saddle-oyster (Anortiia ephippiuni) is a thin, flat, little pearly shell found on old oyster-shells, crabs, 60 Shell Life rocks, and other submerged objects, and is not un- reasonably though quite inaccurately regarded by the 'long-shore folk as the young of the true Oyster (Ostrea). It is not even closely related to the true Oyster, nor is it edible. It is by no means an easy task to persuade fishermen that these are not young oysters, but the quickest method of convincing them is to prise off the Saddle-oyster and exhibit its under- side as shown in our figure. It is then seen that there is a pear-shaped orifice in the lower valve through which an attachment plug passes and fixes the Saddle-oyster to its chosen support. No genuine Oyster is attached in this way, nor has it a hole in its shell. The Common Saddle- oyster is about 2 inches across when full - grown, variable in outline, but more or less circular. It is never very thick, but varies Side view of Saddle-oyster, * showing mode of attach- in this respect according to age. Outside it is dull white in colour, or tinged with yellow, pink, or brown ; within it is polished and opalescent. The lower valve in its growth follows the modelling of the surface to which it is attached, whether that be the smooth rounded stem of a huge seaweed, the rough sur- face of the rock, or the ribbed shell of a scallop. The upper valve, of course to a less degree, follows the shape of the lower. Normally the lower valve is flat and the upper one convex. There are no hinge-teeth as in the Nut-shells, though there is a half - moon shaped pad of cartilage to keep the valves apart when the single muscle is relaxed. The plug by which the shell is fixed to its support is ^{ut-shells and Mussels 61 attached to the upper valve and passes through the lower one. It appears to represent the byssus-threads of the Mussel and Scallop united into a solid mass. The expanded end evi- dently corrodes the living surfaces to which it attaches, for it is frequently found to be lodged in a little pit. The animal varies in colour from yel- Ri ht side of Anomia, with sheii -removed loW tO red and fl, opening for hinge; m, adductor muscle; , T . n, calcified byssus brown. Its mouth is large, and furnished with a pair of long slender lips. As the animal does not burrow, and is usually found solitary, it can develop its shell pretty equally in all directions ; the mantle is therefore more or less circular like the shell, its margin fringed with two or three rows of yellowish filaments. Again, because it is not a burrowing or otherwise active animal, the white cylindrical foot is very small. There is a variety (aculeata) in which prickly scales are developed on the upper valve. The only other British species is the Ribbed Saddle - oyster (A. patelliformis), smaller than the last, and attaining to little more than half its dimensions. From 20 to 30 waved ribs radiate from the beak to the margin, and the shell is often ornamented with 62 Shell Life streaks or spots of red-brown, and by a number of fine overlapping scales. It is a common but little- known species, its range being only between the depths of 10 and 86 fathoms. Both these species appear to owe their security alike from storm and enemy to the thin flat form that sits so tightly on its chosen base, and affords little opening to the predatory fish or bird that might consider its thin body worth prising off. The Ark-shells (Area} present an appearance very different from the exceedingly thin Saddle-oysters. The Common Noah's Ark (A. tetragona} is a quaint little yellow and brown box - like shell of distorted aspect that loves to spend its time in the crevices of rocks, or attached by its byssus to the empty shells of other bivalves. A perfect specimen is covered all over with ridges which radiate from the beaks to the lower margins, whilst other but less prominent ridges cross these at right angles ; but owing to its habit of grubbing in crannies and among rubbish, the greater portion of this ornamentation gets rubbed off, as shown in the illustration, and consequently it is not easy to obtain a good example. The beaks are wide apart, and the 40 to 50 hinge-teeth are of simple form. Towards the hinder margin of the whitish mantle there is a number of closely grouped ocelli dark spots that are not true eyes but which are so sensitive to changes in the intensity of light that they serve the same purpose. They consist of cells filled with a dark pigment and covered with a cuticle of high refractive power. Real eyes are DOG COCKLE EXTERIOR ; 2 DITTO, INTERIOR ; 3 GREEN CRENELLA. 3{ut-shells and Mussels 63 seen in the larval condition of many species, and this is part of the evidence that the bivalves have degenerated from a higher primitive type. The conical white foot has a deep central groove, through which a dark green byssus is spun. The porcelain- lined interior of the shell bears large oval impressions of the muscles, and the inner margin is marked with a series of indentations, those of one valve fitting into those of its companion. The Noah's Ark occurs on all our coasts, at all depths. There are four other native species : one, the Hebridean Ark (A. pectunculoides), with thinner shell, finer sculpture, and the left valve larger than the right, is found chiefly in deep water (35 to 100 fathoms) round Shetland and the Hebrides. Another, the Milky Ark (A. lactea), has valves of equal size, their white colour partially hidden by the brown velvety epidermis. The animal is not much given to burrowing, but chiefly attaches its short horny byssus-threads to the inside of old shells and to rock-crevices between 15 and 25 fathoms, on all our shores. The Dog - Cockle or Comb - shell (Pectunculus glycimeris) has an appearance quite distinct from any other native species, and requires very little description to enable one to identify it. The shell is nearly circular, of a dull yellowish - white colour, irregularly marked with zigzag lines and conical patches of dark red. The epidermis forms a thick dark brown velvet, but from most specimens that are washed up the beach this is all rubbed off. On specimens dredged up from the deeper water it 5 64 Shell Life affects (7 to 90 fathoms), a band of epidermis will usually be found bordering the lower margin. Large examples measure 2| inches across. It would appear that many fishes not strong enough to crush this solid shell yet make attempts to wrest its valves apart, for great preparations have been made to keep off such enemies. The valves are united by a number of bundles of ligament, attached to long triangular cavities sunk in the shell between the beak and the broad hinge-plate. The hinge-teeth are thick, and in adults number about six on each end of this plate, which is plain in the centre, though young individuals exhibit a few minute teeth here. The impressions of the mantle and muscles are very deep on the interior, and the flat, lower margin is impressed with about 50 teeth, in appearance like the edge of a coarse comb. Those of the two valves interlock, and so prevent the slightest shifting by the most powerful assailant when the shell is closed. In spite of this, it has one enemy that it cannot defy. This is the Cat-fish, which cracks the stony shells with its long powerful teeth as though they were nuts. The animal is of sluggish habit, and lives on the surface of gravel and among "nullipore," all round our coasts. It does not burrow, and therefore has no siphons, but the edge of the mantle is somewhat contracted and protruded at the hinder side of the shell ; at this part, too, it is studded with a great number of black eye-spots. The Eared Limopsis (Limopsis auritcc) somewhat resembles the Dog - Cockle internally, though the shell is less round and owes its name to a fancied likeness to Lima, the File-shell. Although common S\ut-shells and Mussels 65 as a Tertiary fossil, in a living or recent state it is rare. A few specimens have been taken in deep water (85 fathoms) off the Shetlands. It is a very small, glossy white shell, marked with fine lines radiating from the beak, and crossed by irregular ridges. The yellow-brown epidermis takes the form of a fringe of long hairs. The margins of the shell are rounded except behind the hinge, where its straightness gives the eared appearance to the shell. Like those of the Dog-Cockle, the strong teeth of this species are in a continuous line, but confined to the hinge - plate. The lower margins are devoid of teeth. It has a long thin foot, by means of which it- creeps and climbs, and spins an almost transparent thread. The Common Mussel (Mytilus edulis) is one of the most useful of the Mollusca to mankind, for in addition to its wide use as a food, it is of great value as a bait in the long-line fishing. Strongly gregarious in its habits, it attaches itself to rocks, timbers, and masonry by its tough byssus spun by the short dark- brown foot. This habit of associating in closely packed masses has doubtless led to the contracted wedgelike form of the shell, and to the absence of in this case unnecessary hinge or marginal teeth. Occasionally a few small hinge - teeth are developed, but as the species indulges in very little locomotion after early life these are. not much needed. The mantle has a double margin, the outer one plain, whilst the inner is at different parts fringed or toothed, and on the hinder part formed into an im- perfect siphon. Though the Mussel is always found hung up by its 66 Shell Life byssus, it is by no means a prisoner. It possesses the Common Mussel (Mytilus edulis), closed and attached by the byssus (nat. size) power of separating itself from these threads. In an aquarium when a Mussel has attached itself and then S^ut-shells and Mussels 67 grown dissatisfied with its position, you will see the broken and discarded byssus-ends in patches all over the tank. Mussel-beds on some parts of our coasts have been jealously watched because of their power to hold the mud and sand, and prevent the foreshore shifting away with the tides and currents. The story of Bideford Bridge is founded upon the know- ledge of the bind- ing power of the byssus. Most books mentioning Mussels repeat the legend that Mus- sels instead of mortar bind the stones of the bridge together, and that, there- fore, the town authorities forbid the removal of the mollusks that throng its piers. It is true that a prohibition of this sort exists, but it is due to a conviction that the Mussels keep off the wear and tear of the tide. Mussels at times give rise to very unpleasant symptoms in those who have eaten them, occasionally even causing death. All kinds of theories have been invented (nat. size) lantle edge; 6, foot; c, byssus; d, e, muscles of the foot; /, mouth; g, lips; h, lobe of mantle; i, j, gill plates 68 Shell Life to account for this unwholesome condition, but it would appear to be due to their growth in the com- paratively stagnant waters of harbours, or to their being laden with spawn. In various parts of the coasts of Europe, Mussels are in a sense cultivated by placing boughs of trees on the mud, which become covered thickly with Mussels. The boughs are taken up after a few years and sold by weight. The accompanying woodcut showing the various parts of the animal will help to make clear further descriptions of the bivalves. The large Horse Mussels are by most authors separated from the genus Mytilus and known by the name of Modiola. Of these we have several distinct species. Their shells are more oblong than wedge- shaped, quite without teeth, and the byssus though much finer is also more ample. Instead of hanging themselves up, they burrow, and some spin a kind of byssal nest around themselves in which gravel and other marine rubbish is mixed up. The affix " Horse " signifies that these Mussels are coarse and unfit for food. The Common Horse Mussel (M. modi- olus) may be distinguished readily from the Mussel by the fact that the beaks instead of being at the extreme pointed end of the shell are at a slight distance from it. The thick solid shell is purplish yellow in hue, but its true colour is dis- Common Horse * Mussel (re- guised by the dark brown epidermis which, in young specimens, becomes drawn out into long fringing processes. As in the Mussel, the impressions of the mantle and muscles are and Mussels 69 well marked. The animal, too, may be at once identi- fied by its difference in colour from the true Mussel. The latter has a creamy white tint, but this is dark orange ; the foot red, whitish towards the thick and wrinkled base. Both margins of the mantle are without fringe or toothing, though covered with delicate cilia. Its habitat is a muddy gravel at various depths between low water and 80 fathoms, most plentifully on our northern coasts. Its usual size is about 5 inches long, but it has been found over 9 inches in length. Its roomy interior is a favourite resort of the Pea-crab, which appears to live on the most friendly terms with it, and to avoid all risk of injuring its host has got rid of every one of those angles and sharp edges that characterise most crabs, and is now as smooth and glossy as glass, with every edge rounded. There are several other British species described, of which one or two are possibly only juvenile forms. The Bearded Horse Mussel (M. barbatus) is little more than 1 inch long, with an orange or scarlet shell, mostly hidden by a thick yellow-brown epidermis, which on the back and front of the shell is so split up as to form a fringe of thorns. Each of these thorns is bearded along one side only, as shown in the figure of a small portion. It occurs on the south and west coasts of England and Wales ; rarely on the east ; also on the south and west of Ireland. Its habitat is on rough ground from low water to 18 fathoms. The Tulip Horse Mussel (M. adri- atica) has a broad convex shell, slightly smaller than Shell Life the last, thin and glossy, of a yellowish hue, the hinder portion being also usually marked with rosy or purple streaks after the manner of a tulip. The thin polished epidermis is almost transparent. It occurs very locally in Scotland, more frequently in the south of England, around Ireland, and along the Welsh coast, preferring a bottom of gravel, or sandy mud, at depths ranging from 7 to 40 fathoms ; but it cannot be reckoned as at all a common shell in British waters. The general aspect of the Bean Horse Mussel (M. phase- olinus) is similar to that of the Bearded Horse Mussel, owing to the manner in which the epidermis is split up into slender processes. But the difference may be seen at once if one of these filaments be examined, for neither of its edges is bearded as in M. barbatus. Stripped of this shaggy coating the shell would be seen to be very much the shape of a kidney-bean, as indicated by the name phaseolinus, and of a yellow colour tinged with purple. The hinge-plate is sculptured into a series of round teeth. It is about three- fourths of an inch in length. It is common on all our rocky coasts from low water to a depth of 86 fathoms. It often disguises itself by spinning up fragments of shell and gravel with byssus into an outer envelope. The " crenulated " or notched hinge and upper margin of the last species constitutes a connecting link with the genus Crenella, which has obtained its name from such ornamentation. The shell resembles that of Nucula in the fact that it is entirely Bean Horse Mussel -s hells and Mussels 71 composed of " mother-o'-pearl." The mantle forms only one siphon, that for getting rid of waste, and this is very short, fresh supplies being taken in by the open front. The foot is of peculiar construction, consisting of a cylindrical stalk and a tongue-shaped expansion which is used for crawling. Instead of spinning an extensive byssus, these content them- selves with a single thread by means of which they suspend themselves. The genus is now restricted to two species, though formerly those now forming the genus Modiolaria were included in Crenella. The Glossy Crenella (C. rhombea) has a solid- looking, glossy white shell, marked by delicate radiating ribs, and covered by a slight pale yellow epidermis. The "broad hinge-plate is notched or creriulated as already noted, and bears a wedge- shaped tooth with notched edges. The interior edges are also crenulated, so that the valves securely interlock all round. It is less than one-quarter of an inch in length, and occurs on rocky coasts in the south-west of England and round the Channel Islands from low water to about 20 fathoms. The Cross- cut Crenella (C. decussata) is more oval than sa^ the last, of the dimensions shown in the figure. ^^_ It is also glossy, but the number of ribs is cut smaller, and they are crossed by fine hair- c like lines. At the points of contact these lines are slightly raised into minute rounded points. The epi- dermis is thicker and of a darker hue, so that the general appearance of the shell's colour is pale olive. It affects gravelly sand on our northern coasts, from Yorkshire and Northumberland to the Shetlands, and ranging from 3 to 70 fathoms in depth ; it 72 Shell Life also occurs oft' the coast of Antrim, Ireland. It is very active, and likes to climb and hang suspended by its thread. The Modiolarias, though formerly regarded as Crenellas, which we retain as a popular name, differ from these in several small but sufficiently important points. The mantle forms a distinct incurrent tube in front and an excurrent one behind. The foot is strap-shaped, and may be extended until it is a mere thread two or three times the length of the shell. The shell is rhomb-shaped, but instead of the ribs on the surface extending equally all over the shell they are in two series, which leave the centre of the valves plain. The hinge-plate is notched as in Crenella, but as a rule the central or cardinal tooth is wanting. There are four British species. The Marbled Crenella (M. marmorata) though somewhat angular is roughly oval in shape, thin and glossy, pale green marbled with red- brown. Its byssus is almost trans- parent, but tolerably strong. It lives among the root-like suckers of the larger seaweeds, in the crevices of rocks, the interior of empty shells, and very commonly embedded in the tough coat of the simple ascidians. An average specimen of Ascidia mentula may yield as many as twenty of these mollusks, which do not appear to cause any inconvenience to the host. It occurs on all our coasts, but must be sought below the lowest tide-mark, in what are known as the Laminarian and Coralline zones. If not satisfied with its present quarters, it displays considerable activity in seeking others, stretching its foot to its greatest extent, and having ^ut-s hells and Mussels 73 taken hold by its tip, pulling itself rapidly along by contracting its foot again. Having secured a corner to its taste, it spins its byssus and becomes fixed for the time. The Ribbed Crenella (M. costulata) is a much smaller and brighter species, the shell pi'oportionately narrower, cream coloured marked with purple-brown streaks, which are often zigzag, and which show through the pale green epidermis. Occasionally it attains the length of half an inch. It is local on the coasts of Devon, Cornwall, Wales, Donegal, and the Island of Herm, where it may be found spun up under stones, or on small seaweeds, in the lowest range of rock-pools, often with shell fragments and gravel mixed up with its byssus. The Green Crenella (M. discors) is slightly longer and much broader than the last, yellowish brown, with a rather thick green epidermis ; less angular than the others. The animal sews together branches of the common coralline and other small seaweeds that it may dwell in safety within the nest. It is very generally distributed, and may be found abundantly in rock-pools at half -tide and below. The Black Crenella (M. nigra) is so-called because in aged specimens the epidermis assumes a black tint ; more frequently it is something between a purplish brown and dark olive when looked at closely. The colour and the sculp- ture at once distinguish it from the others. The two sets of ribs from the beaks are crossed by a third and coarser transverse set, which form a network, often with minute knobs at the 74 Shell Life intersections. It is a purely northern species, being found round the coasts of Scotland and Shetland, extending south only as far as Yorkshire and Durham ; occurring in muddy gravel at depths ranging from 7 to 90 fathoms. Large specimens may measure as much as 2i inches. It is known to northern fisher- men as the "Corduroy Mussel." These are the only genera of Filibranchiata repre- sented on our coasts. the Oyster and its allies we reach the third order of bivalve moll use a the Pseudolamellibranchiata a small order characterised by a further advance in gill - structure. The united filaments of the gill are not merely so long as to require folding back until they practically constitute four gill-plates on either side of the foot, but the edges of these plates may be united to the foot and the mantle respectively. The edges of the mantle are quite open all the way round, the foot is very small, arid the foremost of the two muscles for closing the valves is usually undeveloped. The only native representatives of this order are the Fan Mussel (Pinna), the Oyster (Ostrea), the Scallops (Pecten), and the File Shells (Lima). The Fan Mussel (Pinna rudis) has the distinction of being our largest native mollusk, adult specimens 76 Shell Life varying from 10 to 15 inches in length, with a greatest breadth of more than half that measurement. The shell is wedge-shaped, the beaks at the extreme front, the broad end gaping and closure impossible. For two-thirds of their upper margins the valves are connected by a narrow, horny, elastic ligament, set in a fold of the toothless hinge-plate. The glossy, horn-coloured, thin shell is marked by lines radiating from the beaks to the hinder margin, and lines of growth crossing these. The animal, which varies in colour from yellow to red-brown, uses its foot chiefly for spinning the strong and abundant byssus by which it moors itself to the bottom. The connection between form and habit is at once seen in all the members of this order : they are inactive creatures, so the foot, which is primarily a locomotive organ, has dwindled to small proportions. The byssus shown Oysters and Scallops 77 in the figure has been worked up, as an object of curiosity chiefly, into muffs and other articles, and when mixed with silk has been woven into gloves. Although the Fan Mussel occurs all round our islands, in muddy gravel or sand, from low water to a depth of 80 fathoms, it cannot be regarded as a common species. Where it does occur it will be found in some numbers, for it is gregarious in habit, like all the species mentioned in this chapter. The pointed forepart of the shell is inserted in the ground, so that the broad open end is uppermost. The fisher- men avoid the ground where the Fan Mussels are Interior of Fan Mussel right valve from fear of having their nets destroyed by the sharp knife-like edges of these broad ends. I have already referred briefly to the little Pea-crab (Pinnoteres) as lodging permanently in the shell of the Mussels and Horse Mussels; still more does it affect the Fan Mussel, in which retreat it came under the notice of Pliny and other ancient writers, who called it Pinna's Friend, and invented many marvellous fables of the doings of these strange partners. Except on the supposition that the crab acts as a housemaid or scavenger it is not easy to understand what advantage the mollusk derives from the partnership. Crab Shell Life architecture is rich in angles, sharp edges, and spines, to serve various purposes in their lives ; but the Pea- crab has given itself up so whole-heartedly to the comfort of its friend that it has got rid of every angle, every sharp edge, every spine and stiff hair. All its parts are rounded, and polished with a surface like glass, so that the movements of this strange little crustacean between the gills of the Pinna cannot cause injury to the very delicate tissues of the mollusk. The Oysters are represented in our fauna by the solitary species which has from the earliest human period been regarded as a luxury, because the demand appears always to have exceeded the supply ; and concerning whose structure, growth, artificial cultiva- tion, and commercial value very much has been written. The Common Oyster (Ostrea edulis) needs little description, its shell being at least as familiar in the streets of inland cities as it is on the seashore. Attention may be called to the fact, however, that the valves are not equal in size or form, the lower (left) being larger and convex, and the upper (right) is flat or slightly concave. Whilst the left is frequently marked by overlapping plaits, folds, and flat spines, the right is usually plain. The shell of the very young Oyster is round in outline, but Oyster, with right valve removec GREAT SCALLOP ; 2 QUIN (WITH TUBES OF SERPULA) ; 3 QUIN, WHITE VARIETY. Oysters and Scallops 79 its succeeding growth will in all probability greatly modify this form. At an early stage of existence the left valve becomes cemented to a stone, an older shell, or to some other object on the bottom, and thenceforward remains a fixture. It has, therefore, no need of a foot either for locomotion or for spinning a byssus, and the foot is absent. The mantle has a double margin with a fine fringe ; the lips are large and nearly triangular. In the adjoining figure it will be seen that the solitary muscle for closing the valves is placed nearly in the centre of the shell. In the species considered in the previous chapter there were two such muscles, one at each end of the shell but away from the beaks. In Pinna, though these muscles appear to have changed their positions, it is really the beaks that have moved to the extreme front of the shell. In Ostrea, one muscle has entirely gone, but the remaining one is much enlarged. There is a thick, strong, curved pad of cartilage between the beaks to keep the valves open, and a short ligament on either side of it. The hinge-plate is thick, but not furnished with teeth. Having regard to the number of natural foes, apart from man, the most rapacious of them all, it is not surprising to learn that the progeny " spat " of one Oyster may be anything from a few hundred thousands to sixty millions. When discharged by the parent these are furnished with delicate cilia, and by lashing these they float through the water during the first two days. They then settle on some suitable foundation, to which they become permanently attached or they perish. The character of the weather at this period is of the utmost importance to the future 6 8o Shell Life Oyster supply; and the Oysters have selected the summer months as affording the greatest chance of success. A warm day and a quiet sea are the favourable conditions required ; with a low temper- ature and troubled waters there is every probability of the spat being destroyed, or, what is almost as bad, carried far out to sea. Left on their natural banks Oysters are full-grown in about four years, but when dredged and laid down again in the culture beds they take several years longer. " Natives " are those supposed to have passed the whole of their lives in the beds about the mouth of the Thames and Medway, but many of them no doubt are those that have been dredged in distant parts of the coast, purchased by the Kent and Essex merchants, and relaid for a year or so. Oyster- dredging is regulated by local fishery bylaws, which fix the minimum limit of size at which dredging is legal ; 2| inches, for instance, being the minimum at Falmouth, the Oyster then being about 2| years old. They are considered to live about ten years, but to be at their best at five years, when the shell measures as many inches across. The " Green Oysters," or huitres de Marennes, of Normandy have been specially fattened on a green diatom (Navicula ostrearia) in ponds rich in this particular form of microscopic plant -life. In the course of several years of this diet the Oyster in turn becomes green, and acquires a special flavour. Both on the natural sea-banks and the estuarine beds to which they are transplanted, Oysters have a number of enemies to contend with. Starfishes and crabs are the best known of these, and they can be Oysters and Scallops 8 1 captured and destroyed ; but a more insidious foe is not evident until its mischief is done. This is a small orange sponge (Cliona) that bores a network of tunnels ramifying completely throughout the shell, rendering it rotten, and compelling the Oyster con- stantly to deposit new layers of shelly matter within to keep the intruder out. Whelks and other mollusks with drilling power bore through the shells and eat out the Oyster ; whilst the octopus with his parrot- like beak, and the skate with its powerful teeth, also add to the destruction. The Oyster occurs naturally on all our coasts ranging in depth from low water to about 45 fathoms. The Scallops (Pecteri) are not only the near allies of the Oyster, but some of them share the same beds with their more valuable relatives. Though the Oyster is more highly esteemed on account of its commercial and gastronomic import- ance, the Scallops must be pronounced at once more beautiful and more interesting. The shell is more nearly symmetrical, though the valves are usually unequal, and the strong even ribs with which the surfaces are ornamented has made the shell familiar in decoration of many kinds. This shell though strong is thin, though hard is light. The strength is largely due to the hollow ribs, which make possible the lightness necessary for submarine flight, small Scallops and Quins being remarkable for their power of rapidly flitting with a zigzag course through the water by the opening and rapid closing of their valves. A glance at the interior even of an empty shell will show that the muscle for closing the valves is very large, and must conse- 82 Shell Life quently be very powerful. The ribs of the Scallop shell serve another important purpose besides that of combining strength with lightness : at the lower margin the ribs and intervening spaces of the two valves so accurately fit together that with the almost central muscle holding the valves together any shifting of them to right or left is impossible. The development of the "ears" at each side of the beak gives similar strength to the upper margin, and allows of the employment of a long though narrow ligament. The foot is developed as a finger- like organ, occupied in the spinning of byssal threads, and space is left between the ears for the passage of these, the two valves being kept slightly apart at this place by a little boss. Ordinarily the shell is kept slightly open by the pad of elastic cartilage between the beaks, and then the mantle is seen to great advantage. Its margin is double, the inner finely fringed and the outer edged with long tentacles, and at their base gleam a row of large and brilliant opalescent " eyes," whose optical powers appear to be of a relatively high order. All the British species are unattached with the exception of The Hunchback Scallop (P. pusio), which in the adult state becomes attached like an Oyster by its lower valve. Though it begins life with as symmetrical a Hunchback Scallop She11 RS the therS > & llaS & likhl g for contracted quarters, such as the interior of vacated shells, clusters of certain corallines (Escliara), etc. After attaching the newest portion Oysters and Scallops 83 of its right valve to its support, its further growth proceeds unequally ; so that the distorted appearance ensues which has suggested the title of Hunchback as a fitting one, though Linnaeus called it piisio (a youngster), from what he evidently regarded as its immature or unexpanded appearance. In its early and regular condition the shell is longer from back to front, like the other species, but as maturity comes to it the distance from beaks to lower margin becomes greater than the length. The valves, too, that had formerly been equal in size, now become unequal, the upper often larger and more convex than the lower. The sculpture consists of larger and smaller sharp ribs, which alternate, and in an adult number about 70, here and there rising into prickly scales. It ranges through all shades of colour, from white through yellow and red to brown, streaked and blotched with other tints of the same series. The posterior ear is larger than the other; and the ocelli are few in number. It may be found where the coast is rocky, ranging from 5 to 85 fathoms. The Variegated Scallop (P. varius) has only from 25 to 30 ribs of equal thickness, often bearing blunt thorn- like plates on their upper sides. The ears are unequal, the hinder one being the larger. Its colour and markings are much like those of the Hunchback, but its ocelli of which there are about 30 are smaller than in that species. It is well distributed all along our coasts, from extreme low water to a depth of 40 fathoms. 84 Shell Life The Quin or Queen (P. opercularis) is more nearly circular in shape, thin and smooth, marked by 18 or 20 broad, rounded ribs, sometimes with scales upon them. The ears are almost equal. The colour varies from white to yellow, orange, pink, red, brown, or purple, often marked with streaks or spots of other colours. The animal is as varied in colour as its shell. The 35 to 40 black ocelli have a pupil-like spot of greenish grey. Full-grown specimens measure from 2| to 3 inches across. The Quin is more partial to sandy than to rocky shores, and that is probably the reason why it is less given to fixing itself, and more addicted to flitting like a submarine butterfly. It is strange that this power of flight should be so little known to fishermen : I have caused the most profound as- tonishment in some experienced members of this class by showing them Quins in full activity in an aquarium-tank. This species is much used for food on some of our coasts, the oyster-dredgers obtaining great numbers from the oyster-banks and selling them for a few pence per hundred. The Seven-rayed Scallop (P. pes-lutrce) is also almost circular in outline, but at once distinguished from the others by the very different sculpture, the seven ribs being widely distant from each other. Between these strong ribs the somewhat glossy shell is very finely grooved. In the upper valve the ears are almost equal, but in the lower i VARIEGATED SCALLOP ; 2 SEVEN-RAYED SCALLOP ; 5 TIGER So 6 MOTTLED SCALLOP; 3 HEART FILE-SHELL; 4 TRIANCJUI.A ASTARTE-SHELL J 7, 8 FURROWED AsTARTE-SHELL. Oysters and Scallops 85 one the right ear is distinctly larger. The shell is ruddy brown in colour, marked with white, and measures \\ inch across. It is entirely a northern form, North- umberland marking its most southern range on our coasts ; it has a prefer- ence for rough ground and deep water, what is termed its bathy- . Seven-rayed Scallop metrical range lying between 20 (one-fourth nat. and 90 fathoms. size) The Tiger Scallop (P. tigrinus) has a smaller and proportionately thicker shell, covered with fine even corrugations but with only a few distinct ribs. The ears are very unequal, that to the left of the beak being three or four times larger than its fellow. It ranges from yellow (occasionally white) to purple, with the streaks and spots of other hues that have suggested its names. The animal varies from creamy white to red, and its 10 brown ocelli have pupils of gold. It is fairly plentiful wherever the bottom is sandy or gravelly, and is fond of hiding in the interstices of masses of coral or clinker, whence it flits at pleasure. Almost any stony mass from the bottom will be found to harbour a number of living examples of this species, providing its surface is at all broken up into minute caverns, where the little Porcelain-crab and many another marine animal will also be found. Testa's Scallop (P. incomparabilis) is very similar, but with a broader, flatter, and thinner shell, less prominent beaks, and more equal ears. Its colouring is brighter, and as a rule the inside of the shell is without the crenu- 86 Shell Life lations which enable the valves to interlock. It is recorded from deep water (18 to 80 fathoms) at Shetland, Skye, Antrim, Galway, Exmouth, and Guernsey The Mottled Scallop (P. striatus) differs but slightly at first sight from Testa's Scallop, but it is " larger, thinner, and more fragile," the ribs are thickly covered along their ridges with projecting scales, and crossed by minute and irregular raised lines. The colouring, though similar, is less bright. The whitish animal has 25 crimson pupilled, blue-black ocelli, of unequal size and irregular disposition. It is found on hard ground in from 12 to 90 fathoms of water round Shetland, Scotland, north-east England, Ireland, Man, and Scilly. The Pygmy Scallop (P. similis) is a minute and exceedingly fragile species, of almost circular form. The lower valve is much smaller than the upper, and looked at from above the right ear is larger than the left. The sculpturing takes the form of fine concentric lines instead of the usual radiating ribs ; the colour white or yellowish, streaked or mottled with brown or white. The animal has about 20 unequal ocelli in two series, black with a pearly centre. It prefers sandy bottoms of a muddy quality, and ranges from 2 to 80 fathoms, all round our islands, but is nowhere very plentiful. The Great Scallop or Clam (P. maximus) differs Oysters and Scallops 87 from all the other species in the inequality of its valves, the lower being very convex outside, whilst the upper is flat with a slight concavity towards the beak. This upper valve is also smaller than the lower, so that the lower margins do not meet. The shell is thick and solid, ornamented and strengthened by about 15 broad ribs, which are themselves corru- gated. The lower valve is white suffused with pink and pale yellow, but the upper valve has the ribs dark red, and the intervening channels brown, the whole colour paling away to the beak. The animal is pink or red, the mantle marbled with brown and white. There are from 30 to 35 large unequal ocelli in two series, greenish or dark blue. The young ones spin a byssus and suspend themselves by it, but before they have become adult they appear to have lost this power, or to have learned that their shells have acquired sufficient weight and solidity to resist movements of the lower waters. It occurs generally around our islands in water of from 7 to 80 fathoms. The saucer-like lower valve has long done duty as a drinking vessel. Closely related to the Scallops are the File-shells (Lima), so-called on account of the rasp-like character of the shell sculpture. The valves of the shell are uniform and always white, and the mantle is not ornamented with prominent ocelli at the margins. But though not well developed and conspicuous they are there, and to make up for their deficiency the tentacles which fringe the mantle are exceedingly long and numerous, and wave about like the tentacles of the sea-anemones. During early life the File- shells flit through the water like the Scallops. The 88 Shell Life foot of the animal is finger-shaped and grooved ; and its lips are furnished with tentacles like those of the mantle. Like the Scallops the File- shells spin a byssus, which may be an easily detachable cord whereby they temporarily attach themselves, or may be an enveloping tissue like that of the Horse Mussel, only in this case it would be plastered over with excre- ment, gravel, shell fragments, and sea- weeds, forming a nest in which are several youngsters or one adult. The native species are four in number. The Elliptical File-shell (L. elliptica) is a small species confined to the waters of the west coast of Scotland and Shetland. Its shell is oval or elliptica], thin and glossy in spite of the 30 or 40 fine ribs with toothed crests which radiate from the prominent beaks. The valves have small tri- angular ears, and are connected by a slight ligament. The body and foot of the animal are pale orange, whilst the tentacles are more pink in hue. It inhabits sandy mud in water from 15 to 85 fathoms deep. The Heart File-shell (L. subauriculata) is smaller than the last, more oblong, more convex, and with only 24 ribs, of which the middle one is the largest. The beaks projecting beyond the hinge are very prominent. The animal agrees in colour with the white shell, and uses its white foot for crawling. It is generally dis- tributed round our coasts where there is a sandy or gravelly bottom at a depth from 18 to 90 fathoms. Oysters and Scallops 89 The Fragile File-shell (L. loscombii) differs from the preceding in the fact that the valves of the shell are not equal sided. The ribs number from 40 to 60, and are very fine and sharp. The upper side of the shell gapes slightly. The animal is coloured bright orange, and the tentacles of the same hue curling back over the white shell present a striking contrast. It is generally distributed where there is mud or gravel between 5 and 100 fathoms. It is one of the species that weave nests, though not invariably. If the bottom is soft it sinks chambers in it, but where the ground is hard some protection is needed against members of the Cod-family who have a weakness for Lima-flesh ; then it spins a nest, and decorates the exterior with shells or fragments of shell of other mollusks and of crustaceans. The Gaping File-shell (L. hians), our largest species, is more solid and less glossy than the others ; its ribs stronger and rougher. The triangular ears are unequal, and the pure white colour which distin- guishes it in early life afterwards becomes more or less discoloured. The valves gape along the front margin, and discover the red animal. The orange mantle is fringed with a thousand or more filaments which, curling over the shell, are in constant movement. Like the tentacles of the anemones, these have the power of taking hold ; and by Gaping File-shell . . r , .,.,.. placing one s finger among this living fringe the Lima may be drawn to a considerable distance. It affects harder ground than its con- 90 Shell Life geners, in water from 12 to 40 fathoms. Here it builds its nest under large stones, mingling with the byssus - threads bits of nullipore and File-shell in its nest (nat size) fragments of shell, lined within with excrement. The young ones often associate, several in one nest, but the adults are quite solitary. They frequently, however, accommodate guests, who in all probability Oysters and Scallops act as scavengers. Among these are the little Porcelain-crab (Porcellana longicornis) and a marine worm (Polynoe). The Hermit - crab who lives in cast-off whelk-shells has similar messmates who do their best to keep the house clean for their host. This family also contains the Wing- shell (Avicula kirundd), one of the Pearl - oysters, and closely allied to Pinna. It is like a small Pecten whose hinder " ear " has grown to an inordinate length, so that it resembles a wing rather than an ear. Its home is in the Mediterranean, but it is occasionally taken on our southern shores, perhaps being brought hither by currents in its earlier stages. Several fishes, crabs, and jelly-fishes also make their way from the Mediterranean to the coasts of Cornwall and Devon. Gaping File-shell- interior HE creatures to be described in this and some following chapters differ from the fore- going in the higher develop- ment of their respiratory organs. In the Mussel family we showed that the gill-filaments had got so long that they had to be folded over so that the gills appeared to be fourfold on each side of the visceral mass. In the Oyster and Scallop family advance had been made upon tin's development by the ends of the turned-over gills uniting with the foot and the mantle respectively. The present chapter deals with mollusks in which the two folds of each gill- plate have been partially united by trusses which leave internal spaces and increase the respiratory capacity. There are usually two muscles for closing the shell, and the mantle-edges are united at one or more points. The group includes both marine and Heart-Cockle and Fresh-water Cockle 93 fresh-water species, so we must at times turn from the seashore to the river and pond. The animal in the first genus A starte has an almost round body, flattened from the sides. The lips are large ; the mantle thick, not fringed with tentacles, but part of it forms a short excretory siphon behind. The foot is conical and small, though tolerably powerful. The shell is more or less tri- angular and thick, somewhat flattened, with concentric furrows. It is covered by a thick yellow or brown epidermis, and has prominent beaks. In front of the beaks will be found a dark depression called the lunule, found in many other genera of bivalves, and here heart-shaped or lance-shaped. Internally the valves are furnished with three central teeth (cardinals) below the beak, and a ridge-like tooth (lateral) on either side. There are three native species. The Furrowed Astarte-shell (A. sul- cata) has from 24 to 40 thick ridges, and is white beneath the brown epi- dermis. The broad hinge-plate bears Furrowed Astai three cardinal teeth, one small and indistinct, two large ; laterals indistinct. The margin is thick and notched within. It partially embeds itself in sand and mud all round our islands in water from 7 to 145 fathoms deep. It is by no means active, getting its microscopic food in plenty without the necessity for pur- suing it. The Flat Astarte-shell (A. compressa) is only about one-half the length and breadth of the last named, and may be distinguished 94 Shell Life from younger examples of that species by its flatter, more equilateral valves, and the slight depressions between the ridges. The interior margin has a plain bevelled edge, not notched. This is a local species of northern range. It has been found in sand and mud off the coasts of Yorkshire, Mull, and Antrim, in from 20 to 40 fathoms of water. The Triangular Astarte- shell (A. triangularis) is the smallest of the trio, and, as its names indicate, has three almost equal sides. It is thick in proportion to its size, and the valves are almost without the thick ridges of the two foregoing species. Where these are present they are few and not very prominent. The yellow or brow r n epidermis, which is streaked with darker tints, disguises the white of the shell. The margin may be either toothed, or plain and bevelled. It occurs locally in from 3 to 60 fathoms of water. A fourth species (A. crenata) has been dredged between the Hebrides and Faroes, but can scarcely be regarded as British. Attention should be called in connection with the Astartes to the development of the hinge-teeth. We shall gradually come upon species that are more or less advanced in this respect, and we wish our readers to consider these teeth in relation to the habits of the animal. A deep-burrowing species that is provided with long siphons, rendering frequent visits to clean water unnecessary, is also in little need of very powerful hinge-teeth. As a matter of fact the shell will be rarely closed ; and powerful locks would be thrown away on an open house. But the Astartes only partially embed themselves in the ICELAND CYPUINA ; 2 HEART COCKLE. Heart-Cockle and Fresh-water Cockle 95 mud so little that they need no long siphons; sufficiently, however, to make the presence of ribs upon the shell an advantage these helping to keep them firmly in place when they have withdrawn the foot and closed the valves. In the Iceland Cyprina (Cyprina islandica) we have an example of a single species constituting the sole living representative of its genus, though of the fossil species of that genus we know nearly a hundred. The shape of the valves is shown in the figure, but if the complete shell be looked at from behind it will be seen that in that aspect it is heart - shaped. It is a thick and slightly glossy shell, with numerous irregular concentric raised lines, which are stronger towards the margins than in the middle. The colour is white tinged with yellow and pink, but the brown epidermis hides this. The beaks are prominent and considerably curved. Along the upper edge of each valve there is a groove which holds one side of the ligament. The hinge-plate is broad and bears three strong cardinal teeth. The laterals are also strong in the left valve, but ior of Cyprina . . & in the right they are very slight. It measures between 4 and 5 inches in length, and almost as much from the beak to the lower 7 96 Shell Life margin. The animal is of a creamy tint, and the mantle forms two short tubes behind, whose mouths are fringed with delicate tentacles. The long foot is broad at the base, but runs to a sharp point. By the aid of this powerful instrument the Cyprina burrows in the muddy sand, but not deeply, as may be gathered from the shortness of the tubes and the sculpture of the shell, slight as that is. It is found on all our coasts, at all depths from low water to 100 fathoms. The Heart-Cockle (Isocardia cor) when viewed from the side appears almost round, but from either end it is seen to be more com- pletely heart-shaped than Cyprina. The beaks are curved spirally towards the front, and from this point they present the appearance of the illustration. The thick shell is yellowish white in colour, but this is quite hidden beneath the red -brown epidermis, which bears stiff short hairs set in numerous lines radiating from the beaks. The thick, broad hinge-plate bears two cardinal teeth and two laterals. All these interlock and form a powerful safeguard against the shifting of the valves. The animal is whitish, the borders of the mantle orange, and the strong tri- angular foot of the same colour. The siphons are very short, with _ broad, fringed Beaks of Heart . Cockle openings which are at the centre of the lower margin. Full-grown specimens average 4 inches across the longer axis of the shell, and almost as much at right angles to it. The Heart-Cockle and Fresh-water Cockle 97 strange situation of the siphons is explained by the habit of the Heart-Cockle : by means of the foot the shell is embedded, beaks first, in the slope of a muddy bank, so that only the lower margin of the shell with siphons is ex- posed. It is a local shell, and its distribution is almost con- fined to Devon, Cornwall, the west coast of Scotland, and the Interior of Heart-Cockle south and east coasts of Ireland. The Northern Lucina (Lucina, borealis) is also an almost round shell viewed from the side, but from either end it is seen to be a much flatter shell than the preceding. Its whiteness is hidden by a yellow-brown epidermis, and its surface is relieved by a series of low but sharply cut concentric ridges. The pointed beaks. Northern Luctna * A in spite of their small size, are tolerably distinct. The hinge-teeth are two strong cardinals with a long lateral on each side of the beak. The interior margins are smooth and bevelled. The animal is white, with short thick lips and extremely short siphons. The long slender foot emerges from the shell at about the centre of the lower margin, and serves chiefly as an anchor to moor it to the gravel and sand upon which it lies all round these islands, from extreme low water to upwards of 100 fathoms. There is a second species the Prickly Lucina (L. spinifera) which is of more local occurrence. The shell is more triangular than the last named, the epidermis of a much paler tint, the beaks less 98 Shell Life prominent, and the ridges somewhat overlapping, their terminations giving a spiny character to the upper margin. There is but one cardinal tooth in the right valve, but in the left there is a small additional one. It is more plentiful on our northern shores than in the south, and especially on the west coast of Scotland. In the next genus, the Hatchet-shells (Axinus), the smooth shell is more globular, though with a triangular outline, the hinder portion furrowed. The beaks are considerably recurved, but the hinge-teeth are entirely wanting, though an excavation in the right valve and a corresponding eminence in the left have somewhat the appearance of teeth. The margins of the shell are not toothed. The thickened margin of the mantle is open all round and not prolonged into siphons. The long slender foot is almost cylindrical. There are five British species, all small and all living on muddy - sandy shores. The Rusty Hatchet - shell (A. ferruginosus) is the most plentiful of these, and gets its name from a rust-like deposit over the epidermis which protects the thin, white, almost globular, shell. It occurs between 30 and 100 fathoms, chiefly off Skye, Shetland, and the west of Ireland. The Wavy Hatchet-shell (A. flexuosus) has a more oval and less glossy shell. The terms "wavy" and "flexuosus" apply to the upper margin behind the beaks. The hinder margin of the mantle is con- tracted so as to form some approach to a siphon or the aperture of one. This species is widely distri- buted, and ranges between 3 and 90 fathoms. The Skye Hatchet - shell (A. croulinensis) is obliquely oval, swollen, more solid, and longer than the last ZEBRA MUSSEL ; 3 ROUND DOUBLE-TOOTH ; 4 RUSTY MONTAGU-SHELL : 5 WAVY HATCHET-SHELL ; 6 PRICKLY LUCINA ; 7 MONTAGU'S URCHIN-SHELL ; 8 TWO-TOOTHED URCHIN-SHELL Heart-Cockle and Fresh-water Cockle 99 named. The white shell shows through the thin epidermis. The tooth-like folds of the hinge-plate are stronger than in either of the other species. It is a rare species, and appears to be restricted (in Britain) to Skye and Shetland, where it occurs in deep water, between 45 and 85 fathoms. The Round Double-tooth (Diplodonta rotundata) is almost round in outline, somewhat glossy, with irregular concentric ridges; white, but covered in front by the yellowish epidermis. There are two car- dinals and two laterals in each valve, one of the cardinals in each being cleft in order to receive the undivided one of the opposite valve. The animal is white, with large free lips, and the mantle edges are united, save for the large aperture on the lower margin where the foot emerges, and for the incurrent and excurrent orifices on the lower margin. The shell is about 1 inch long, and almost as deep from the beak to the lower margin. It is found on the surface of sandy mud in from 12 to 20 fathoms, chiefly on our southern shores, but also locally on the west, as at Lundy, Anglesea, and Fishguard. There are six little bivalves of local occurrence that have been named after Colonel Montagu, who first discovered and described them. His name in the Latinised form of Montacuta stands for that of the genus. As they have no popular name, we think it fitting to call them Montagu-shells. Montagu's Urchin-shell (M, substriata) is a small, yellowish, oval, semi-transparent shell, about a quarter of an inch in length. Its valves are marked by about a dozen faint ribs radiating from the beaks, but not reaching to the front margin. The animal spins a TOO Shell Life byssus, and on the lower margin there is an indentation whence this issues. There is a long tooth on each side of the hinge-line, those of one valve interlocking with those of the other. The animal agrees with its shell in being almost transparent. The rear portion of the fringed mantle forms a brief tube for the out- ward current of water, and the foot is large- and powerful. From 8 to 100 fathoms deep is the range of this species on all our shores, but not on the sand or mud affected by its allies. It has a more remark- able habitat, being found only on living Sea Urchins, and chiefly on the spines of the Heart-Urchins, such as Spotangus purpureus, Ecldnocardium cordatum, and Bryssus lyrifer. To these spines it is attached by the coarse byssus-threads, and no doubt it selects this strange position in order to share the food of the Urchin. The Heart - Urchins, it may be mentioned, bury themselves in the sand, and appear to exist by continually swallowing it and digesting out the organic matter mixed with it. The Urchin's mouth is a shovel-shaped aperture on the lower surface, and Montagu's-shell is attached to a spine in front of it where the indraught of sand is likely to bring minute food - particles to the mollusk. The two - toothed Montagu - shell (M. bidentata) is less oval than the last, approaching nearer to square ; flatter, and much less transparent ; whiter in colour. The teeth in the right valve are shorter and broader than those in the left. The mantle has its margin fringed with bright silvery teeth, and forms a very brief tube behind. The large broad foot is somewhat triangular in outline. It may commonly be found on all our coasts, in water from 10 to 70 fathoms, nestling in Heart-Cockle and Fresh-water Cockle 101 the crevices of old bivalves, sometimes in the burrows of the Boring- sponge (Cliona) in old oyster- valves. Its greatest length is only a couple of lines. The rusty Montagu-shell (M. ferruginosa) is more oblong, greyish white in hue, but this is hidden by a rusty-looking incrustation that covers the epidermis, and is no doubt due to the peculiar habitat of the creature. The front teeth differ from the back, and the opposite front pair differ somewhat from each other in order that they may interlock. It affects the burrows of the Heart-Urchin (Ecliinocardium cor- datum), and often is attached by its byssus to the bristle-like spines of the Urchin, and is dragged about with every movement of the Urchin. We have now to briefly describe four small genera, two of them each represented by a solitary species. They are all small, and consequently little known to the average seaside visitor, and have no popular names. We must therefore utilise their scientific names as far as possible. The Globose Kelly-shell (Kellia suborbicularis) is more or less globular, equal-sided, thin, glossy, with faint lines running across from the beaks, and others parallel with the lower margin. The thin and iridescent epidermis gives a greenish hue to the white of the shell. In the right valve the two strong teeth are laterals ; they are repeated in the left valve with the addition of a cardinal. Both shell and animal are nearly transparent. As shown in the first figure, the mantle extends considerably beyond the shell margin, and its edges are united all round. There is a large opening on the lower margin to allow passage for 102 Shell Life the strap-shaped foot ; it is greatly extended in front to form an incurrent tube, and a small opening behind serves as an excurrent siphon. The longer diameter of the shell is from one- third to a half -inch. The small creature interior of moves freely by means of its foot, and Ke'iy b h S Iii attaches itself by an almost invisible thread, hanging in the position shown in the figure. It is fond of taking refuge in muddy discarded shells in rock-crevices, and about the tangled suckers of the larger seaweeds. Its vertical range is from extreme low water downwards. The Minute Kelly- shell (K. minuta} is much smaller, its longest measure- ment being only one-twelfth of an inch. It has a thin, semi-transparent, glossy shell of a purple-brown tint, darker at the beaks and paler in front. Its principal markings are the irregular lines of growth. There is but one siphon in this species. The foot is comparatively large, J^nu^ed very flexible, and much used by the animal for climbing seaweeds. It is found in great abundance all round our coasts at low water and a little beyond. It has sometimes been called the Mullet-shell because of the fondness of that fish for it. Mr. Hyndman took about 35,000 of these shells from the stomach of a single mullet. This certainly showed praiseworthy industry on the part of the fish in the collection of food, as well as testifying to the good qualities of the mollusk as a fish-food and to its astonishing fecundity. In the matter of size the Ruddy Lassea (Lascea rubra) comes between the two Kelly-shells, being about the tenth of an inch in length. The shell is Heart-Cockle and Fresh-water Cockle 103 oval, unequal-sided, white, deeply tinged with red towards the upper margin, and covered by a yellowish epidermis. There are two lateral teeth in each valve, but in the left valve there is in addition a small cardinal. The mantle does not extend so much be- yond the shell as in Kellia, but in front it forms a protuberant incurrent tube. The excurrent orifice is not seen beyond the shell margin. The long, tongue- shaped foot is used for similar purposes as in the last-named species, and a byssus of less simple character moors it to rock-crevices, to corallines and other seaweeds, chiefly between tide-marks, all round our coasts. It is a species that retains its eggs until they are hatched. These are produced in batches of from 12 to 20, and when sufficiently developed the fry are shot into the world of waters through what ordinarily serves as the incurrent siphon. The Coin - shells (Leptori), so - called from their resemblance to a small coin (lepton), are represented by five native species. They differ in several respects from the creatures just described. The shell is more liberally provided with hinge-teeth, there being a cardinal and two laterals in each valve. The mantle, which is fringed with long tentacles, protrudes nearly all round, and the foot can be flattened in such manner that it resembles the foot of a snail, and is used in similar fashion. The Scaly Coin- shell (L. squamosurn) is almost square and flat, its substance thin almost to transpar- ency, glossy, and white. It is finely ribbed in two directions, the spaces left between the network thus formed giving the surface the ap- pearance of being minutely pitted. Inside the shell is 104 Shell Life iridescent, marked with fine irregular grooves which run from the beak to the lower margin. The cardinal tooth is small and erect, whilst the laterals are long and plate -like. The white animal has a short excurrent siphon, and a bluish foot streaked with white. The fringe of tentacles around the mantle is shown in the figure, where will also be seen one tentacle above the foot developed abnormally as compared with the others. When the creature crawls along it waves this tentacle about, appar- ently using it as a sense-organ, feeling its way and ascertaining the presence of food. It is a southern species, its distribution here being restricted to Dorset, Devon, Cornwall, the Channel Islands, and the south and west of Ireland. Like the Montagu- shells previously described, it has a preference for the company of a creature belonging to an entirely different class of animal life. In this case the mess- mate is a singular crustacean, known as Gebia stellata, that burrows in muddy sand. No doubt the Lepton acts, to some extent at least, as a scavenger, feeding upon the excretions and surplus food of Gebia, whilst the flatness of its shell enables it to keep out of the way as the Gebia scuttles up and down his burrow. The Shining Coin-shell (L. nitidum) is a much smaller species, as will be seen on reference to the figures, which are of the natural size. It differs from squamosum by the shell being less flat, less thin, with the beaks more prominent, and the animal appearing to be more gelatinous. The lower edge of the shell is less straight, and the fine rib-marks run only in one direction that is concentrically. Heart-Cockle and Fresh-water Cockle 105 The shell is white with a tendency towards a yellowish tint, which is the hue of the opalescent epidermis. An enlarged figure of the hinge-teeth is given ; they are more highly developed than in squamosum. The foot is more distinctly blue, necked shining co with white, and the siphon is placed in and enlarged hinge front instead of behind. It occurs sparingly on all our coasts where there is coarse sand, between 10 and 90 fathoms. The form sometimes described ^^ as a separate species under the name of the |^Jp Convex Coin-shell (L. convexum) appears to convex be a variety (convexa) of L. nitidwm. It is Coin - distinguished by the shell being slightly more convex, and marked all over with coarser pits than those found only round the beaks in the type. The Furrowed Coin-shell (L. sulcatulum) is almost circular in outline and flattened; its substance thin and almost transparent, like that of L. squamosum, but instead of the pit marks we have here a numerous series of broad concentric ribs covering the surface. The cardinal tooth in the left valve is strong and erect, whilst the corresponding one in the right is very small. The length of the shell is only about one-twentieth of an inch. It appears to be a southern form, and has been found in the Channel Islands among corallines below the lowest tide-marks. . Clark's Coin-shell (L. clarkice) is another minute species, but of more yellow tint than the last, streaked with fine white lines that radiate from the beak. Instead of the ribs of L. sulcatulum, the sculpture here consists of numerous fine concentric grooves. The outline is io6 Shell Life triangular-oval ; and the cardinal tooth in the left valve though strong is more oblique than erect. It has been found on gravelly sand on various parts of our coasts, both north and south, ranging in depth from 18 to 80 fathoms. Turton's Weasel-eye (Galeomma turtoni) is the sole British representative of its family and genus. The thin oval shell is equal-sided, with minute beaks, and gapes widely in front. The hinge is without teeth, and there is no epidermis. The animal has a long foot flattened to form a narrow sole, upon which it glides after the manner of a snail. The edges of the mantle are joined, but at the front there is an orifice for protrud- ing the foot, and there is a siphon at either end. Contrary to the habit of most bivalves, which keep their shells as nearly closed as possible, the weasei-eye Weasel-eye spreads open its valves to the fullest extent, and so flattened out, as in our first figure, it glides over the weeds and corallines, in water between 5 and 20 fathoms, on our southern coasts. It attaches itself by a byssus, but when it wishes to move away the byssus is thrown off from the foot. It will be at once seen in the light of previous remarks that there is distinct relation here between the habits of the creature and the absence of hinge-teeth. A mollusk that uses its widely expanded valves to protect it has little need of the teeth with which many other species lock their valves together so the teeth are not developed. Leaving the seashore for a time, we must repair to NUT OKH-SHKI.L ; 2 HOUNY ORIJ-SHKI.I. ; 3 OVAL OKU-SHELI. ; 4 LAKE OUB-SHELI 8 SHINING PEA-SHELL; 9 Rosy PEA-SHEM.. Heart-Cockle and Fresh-water Cockle 107 the fresh- water pond or stream, in order that we may consider some of its inhabitants in their proper order. There on the mud or climbing the weeds we shall find a number of little bivalves, to which the popular name of Fresh-water Cockle has been applied. The nine species found in this country belong to two genera of one family the Sphseridse and are not at all related to the true Cockles (Cardium). Their thin shells are more or less globular, the valves being of equal size but not equal-sided. The hinge is provided with both cardinal and lateral teeth, and their general character may be gathered from this figure of the hinge of Sphcerium corneum. The animals are very active, and by means of the mobile foot can riot only climb weeds, but by spreading it out on the surface of the water can float with their shells inverted after the manner of Hinge-teeth the pond-snails. From such a position SjJuartom they often descend gradually to the bottom by spin- ning a thread of mucus, the end of which remains at the surface or attached to a floating weed. By means of these threads they can reascend to the surface or remain suspended half-way. They hibernate in the fine soft mud at the bottom, becoming active again when the warmth of spring has penetrated to those depths. The eggs are retained in a brood-pouch within the gills until they hatch, and the young remain there for a time, finally being shot out through the siphon when developed sufficiently to take care of themselves. The four species of Sphcvrium have each two siphons, a character which serves to separate them from the five species of Pisidium. which have one siphon only. io8 Shell Life The Horny Orb-shell (S. corneum) is common in most ponds and streams throughout the country. The beaks are placed almost in the centre of the upper margin of this almost globular shell, which is covered with a thin glossy epidermis. The colour is that of horn with some lighter bands running parallel with the lower margins. The teeth are well developed. The length is about half an inch, and the animal's span of life is about two years. The Nut Orb-shell (8. rivicola) is a much larger, more oval, and more solid-looking shell, and its colour is yellowish brown. It is covered by a thick brown epidermis, and has strong concentric ribs. The hinge-teeth are similar to those of S. corneum, but much stronger. The interior of the shell has a pearly coating. The animal, like 8. corneum, is greyish, but the broader foot is less pointed, and the shorter siphons are nearly of the same length and whiter. Though not found in stagnant water, it is not partial to rapid streams ; but may be sought in the gently flowing rivers, brooks, and canals of England, from north Somerset and Surrey to south Northumberland. The Oval Orb - shell (S. pallidum) is a local shell of oblong form, much flatter than the foregoing, thin and semi-transparent, with fine concentric grooving. The animal is white, with a long tongue-shaped foot, and the long siphons are connected almost throughout their length. It occurs only in England, and there its range is limited to Surrey, Middlesex, Warwick- shire, Lancashire, and Yorkshire, where it is found in ponds and canals. The last of the quartette, the Heart-Cockle and Fresh-water Cockle 109 Lake Orb-shell (8. lacustre), when looked at from the side is much like S. corneum, but from either end it is seen to be somewhat compressed, the beaks central, and usually capped by the nucleus of the shell ; very thin, semi-transparent, and glossy, of a greyish-brown hue. The white animal has a foot twice the length of its shell. The siphons of this mud-loving species are long, and exhibit a marked difference between the respiratory and excretory tubes : the former being cylindrical with a wide mouth, whilst the latter is slightly conical with a small mouth. It is well distributed over England and Wales in still waters, but is only found locally. As already indicated, the five species of Pea-shells (Pisidium) may be recognised as such at a glance by their possession of one siphon instead of two. Their shells are also much smaller and less equal-sided than those of the Orb-shells. The River Pea-shell (P. amnicum) is solid, glossy, somewhat tri- angular, and swollen ; deeply grooved, greyish brown in colour, with a thick epi- dermis, and a quarter of an inch in length. The greyish animal is almost transparent, with a long broad foot and a short siphon. It is generally distributed in running waters. The Foun- tain Pea-shell (P. fontinale) is similar in shape to the last, but smaller, less solid, faintly grooved, of a paler grey colour, with more prominent beaks, and a thin epidermis. It is widely distributed in similar situa- tions to those affected by the last named. The Small Pea-shell (P. pusillum) is oval and thin, with little gloss, finely but irregularly grooved ; of a brownish- no Shell Life grey colour, with very thin epidermis, and the beaks nearly central. The animal is pale pinkish, with a long slender foot, and short conical siphon. It is the only native Pisidium of an oval form, so it will be readily identified by this feature, and by the almost central position of the beaks. It is generally dis- tributed in pools, ditches, and marshy places. The Shining Pea-shell (P. nitidum) is nearly round, very glossy and iridescent, pale yellow or pale brown, more strongly grooved than in the other species. The interior is whitish. The animal is also whitish, with a long, finely-pointed foot, and short, funnel- shaped siphon with a notched margin. It is found in lakes and ponds throughout the country. The Rosy Pea-shell (P. milium), though very glossy like the shell of P. nitidum, and grooved in a similar manner, is more nearly oblong than round, and the lower margin is straight instead of curved. In colour it is yellowish or pale brown, the interior pearly and white. The animal varies in hue from white through yellow to rosy red, and has a long, slender, some- what conical foot. Like the other species, this is generally distributed throughout the country in still waters. All these Orb- shells and Pea-shells are but tiny representatives of the marine Cockles, and, of course, are cockles only by popular courtesy. The Fresh- water Mussels are even more widely separated from their salt-water namesakes, though our native species are not of the insignificant sizes of the Fresh- water Cockles. It has been suggested that all of these fresh-water bivalves have originated in marine, or at least estuarine, species which have become Heart-Cockle and Fresh-water Cockle 1 1 1 accustomed to a certain admixture of fresh water, and have gradually wandered farther up the rivers and their feeders until they have finally become used to water that is absolutely fresh. As they have got into quieter waters, where, too, enemies are less abundant, their shells have become thinner and less solid, with modifications of the animal to match. The Pearl Mussels (Unio) are represented in our waters by three species, of which the best known is the Painter's Mussel (U. pictorum), so called be- cause the valves were formerly used to hold artist's colours, just as they are used to-day to hold the gold and silver for illum- inating. The oblong compressed shell is covered by a thin epidermis through which show the yel- low ground-tint, the Painter , s Musse| parallel lines of brown, and the rays of green on the hinder part. The beaks are considerably forward from the centre ; the lower margin is almost straight. The interior is pearly, and the muscular impressions are distinct. A notched tooth on the front of the left valve fits into a groove formed by the margin of the shell and a strong tooth on the right valve ; whilst a long plate-like tooth on the back of the right valve fits into the groove of a similar plate on the left valve. The animal has a large, broad, tongue-shaped foot of a reddish or yellow colour, with which it burrows into the mud of ponds and slow rivers. Owing to the thinness of the epidermis on the beaks these being 1 1 2 Shell Life the oldest portions of the shell the shelly matter at this part frequently becomes eaten away by the action of gases dissolved in the water. It is about 3 inches long. The animal is coloured light red tinged with grey, and the mantle is bordered with brown. The siphons of Sphcerium and Pisidium are represented in Unio by a couple of orifices on the hinder margin of the mantle, of which the dark brown upper (excurrent) is somewhat more elongated than the lower grey (incurrent). This may be regarded as an English, rather than a British, species, for it occurs only in the rivers and ponds of England and Wales, and does not extend north of Northumber- land, or occur in Ireland. The Swollen River Mussel ( U. tumidus) is a slightly more solid shell than the last, and viewed endwise presents a much greater thickness hence its name. In colour it is a glossy brown, the lines of growth often tinged with green. The interior is bluish and pearly, with strongly marked impressions of both mantle and muscles. The hinge -teeth, though similar to those of the last named, are of a stronger character. The animal differs in colour from V. pictorum in being greyish instead of red. Its distribution is nearly the same as that of U. pictorum, except that it does not occur north of Yorkshire. Both of these species produce pearls, but they are very small and of inferior quality. The Pearl Mussel is U. margaritifer, which has a shell of more oblong shape, much flattened, though of solid material. There is no gloss upon its rough, blackish-brown surface. Its length is about 5t inches. The interior is pearly, but in this case the tint is flesh-colour, varied with Heart-Cockle and Fresh-water Cockle 1 1 3 stains of dull green. The animal is usually greyish with a tinge of red. It is a northern species, not occurring south of Pembrokeshire and Yorkshire. This is the species which produces the British pearls, at one time a somewhat important article of jewellery. The so - called " fishery " appears to have been abandoned, probably on the ground that " the game is not worth the candle." We are told that in the Pearl Mussels, showing pearl within the shell, and detached pearls (1-8) middle of the eighteenth century the Perthshire Tay in three years contributed to London pearls valued at 10,000. These varied in hue from white, through pink and green to brown and black, the white pre- dominating, and the pink most in demand. The peasants used to collect the mussels from the mountain streams just before the corn-harvest, and in the oldest and most deformed specimens they were most likely to find the pearls. Yet it is said that not n 4 Shell Life one per cent, of the shells contained a pearl, and that only one pearl in a hundred had any great value. The best of these, very regular in form, clear in colour, and the size of a pea, would be worth 3 or 4. The Swan Mussels (Anodonta), of which we have two forms, are less regular in outline than the Pearl Mussels, and are, as their scientific name indicates, practically toothless, though the hinge - teeth are represented by sharp ridges on the valves. I have already described their structure in the Introductory Chapter. They occur in similar situations to those affected by the Pearl Mussels, but are more generally distributed throughout Great Britain. The large Swan Mussel (A. cygnea) has an oval shell, but with a straight hinge-line, and with the beaks placed well away from the centre, forward. The Heart-Cockle and Fresh-water Cockle \ i 5 forepart is swollen, and the upper part above the beaks compressed. Greenish yellow is the colour of the shell, which is covered by a thin, brown, glossy epidermis. The lines of growth are strongly marked, and the interior is white with a pearly iridescence. The animal is grey, tinged with red or yellow ; the large foot yellow or orange ; the edges of the mantle tinged with brown and fringed. It occurs in slow waters and ponds almost throughout Britain, usually in large colonies. It is calculated that full-grown specimens are twelve or fourteen years old. The Duck Mussel (A. anatina) is considered by many conchologists to be merely a variety of A. cygnea. There can be no doubt that it is very closely related to it, and probably arose quite recently as a variety, but it appears to be now a permanent form, and per- haps would be more cor- rectly described as a sub-species of A. cygnea. The shell is proportionately longer, and less swollen, of thicker material, olive or brown in colour, with darker concentric bands, and with green rays from the beaks. The hinge-line is slightly curved, and higher than in A. cygnea. The animal differs from its congener chiefly in the larger size of the lower siphon, which is also fringed with more numerous and more delicate tentacles. It is found in similar situations to the last, but is not so widely distributed, and does not appear to occur in Ireland. u6 Shell Life The only remaining fresh - water bivalve to be described represents a distinct family the Driessensiidae. It is the Zebra Mussel {Driessensia polymorpha), which is very similar in appearance to the Common Mussel (Mytilus) of the sea-coasts, but differs from it in having a partition extending across the tip of each valve and thus dividing this portion of the interior into two. The shell is sharply keeled along each valve, and is dull brown in colour. The hinge is without teeth, and the pearly interior is but faintly marked by the muscular impressions. The animal is dark hued, with a paler, clearer, slender and cylindrical foot which spins a strong byssus. From all this it will be seen that Driessensia approaches much more nearly to the marine species than to other fresh-water bivalves. All the latter retain their eggs until they hatch; Driessensia, like the marine bivalves, discharges her eggs into the waters, and the young larvae that come from them are free swimmers. They appear in the middle of the summer on the surface of the water in great numbers. After apparently feeding on the microscopic plant-life of the surface for about eight days, they sink to the bottom. By this time the foot has formed and become very long and narrow, and the shell round, much like that of Sphcerium. The swimming organ the velum has disappeared, and in future the creature must use its foot and its byssus for locomotive purposes. Another point connecting this species with those of the sea is the fact that the edges of the mantle are united almost throughout their length. Heart-Cockle and Fresh-water Cockle 1 1 7 The history of Driessensia in this country is very singular. Geological evidence shows that in later Tertiary times this species was abundant, not only in Britain but over a good portion of Continental Europe also. Then it vanished without leaving any evidence why, but held its ground in the Aralo- Caspian rivers, whence during the last one hundred and fifty years it has been spreading once more over Europe. In 1824 Mr. J. Sowerby discovered that it had reached London. It was found in the Thames and the Surrey Commercial Docks, and the very natural conclusion was reached that it had come over from the Baltic attached by its byssus to some of the timber - laden vessels. It has since spread very considerably about the country, and we have even heard it whispered that a certain London water company has occasionally supplied it to their customers, who had only bargained for water. HE members of the Tellin family (Tellinacea) are dis- tinctly deep burrowers in sand or mud, and this habit has had effect in developing the foot to be a powerful organ, and in lengthening and separating the siphons to give them greater power and mobility that they may reach up above the sand to the clear water. The lips also are large, the gills unequal in size, and the mantle fringed with tentacles. The general appearance may be gathered from the figure opposite. The name Tellina was applied by Dioscorides and other of the ancients to certain species of marine mollusks, not neces- sarily those for which the word is now used. There are seven British genera in the group, with over a score of native species. The Pomegranate Tellin (T. balaustina) had its name suggested to Linnaeus by the resemblance Wedge-shells^ Venus-shells, and Cockles 1 1 9 between its colouring and that of the pomegranate- flower. It is a thin almost transparent shell, some- what swollen and of a triangular-oval outline. The surface is slightly polished, marked by exceedingly fine lines and slightly raised concentric plates, which, however, have in many specimens been rubbed off. The colour is white, delicately tinged with yellow, whilst from the beaks to the lower margin faint streaks of pink radiate. The beaks are small, incurved, and almost touch. The epi- dermis is thin and iridescent. The interior, which is tinged with orange, is polished. It is about 1 inch in length. The animal is semi-transparent, greyish white, with transparent tubes. It is an inhabitant of fine sand in deep water (18 to 80 fathoms); but although generally distributed in the Mediterranean, and found in many parts of the North Atlantic, it does not appear to be plentiful anywhere on our shores. It has been found at Falmouth, in the Moray Firth, at Stornoway, Skye, Shetland, and in Birterbury Bay, County Galway. The Blunt Tellin (T. crassa) has a yellowish-white shell with faint pink rays from the beaks to the lower margin, and marked by numerous strong concentric ribs. The left valve is much natter than the right. In young specimens the shell may be found covered Tellin, with foot an extended 120 Shell Life with a fibrous yellow-brown epidermis, but this soon gets completely cleaned off as the mollusk burrows in the sand. The Baltic Tellin (T. balthica) has a glossy shell, somewhat triangular when viewed from the side, but rather globular as seen from the end. In colour it varies from white to crimson, occa- sionally with bands of a deeper tint; and the surface finely grooved. The animal is yellowish, tinged with brown ; the upper siphon larger than the lower. Its habitat is in sandy gravel and mud, between tide-marks, all round our coasts. The Thin Tellin (T. tennis) is triangular-oval, flattened, thin, and semi-transparent, varying in colour tic Te||in from white, through yellow to rose; the right valve larger than the left. The animal is yellowish white, its siphons nearly equal in length. It frequents sandy beaches about low-water mark, but it does not burrow deeply. The Bean - like Tellin (T. fabula) has a triangular- oval, thin, and semi-transparent shell, glossy, pearl - white tinged with yellow. The animal is similar to that of the Thin Tellin, of a clear white colour and with slightly longer siphons. It is common in sandy bays from low water to 15 fathoms. The Rough Tellin (T. squalida) is flattened and thin, the valves slightly unequal, opaque, satiny, of JEAN-LIKE TELLIN ; 2 ROUGH TELLIN ; 3 DONAX-LIKE TELLIN ; 4 LITTLE TELLIN 5 BRITTLE TELLIN; 6 THIN FURROW-SHELL; 7 WHITE FURROW-SHELL; 8 PEPPERY FURROW-SHELL. Wedge-shells^ Venus-shells, and Cockles 1 2 1 a pale orange tint, reddish near the beaks. The animal is whitish tinged with flesh - colour; the tubes speckled and the mantle- edges strongly fringed ; foot large. It is not a common species, but it may be found on sandy shores on the south and west of these islands, at depths between 7 and 15 fathoms. The Donax-like Tellin (T. donacina) is triangular-oblong, compressed, somewhat glossy, of a yellowish - white colour with pink rays. The animal is white, with the edges of the mantle finely toothed, and the long slender tubes marked with white along their sides. It burrows in shell-sand and nullipore, between 4 and 25 fathoms. The Little Tellin (T. pusilla) is very like the last mentioned, but smaller, more convex, and more solid. Its colours, too, are brighter, and may be white, yellow, pink, or rose, with rays of deeper tint. The animal is transparent white, the edges of the mantle quite plain, and the siphons nearly con- tiguous and equal in size, the excurrent being four or five times the length of the incurrent. The foot is toothed along the sides. It occurs on sandy shores at depths from 3 to 85 fathoms. The Brittle Tellin (Gastrana fragilis) has been separated by Schumacher from the genus Tellina, because of its more wedge-shaped and swollen shell, and because the lateral teeth of the hinge are want- ing and the cardinal teeth of the left valve are very unequal in size. This,, the only British species so separated, has a rather thin, but opaque, shell of triangular form and pale yellow hue, with fine 122 Shell Life concentric ridges. The animal is yellowish white, with a large foot, and tubes nearly twice the length of the shell. It is a local species, found burrowing in sand between low water and a depth of 12 fathoms. The Furrow-shells (Scrobicularia) are so-called on account of the shape of the cartilage-pit, which is in this genus a narrow chink under the beak. The shell differs from that of Tellina in the fact that while the right valve has two cardinal teeth, the left has but one. The shells are white, with concentric grooving, and gape behind for the extrusion of the siphons. The Prismatic Furrow - shell (S. prismatica) is almost flat, of an oblong wedge- shape, thin, fragile, and semi - transparent, highly polished but minutely striated. The prismatic effects are due to the thinness of the epidermis. The animal, which is very active, is pearly white ; its foot large and pointed, its siphons slender, and the mantle edges finely fringed. It is not a common species, though generally distributed on sandy ground in from 3 to 90 fathoms of water. It may be obtained most easily from the stomachs of flat - fishes and haddocks. The Glossy Furrow-shell (S. nitida) is more oval than the last, and the valves gape more widely. The animal is clear white, with a large foot and very long siphons; the mantle is fringed with short cilia. It is a more local species than prismatica, and occurs in muddy sand between 3 and 100 fathoms. The White Furrow-shell (Syndosmya alba) is oval, thin, opaque white, polished, but with minute con- centric grooves. The animal is whitish tinged with Wedge-shells > Venus-shells, and Cockles i 2 3 blue and spotted with pure white ; the siphons are as long as the shell, and the mantle is edged with several rows of minute fleshy points. It is a mud - lover and social, and may be found in quantity in bays and estuaries from extreme low water to 40 fathoms. In spite of its dirty surroundings, the shell is always remarkably clean. The siphon- tubes are protected from the mud by a light- brown epidermis. The Peppery Furrow - shell (8. piperata) is triangular - oval, nearly equal - sided, thin, opaque, flattened, without gloss; the colour is greyish white, stained with yel- low or black from contact with the mud ; the epi- dermis glistening. The accompanying figure of the hinge-plate in this species will give a good idea of the character prevailing in this group, where the lateral teeth are greatly reduced or wanting. The hinge-plate it will be seen is thick, broad in the centre. There are two cardinal teeth in the right valve, thin, plate-like, and parallel ; in the left valve there is one car- dinal, but often this is double. There are no laterals, but their purpose is served by the ridged sides of the hinge-plate, which keeps the valves from shifting. The animal has a pale yellowish body, the mantle - edge scalloped irregularly and minutely Hinge-plate of Peppery Furrow-shel 124 Shell Lift fringed. On some parts of our coast this mollusk .is known as the Mud Hen. It has a fondness for stiff mud and clay beds at the mouth of rivers, a little below low-water mark. It burrows to a depth of about 6 inches, keeping open cornmunciation with the water above by means of its long tubes. The Thin Furrow-shell (S. tennis) is a much smaller and more triangular species than the last ; more con- vex, thin, opaque, iridescent; greyish white, often stained by burrowing in clay. The animal is white, with a delicate fringe to the mantle. The inhalent tube is twice the length of the shell, the exhalent tube one - third less. It appears to be fond of brackish water, for it is found chiefly in mud at low water along the estuaries of the south coast from Kent to Devon. The Wedge - shells (Donax) are more triangular than the Furrow-shells, the valves glossy though partially scored by crossing grooves. The beaks are a good deal behind the middle line. The valves do not gape behind, and their inner margins are usually " milled," so that the closed valves interlock. There are two cardinals in the left valve, a double central one in the right, and a lateral fore and aft in each. The animal has a fringed mantle, short thick diverging siphons, and a very large and pointed sharp -edged foot. They are found in sand from low-water mark to about 8 fathoms, but as they burrow only an inch or so below the surface there is no necessity for long siphons. The Banded Wedge- shell (D. vittatus) is the best - known species. It is variously coloured yellow, brown, olive, or purple, often with three white rays from the beaks, and with Wedge-shells* Venus-shells, and Cockles 125 concentric bands of deeper tint than the ground colour. The animal is very agile, of a purplish red or yellow colour ; the siphons are pale ^^^ orange, and not more than ^^^ : ^jjj^ -"^ half an inch in length. It is plentiful at low water in most sandy bays. The Polished Wedge - shell (1). politics) may be at once distinguished from the preceding by the absence of the milling along the inner margin of the valves. The colour is chestnut-brown varying towards olive, with a broad cream- coloured ray and some marbling Polished Wedge-shell 11 j i -r, -t of the same tint. It burrows in sand at extreme low water and a few fathoms below it, chiefly on the coasts of Devon, Corn- wall, and the Channel Islands. The Abrupt Wedge-shell (D. trunculus) has been taken occasion- ally on our southern shores. It is larger than the Banded Wedge-shell, and may be distinguished from it by being more acutely triangular, the striations more delicate, and the inner edge not milled beneath the hinge-ligament. Further, the hinder part of the shell does not slope gradually to a point, but abruptly as though cut off. The Trough - shells (Mactra) are represented by five or six species. The shells are triangular-oval, swollen, with a slight gape behind. There are two erect diverging cardinals, and large plate-like laterals on each side of them two in the right, one in the left valve. These lateral teeth have their edges milled in M. elliptica, M. solida, and M. sub- 126 Shell Life truncata. The animal has a thick mantle with fringed edges. The siphons are united throughout their length, but the exhalent tube is fitted with a tubular valve. The foot is large, tongue-shaped, and very extensible, used for burrowing and leaping as in the Cockles. They inhabit sandy coasts, burrowing but slightly below the surface, and ranging from low- water mark to about 35 fathoms. The Thick Trough-shell (M. solida) is, as its names indicate, both thick and solid. In shape it is very nearly an equal -sided triangle, only the angles are rounded. Its colour is yellowish white, and it is marked with slight concentric grooves, but in spite of these the surface is quite smooth. The measurement from end to end is less than that from the beaks to the lower margin. The animal is white or yellow tinged with brown. The siphons are short, their mouths fringed with yellow or red filaments. It is common in coarse sand at low water and a few fathoms below it, all round our islands. The Elliptical Trough - shell (M. elliptica) is by some authors regarded as a mere variety of M. solida. The shell is smaller, thinner, more elliptical than triangular, the greater measurement being from back to front, instead of from beak to lower margin. It . , /-,/x , occurs m deeper water (10 to 100 fathoms) than M. solida. The Cut Trough-shell (M. suUruncata) has the ends of the shell much contracted, so that the beaks are very prominent, and the general aspect is hatchet-shaped. There is a heart-shaped depression i ABRUPT WEDGE-SHELL; 2 BANDED WEDGE-SHELL; 3 GLAUCOUS T H 4 THICK TROUGH-SHELL ; 5 ELLIPTICAL TROUGH-SHELL Wedge-shells, Venus-shells, and Cockles 127 both before and behind the beaks. The animal has the mouth of its siphon-tubes fringed with two rows of yellow or red filaments. The foot is yellowish and slender; the mantle with a toothed edge. It lives in coarse sand from low water to 27 fathoms. In the north of Ireland it is known as Lady Cockle ; Cut Trough . sheM in the Clyde district it is the "Aikens." The Rayed Trough-shell (M. stultorum) is of the same general shape as M. solida, but thin and glossy, and the yellowish ground is largely covered by broken rays of brown from the beaks to the margin. The animal is white, tinged with blue ; the mantle fringed with white filaments ; the Rayed Trough-shell f ot white > thick. It is common on all our shores, the animal burrowing in sand between extreme low water out to 18 fathoms. The Glaucous Trough-shell (M. ylauca) is triangular-oval, rather thin and glossy ; yellowish white, with rays of yellow-brown or fawn colour, and the upper margins marked with brown. It is covered with a brown, satiny epidermis. The animal is white, its mantle fringed with white fila- ments ; the siphon-tubes short and conical, tinged with yellow and streaked with red-brown. It is a rare species, but it occurs on the Cornish coast, where it ranges over the sand in shallow water, quickly burying itself to a depth of two or three inches when the tide goes out. 9 128 Shell Life The general characters of the mollusks comprising the sub-order Veneracea are an almost round or oblong shell of equal valves, whose hinge has three diverging cardinal teeth, the muscular impressions oval and polished, and the mantle impression showing a deep sinus into which the siphons are retracted when not in use. The animal has unequal gills which are slightly folded ; the foot is large, tongue- shaped, and adapted for burrowing in sand, gravel, or mud, in which the species live. The siphons are unequal, cylindrical, and in general short, showing that the mollusk does not go far below the surface, and in most cases they are speckled in a way that makes them har- monise with the sand. The deep sinus of the mantle-impression is a character serving to distinguish any member of the family from related genera. A good example of the family may be found in the Smooth Venus (Venus chione), whose massive shell may be found after gales thrown up on sandy beaches of the Cornish coast. But our enumeration of the species must begin with one that is not so typical, because, its tubes being so very short their withdrawal has not produced a deep sinus in the impression of the mantle within. The Little Circe-shell (Circe minima) is the only native representative of its genus. It has a nearly round, flattened shell, with broad, flattened, plate- Wedge-shells, Venus-shells, and Cockles 129 Enlarged plan of hinge Little Circe-shell like ridges with slight furrows between. It is of various tints, white, yellow, red, brown, purple, sometimes streaked, rayed, or spotted with deeper shades. The animal is transparent greyish in colour, the mantle spotted with brown and fringed with short cylindrical points. The tubes are unequal in length. Its habit is to burrow slightly among sand and nullipore in from 5 to 85 fathoms of water. The Rayed Artemis (Dosinia exoleta) has an almost circular shell thick, solid, flattened, and covered with ridges, but, unlike those of Circe, these are finer, much more numerous, and overlap. It is cream coloured, marked with several faint rays of red-brown, and some irregular spots of the same colour scattered over the rays. Owing probably to the epidermis being worn away in early life, this shell has the appear- ance of having been tossed about a good deal on the shore, and it was this aspect, no doubt, that struck Linnaeus when he named it exoleta worn away. The animal is pale yellowish, the mantle fringed with white lashes, and the siphons short and united. The large foot is white and axe-shaped. All around these islands it may be found in sandy bays at a Rayed Artemis Interior of Rayed 130 Shell Life depth of a few fathoms. The Smooth Artemis (D. lupina} is similar to the Rayed Artemis, but smaller, smoother, and less round in outline. The sides and lower margin may be, indeed, in Jeffreys' words "an arc of three-fifths of a circle." The animal is greyish white in colour, the mantle-margins fringed with short tentacles. The siphons are united except at the mouths, and are capable of extension to three times the length of the shell, showing that this species is in the habit of burrowing more deeply than the previous one. It is equally common, and may be found as near as low-water mark on sandy ground. The Smooth Venus (Venus chione) is one of the finest of our native species ; its thick, heavy shells Smooth Artemis being nearly 4 inches in longest diameter. Its shape is described as triangular-oval. In colour it is a light pinkish brown, with a varying number of narrow rays of darker hue from the beaks to the lower 5 PULLET CARPET-SHELL. Pledge-shells^ Venus-shells, and Cockles i 3 i margins, which are round - edged, and perfectly smooth. The concentric lines are so slight that they at first sight appear to be more due to colour than to sculpture ; and the character of the epidermis is such that it resembles a coat of varnish. The animal is flesh-coloured with a tendency towards orange. The mantle is slightly scalloped along the lower margin, and has a few tentacles at the front. The orange tubes of this species are not united all the way, and their mouths are fringed with black-tipped tentacles. The large, thick foot is dark flesh-tinted. It is not generally distributed, its range in our waters being confined to the south and west, where it dwells in sand at depths between 12 and 25 fathoms. It is a good edible species, not only for man, but is also appreciated by fish and bird ; hence its thick hard valves, which probably are | nterior of smooth Venus needed not only to resist the jaws and palate teeth of big fishes, but to prevent injury from rolling about in great commotions of the lower waters. We have seen it washed up on Cornish beaches after continued heavy gales, and have seen the Razor-bills and Puffins attack it with their powerful bills, nipping off a little of the shell at one end to admit the point of their beak in order to sever the adductor muscle which keeps the valves closed. It is to these muscles and the exceedingly powerful hinge-teeth that the inviolability of the shell is due, for there are no cogs along the margins by which the valves may interlock. 132 Shell Life with white. The Banded Venus ( V. fasciata) has a solid shell with sharp-edged concentric ribs, variable in colour through yellow, pink, red, to brown, marked by several rays of darker tints. The margins of the shell inside are beautifully milled, except just below the ligament. The animal has its mantle bordered with red and fringed The short yellow tubes are united, save at the tips, where they are fringed with white. The thick, white foot is lance-shaped. It is a generally distributed species, occurring on all our coasts, at all depths, among gravel, sand, and nullipore. The Pale Venus (F. casino) is very similar to the last, but much larger (If inches across), the ribs on the shell more plate-like, and less robust, more strongly scored between the ribs, more unicolorous and pale. Of wide distribution, but only local occurrence, on sandy ground, from 5 to 90 fathoms. The Warty Venus ( F". verrucosa) is still larger than the Pale Venus, and an advance is made in the passage of the ribs to concentric ridges which are, in this species, broken into wart-like irregularities, especially towards the hinder margin. From the beaks to the lower margin, crossing as it were beneath the concentric ridges, run a great number of evenly and closely set ribs, which are more evident in the older portion of the valves where the ridges are less prominent. The lower margin is milled inside, as shown by the figure of the interior of a left valve. Wedge-shells i Venus-shells, and Cockles 133 It is a dull, rough-looking shell of drab or pale brown colour, sometimes with a few darker rays, and its distribution is restricted to the south and west coasts, where it occurs in fine gravel and sand at depths between 7 and 20 fathoms; in the Channel Islands it may be found at low water. The Oval Venus (K ovata) has a dull shell of triangular-oval shape, whose longest diameter is little more than half an inch. From 40 to 50 ribs radiate from the beaks, and are crossed by half that number of concentric thread-like ribs, a scale or wart arising where the lines cross. The colour is yelldw tinged with pink or red, and occasionally blotched or spotted with red -brown. The inner margin is milled all round. The short siphons are of equal length, and connected almost to the mouths. It lives among sand and nullipores from extreme low water to deep water. The Striped Venus (V. gallina) is of somewhat triangular form, the shell solid, of a pale yellow hue, with three obscure rays of red-brown spots. Its sculpture consists of overlapping con- centric ribs. The inner margins are milled. The animal is white, and the white filaments which fringe the mantle are disposed in tufts. The long slender siphons are united almost throughout. It is generally distributed and common in sand, from low water to 85 fathoms. The Clam (V. mercenaries), an American species, has 34 Shell Life become naturalised in the Humber, where it was first observed in 1864, from which date it appears to have gone on increasing in numbers. As it is an edible species highly appreciated in the United States its continued increase will probably bring joy to local epicures. It may be noted that the word " niercen- aria" refers to the former use of these shells in making " wampum " the strings of beads which passed as money among the North American tribes. The Wavy Venus (Lucinopsis undata) is very like the Round Double-tooth (Diplodonta) described in the previous chapter, but whereas that is a strong, glassy- white shell, this is chalky-white and fragile. It differs from the other Venus- shells in being thin and almost transparent. It is almost circular in outline, swollen and smooth, without ribs, but marked by sunken concentric lines. Its colour is white tinged with yellow near the beaks. The impression of the mantle within is very broad, and the sinus extends far up towards the beaks. The mantle-margin is wavy or uneven, but neither fringed nor toothed. The orange siphons are widely separate, protruding from the lower rather than the hinder margin, and the lower tube is longer than the upper, while both are fringed. It is a common species everywhere in fine sand, even when mixed with mud, and ranges between 3 and 100 fathoms. Full - grown specimens measure 1 to li inch in diameter. Wedge-shells, Venus-shells, and Cockles i 3 5 The following four species, though belonging to the same family, form the genus Tapes, and are famil- iarly known as Carpet-shells from the colour-markings suggesting the patterns of tapestry. The shells are solid, more rhornboidal than triangular, and the beaks are set very near the front extremity. This character, combined with the shape of the shell, is sufficient to determine the genus, and the four native species are so distinct from each other that they may be readily identified. The Golden Carpet-shell (T. aureus) is yellowish white with little gloss. Finely incised, crowded but shallow lines run from the beaks to the margins, and are broken by the very distinct bands marking periods of growth, and which are often greyish in tint. The margins of the shell are quite plain. It is confined ***** chiefly to our south and west coasts in sandy gravel between 3 and 18 fathoms. The Banded Carpet-shell (T. virgineus) is more dis- tinctly oblong than the last. The exterior of this shell has polish, though it is not very glossy. The surface scarcely appears broken by the flattened, close-pressed ribs, which are slightly rounded only at the front and back. The ground colour is P ale yellow, overlaid with dots, spots, and splashes of purplish brown, which are arranged in about three wedge- shaped masses, leaving clear rays between them. The glossy interior is tinged with yellow, orange, or purple in its upper half. The margin of the 136 Shell Life Banded Carpet-shel interior mantle is partly toothed and partly waved and scal- loped. The siphons are separate for only a fourth of their length, and are pale yellow, tinged with brown and purple, and with fringed mouths. It is a generally distributed species, and may be found among sand and nullipores from low water to over 100 fathoms. The Pullet Carpet-shell (T. pullastra) is triangular- oval, yellow, marked especially on the hinder part with dark purple-brown. The concentric lines are finer and closer on this shell as compared with the last, and in addition there are a vast number of delicate lines radiating from the beaks. The colouring is in some specimens very suggestive of the plumage of a speckled hen, and it is probably from such individuals that the mollusk has got the name of Pullet, which is locally applied to it on parts of the Devon coast. The animal varies in colour from white to grey and yellow, and its mantle- margins may be waved or jagged. It is quite a common species, and may be found in the muddy sand of the shore between tide marks, in crevices of the rocks or in the root-like bases of the larger seaweeds. In these situations, or in the deserted holes of rock-boring mollusks, it usually spins a byssus after the manner of the Mussel. The Cross-cut Carpet -shell (T. decussata) is decidedly the Carpet-shell, but it is the back of the tapestry that is shown by its sculpture. The lines from the beaks break the surface up into Pullet Carpet-shell (one-fourth nat size) Wedge-shells, Venus-shells, and Cockles 137 radiating wavy ribs which are crossed and broken by concentric lines. There is not the faintest gloss or polish on the shell. Its colour is a yellowish drab, stained irregularly with purple. The animal is cream coloured or grey, its mantle-edges scalloped or edged with white ; the siphons separate throughout their length and fringed with brown at the orifices. This species appears to be confined to the south and west coasts, where it burrows in the gravel and sand about low- water mark. The Banded, the Pullet, and the Cross-cut are used in different parts of the Continent as human food, and the two last named are eaten in Sussex and probably some other parts of this country. In external appearance the Rock Venus ( Venerupis irus) offers little resemblance to the Carpet-shells, yet a glance at the interior shows very near relation- ship. The valves do not fit closely at the hinder end, showing that the siphons are rarely withdrawn. There are fifteen or more concentric ridges, thin and high, with toothed edges, and beneath these, running from the beaks, a crowded series of fine lines. The animal is white, tinged with pink, the siphons united for half their length, and the valve of the lower protruded beyond the fringe. The foot is rather small, compressed, and adapted for spinning a byssus. The favourite habitat of this species is in the holes of limestone rocks bored by Saxicava, also in the 138 Shell Life cavernous bulbs or so - called roots of the large Laminarice. But it is only in parts of the west and south-west that it need be looked for, such as the shores of Cornwall, Scilly, Guernsey, Devon, Dorset, Glamorgan, and Pembroke ; it also occurs round Ireland, except on the north. Its zone is that of the big seaweeds a little below extreme low water. The form varies according to habitat. That figured is the finest, and it lives either in rock chinks or in the empty valves of Pholas dactylus. The Rock -borers (Petricola, lithophaga and P. plioladiformis) are not British, but they are found occasionally on our shores. They bore into limestone and mud. The first named which is also figured is a native of the Mediterranean and the French coasts, but Rock-borer (Petricola litKopUo,^ the S6COnd COm6S frOU1 N rth America. This, which has a more elongated, more strongly ribbed shell than P. litliophaga, appears to have got established in recent years about the estuary of the Thames/- and in the river Crouch, Essex ; it has also been taken at Hernc Bay just above low water. It is very probable that it has been introduced among oysters that have been imported from America and laid down in these districts. The Cockles are the British representatives of the sub-order Cardiacea, which gets its name from the conventional heart-shape (Karelia) of the closed shell when viewed endwise. The two valves are exactly alike, very convex, with prominent beaks, from which strong ribs radiate. These ribs and the in- SPINY COCKLE ; 2 PRICKLY COCKLE ; 3 KNOTTED COCKLE ; 4 LEAST COCKLE. Wedge-shells, Venus-shells, and Cockles 1 39 tervening furrows being continued right to the margins of the shell, those of the two valves inter- lock, fitting in a very accurate manner. There are one or two cardinal teeth in each valve, and a strong lateral on either side at some distance from the cardinals. The gills are long and much folded back, the siphons rather long, the foot large, long, and cylindrical, the mantle - margins jagged. These mollusks live in sand and mud, from low water to a considerable depth, and by means of their foot can rapidly sink into or rise above it. Pigment spots serving as visual organs are scattered over the margins of the mantle and over the tubes. The Spiny Cockle or Red - nose (Cardium aculeatum) is the largest of our native species, and measures as much as 3 inches across. The valves are somewhat thin and glossy, covered by about 20 strong broad ribs that radiate from the beaks and bear a number of stout curved spines whose points are directed backwards. The colour is yellowish tinged with red. The animal is coloured bright red, and the red foot, which gives it the popular name of Red-nose, is long and awl-shaped. It is found in deep water along sandy shores, chiefly in South Devon ; at Weymouth, Guernsey, and Dublin Bay. The Prickly Cockle (0. echinatum) is not so large as the foregoing, being little more than 2 inches across ; but the shell is more solid, has a duller surface, and a less oblique curve to the front margin. The radiating ribs bear short, stout, triangular spines, curved backwards. The colour is yellowish white, stained with red. The animal varies in colour from white to pink ; the foot is finger shaped, with a flesh- 140 Shell Life coloured or red skin, twice the length of the shell. It is common on sandy shores on all our coasts, ranging from 5 to 100 fathoms. At Jersey very fine specimens may be taken from muddy sand at low water. The Rough Cockle (C. tuberculatum) resembles the last species in general appearance, but differs from it in having a larger, more solid, and globular shell. The ribs are coarser, and the spines upon them are inter- rupted by intervening spaces, whilst in (7. echinatwn the rows are continuous ; some of the Rough Cockle spines (in tuberculatum) are short and blunt, others flattened. This also is a southern form, found in sand at extreme low water to about 12 fathoms on the coasts of Dorset, Devon, Cornwall, Guernsey, and Bantry. Diameter 3 inches. The Warty Cockle (C. papillosum) is a small species whose longest diameter is little more than half an inch, the shell globular, solid, glossy, with about 25 flat ribs close together. It is coloured yellow and streaked with reddish brown. It occurs in the Channels Islands in coarse sand, between 15 and 20 fathoms. At Herm it has been taken at low water. Fresh valves have also been dredged at Falmouth (19 fathoms), and Scilly (40 fathoms). The Little Cockle (6 y . exiguum) has a small, solid, dull shell, with about 20 compressed ribs, which are covered in young examples with white warts ; white or yellowish, sometimes streaked with brown. It is pretty generally distrib- uted along our shores, occurring in soft ground a Wedge-shells, Venus-shells, and Cockles 141 little beyond low-water mark. The Banded Cockle (C. fasciatum) is another minute species, with about 25 ribs bearing overlapping scales. The shell is thinner, the valves less swollen. The name is suggested by the reddish-brown bands, but these are by no means unfailing marks of identity, for the species is a very variable one. The animal is white, with a plain-edged mantle, and the long, slender, finger-shaped foot is trans- parent. It is a common shell on all our coasts where there is gravelly sand, in from 5 to 90 fathoms of water. The Knotted Cockle (C. nodosum) is similar to the Banded Cockle, swollen near the beaks, with from 24 to 28 ribs, covered with little knobs or oval plates. The colour is white, sometimes tinged or banded with yellow or brown. The white animal is somewhat transparent ; the mantle fringed with white filaments, and the siphons pale yellow ; foot white. It is generally distributed, and occurs among sand and shell - gravel at depths between 3 and 86 fathoms. The Common Cockle (C. edule) is so thoroughly well known that it stands in need of little description. The shell is somewhat rhomboidal, solid, and with- out gloss, traversed by ribs varying in number from 24 to 28, and by minute lines crossing each other at right angles. The animal has a white body, but the mantle is pale yellow, its edges with a short white fringe. The short 142 Shell Life siphons are separate throughout, with white fila- ments along their sides. The white or yellow foot is proportionately small, thougli long, and ends in a thin flat point. It occurs in great numbers on all our sandy shores from low water to about 5 fathoms ; and a smaller, thinner variety extends up estuaries into brackish water, as, for example, up the Thames as far as Gravesend. It is said to occasionally depart from its burrowing habit and to take to climbing up submerged posts, spinning a byssus to aid it. The raking in of Cockles for food and bait forms no inconsiderable item of what is comprehensively called the fishing industry. The Least Cockle (G. minimum) might at first sight be taken for a young example of the last mentioned. It has a roundish-oval, thin, glossy white shell, crossed by 28 or 30 flattened, radiating ribs, which bear minute arched scales. It is subject to little or no variation, but individuals that have lived in coarse sand may be found with the ribs cleaned off by attrition, whereas those found in muddy sand have the ribs beautifully sharp and fresh. It is not widely distributed; but it has been found off the west of Scotland, Shetland, Ireland, Isle of Man, Scilly, Lundy, the Smalls, and West Orkneys, burrowing in fine sand at depths between 5 and 100 fathoms. The Smooth Cockle (0. norvegicum) differs from all the others in appearance, not only by reason of its smoothness, but also of its shape. The shell is distinctly triangular in outline, wedge-shaped when viewed from the ends, and crossed by about 40 ribs, which are all but obliterated owing to their lowness and the shallowness of the intervening grooves. The i SMOOTH COCKLE LARGE SUNSET-SHELL ; 3 RIBBED SUNSET-SHELL ; 4 OVAL PIDDOCK Wedge-shells, Venus-shells, and Cockles 143 colour is whitish, faintly mottled with flesh-tint where the greenish-yellow epidermis has been worn off; at the ends of the valves there is no trace of the ribs. The animal is yellowish white in colour, the mantle tinged with red and its edges plain. The siphons are separated throughout their length but united at the base. It has a large and powerful rounded foot, with a rough flesh-coloured coat. It is a local but plentiful shell, dispersed generally along our shores in from 5 to 80 fathoms, where there is sand or nullipore. HE species included in this chapter form several sub - orders, the first of which is the Myacea, agreeing pretty closely with Cardiacea in the form of the gills arid the mantle, the variability of the mantle impres- sion, and the want of uniformity in the union of the gills. But the foot instead of being cylindrical is more or less flattened from the sides, and more tongue-shaped than finger-shaped. The shells gape at one end or both, and this, as we have already pointed out, is due to the fact that the siphons are almost constantly extended, and consequently when the shell is enlarged by normal growth these edges are not permitted to come together. The subjoined figure, showing the position of the Blunt Gaper when alive, will help to explain this constant ex- (papers, Piddocks, and Ship-worms 145 tension of the siphons. The Gaper burrows deeply into sand and mud, not for its food, but for safety its flesh being prized by fishes. At the recess of the tide they are searched for by gulls, and if they are too near the surface they pay the penalty with their lives. Their siphons are stretched upward until they reach the water, when their mouths are opened and the streams set in motion : one downward, charged with micro- scopic life to be filtered out and used as food ; the other, upward, discharges the water that has passed over the gills and been relieved of its oxygen. The first genus in this group is the Sunset-shells (Psammobia), of which four species are found in our seas. They have long slender shells, much compressed and gaping slightly at each end, the foot being usually extended as well as the siphons. These siphons are long, and separate ; the foot comparatively large; and the mantle -edges fringed. The popular name is due to the fact that the yellowish shells are Hinge-teeth of marked by radiating bands of red, the notion being that when a valve is held with the beak below these red bands present the appearance of beams from a sun that has just sunk below the horizon. The character of the cardinal unt Gaper 146 Shell Life teeth is shown in this figure of a right valve ; in the left valve the hinder cardinal is much smaller and not cleft. The beaks are turned slightly to the hinder end of the shell. The Tellin-like Sunset-shell (P. tellinella) is thin, glossy, yellowish white, marked with fine concentric ribs, the grooves as well as the ribs being polished, and the radiating bands are of pink, red, or violet. A streak of crimson usually runs along the upper edge of the valves before i like sunset sheii au< ^ behind the beaks. The in- terior is highly polished, with the external colouring repeated. The animal is white, its mantle with a tooth-like fringe, and the upper (excurrent) siphon is marked by fine lines of white from end to end. This brilliant little mollusk occurs locally all round our coasts, burrowing in sand between 4 and 85 fathoms, and occasionally swimming after the manner of the Pectens by flapping its valves. The Ribbed Sunset-shell (P. costulata) differs from the last chiefly in the character of the posterior slope of the shell, which bears from 12 to 20 slight but sharp ribs running from the beak to the hinder margin, which is notched in consequence. In addition the shell is thinner, the valves unequal, and the less regular rays are of deeper tints. The animal is white tinged with pink, the mantle edges thickened and slightly fringed. This is more local than the last, and can only be obtained by dredging, as its habitat is in fine sand in from 15 to 85 fathoms of water. It is slightly more than 1 inch in length. (papers, Piddocks, and Ship-worms 147 The Faroe Sunset-shell (P. ferroensis) is larger, more opaque, and duller, marked with close low concentric' ridges, which become higher just before reaching the clearly marked posterior slope, across which they are very distinct. In that particular region they are crossed by half a dozen (on each valve) Faroe Sunset . she fine radiating ribs from the beaks. The shell is more or less covered by a dull greenish epidermis, but where this is worn away the colour is seen to be pink with indefinite rays of a deeper tint and small oval spots of white. The inside is coloured with some shade of purple, and very highly polished. This is a common species on all our coasts, in sand, at depths between 4 and 90 fathoms of water. The large Sunset-shell (P. vespertina), which is the largest of the native species, is of a more oval form. It is somewhat solid, compressed, and glossy where the thick olive epidermis has worn off. Where it is thus bared the shell is seen to be of a yellowish-white hue with rays of purple-brown or lilac. The sculpturing of the surface is very slight, and has the appearance of having been worn down; it consists of concentric ridges, and more evident lines of growth, crossed by obscure radiating lines. Interior coloured yellow or purple. The animal is yellowish white in colour, with a fringed mantle, and a broad thick foot. It is a local species, but found widely distributed, chiefly on the south and west coasts of both England and Ireland, and on the west coast of Scotland. Like the others 148 Shell Life of its genus, it is a sand-dweller, and its range is from extreme low water to 4 or 5 fathoms. It attains a maximum breadth of 2i inches, and fairly large specimens are used for food in the west of Ireland. Of the Gapers (My a) we have only three species, and one of these we have already figured as a type of the sub-order. The siphons are connected throughout their length, and though they may be, and are at times, completely withdrawn into the shell, they are usually kept fully extended. This has caused the hinder end of the shell to gape widely. They are deep burrowers, and therefore Hinge and cartilage process of Gapers assume the position shown in our figure, the foot downwards and the siphons reaching straight up through sand or mud to the water above, with the long axis of the shell at right angles with the surface. Looked at from this point of view it will be seen that the fore-end of the shell is shaped like the bows of a boat, that the tongue-shaped foot may pull it down more easily. These shells are commonly buried to a depth of eight inches, some- times a foot. There is a remarkable development of the hinge-teeth beneath the beak of the left valve in the shape of a hollow shelf to hold the cartilage, with corresponding ridges to fit it in the right valve. Capers, Piddocks, and Ship-worms 149 The Sand Gaper or Old Maid (IT. arenaria) has the valves of the shell not quite equal, the right being a little larger than the left. The shell is traversed by coarse, irregular, concentric lines, partially covered by a wrinkled, papery- looking epidermis of a muddy grey colour. The shell gapes at each end, and the epidermis is continued back over almost the entire length of the siphons, as though they required protection from the ma- terial through which they have to push. Where the epidermis is worn away the shell is a dirty white, stained with rust near the beaks. The mouths of the siphons are coloured with red and fringed. It is a generally distributed species, and is found in soft ground from low water to about 25 fathoms. It has a preference for estuaries, and has no objection to brackish waters. Large numbers are consumed for food, under the name of " old maids " and " clams," on some parts of our coasts. The shell is about 4 inches wide when full-grown. The Blunt Gaper (M. truncata) is very like the foregoing species, except that the shell which is about one-third less in width than that of M. arenaria ends abruptly behind as though sawn across, and there is less disparity in the size of the valves. It is found in similar situations to Old Maid (one-fifth nat size) 150 Shell Life the other, with a marked preference for the open sea over estuaries. The Small Gaper (M. bingJiami) has a wedge-shaped shell, with unequal valves which gape behind, smooth, and with fine lines instead of the coarse ones of the other species. It is white beneath the epidermis, which is pale brown. The siphons are short, especially the incurrent one. This species does not burrow in the ground as its congeners do: instead, it takes possession of holes that have been made by the Rock -borers (Saxicava), the empty tubes of Serpulae, and the crevices of the so-called roots of the great Tangles and Wracks, between 5 and 25 fathoms. It attaches itself by means of a byssus. Individuals that live this free, out-of-door life, so to speak, are liable to be mis- taken for Saxicava or Tkracia. The Basket - shells (Corbula), though a large genus, are repre- sented in this country by a single species, the Common Basket -shell (C. gibba), in which the unequal size of the valves noticed in Mya is much accentuated, so much indeed that the left valve appears almost like an operculum to the right. The shell is also drawn out behind to make a cover for the siphons, which are so short as to be only slightly protruded. The shell is white tinged with Blunt Gaper (one-fifth nat. size) (papers, Piddocks, and Ship-worms 151 Sasket- shell, showing hinge-teeth yellow and brown, ornamented by concentric ribs in the right valve, but these become mere raised lines in the left. The hinge-teeth in the right valve consist of a thick, curved cardinal, flanked by a ridge- like lateral on either side ; in the left valve the cardinal is hollowed to take the cartilage, and beside it is a cavity to fit the cardinal of the right. The animal has a comparatively large and thick foot, which it uses for burrowing just below the surface of sandy and gravelly shores, from extreme low water to about 70 fathoms. There are, however, other Basket- shells beside those of the genus Corbula, of which the subjoined figure of the Pointed Basket-shell (Necvra cuspidata) will serve as a type. In this genus, of which we have three species, the shells are thin, fig-shaped, and with unequal valves, though the disparity is not here so great as in Corbula. The siphons are longer, and the hinder part of the shell is drawn out to partially cover them ; their orifices are protected by long tentacles whose ends are divided into several finger-like points. The Pointed Basket-shell (N. cuspi- data) is much drawn out behind, tolerably solid, more so than in the other species, much swollen, and the left valve larger than the right. Its colour beneath the red-brown epidermis is whitish. The horn- Pointed Basket-shell 152 Shell Life coloured cartilage is covered by a chalky band (ossicle) free from the shell, and a strengthening rib runs from under the beaks towards the centre of the siphon-outlet. It has been taken from deep water (12 to 90 fathoms) in muddy sand, off various parts of our coast, but chiefly Scotland and north-west England. The Short Basket-shell (N. abbreviata) is almost transparent and extremely fragile, of a triangular-oval shape, swollen, and the valves almost equal. The surface is slightly glossy, ornamented by about a dozen concentric folds, and a curved sharp rib which runs from behind the beak. It is greyish in colour, covered by a yellow-brown epidermis. It has been taken chiefly in deep water (40 to 75 fathoms), off muddy ground, in Loch Fyne and around Shetland and Skye ; though in the Kyles of Bute it has been found in 18 fathoms. The Fine -ribbed Basket - shell (N. costellata) is similarly semi-transparent and fragile with the previous species, but is much smaller, less swollen, the valves less equal, marked with from 20 to 30 fine ribs radiating from the beaks. It has been taken with the last mentioned, of which it may be only a variety. Another small genus of this order is known as the Otter-shells (Lutraria), of which we have two species. The shells gape at each end like those of the Gapers, and the long siphons are similarly covered by a coarse epidermis ; but there are differences in the hinge-teeth which separate Lutraria from My, that of the Otter-shells closely resembling the cardinal teeth of the Trough-shells (Mactra). There is a spoon-shaped hollow for receiving the cartilage in (papers, Piddocks, and Ship-worms 153 each valve ; in the left valve there is a double cardinal just below the beak which fits into a cavity of the opposite valve formed by two large diverging cardinals. The ligament uniting the valves is exceedingly short, and admits of con- siderable movement of the ends with- out opening the shell throughout. With the valves in their ordinary positions the shell gapes equally at each end, but the arrangement of teeth and ligament is such that the front of the shell may be entirely closed by more widely expanding the rear, or the hinder gape may be nearly closed by separating the fronts of the valves. They burrow vertically into deep mud, the siphons reaching up to the surface, and the only evidence that Lutraria lies perhaps a couple of feet below is an occasional spurt of water from the excurrent siphon. To dig them out from this deep retreat is the only way to obtain living examples ; but as the situations they frequent are usually beyond the lowest of tide-marks, this is 110 easy matter. Yet the people of Herm, one of the Channel Isles, contrive to get a sufficient number to eat; they know them under the name of " Clumps." It is an open question whether the two so-called species are not forms of the same. The Common Otter-shell (L. elliptica) is elliptical in shape, somewhat flattened, solid and heavy without being very thick. Where the olive Oblong Otter-shell (one-fourth nat size) 154 Shell Life epidermis has been worn off the shell shows a dirty- white coloration. The growth lines form the principal surface ornamentation, though there are finer lines between, but these are quite obscure. In addition to the cardinal teeth already described, there are in this species two laterals in the left valve and one in the right, though only the foremost of those in the left is at all distinct. Full-grown specimens measure 5 inches the longest way by 3 inches at right angles. The animal is white ; the mantle edges closed for two-thirds of their extent, and fringed with white. The siphons, connected throughout their length, are included in a common sheath, which is 12 or 15 inches in length, covered by an extension of the shell epidermis. The large thick foot is capable of considerable extension. It may be found all round our islands from just below low- water mark to a depth of 15 fathoms; it has a fondness for the more muddy ground of estuaries. There is a variety (intermedia) which is so well named that it Qapers, Piddocks, and Ship-worms i 5 5 strengthens the doubt as to the specific distinctness of elliptica and oblonga. The points by which the Oblong Otter-shell (L. oblonga} is distinguished from the foregoing are : the shape of the shell is more slender, with an upward curve behind, not quite so flat, more solid ; the front cardinal tooth of the right valve is double, the only lateral is on the fore-part of the left valve. Its habits are the same as those of the foregoing, but it is of more local occurrence, and appears to be a more strictly southern form. Its longest measurement rarely exceeds 4 inches, but sometimes reaches 5 inches. Both species are subject, from Smooth Short Razor their attitude, to be annoyed by grains of sand slipping between the mantle and the shell. These have to be cemented over and left as evidence by which the collector may know of their trouble. We now reach the Razor-shell family, characterised by having the valves of the shell of equal length, long and narrow, gaping at both ends. The animal has a large and powerful foot of a more or less cylindrical shape. The Short Razor-shell (Solecurtus scopula) is of an elliptical shape, convex, with a central depression, crossed by a large number of overlapping low ribs, some of which radiate from the beaks to the front 156 Shell Life end, and the remainder cover the hinder end. The colour is yellowish white, and the epidermis is brownish yellow. The hinge is strengthened by a shelf-like rib on which are in the right valve two strong curved cardinals, in the left one cardinal and a short lateral behind it. This is a local species found in sand in from 20 to 85 fathoms, but some- times being taken from a little below the extreme limits of low water. The Smooth Short Razor (8. antiquatus) has the shell more compressed, the ribs and lines less distinct; the colour white, epidermis yellow-brown. The cardinals are larger, with jagged crests. It is Egg-shell Ra found sparingly on all our sandy shores in from 4 to 50 fathoms. The Egg-shell Razor (Ceratisolen leyumeri) occupies a position between the Short Razors and the Razor- shells (Solen), having the beaks almost central as in the former, but the shell material is similar to that of Solen, as also are the teeth. The shell is semi- transparent and glossy, finely grooved in the line of growth, and yellowish white in colour. Epidermis pale or deep yellow ; thinner and paler above. There are two cardinals in the left valve, and one in the right that fits between them ; the laterals are one in each valve, a little behind the cardinals. The interior is pearly white, faintly marked by the Qapers y Piddocks, and Ship-worms 157 mantle impression. The animal is pale yellowish the mantle tinged with red, and its edges fringed where not united. The siphons are distinct for the greater part of their length, reddish ; and the purple- red foot is club-shaped when extended It lives in the sand of extensive bays on the coasts of Hampshire, Devon, Wales, and Ireland, at the limits of low water. The Pod Razor (S. siliqua) is known in Scotland as the Spout-fish. The shell is familiar enough to all who wander across sandy shores after the spring tide has receded, though it is only the empty and mostly broken valves they see. When full - grown these shells are 8 inches long and 1| inch broad. A glance at the exterior of one of these valves is very instruct- ive, for it shows at once in what manner the shell is enlarged. In most of the bivalves we have been considering the concentric ridges point to the fact that on three sides of the beaks the shell-margins have been added to pretty Deduced)"" equally ; or, if the ribs were more closely crowded at the ends than towards the front margin, that less material was added to the ends than to the lower edge. The lines on the shell of the Razor show us clearly that the chief addition is made to the hinder end of the valves, next to the lower margin, very slightly to the upper margin. To the front end scarcely any addition is made certainly 158 Shell Life not so much as half an inch during the entire life of the Razor. This mode of enlargement explains why the hinge occupies its singular position at the extreme front of the upper margin. In the left valve this hinge consists of two stout curved cardinals, and one or two long hooked laterals behind them and below the ligament; in the right valve there is one thin broad cardinal that fits between the cardinals of the other valve, and behind it a single lateral fitting under the hook of its fellow in the left valve. It is remarkable how so one-sided an arrangement suffices to keep the long and heavy valves together. That it does suffice is evident on handling the empty shells ; yet during the life of the mollusk the power of the hinge-teeth is greatly reinforced by the adductor muscles, whose positions are marked by the shaded portions in the above figure. The animal is of a pale drab colour, with a yellowish, tongue-shaped foot. Except at the fore- end for the passage of the foot, and a minute opening on the lower surface, the mantle-edges are united throughout. The siphons are exceedingly short, united, and their openings fringed. At the base of these filaments there are grooves in which are situated pigment spots highly sensitive to light; and a shadow cast over the sands when the Razors are (papers, Piddocks, and Ship-worms 159 exposed is sufficient to cause their sudden disappear- ance. They burrow in the sands about extreme low-water mark ; not vertically but diagonally. When the sands are covered with water their shells are at the surface with the siphons exposed, but when the sea goes out they retire beneath the sand, going to the depth of a foot or two. If dug up and placed upon the surface they bury themselves with the rapidity of a mole. They can also dart rapidly through the water, apparently by ejecting water through the siphons. In many places they are considered excellent food, and for this purpose they are caught with a bent or barbed wire thrust through the open valves. The shells sometimes show at the hinder end that like Lutraria they have no means of ejecting sand that gets between the mantle and shell, so are compelled to cover it over with a coat of shell - matter. The late Mr. D. Robertson of Cumbrae relates a singular experience. On the recess of a spring tide he found three examples of this Razor, whose shells protruded above the sand to the extent of an inch and a half, and the mollusks were unable to pull them down lower. To each shell was attached several mussels who had attached their byssus threads before the Razors realised what it meant; but when the extra-low tide came these tightly-moored mussels effectually prevented the withdrawal of the Razors. The Sword Razor (8. ensis) in most respects agrees with the Pod Razor, except that the shell is curved as shown in the figure, and it never attains the dimensions of the former species 4 inches being about its maximum length. It is more slender ii 160 Shell Life than young Pod Razors of similar length, and it inhabits deeper water, being found usually between 3 and 20 fathoms, but at Jersey and Herm it occurs Sword Razor (slightly reduced) at low water. Linnaeus regarded it as a variety of S. siliqua, and I think it very likely that he was right. The Transparent Razor (S. pellucidus) is similar to the last named in form, but with thinner though scarcely transparent shell, and the hinge not quite so near the end. Length about 1^ inch. It is very doubtful whether this again is any more than a juvenile form of S. siliqua. The Grooved Razor (S. vagina) resembles 8. siliqua generally, but is more cylindrical, quite straight, of equal size from end to end, and possessing but one cardinal in each valve, which is rounded and stalked. Its English name is due to a constriction at the fore-end " as if it had been tied while in a soft and plastic state with a string" (Jeffreys), but this constriction is frequently found in specimens that otherwise agree with S. siliqua. I fear there is but one British species of Solen, with several variations from the typical form. The Rock-borers (Saxicava) have the mantle entirely closed, save for a narrow orifice to allow the passage of the finger-like foot; the siphons are long and partially united ; the shell gapes at each (papers, Piddocks, and Ship-worms 161 end ; the teeth are obsolete or wanting altogether ; and the mantle impression shows only a shallow sinus. They bore holes, chiefly in limestone, and live in these cells with only their red siphons visible at the entrance. The Wrinkled Eock- borer (S. rugosa) is a very common shell, yet it is very seldom seen save by the conchologist, who knows where to find it and how to chip it out from its cell in the rock. The shell has an odd, distorted appearance, being much stouter in front, and pinched in the middle of the lower margin, gaping behind or at each end, and with one valve often larger than the other. It is dirty white in colour, with a dull, rough surface, irregularly wrinkled in concentric fashion. The teeth, when present, are two small erect cardinals in the left valve receiving one small cardinal in the right valve. The animal is whitish tinged with yellow. The siphons represented in our figure as being retracted as far as possible are capable of great extension, and are covered almost throughout their length by a brown sheath, somewhat similar to that of the Gapers; their extremities are red. Wherever chalk, limestone, or red sandstone is found on our coast, there this species may be looked for from a little below ordinary low-water mark to a depth of about 30 fathoms. When touched or alarmed it forcibly ejects a stream of water from its siphons. A small variety, often distinguished as a separate species (S. arctica), spins a slight byssus and attaches itself to the so-called 1 62 Shell Life roots of the larger seaweeds. The shell is more angular, the wrinkles become ridges, and the teeth are more evident. Its specific distinction from S. ruyosa is very doubtful. Norwegian Rock-borer (8. norvegica). A much larger species, attaining the dimensions of 3 inches by 2, has been found in deep water (30 fathoms) between the Dogger Bank and the east coast of England, where it bores into thick mud. The out- line of the shell is an irregular oval, the right valve larger than the left. It gapes at both ends, and is similar in colour, texture, and ornamentation to its smaller relative. The teeth are similar to those of the foregoing. The siphons are protected by a dark leathery sheath, and the lower tube is larger than the upper one. From its restricted area in British waters, and the difficulty of obtaining specimens, it is one of the most highly priced of native shells in the catalogues of the dealers, a good example costing a sovereign. The Flask-shell (Gastrockcena dubia) bears some resemblance to a young mussel when viewed from above ; but below, towards the foremost end, there is an enormous oval gape as shown in our figures. It is very variable, smooth, of the whitish grey so frequent in the shells of borers, but covered with a yellow-brown epidermis. There is a broad thin hinge-plate, but no teeth in either valve. The animal is pale reddish brown, with the mantle lobes united below and having only sufficient aperture to (fapers, Piddocks, and Ship-worms 163 allow the foot to protrude. The siphons are long, semi-transparent, united, and capable of extension to several times the length of the animal. It bores into limestone, old shells, and red sand- stone, but always fashions for itself, when full-grown, a flask-shaped jacket composed of shell-fragments and sand cemented together. It occurs only on the south coast of England, the Welsh coast, and the south and west of Ireland, from low water to 20 fathoms. At Torbay its burrows in the new red sandstone are beautifully finished off as though lined with porcelain. Fiask-sh The Piddocks form the sub-order Phola- dacea. They are all borers into rock or wood, and they exhibit a remarkable advance in shell develop- ment, the typical species being pro- vided with supplementary valves in addition to the two that normally enclose the animal. The white shell gapes at each end, and though thin and brittle, is exceedingly hard, the front part often armed with toothed Case of Flask-shell ridges that form a good rasp. There are no hinge-teeth and no ligament, the valves being held together by the adductor muscles only. The hinge-plate is continued outside, and folds over the upper margin of the shell, where it is protected by a portion of the mantle. To protect the mantle, one or more accessory valves cover it at this part. The front pair of adductor muscles are attached to the hinge-plates, where their impressions will be found. The mantle impression 1 64 Shell Life has a very deep sinus, showing that the siphons are fully retracted. The animal is somewhat club shaped : the siphons large, united nearly to the fringed orifices, and covered by a sheath as in the Gapers ; the foot also large, but short. They perforate, in shallow water, rocks, wood, and other substances that are not so hard as their shells, making vertical symmetrical burrows. Having made a burrow whether in limestone or in thick mud the maker of it remains in it for life. This is very different from the habits of ordinary burrowing mollusks, (papers, Piddocks, and Ship-worms 1 6 5 who are constantly changing places. They seldom interfere with each other by breaking through their neighbour's party-wall, but as a rule make their burrows to run parallel. The boring appears to be effected by the flattened foot, assisted by the rasp-like forepart of the shell in some species. The native species are : The Common Piddock (Pholas dactylus), the largest by far of those found on our coast, its elongated shell often measuring 5 inches in length. Each valve is traversed by from 40 to 50 rows of prickly scales, Right which are most developed in the front part. There is a pale brown epidermis, but it is mostly worn away except at the edges. The accompanying cut shows the interior of a right valve of this species. The hinge-plate, reflected over the beak in a double fold, is strengthened beneath by a number of transverse partitions, as shown in this figure. Within the shell there runs down from the hinge-plate a curved shelly band, called an apophyse, to which the muscles of the body are attached. Upon the external folds of the hinge- plate, what are known as the accessory valves are placed ; but it must be remembered that these are Portion of hinge-plate 1 66 Shell Life not of the same character as the two large valves that enclose the animal, so that it will be better to speak of them as dorsal shields. In this species there are four of these dorsal shields; two in front and side by side, a third more solid, behind and inter- locking with these, whilst the fourth is long and slender, and protects the mantle and upper mar-gins of the valves. The animal is whitish like its shell. The siphons are covered with little fleshy points, the sheath brown or speckled. Although chiefly found in the English and Bristol Channels, it is recorded from Seacombe, Lancashire, and along the south, east, and north coasts of Ireland. It Dorsal snieids is not particular m its choice of material in which to bore, chalk, slate - rock, red sandstone, submerged wood, and even peat, being selected in dif- ferent localities. The White Piddock (P. can- dido) is a smaller species (less than 3 inches long), and has a thinner, more convex shell than the foregoing, the prickles form from 25 to 30 rows only, the front gapes less. The reflected hinge-plate forms but a single fold externally, which is not partitioned off into cells : and there is but one dorsal, lance-shaped shield with Qapers, Piddocks, and Ship-worms 1 67 a central groove. The animal is white, tinged with brown ; the siphons longer and more slender in pro- portion than in the Common Piddock, and longitudinally grooved within. It is a very sensitive creature, and readily takes alarm, retiring into its chamber. It is about 2f inches long. The Little Piddock (P. parva) has a more solid, less convex shell than the last, and is traversed by many rows of overlapping scales, chiefly on the fore- part of the valves, gradually getting less towards the middle, and scarcely evident behind ; often stained with red from the clay and red sandstone in which it is found. The beaks are much nearer the centre than in the other species. The hinge - plate is fur- nished with a knob, apparently to prevent the valves coming too close together at that part. As in the White Piddock, there is but one dorsal shield, and this is of similar pattern to that of P. Candida. It is a south coast species, and has been found also in Guernsey, Dublin Bay, and near Belfast. Its length is about 2 inches. The Oval Piddock (P. crispata) has the shell oval instead of oblong as in the other species ; convex, solid, coarse-looking, with a broad furrow extending from the beak to the lower margin almost in the middle of each valve. In front of this furrow there are about 20 rows of overlapping sharp scales. The Little Piddock 1 68 Shell Life broad hinge-plate folds over and is attached to the beaks, but there is no knob as in the last species. The dorsal shield is exceedingly small, and of tri- angular form. The animal is of a red-brown colour, with long siphons; these have the orifices fringed with branched filaments. It is a little more than 2 inches sometimes as much as 4 in length, and has been found on many parts of our coasts embedded in mica-schist, shale, oolite, Oxford clay, etc. The Paper Piddock (Pholadidea papyracea) has a shell that is exceedingly thin and delicate, oval and convex, the forepart with transverse ridges cut into little teeth. The beaks approach towards the centre of the upper margin as in the last two species. The broad hinge-plate is reflected over the front. In addition to the short apophyses, there is what may be re- garded as a triangular cardinal tooth in each valve. The dorsal shield consists of two small plates, often united. At the hinder end of the shell there is a remarkable horny cup surrounding the siphons which are entirely connected throughout their length. This cup, which is not found in young specimens. Paper Piddock , , , , , . . ^ , ,, appears to be the beginning or a sheath to surround the siphons, but which is not further developed in this species. It burrows in sandstone, hard clay, peat, and submerged wood, chiefly along the coasts of Devon and Cornwall, and at various places round Ireland ; at low water of spring tides. The Wood Piddock (Xylophaga dorsalis) is a con- Gapers, Piddocks, and Ship-worms 169 necting link on one side with the foregoing Picklocks, and on the other with the destructive Ship-worm (Teredo), yet to be mentioned. The shell is like that of a Pholas, but remarkably abbreviated, being in fact globular in shape. It is glossy and almost transparent ; crossed near the front end by a furrow with marginal ridges. There are two dorsal shields, similar to those of the Paper Piddock, but propor- tionately larger. The globular animal has long and slender siphons, connected throughout the greater part of their length, and marked by crested ridges. The foot is thick and capable of con- siderable extension. There can be no doubt, in this case at least, that the foot is the boring instrument, for the Wood piddock epidermis is conspicuous over the front of the shell, where it would be rapidly worn off if the shell were used as a rasp. This species is called the Wood Piddock, because it neglects the rocks and bores only into submerged or floating timber, preferring oak, pine, and birch, and evidently not objecting to other vegetable substances, for it has been found in the tarred hemp envelope of an ocean cable. It penetrates only to a sufficient depth (1^ inch) to bury itself, as shown in our figure. The remaining genus (Teredo) of this sub-order includes a few species of insignificant appearance, but of sufficient power to have made them the despair for centuries of all who owned wooden ships, timber-built quays, piers, and stages in salt water. The people of 1 70 Shell Life Holland have more than once had their welfare perhaps their existence threatened by the ravages of the Ship-worms among the piles of their embank- ments. In the days of "the wooden walls of England," prior to the use of copper-sheathing, we also suffered greatly ; but now that so many of our vessels are of iron or steel, the Ship- worm's sphere of activity must be greatly curtailed. The " infallible " remedies in the shape of washes and paints that have been put forward to check the ravages of this little sea-monster must number several hundreds. This, perhaps, is a matter that, could it be known to the Ship-worm, might cause it to feel proud, that it had instigated so much enterprise in others. Most of this, however, must have been misdirected zeal ; but there is one case on record of its having inspired a great piece of engineering. The elder Brunei is said to have declared that the method adopted in the construction of the Thames Tunnel was suggested to him by the Teredo. The Ship- worms are very like Wood Piddocks, with an enormous development of the siphons, which may exceed a couple of feet in length. The shell is even more gaping than that of the Piddocks, for the valves touch only at the beaks and at a point on the opposite margin ; it is helmet-shaped, marked as in Xylophaga, Gapers, Piddocks, and Ship-worms 171 but without any dorsal shield. Each valve is three- lobed, and the hinder lobe is usually spoken of as the auricle or ear. The animal differs from the shell in its shape, which is worm-like, and for the protection of this part a chalky tube is secreted of great length in some foreign species, and extending to a couple of feet in our own T. norvegica. At the mouth of this tube the animal has developed a pair of accessory valves (known as pallets) in the shape of paddles, the handles of which are attached to the body, and the blades serve to close up the tube when the siphons have been withdrawn. They all burrow into submerged vegetable substances, including all kinds of timber, and are never found in rocks. They appear to do all the boring by the action of the small foot, though it is probable that the valves may be used to enlarge and round off the cell. The burrows run with the grain, and consequently parallel with each other. It is popularly supposed that the Ship-worms destroy timber in this way to serve as food, but though the excavated material is passed out through the exhalent siphon it does not appear that the animal derives any alimentary benefit from it, but derives its nutriment from the microscopic life of the seas, just as the oyster and the cockle do. The species are: The Common Ship - worm (T. navalis), usually about a foot long, sometimes as much again. The shell is rather thin, and finely ridged. The pallets have an oval blade, which is indented deeply at its free end, glossy without, polished and flat within. It is found in pine, elm, oak, and teak that have been used for boat-building, piers, piles, etc. This is the Shell Life Norwegi shell; 2, pallets; 3, part of sheath, broken to show internal plates species that has caused so much damage and anxiety to the Dutch. The Norwegian Ship - worm (T. norvegica) is very similar to the last, but larger in all respects, the shell more solid and coarser in its sculpture. The large pallets have oval blades with squarish ends, con- cave on the inner side. Although found all round our islands, it is a local species, and appears to con- fine its attentions to fixed timbers, and to let floating spars and logs pass. The Guernsey Ship- worm (T. pedicellata) is also very similar to the Common Ship-worm, but much smaller in every way ; probably, indeed, it is only the young condition of a variety. Its chief claim to be considered distinct lies in the shape of the pallets, which have long stalks, a square blade, and an oval portion between the blade and the stalk. It has been found in submerged timber in several of the Channel Islands. The Drifting Ship - worm (T. megotara), although occasionally found in fixed timbers on our shores, is chiefly known to us as a common inhabitant of the drifting logs and spars that come no one knows whence, and get cast on our shores in stormy weather. Full-grown specimens are intermediate in size between T. navalis and T. norvegica. There is an expansion of the hinder margin of each valve known as the ear Gapers, Piddocks, and Ship-worms 1 7 3 or auricle. In the present species this auricle is very large, and the hinge-plate is very broad and thick, with a knob and a tooth in the centre. The sheath, too, is shorter, and often absent. Several other species of foreign origin are fre- quently found in drift-wood on our shores. The animals comprised in the sub-order Anatinacea have a single gill on each side, the outer fold of which is prolonged over the back; the mantle margins united almost throughout ; the siphons more or less united and their orifices fringed. The shells are thin, the valves often unequal, usually coated with nacre within. The impressions of the mantle and muscles are not well marked. The Pandora-shell (Pandora incequivalvis) not only has the valves unequal, they are inequilateral also. They gape behind where the short siphons protrude. It will be seen in the figure that these siphons are united almost to their full length, yet diverge considerably from each other. The left valve is flat, the right convex and overlapping the left. They are of variable thickness, glossy without and of a pearly white colour. The horn-coloured cartilage reposes in a groove of each valve. The hinge-plate of the left valve bears a rib which Left valve of Pandora ^ s ^ a corresponding furrow in the other valve. There is one cardinal tooth in each valve, that of the right valve being erect, that of the left horizontal. The Channel Islands, Weymouth, and Studland are the only British 174 Shell Life localities for this species, and there it may be found burrowing slightly in the sand at low water. It has a trick of squirting water from its siphons when alarmed, like the Piddocks. There is a variety obtusa found in deeper water (from 7 to 50 fathoms), and the difference in habitat has produced a corresponding difference in the shape of the shell. The normal shallow-water form has to burrow beneath the sur- face in order to escape the effects of the surf, and consequently its shell is extended into a blunt beak behind to protect the lengthened siphons. In deeper water there is no fear of such disturbance, and there is no need for burrowing so deeply ; therefore the siphons are shorter and the shell less drawn out behind. This is another object lesson in Nature's manufacture of species. The Norwegian Lyonsia (Lyonsia norvegica) is in general shape much like Pandora, but the upper margin is more horizontal, and there is less difference in the size of the two valves. It is very thin, but opaque and yellowish ; the surface made dull by fine radiating lines crossed by the lines of growth. The pale brown epidermis is gelatinous, and has the property of attaching grains of sand and fragments of shell to itself. The golden cartilage is contained in grooves as in Pandora, and the hinge-plates are similarly ribbed and furrowed ; but the cartilage is covered by a plate, called an ossicle, that is not attached to the shell but formed separately. The interior of the shell is iridescent. The animal is white with a yellowish tinge. The forepart of the mantle has a slight fringe of a few projecting points. The siphons are short, fringed at their orifices, and having a few filaments round the Qapers, Piddocks^ and Ship-worms 1 7 5 base of each. The white foot is tongue -shaped, extensible, and grooved for the production of a byssus. It is not a common shell, but it occurs all round our islands on sand between 4 and 86 fathoms. Where these conditions exist it may also be looked for in the stomach of the Red Gurnard. It is about If inch in length. The species of Thracia have nearly oval, more symmetrical, and somewhat flattened, thin shells, with a free ossicle as in Lyonsia. The shells gape behind to allow of the continuous extrusion of the long separate siphons. The Thin Lantern - shell (T. prcetenuis) has the right valve less flat and a trifle larger than the left, which it slightly overlaps. It is finely marked with lines parallel to the edges of the shell, and the hinder slope is also studded with minute tubercles. The shell itself is white, ., Thin Lantern-shell but the epidermis is or a creamy (two-thirds nat. size) tint. The dark coloured ligament behind the hinge is so small that it cannot be seen in dried specimens. Attached to the hinge-plate is a spoon-like receptacle for the golden cartilage. The ossicle is sickle-shaped. The animal, includ- ing the tongue-shaped foot, is white. It occurs in sand on many parts of our coast from extreme low water to 60 fathoms. It measures about 1J inch across. The Papery Lantern-shell (T. papyracea) is smaller than the last, much thinner, less equivalve, and more convex. Ligament pale and large; carti- lage more brown than golden, its pit or spoon more oblique ; the ossicle shaped like half a ring. The 1 76 Shell Life animal varies in colour from white to pale brown. The siphons are short and wide, marked at their extremities with faint lines. The foot has a bluish tinge. It is found in sandy bays a little below extreme low- water mark. The Large Lantern - shell (T. pubescens) is larger, more solid, Papery Lantern-shell an( I lllOre OVal ; the left Valve a, ossicle; 6, ditto in position smaller and flatter than the right. The surface is marked with fine granulations, and the part near the hinge is concentrically ribbed. The colour is dull pale yellow. It is nearly 4 inches across. It is found only in deep water off the coasts of Dorset, Devon, and Cornwall. The Convex Lantern-shell (T. convexa) is swollen, almost four-sided, thinner than the last - named, but solid and glossy, and with more delicate ornamentation the granula- tions in wavy lines. Its colour is pale brown. It measures a little over 2 inches. It burrows deeply in muddy sand, in from 4 to 70 fathoms of water, on all our coasts, but li\ 7 ing specimens are sometimes washed up the beaches. The Little Lantern-shell (T. distorta) is the smallest of the British species, and measures little more than half an inch. It is very variable in shape, and, owing to its habit of dwelling in the burrows of Saxicava, and in rock crevices, it is usually distorted. It is proportionately of more solid structure than its congeners, of a white colour and without any gloss. The dingy brown epidermis gets rubbed off in its favoured haunts, and can only be detected at the edges of the shell. The Piddocks, and Ship-worms 177 granulations are arranged in irregular concentric lines. Ossicle half-moon shaped. It is a local species, but not confined to any particular stretch of our shores. It appears to range from a depth of 5 to about 35 fathoms, hiding in old shells and rock, crevices. Occasionally at extreme low water it may be found nestling among tufts of Corallina. The Skye Gaper (Poromya granulata) is a fragile little pearly shell, with almost equal valves, of rhomboidal form, gaping behind ; the right valve overlapping the left. It is ornamented by minute and rather crowded granulations, and dusky coloured, with traces of the brown epidermis at the edges only. Hinge-plate thickened, bearing in the right valve an erect thick cardinal, in the left a small triangular cardinal and a plate-like lateral behind. There is no ossicle. The animal is cream coloured, with a long, slender, transparent foot. The siphons are short and thick, encircled at their base by about 20 long filaments which curve back over the shell. It is found in mud on rocky shores in Skye, at a depth of about 40 fathoms. This little mollusk has the distinction, not only of being the only native repre- sentative of its genus and family, but also of its Natural Order, the Septibranchiata, which is dis- tinguished from the other orders by the gills being replaced by a muscular partition (septum), which reaches from the first adductor muscle to the siphons. E have now left the headless, toothless bivalves, and are about to make acquaintance with higher groups Uni- valves or Gasteropods, the mollusks that slide on the lower surface of the foot, and that have heads, eyes, and jaws. But we make the transition from one class to the other through a small intermediate class univalves truly, but with only a low organisation as compared with that of the Gasteropoda. This is the order Scaphopoda or Tusk-shells, so- called from the curved tubular shell that bears some resemblance in miniature to the tusk of an elephant, and is open at each end. The animal is of similar shape to its shell, with a rudimentary eyeless head, which is covered by the mantle as in the bivalves. There is a projection of the pharynx, and on this is Tusk-shells, Mail-shells > and Limpets 179 situated the mouth. The buccal mass may be found at the base of the long, pointed, and bilobed foot, which projects from the large end of the shell. Within the buccal mass is the tooth-ribbon or radula, similar to those described in pages 44-46 ; but in this class it differs somewhat from all the others. It is broad and oval, with only 5 teeth in a row ; the central tooth a broad simple plate, the lateral strong, arched, with two or three points, and the marginal is a four-sided simple plate. The sexes are separate in these creatures, the liver is paired and consists of a number of radiating tubes, but there is neither special respiratory organ, heart, nor circulatory system. The nervous system is similar to that of the bi- valves. Around the mouth are bunches of fila- / , Elephant's Tusk-shell ments (capta- cula), which are thrust out for the purpose of catch- ing the Foraminifera and minute mollusks upon which the Dentalium feeds. The edges of the mantle are united, so that it forms a tube open in front and behind, and the entire surface of this appears to absorb oxygen for purifying the blood. It will thus be seen that these mollusks form an actual link connecting the bivalves with the uni- valves. In most points they agree with the bivalves ; in only two respects the shell and the radula do they agree with the univalves, and even in the matter of the shell they begin life as bivalves, for in the embryo this consists of two plates which later i8o Shell Life become united to form a tube. There are two native species : The Elephant's-tusk Shell (Dentalium entalis) whose white shell tapers, and curves slightly up- wards, solid and smooth ; marked by the ti*ansverse lines of growth, finely scratched longitudinally at the narrow end, which is cut off obliquely in mature specimens and furnished with a tubular appendage. It is also often notched at this end on the lower (convex) side. The animal is white, the captacula with oval tips, and the lobes of the foot scalloped irregularly. It is found buried in sand at all depths below 3 fathoms, usually in companies ; more plenti- fully on the north than the south coasts. The Grooved Tusk-shell (_D. tarenti- num) differs from the foregoing in being a little shorter and stouter, more solid, more curved, and with Grooved Tusk-shell a duller surface. The colour, too, is a cream tint. The lines of growth are less evi- dent as sculpture, but are sometimes indicated by brownish coloration. The tubular appendage at the smaller end is central ; there is no notch in the shell, but the hinder half is regularly grooved longi- tudinally as shown in the section above the accom- panying figure. The animal has a yellowish tinge ; the captacula are ringed and end in little disks ; and the foot-lobes have a wavy margin. It occurs in similar situations to the last, from extreme low water to a depth of 25 fathoms. The Mail-shells (Chiton) introduce us to the class Gasteropoda, to which all the Univalves belong. It is a vast assemblage of orders, genera, and species. Tusk-shells ', Mail-shells, and Limpets 181 The orders are only four, but several of these are so large that they have been divided into sub-orders. The first of these orders (Amphineura) consists of the Mail - shells and some worm - like forms. The Mail-shells alone constitute the sub-order Polyplaco- phora. They differ from the vast majority of Gasteropods in not being exactly univalve, for the shell consists of eight overlapping segments or plates, the whole series surrounded by a muscular marginal belt (the girdle) which partly retains them in position. There is sufficient freedom of movement in these plates to allow the Chiton, when alarmed, to roll up after the manner of a Wood-louse. The under portion of these plates is of the ordinary shelly material, but the upper layer is chiefly of chitin. This layer is the sculptured portion, and it is divided off into three 182 Shell Life triangular areas, known as the median and lateral areas. The first and last plates are not so divided, and are generally sculptured in harmony with the lateral areas of the intermediate plates. Turned over on its back the Chiton will be seen to have a close likeness to the underparts of a Limpet. But closer inspection will show that though it has a head there are no tentacles and no eyes. The respiratory organs, too, differ from those of the Limpet. These matters we have already dealt with in the early chapters. As the shell-plates are perforated by numerous pores whose mouths are occupied by sense organs, it is probable that the animal can get on as well without eyes as the Limpet can with them. The Mail-shells are provided with a radula of much more advanced type than that described in the Tusk-shells. In that of Chiton there are 17 teeth in each row. There are ten or twelve native species of Chiton; the large figure on the previous page is not British but a well-known West Indian species (C. squamosus), selected as a type on account of its superior size. The British forms are : The Bristly Mail-shell (G. fascicularis), whose dis- tinctive feature is the spiny girdle and the series of tufts of bristles along either side of the shell-plates. The latter are shield-shaped with a central keel, and equal to three-fifths of the entire breadth of the animal. The colour varies a good deal from yellow and orange to pink, red, or deep brown, marked with lines and Underside of Chiton, and a, profile of head i VELVETY MAIL-SHELL; 2 GREY MAIL-SHELL; 3 WHITE TORTOISESHELL LIMPET ; 4 KEYHOLE LIMPET ; 5 TO 10 COMMON LIMPET AND VARIETIES. Tusk-shells, Mail-shells, and Limpets 183 blotches of white, green, or brown. The head-plate has five slight marginal notches, the other plates two each. The orange-coloured foot is oblong in shape, broader in front and running off to a blunt point behind. It may be found all along our coasts on the under-side of stones and the face of rocks, stationary and avoiding the light by day, and ranging in search of food by night. Its range extends from low-water mark to about 25 fathoms. The Velvety Mail-shell (C. discrepant) is similar in many respects to the former species, but larger and proportionately more slender. The girdle is broader, covered with a dense greyish pile, from which arise tufts of white or reddish spines as in C. fascicularis. Plates shield-shape, one half the width of the animal, greyish, mottled with brown, the keel darker, notches deeper. The two species have the surface of the plates covered with granulations like shagreen ; but in Hanley's Mail-shell (C. hanleyi) the granules become tubercles arranged in lines. There is no distinct keel, and the margins are not notched. The colour is ashy brown. The narrow girdle is clothed with short pale spines, with a tendency to form tufts behind each plate. This is a deep-water species, obtained by trawling at depths between 20 and 80 fathoms. It measures about one- third of an inch. The Latticed Mail-shell (C. cancellatus) is very convex, plates narrow, covered with minute round granules, arranged in chain-like rows, the links pro- ducing a lattice-like effect. There is no keel, and the margin is not notched. The colour is very pale 1 84 Shell Life yellow. The narrow girdle is fringed with short spines, and the surface coated with polished yellowish granules. It is less than a quarter of an inch long ; and it may be found on stones and about the smaller seaweeds just beyond low- water mark. The Grey Mail-shell (C. cinereus) is similar to the last species, but larger and more compressed ; shell with slight but distinct keel, the sculpturing not producing the latticed appearance. The girdle is broader, and more thickly covered with granules. The colour of the shell varies from pale yellow to brown, streaked with dark lines, but the general effect is an ashy grey. It is one of the most frequent of all our Chitons, and may be found on rocks, stones, old shells, etc., on all our shores from low water downwards. The White Mail-shell (C. albus), which is less than half an inch in length, is a local northern form. Its white has a yellow bias, but it is unmarked by lines or mottling of another tint. It is similar in general appearance to the Grey Mail-shell, but is more slender and convex, has a more prominent keel, the granula- tions finer, more radiating than chain - like. The margins are slightly notched ; the head-plate having 13 notches, the tail -plate 11, and the intervening ones 2 each. The brownish girdle is broader and more regularly beaded, whilst its margin is fringed with short spines. It occurs in the Isle of Man, and at various places on the coasts of Scotland, Shetland, and the Orkneys. The Bordered Mail-shell (C. mar- ginatus) is similar to C. cinereus, but larger, narrower, and more convex ; the plates broader, with a surface like shagreen, mottled or variegated with yellow, red, and green, and their edges deeply notched. Tusk-shells, Mail-shells , and Limpets 185 The girdle is evenly covered with minute granules, vari-coloured, and fringed with short yellow spines. It is one of our commonest forms, and may be found everywhere under stones at various depths, even above ordinary low- water mark. It is represented of the natural size in our figure. The Red Mail-shell (C. ruber) is much like C. marginatus, but more slender, more convex, of a reddish-brown tint, and presenting a smooth appearance. The girdle, too, is broader, and chequered with small patches of red and white. It is a species of general distribution on our coasts, from low water to a depth of 20 fathoms, where it may be found on rocks, stones, and at the base of the Laminarias. The Smooth Mail-shell (G. Icevis) is convex, broad, and glossy, marked with microscopical scratches and minute tubercles. It is reddish brown in colour, veined with white, or variegated with green or pink. The head-plate has from 16 to 20 deep notches, the tail-plate 15, and the others 2 each. The broad girdle is covered with small spine - like scales, their tips towards the margin, which is thinly fringed with short pink spines that readily fall off. The animal is about an inch long. It is widely distributed, and extends from extreme low water to about 70 fathoms. The Marbled Mail - shell (C. marmoreus) is the largest of the British species. It has a broad glossy shell, almost smooth to unassisted sight, but under a lens showing many minute tubercles ; coloured with red- i 86 Shell Life brown marked with streaks and specks of white or yellow. There is a fairly broad girdle of dusky brown fringed with very short yellowish spines. The head-plate has 8 notches, the tail-plate 9, and the intervening plates 2 each. It occurs among stones and weeds a little beyond low water, but not south of Yorkshire. Through the Limpets we become ac- quainted with the order Prosobranchiata, Marbled which includes the great majority of native Gasteropods. The name signifies that in this order the plume-like branchiae or re- spiratory organs are usually placed in front of the heart. The animals have a distinct head, which is furnished with a pair of tentacles and a pair of eyes. They are mostly marine animals, protected by a shell and mostly by an operculum ; the sexes are separate. It is divided into two sub-orders, and these again into sections. The species described in this chapter belong to the sub-order Diotocardia, most of the animals comprising it having two auricles to the heart, but the Limpets are exceptional in that they possess only one auricle and one ventricle. The Tortoiseshell Limpet (Acmcua testudinalis) has a conical but depressed shell, with growth lines fairly strong, and with fine scratch - like lines both radiating and concentric. It is rather thin, with a dull surface, the ground colour grey, irregularly marked with reddish brown, sometimes with white in addition. The interior is polished, except the broad, bevelled margin, Tusk-shells, Mail-shells, and Limpets' 187 which is only smooth. Half-way between the margin and apex is a chocolate mark of horseshoe shape. The animal is white, with a large head and long awl- shaped tentacles, with small eyes at their base. Foot oval and broad. It occurs under stones, from low water to a depth of 20 fathoms, but comes no farther south than Northumberland and Durham. One form of it found on the narrow leaves of Sea Grass (Zostera tnarina) has the shell compressed so that it becomes narrow and higher. This form is sometimes dis- tinguished as A. alvea. The White Tortoiseshell Limpet (A. virginea) is similar to the last, but only half the size, rather glossy, pinkish, with brownish and white rays, rather than white, though a pure white variety occurs at Scarborough. Its ordinary length is little more than a quarter of an inch, but at Guernsey it exceeds half an inch. It is generally common on stones just below low-water mark. In Acmcea the apex of the shell is turned forwards; in Lepeta backwards. The Fulvous Tortoiseshell Limpet (Lepeta fulva) is rather smaller than the last ; of a yellow, bright or dull orange colour, with white rays and fine radiating ribs ; thinner and semi-transparent, not glossy. The Blind Limpet (L. cceca) is white, thin, finely grooved from the beak, about half an inch long. The animal is whitish, with short tentacles, but no eyes. It is a Scandinavian species, which has been taken occa- sionally in a dead state from deep water between Scotland and Shetland. The Curled Limpet (Propilidium ancyloides) is another eyeless species similar to Lepeta, but with longer tentacles, and the beak of the shell curled 188 Shell Life backwards into a spiral. Within it has a triangular shelf-like plate, occupying half of the crown. It is a deep-water (18 to 100 fathoms) species, plentiful on nullipores around Ireland, Scotland, and Shetland. The Common Limpet (Patella vulgata}. So generally common and well-known a species is in need of no description, beyond saying that the shell is conical and solid, with ribs radiating from the beak. It is variable in colour, some young specimens being olive-grey, others more yellowish with purple rays. As it gets older the beak gets completely worn away, the ribs rubbed down, and possibly the whole surface made smooth and almost even. Other old specimens get covered with nullipore, or support a forest of delicate weeds. The inside is very glossy, being coated with nacre, which exhibits greenish opalescent gleams. Through this layer the purple rays may be seen more or less clearly, though all trace of them may have gone from the outside. In the centre there is a large white patch showing the attachment of the muscle ; it is in the shape of a broad-mouthed amphora. A less distinct depression around it marks the attachment of the mantle. The general appearance of the Limpet from beneath when detached from the rock is shown in the cut. In the centre is the broad muscular " foot " by which adhesion to the rock is effected ; in front of it the distinct head, with mouth, paired tentacles, and eyes ; around the whole is the fringed mantle, and between the mantle and the foot there extends a frill of gill- Common Limpet Tusk-shells, Mail-shells, and Limpets 189 plates. There is reason to believe that the primitive Limpet was not endowed with this extensive frill, which is a more recent development to fit the species for changed habits. In the Tortoiseshell Limpets the breathing organ is a single plume-like gill attached to the right side of the neck, and protruded when the creature goes a-walking. It is believed that the original Limpet had a pair of these plumes, one on each side ; and if the modern Limpet be taken from its shell, and the mantle cut away so as to expose the upper side of the neck, a little yellow body will be found on each side of it. These are the remains of the true gills, which have gradually dwindled away to useless vestiges as the new and from the func- tional point of view more important frill has developed. It is probable that, like Acmcea, the primitive Limpet lived constantly in the water, and consequently the work of the two small gills ever exposed to the water was sufficient to keep the blood oxygenated ; but now the Limpet spends the hours between the fall and rise of the tide entirely out of water, and can only manage to keep its gills sufficiently moist to carry on the process slowly. It therefore seems probable that, in order to keep the blood pure, the slower respiration must be maintained over a much larger surface. The change of habitat and the development of these pseudo-gills might go on pari passu: early Limpets with merely the beginnings of the frill restricting themselves to those lower rocks that are only uncovered for a short time. But this is not the only change produced in the Limpet by its altered habits. As it has learned to endure fresh water by its exposure to rains and to 190 Shell Life the, in some places considerable, percolations from the cliffs, so also the shape of the shell appears to have been modified. Canon Norman pointed out years ago that " the nearer high-water mark the shell is taken, the higher-spired, more strongly ribbed, and smaller it will be; and that the lower down it lives, the natter, less ribbed, and larger it becomes." This result, I should suppose, is due to the action of natural selection. One of the principal enemies of the Limpet is the Oyster-catcher, whose bill is admir- ably adapted for wrenching it from the rock when its shell is slightly lifted for fresh air or locomotion. It will be evident that the flatter, smoother, and larger the shell may be, the more easily it may be lifted, so that the birds are more likely to select such specimens in preference to the less easily obtained small, high-spired, and ridged examples : the former, therefore, must become scarce on the rocks most quartered by the larger shore-birds. The tongue (radula) of the Limpet when uncoiled is found to exceed the shell in length; it is furnished with nearly 2000 teeth, with which it scrapes the surface of the rocks, clearing off the delicate growths of weeds and leaving a peculiar zigzag track. The means by which the Limpet adheres to the rock has long been a fruitful subject for controversy, many naturalists appearing unwilling to believe that it could be held there by the same powers as those that hold the Winkle the muscles and mucous of the foot, which by excluding air establish so close a contact that considerable pulling force is required to dislodge it. Reaumur experimented with the Limpet's 'Tusk-shells, Mail-shells, and Limpets 191 power in this respect, and says that for several seconds it supported a quarter of a hundredweight attached to its shell. Some authors imagined that the foot contained a number of presumably invisible suckers ; others, that by drawing up the centre, after the manner of the street-boy's leathern sucker, it created a vacuum which held it to the rock. Keaumur was troubled by some of these notions, but he disposed of the vacuum theory by cutting a Limpet shell and all right through, and as the two halves still adhered to the rock it was clear there could be no vacuum. It has long been noticed that the Limpet sinks pits corresponding exactly to the margin of the shell, but deep or shallow according to the softness or hardness of the rock. In this way it overcomes the difficulty of shutting down its shell closely upon an irregular surface, by making its own little patch level. Various agencies have been invoked to explain how these pits are sunk ; an acid secreted by the foot, and carbonic acid given off' in respiration, being among them. No doubt on chalk and other soft rocks we need look no further than to the pulling action of muscular contractions of the foot. Even on the hard slaty rocks of the Cornish coast, I have frequently noticed that Limpets taken oft' for use as bait have thin laminae of rock still attached to the foot. But the most remarkable of the Limpet's habits is that of returning to the identical spot to roost after each excursion in search of food. Given a particular area of rocks it would be almost impossible to find two pits so exactly alike that they would equally serve as lodgment for a particular Limpet. 13 192 Shell Life It was this fact, probably, that led some of the earlier naturalists to contend that the Limpet never wandered from the particular spot it had selected in early life, though Aristotle had recorded its food- seeking excursions more than two thousand years before. Not only do they do this whilst still covered by the sea, but after the tide has receded and whilst the rocks are still wet. At such times I have often listened to the noise made by hundreds of Limpets dragging their shells over the rough acorn barnacles, and to the rasping sound produced by the radula as it scraped the minute vegetation off the rock. There is no need to say anything of the importance of the Limpet as food and bait, except that on some parts of our coast this is very great, many tons of the mollusk being consumed yearly by the poor. Judging from the contents of the shell-heaps (Kokken-mid- dings) left near their former rude dwellings by the aboriginal inhabitants of these islands, the Limpet had a much greater importance as a food in earlier days. There are several well - marked varieties of the Common Limpet which have distinctive names given to them, and certain of these have been elevated to the rank of species by some writers. The var. elevata has a smaller, rounder, and higher shell ; var. picta is smaller and thinner, with alternate blue and reddish rays ; intermedia is smaller, flatter, and oval, with yellow centre inside and out, the animal dark - coloured ; depressa, much flatter, more oblong, ribs finer and sharper, beak nearer front, centre of interior orange ; ccerulea, flat, roundish oval, ribs delicate, somewhat irregular, interior dark blue. Tusk-shells, 'Mail-shells, and Limpets 193 The genus Helcion differs from Patella in the fact that the frill of gill-plates arising from the left side of the neck is not continued completely around the animal, but ends in front of the head. In early life the shell of the Blue - rayed Limpet (Helcion pcl- lucidum) is oval, thin, semi-transparent, rounded above, with the slight beak above the front extremity. The colour varies from ochreous to olive, and from B^i'e'-rTyed i_im et the beak thin broken lines of vivid blue run to the margins. The number of these lines varies greatly, but, as a rule, they are about 7, though they may be 40. The animal is cream coloured, tinged with brown ; mantle fringed with long and short filaments ; tentacles slender, eyes small. I have already alluded to the changed appearance of the shell when the animal becomes old (page 36). The young Helcion lives upon the fronds of the larger seaweeds, where it is not very conspicuous, but in later life it descends the rounded stalks, thickening its shell, compressing the sides and fashioning the mouth so that it fits the rounded sur facc accurately. By this time the blue lines have vanished, as being a source of danger rather than security in the new situation, and the shell has no resemblance to its former self. The animal cuts out a cavity in the stalk, which it resembles in colour, and there it remains embedded. The Slit - limpets (Fissurellidce) form a family remarkable from the fact that their limpet - like shells have a slit which serves the purpose of an 194 Shell Life excretory orifice, corresponding with an oval tube in the mantle. The animal has two large gills, placed one on each side. It is probable that from some such form the bivalves were produced, the development of these organs into the plate-like gills producing corresponding changes in the mantle, and consequently of the shell. The Keyhole Limpet (Fissurella yrceca) in the juvenile stage has a distinctly spiral beak and a slit margin, but as the shell grows, and the em- bryonic portion becomes the apex, the slit finally appears like a keyhole at the top of the shell, and the mantle is protruded through it. It is a pale yellowish shell, with rays of some tint of brown, and about Keyhole Limpet 50 rugged ribs radiating from the beak, which are alternately larger and smaller. The animal is some shade of yellow ; the mantle extends beyond the margin of the shell, and is fringed with short stout processes corresponding with the ribs of the shell which are produced by them. A similar fringe decorates the upper part of the foot. The Keyhole Limpet is found all round the British Islands with the exception of the east of England and the east and north of Scotland. It extends from low water to a depth of 15 fathoms. The Punctured Limpet (Puncturella noachina) is much smaller than the last, but agrees with it in having a slit, which does not, however, take the place of the beak, but is a little in front of it, as shown in annexed view from "Tusk-shells, Mail-shells, and Limpets 195 above. The beak remains spiral as in the embryo. The " Keyhole " of the previous species has a thickened margin internally, but in the present species there is a vaulted process beneath the slit. The shell is white, ribbed in a mariner similar to that of F. yrceca, but less rugged. It is a deep- water (25 to 90 fathoms) species, and a northern not being found south of Yorkshire. Common Slit - limpet (Emarginula fissura). In the genus Emarginula the slit instead of appearing in very early life and travelling to the crown of the shell, as in Fissurella and Puncturella, appears when the animal is nearly adult and remains at the margin, becom- ing partially filled up with age. The mantle protrudes from this slit to form . . . , an excurrent siphon, as in the other members of this family. The shell is white, and crossed by ribs much as in the other species, but here they are less numerous. It is generally distributed, and may be found on rocks and stones from extreme low water to a depth of over 100 fathoms. The Rosy Slit-limpet (E. rosca) is a much smaller species, with proportionately narrower shell of distinct Phrygian cap form. The ribs are more equal ^j$^ in thickness, and the pits caused by their Rosy intersection round, whereas in the preceding | .^ lt " et species they are more square. The slit is shorter, the mouth often tinted with bright rose colour, and the usually white shell sometimes tinged with pink. It is a southern form, but may be found commonly in deep water (7 to 25 fathoms) 1 96 Shell Life on the coasts of Dorset, Devon, Cornwall, and the Channel Islands. The Large Slit - limpet (E. crassa) is much larger than the last two species; the white shell measuring 1| inches in length. It is a less elevated cone, and the radiating ribs number between 80 and 100, alternately broad and narrow, each of the former often divided into three. In addition to the concentric wrinkles that cross these, there are radiating rows of minute glistening dots. The mouth of the shell is oval, and is notched in agreement with the ends of the ribs. It has been found under stones at Oban at periods of ex- tremely low water, but otherwise only by dredging on rocky ground off' the west coast of Scotland, Shetland, Antrim, and Dublin, in from 20 to 75 fathoms. The Ormer or Sea Ear (Haliotis tuberculata). The claims of this mollusk to be included among native species are political rather than natural, for its only " station " north of St. Malo is the shores of the Channel Islands, where it is used for food, after a t size) being beaten to make its muscular foot tender. Flat and shallow as the reddish-brown shell is, it is distinctly spiral, with the last whorl very large. Its exterior is rough and shabby- looking, but it is lined with the iridescent " rnother- o'-pearl" which makes these shells so valuable to 'Tusk-shells, Mail-shells, and Limpets 197 the manufacturer of fancy articles. Instead of the 'central or marginal slit, such as we have seen in the Keyhole and Slit-limpets, the Ormer has a long spiral series of round holes. As the creature grows the oldest of these perforations are suc- cessively filled up, the last remaining open serving as an anal aperture; whilst the others admit fresh supplies of water to the pair of branchial plumes, of which the left plume is the larger. Filaments from the mantle also pass through these holes, and doubtless serve as sense organs. The animal has a broad head, from which a short snout protrudes. The tentacles are long and thread-like, connected at their base by a fringed lobe, and at their outer bases are placed the stalked eyes. The large fleshy foot is fringed by two rows of delicate filaments, with green tubercles between. The animal creeps along after the manner of a Limpet, and, like that species, rests with the margins of the shell pressed against the rock, from which, however, rats and birds con- trive to force it. Curled Slit - shell (Scissurella crispata). The minute thin white shell of this mollusk shows an advance towards the spiral form of the snails. The last or body-whorl forms the greater part of the shell, but instead of being spread out and shallow, as in the Ormer, the sides are contracted, and when the animal retires within the orifice is closed by a thin oval operculum. In adult specimens the margin of the shell is slit in front. The animal has a rather long foot, a prominent head, and a pair of long fringed tentacles with the eyes at their base. Along each side of the foot there are two short 198 Shell Life pointed lappets, and beyond these two long fringed feelers. It has been taken on stony ground from 18 to 75 fathoms deep, in Shetland, but the shells were empty ; also at Orkney, Wick, Caithness, Skye, Antrim, etc. TSHfcLL HE passage from the uncoiled Limpets to the strictly spiral cones of the Tops is made easy by way of the Slit- limpets and Scissurella, as shown in the previous chapter. A further advance in that direction is seen in the tiny Dolphin-shells (CyclostreiiKi), of which we have three species. They are more orbicular than Scissurella, and without the slit margin of the almost circular mouth. The coil- ing of the shell round an imaginary axis leaves a deep cavity, known as the umbilicus, which we shall meet again and again from this chapter in our story, and shall find that it is often a valuable clue in the discrimination of species. Another feature encountered for the first time is the operculum, a thin horny plate attached to the hinder part of the mollusk in such manner that when it withdraws into 200 Shell Life its shell the operculum comes last and accurately closes the mouth of the shell. In some species this operculum is composed of hard shell material, but in the Dolphin-shells it is horny and of spiral structure. The Shining Dolphin - shell (C. nitens) is thin, white, glossy, and slightly iridescent, with three whorls and a thickened lip. The animal has a bilobed snout, thread-like tentacles from the head, and tentacle-like appendages to the foot three or four on each side. It is found in the coralline zone on the coasts of Devon, Cornwall, Guernsey, all round Ireland, and the west of Scotland. The other species is the Flat Dolphin-shell (C. serpuloides). The specific name of this mollusk was bestowed because the shell was thought to resemble the shelly tunnel of the Tube-worm (Serpula). It is almost flat, the spire being scarcely raised. It occurs between low water and a depth of 25 fathoms on all our coasts. It is thought by some that the species described below as Trockus duminyi should come here under the name of Circulus striatus, but as the shell alone is known we think it best to retain it provisionally where Jeffreys placed it, as the discovery of the animal will almost certainly lead to other arrangements. The Top-shells (Trochus) are closely related to the Dolphin-shells, as will be evident on comparing the animals with their ciliated tentacles and side appendages, although systematists have placed them in separate families. These differ from the last in the shells always having a layer of pearl beneath the outer coat of shell material, and in the mouth of the shell being oblique and somewhat Top- shells and Pheasant-shell 201 angular. The umbilicus is not always present, and is very variable even in the same species. The head of the animal is furnished with lobes, as shown in this figure of the Grey - top's head. At the " tail " end of the animal an iri- descent horny disk, showing a spiral structure, will be seen ; this is the operculum, which closes the Head of Gre y -to P shell when the creature has retired. The Common Top-shell (T. zizyphinus) is regularly pyramidal with an almost flattened base, solid, and somewhat glossy. Ridges of various sizes run spirally from the sharp apex to the rhomboidal mouth; the largest ridge being that which marks the base of each whorl. The ground colour varies from flesh colour to purple overlaid with interrupted or zigzag streaks of dark red. There are from 10 to 12 whorls in a full- grown specimen. The animal is yellowish, variegated with crimson, purple, and brown. The prominent head has a small bilobed veil ; tentacles with a brown central streak ; eyes large, with black pupils, on stout footstalks. The side appendages are usually four pairs. The oper- culum has 15 or more whorls. Like all the members of the genus, the Common Top feeds upon seaweeds, and it may be found in plenty in the zone below low - water mark, where the great wracks and oar-weeds grow. It also extends to a depth of 85 fathoms, and some of the finest 202 Shell Life examples have been obtained by trawling in deep water. The Western Top - shell (T. occidentalis) is pyramidal, thin, semi-transparent, glossy, opaline, with pale golden spiral ridges, and about 7 whorls. Animal like the last species, but witli usually three pairs of side appendages. The shell is about half an inch high, and somewhat less across the base. It has been found on the fishing banks of Shetland, the Orkneys, and Aberdeenshire, in deep water 40 to 90 fathoms. The Granulated Top-shell (T. granulatus) is solid and opaque; pyramidal, but with the lowest whorl larger than the other nine put together, ridged as in the previous species, and tapering abruptly to a sharp high point. Its colour is pale yellow, tinged and spotted with reddish brown. The animal is similar to the foregoing, but the eyes are dark blue with black pupils, and are mounted on short white stalks ; side appendages three on each side. In height and breadth it is about 1| inches. It is a southern species, and may be sought in the coralline zone along the coasts of Dorset, Devon, Cornwall, and the Channel Islands, in the Isle of Man and on the south and east of Ireland. The name is suggested by the fact that the larger ridges have their surface raised into granular points. The Many-grained Top-shell (T. miliaris) is similar to the last, but smaller, measuring only about half an inch either way, arid the ridges broken into granula- tions by the crossing of numerous oblique grooved lines. The ground colour is more white than yellow, but marked with brown and purple as in the last. Top-shells and Pheasant-shell 203 The animal is covered with short prickly points, and the tentacles which are marked with three lines of brown have blunt tips. The eyes are on the under-side of tubercles at the outer base of each tentacle. Side appendages three pairs, with a brown eye-spot just behind each. It occurs chiefly in the west of Scotland, but has been taken on many other parts of our coasts, even to Devon, Cornwall, and the Channel Islands, in from 2 to 70 fathoms. The Grooved Top-shell (T. striatus) is narrow at base in proportion to height, flattened beneath, the whorls 7 in number, of which the lowest 5 are flattened and distinctly keeled. The whole surface is crossed by innumerable oblique lines which break up some of the ridges into little knobs. The ground colour is whitish, streaked obliquely or speckled with brown. It is about a third of an inch across at base, and a little more in height. It occurs along the south coast from Dorset to Cornwall, in the Channel Islands, and at Cork, Baltimore, Bantry, and Dublin Bay; its habitat from low water to a depth of 15 fathoms, and it appears to be fond of the Crass Wrack (zostera). Montagu's Top-shell (T. nwntacuti) is similar to T. striatus, but a little smaller, the whorls not flattened though somewhat compressed and the base more convex. It occurs on all our shores between 7 and 95 fathoms. In all the foregoing species of Top-shells there is no umbilicus in the adult, though the fry of some species show one temporarily. All the species that follow have this perforation, though in- the Thick Top it is almost filled up in the adult. 204 Shell Life The Thick Top-shell (T. lineatus} is not pyramidal but conical, very thick and dull. Young specimens exhibit the spiral ridges, but these have disappeared in the adult. The ground colour is yellowish or greyish, overlaid by zigzag purple streaks. The apex of the rather low spire is always eroded by the time the shell is full-grown. Whorls 6 ; mouth large and oval, the inner lips bearing a strong tooth- like tubercle. The large shallow umbilicus is partly covered by the inner lip. Its measurements are an inch either way. It is a local shell, but may be found from Dorset to Cornwall, and up the western coast to Anglesey ; also in Ireland and the Channel Islands, between tide-marks. The Round Top-shell (T. duminyi) is a minute shell, which is equally convex above and below, flat spired, and has a very wide and open umbilicus. It is white, semi-transparent, glossy, and has fine whorls spirally ridged. The mouth is almost square. It occurs at Bundoran, Donegal Bay. The Flat Top-shell (T. umbilicatus) is much larger (half an inch across) than the last, flat-based and almost flat-topped, without any approach to the pyramidal form. The spiral ridges are sharper and fewer; the colour grey, streaked with red lines or zigzags ; outer lip bordered with orange and green. It occurs in numbers, feeding on the Saw-edged Wrack (Fucus serratus), in the littoral zone along the south coasts up the Bristol Channel, around Ireland and the Isle of Man, and along the west coast of Scotland. The Grey Top-shell (T. cinerarius) is the most abundant of all our Top-shells. It varies a good 4 i GROOVED TOP-SHELL ; 2 SMALL PEARLY TOP ; 3 SWOLLEN TOP ; 4 COMMON TOP ; 5 GREY TOP ; 6 FLAT TOP ; 7 THICK TOP ; 10 MANY-GRAINED Top ; S, g PHEASANT-SHELL; u, 12 FRESHWATER NERITE. Top-shells and Pheasant-shell Grey Top-sh deal in appearance according to its habitat; those living on the rocks between tide-marks resembling our figure, but when living upon oar-weed below the littoral zone it is much more depressed. There are 6 or 7 whorls ; the lower ones flattened and the upper ones rounded. There are a few thread- like ridges on the body -whorls. The ground colour is light grey, overlaid with crowded oblique streaks of dark purple-brown. The umbilicus is small and narrow, somewhat one-sided. It is very widely distributed all along our shores. Its height is half an inch, and its breadth a little more. The Swollen Top-shell (T. tumidus) is solid, the 6 or 7 whorls less convex than in the last, presenting a turreted appearance ; spiral ribs fine and numerous. Umbilicus large and one-sided. The colour is white or yellow, overlaid with spiral rows of red-brown spots. The mouth oblique, with a slight tubercle in the middle of the inner lip. About one-third of an inch in height and of similar breadth. It is rather common and widely distributed, occurring in the laminarian zone and deeper water down to 95 fathoms. The Painted Top-shell (T. magus) is a very distinct species, the shape of the three largest of the 8 whorls giving the solid shell a decidedly turreted appearance. A number of irregular ridges run spirally round the shell, and these are broken up into little knobs. A more prominent ridge runs round the base of the shell. Painted Top 206 Shell Life The ground colour is pale yellow, almost covered by short streaks of red and purple. Umbilicus wide and very deep, bordered by a smooth broad ridge. It is a species of our southern and western shores, to which may be added Ireland, Man, the Channel Islands, the Orkneys, and Shetland. It affects a sandy bottom between low-water mark and 40 fathoms. Its vacated shell is a favourite cell for Prideaux's Hermit-crab, which has for companion an anemone, the Cloaklet, that wraps the shell completely round, and by secretions from its under-surface dissolves out the mineral portions and leaves only a soft mass resembling sodden paper more than shell. The Pearly Top-shell (T. cinctus); this and the two following species are characterised by their pearly lustre, and their possession of an umbilicus. The shell of the present species is pyramidal, semi- transparent, pure white with a pearly iridescence. The largest whorl has two large and several smaller ridges, some of which are continued along the other 6 whorls. The mouth would be circular but for its interruption by the spiral ridge which encircles the deep umbilicus. It is a small species, its height being one-third of an inch and its breadth a little less. It was first found by Mr. J. G. Jeffreys in 1861, who dredged it on fine sand and gravel in 85 to 95 fathoms, about 25 miles north-north-west of Burra Firth Lighthouse, Unst. The Greenland Top-shell (T. grcenlandicus) is rather rotund and solid, slightly glossy, with fine spiral ribs. There are 6 whorls, and the upper part of each is puckered up irregularly. The colour is a flesh tint, without streaks or spots. The um- Top-shells and Pheasant-shell 207 bilicus is narrow, but very deep. It is a quarter of an inch across and a little less in height. Its British distribution is limited to the west of Scotland, Shetland, and the Orkneys, where it occurs on rocks about the base of the Laminarias, from low water to a depth of 40 fathoms. The Small Pearly Top-shell (T. helicinus) is less conical and shorter than the last, less solid, semi- transparent, and highly polished. There are no ribs, and the suture or hollow line that separates the 5 whorls is less deep than in the last. The umbilicus is also less deep. The colour is orange varying to reddish brown, occasionally tinged on the upper-side of the whorls with blue or purple. It is a quarter of an inch across the base, which is almost twice the height. Its habit is similar to that of the Greenland Top, but its habitat must be extended by the addition of the east coast of Scotland and its continuation as far south as Yorkshire; also Belfast, Dublin Bay, and Connemara. The Pheasant-shell (Phasianella pullus) belongs to a family (Turbinidw) distinct from the Top- shells, and this is its solitary repre- sentative in this part of the world. The home of the genus Phasia- nella is in Australia, where the shells are large, P. australis is 2 inches long and 1 inch across, in the Philippines and India they are much smaller, whilst in the Mediterranean, the British seas, and the West Indies they have dwindled to very small examples. Our own species is no more 14 208 Shell Life than a third of an inch in length, and a fourtli of an inch in breadth, but it makes up for its small size by its exceeding beauty. The animal is very like those of the Top-shells, and like some d of them it moves one half ~\ the foot at a time in Head of l^ia^la (enlarged) g lldin g' The OperCUlum, which we found to be thin and horny in the Top-shells, is solid and shelly, ear-shaped, and concave below. The shell, which is oval, semi-transparent, and highly polished, has usually a clear yellow or white for its ground colour, upon which are laid numerous variable oblique or zigzag streaks and spots of crimson or purple. There is no umbilicus. It is a common species on the south and west coasts of England ; round Ireland; Oban, Mull, Stonehaven, Aberdeen, Caithness, in Scotland ; and the Channel Isles. It may be found feeding upon Chondrua crisp us and the similar Gigartino, mamillosa, a little above and below low-water mark. The Fresh- water Nerite (Neritina fluviatilis) is the sole representative of the family NeritidcK in this country. It takes us away from the sea for a brief space, for this is a mollusk, no doubt descended from the marine Nerites of warmer climes, that has ascended the rivers and become modified by the changed habitat. The shell is obliquely oval, of a solid character, and with a glossy surface. The ground colour is yellowish, and is chequered fop-shells and Pheasant-shell 209 with white, pink, or purple. There are but 3 whorls, and the last of these is equal to at least two-thirds of the whole shell. The operculum is half-moon shaped, corresponding with the shape of the mouth, shelly and solid, coloured yellow or orange, and spirally grooved ; beneath there is a sickle-shaped projection which serves to keep it in position when it closes the shell. The animal which is yellowish grey spotted with black, and has a black head shows its relationship to the Top-shells by its possession of a strong snout. It has long tentacles, almost transparent, streaked with black ; and large black eyes on short foot-stalks. It is found in clear gravel-bottomed rivers, spar- ingly at the mouth where the water is brackish ; more frequently in the upper reaches. The globular egg-capsules are usually deposited on the shell of another individual, and a singular provision is made for the welfare of the young though at seemingly great expense. Each capsule contains 50 or 60 eggs, but only one embryo is permitted to develop, and this sets to work to demolish its brothers and sisters. VERY large number of species now to be described constitute the sub - order Monotocardia the mol- lusks that have only one auricle to the heart, a single gill-plume (the left), one kidney, the nervous system more concentrated, and mostly with a pro- boscis. The Violet-snails (lanthina), of which several species are found washed upon our western shores, are not natives, but their shells are so frequently found in a fresh state, if not tenanted by the living mollusk, that some general reference to them is necessary. They are what are termed pelagic species living entirely at the surface of the sea, where they feed upon the smaller species of jelly-fishes. The destruction of Velella in this way led to the supposition in the eighteenth century that lantkina '^ecklace-sliells and Winkles 21 I produced the Velellce, which were seen apparently issuing from its mouth. For such a mode of life their shell must be thin and light, and to enable them to float unnoticed by sea-birds and fishes it is (lantUna) with its float I, a bubble about to be joined to the float; c, shell; I, float; p, foot; t, head coloured violet, the lower whorls, which are most exposed from above when the creature floats, being of n darker tint, whilst the upper whorls may be white. The mouth of the shell floats uppermost, and 212 Shell Life to steady the creature in this position it fabricates a kind of raft by the excretion of slime in which it imprisons bubbles of air. To the under-surface of this raft the egg-capsules are attached, and on examination of these it will usually be found that those nearest to the animal contain eggs, those in the middle young with fully formed shells, whilst those near the farther end are broken and empty, the young ones having departed. When touched, the Violet-snail exudes a violet fluid which clouds the water around. They have no power to rise or sink at will. At least two species / rotundata and /. Violet-snail and float side view comiminis drift to our shores. They have no eyes, and are sometimes termed the " Blind Snails of the Sea." The Wentletraps (Scalaria) are well known not by reason of our several British species, but because of the high commercial value attached formerly to the Large Wentletrap (S. pretiosa) from China. Rumphius records that in 1701 this shell sold for forty guineas; fifty-two years later the price had fallen 50 per cent, and since then there has been so continuous a slump in Wentletraps that a few shillings are now sufficient to purchase a good specimen. The shells are distinct from those of any other of our native Necklace-shells and Winkles 213 Head of Wentletra mollusks by reason of the ridges that regularly cross each whorl. The almost round mouth has a flat, projecting, and continuous lip. As in many other shells, the stages of growth are indicated by the lips successively formed standing up as ridges, but in few cases do they stand out so prominently as in this genus. The mouth is closed by a horny ear - shaped operculum. The head of the animal is short, but provided with a retractile proboscis of a cylindrical shape. The tentacles are awl-shaped, and at the outer side of their bases the eyes are situated on short stalks. Like lantliina, the Wentletrap animal ejects a purple fluid when molested. Turton's Wentletrap (8. turtonce) is rather glossy, and consists of about 15 whorls, crossed by slightly curved and flattened ridges, of which there are 12 on the largest whorl. The colour is light yellowish brown with three spiral bands of purple-brown, the lowest of which is visible only on the last whorl ; operculum dark brown. The length of the shell is an inch and three-quarters, and it is half an inch across at the base. It is by no means a common shell, but it may be found along the coralline zone on many parts of our coasts. The Common Wentletrap (8. communis) is similar to the last, but the ridges are merely folded back, not flattened, and there are only 9 on the body whorl ; they are also connected from whorl to whorl, so that they form continuous but oblique lines from the apex to the base. The spiral 214 Shell Life bands are not continuous as in 8. turtonce, but broken into short streaks or mottling. Whorls about 15, separated from each other. Operculum dark brown. It attains a length of nearly 2 inches, and its habitat is similar to that of 8. turtonce. Trevelyan's Wentletrap (8. trevelyana) is fawn coloured, thinner than in 8. communis, the white ridges connected as in that species, but narrower and more flattened, with a short spur on the upper part ; there are 14 ridges across the lowest of the 14 or 15 whorls, which are not separated. Operculum pale brown. The shell seldom exceeds 1 inch in length. A deep-water species 15 to 100 fathoms. The Small Wentletrap (8. clathratula) is small, semi- transparent, white, with thin ribs of regular size. There are only 12 or 13 whorls, and the lowest of these bears 18 ridges. Operculum yellow-brown. Length about half an inch. It occurs sparingly in the coralline zone all round our islands. The Aclis-shells (Aclis) are much like those of Scalaria, but without the transverse ridges on the whorls. The mouth of the shell is oval and slightly expanded, the outer lips thickened. The animal is slender, with a long retractile proboscis, long tentacles with the eyes at their base, and the square-fronted foot pushed out in front of the head in walking. . There are only two native species. The A Glossy Aclis (A. supra-nitida) is about a T quarter of an inch in length, white, with or Glossy without spiral ridges, and the oval mouth inclining strongly to roundness. The Little Aclis (A. ciscaris) is only about one-tenth of an inch in length. It is more slender than the Glossy Aclis, 3{ecklace-shelh and Winkles 2 1 5 and has fine strong spiral ridges. Though agreeing in colour, the form is different, the base being proportion- ately narrow, and the whorls fewer. They are both obtained by dredging, and their range extends down to about 80 fathoms, but empty shells are often to be picked out of shell-sand on the shore. Two some- what similar shells formerly included in this genus are now known respectively as Pherusa yulsonce and Cioniscus unicus. The Necklace-shells (Natica) are so-called because of the peculiar manner in which their eggs are arranged in strap-shaped bands which coil into the form of quoits. The capsules (each containing a dozen or more eggs) are connected by a gela- tinous material, at first flaccid and sticky, but by the adhesion and incorporation of sand it becomes firm. These may fre- quently be picked up on the shores of sandy bays. The shells are glossy, almost globular, with a low blunt spire, and a large ear-shaped mouth. The animal has a long retractile proboscis, which is usually concealed beneath a flap of the front of the foot, which is turned up over the creature's head. The Naticas prey upon other species, chiefly bivalves, which they hunt in the sand, and whose shells are drilled by the proboscis. This important organ and the head are protected from injury in their passage through the sand by the frontal flap ; but in con- sequence of this covering the eyes have become very small or are altogether wanting. The Large Necklace-shell (N. catena) is a very 216 Shell Life globose shell of rather handsome appearance, pale buff- coloured and polished, the upper side of the whorls ornamented with a series of dark red or violet zigzag or V-shaped marks. The epidermis is retained only within the umbilicus. There are 7 whorls and a large deep umbilicus. The operculum Large Neckiace-sheii j s horn-coloured. The shell ordinarily (one-fourth nat. size) measures \\ inch each way, but this is often increased to 2 inches. It is tolerably common, between extreme low water and a depth of 10 fathoms, from the south of England to the north of Scotland. The Sordid Necklace-shell (N. sor- dida) is similar to the last named, but somewhat smaller and more deeply, less clearly coloured, more oval longer than broad and thicker, without the markings. The whorls are 5 or 6. The horn- coloured operculum edged with white. It frequents sandy shores Life aspect of .v. catena of a somewhat muddy character in from 7 to 90 fathoms, from Shetland to Scilly, but is more local than N. catena, and the individuals far less numerous. The Greenland Necklace-shell (N. grcenlcmdica) is thinner, almost semi-transparent, without gloss, white, with a cream-coloured epidermis ; whorls 4 or 5. The umbilicus is narrow, and the operculum thin, lemon coloured. Its measurement is less than 1 inch either way. It is a deep-water species, and is dredged from muddy ground in from 40 to 50 fathoms in ^ecklace-shells and Winkles 217 Shetland, and off the coasts of Yorkshire, North- umberland, and Durham. The Common Necklace- shell (N. glaucina) is a pretty little species, plentiful on sandy shores from low water to great depths. The shell is thick and solid, highly polished ; the colour varies from white to orange, Common Necklace . shel| and the markings which are five spiral lines of V's and zigzags vaiy from orange to chestnut. There are 6 whorls, and the spire is blunt. The umbilicus is contracted at the mouth, and the operculum pale horn coloured. The length is little more than half an inch. Montagu's Necklace-shell (iV. montacuti) is the smallest of the native species. It is more globose than the Common species, the colour usually fawn, but varying to buff, often with a whitish band along the upper part of the 5 or 6 whorls, but free from other markings. The spire, too, is shorter, the umbilicus rounder and more open, and the operculum rather more solid. It occurs at depths between 15 and 90 fathoms where there is a sandy or gravelly bottom mixed with mud ; all round the Scottish, Irish, and Manx coasts where these conditions exist, also in the north of England, reappearing in Devonshire and Cornwall. The Iceland Necklace-shell (N. islandica) differs from all the others in its less solid and semi- transparent character, and by having the spire more elevated. Beneath the dull yellow epidermis the shell is white, without markings. There are from 5 to 7 whorls. The umbilicus is small, and the operculum thin and golden yellow in colour. The 2i 8 Shell Life average length is about 1 inch, but the breadth is less than seven-tenths. It is a rare shell, restricted to the north of these islands in from 7 to 80 fathoms, but most of the specimens have been taken from the stomachs of haddocks. We have seen how the various species of Natica partially envelop the shell in folds of the foot and mantle ; in the next species the shell is completely hidden by the mantle. The Transparent Marsenia (Marsenia perspicua) is ear-shaped, with a very small spire, but eleven- twelfths of the whole consists of the body-whorl, which is almost flat. It is exceedingly thin and transparent when fresh, but becomes less clear in dying and loses a little of its form. The animal, which is much larger than its shell, varies a good deal in colour from white to yellow or orange, with spots and blotches which vary to contrast with the ground colour. There is a pair of long awl-shaped tentacles, with black eyes at their base only visible from below, or when the creature swims inverted at the surface. The ground colour and the markings are examples of protective coloration, for the creature feeds upon Compound Ascidians and its colour assimilates to that of its food, whilst its markings resemble the common openings of their colonies. Years ago Mr. Peach devoted a good deal of time to a study of this creature, and found that it resorted to patches of Leptoclinum gelatinosum, as he thought for the sole purpose of excavating a pit in which to deposit its eggs. Professor Herdman, however, a few years ago called attention to the fact that Marsenia fed chiefly upon Lcptoclinum, and that its colouring was protective. Necklace-shells and Winkles 219 We have had many opportunities for checking Herdman's observation, and can fully endorse it. The gelatinous semi-transparent body of the mollusk so closely matches the ascidian that it is difficult to see it, and there is no doubt that the likeness protects it from those creatures that would prey upon it if they could see it. It is probable that the creature and its shell have been greatly modified by its mode of life. It was necessary at first to hide the shell beneath the spotted mantle, then it would be gradually flattened out so that the mollusk's back did not rise so high above the ascidian, and when the resemblance between the two creatures had become sufficiently strong the shell would no longer be necessary as a protecting shield therefore it would be reduced to its present filmy texture. It is not a common species, as it occurs chiefly in deep water down to 90 fathoms but may be found on the recess of the spring tides on the vertical faces and under-sicles of rocks and boulders where the Leptodlnum colonies are. The Velvet-shell (Velutina hvviyata). There is a general resemblance between this mollusk and the last, but though the flaps of the mantle are turned over the shell the latter is not hidden. Its name is due to the character of the thick pale brown epidermis, which is distinctly velvety. The animal feeds upon Alcyonium and other zoophytes, and is found on stony ground in the laminarian and coralline zones (from 1 to 50 fathoms) all along our coasts. The Hairy-Keel Shell (Trichotropis borealis) is a beautiful little shell with a superficial resemblance to 220 Shell Life the Sting-winkle (Murex). It has an elevated spire of 7 whorls, with several spiral ribs or keels upon which the epidermis develops into thorn-like points or bristles of a pale brown hue. It has a small curved umbilicus, and the pear-shaped mouth is closed by a yellow-brown operculum. The animal is white or cream coloured speckled with yellow, and has a short bilobed snout separating the long blunt-tipped tentacles. The small black eyes are stalked. The animal lurches from side to side as it Avalks. It is a northern and local species, its range in Britain embracing the Dogger Bank to the west of Scotland, Ireland, and the Shetlands. Its habitat is in the coralline and deep-sea zones. The Bonnet-limpets (Capulidw) have the muzzle extended, the eyes situated on the base of the tentacles, and but one gill-plume, which is finely and deeply divided. Roughly speaking the shell is limpet-shaped, but with considerable difference. Two genera are represented in this country, each by a single species. They have been considered by various authors never to move from the spot to which they have attached themselves in early life, but judging from my experience with specimens in captivity, I regard this as no nearer truth than the similar state- ment formerly made respecting the Common Limpet. The Hungarian Cap or Cap of Liberty (Capulus hungaricus) is shaped much like the cap of Liberty, the beak or apex being spirally curled back ; semi- transparent, cream coloured, but the greater part of the shell is hidden by a coarse epidermis of dirty pale brown hue, which also hides the radiating ribs. This epidermis is usually rubbed off the upper end of Necklace-shells and Winkles 221 the shell, and overlaps the edge of the mouth. The lines of growth are very prominent, but so irregular that the shell appears to have been broken several times and patched up. They are found from low water to 100 fathoms, at- tached to rocks and shells ; they are particularly fond of oyster and scallop - beds, where they Hungarian c a attach themselves to the upper valves. Their food appears to be both animal and vegetable. Clark and Alder have described this species and the next as carrying their spawn, till hatched, between the muzzle and the forepart of the foot, Cup-and-Saucer Limpet (Calyptrcva, ckinensis). In this species the shell is buckler-shaped or conical, with the beak in the centre ; lines of growth spiral. The outside dull greenish or with a violet tinge ; the inside similarly tinted, but highly polished, with a twisted plate or diaphragm attached to the hinder part. It is a local species, found on the south coast from Milford Haven westward ; also in the Channel Islands. It occurs from low water to a depth of L,m P pet-interior 15 fatllOmS attached to shells Ol' pebbles J in the former situation the cone is very low almost flat but on small pebbles it becomes much more elevated. The pebbles selected for resi- dence often present a surface scarcely larger than the mouth of the shell, so that increase in the dia- meter of the latter gives place to vertical enlargement. Audouin and Milne Edwards declare that the female 222 Shell Life retains her egg capsules beneath her foot until they are hatched. The internal plate of the shell appears to serve for attaching the animal, and obviates the development of a very powerful muscle such as is found in the Common Limpet. The Periwinkle family (LiUorinid(v) have a solid spiral few-whorled shell, with a round mouth closed by a horny operculum. The animal has a broad extended muzzle, and awl- shaped tentacles with the eyes at their single row of teeth base. The under-side of the foot is of periwinkle'" inai 'ked by a central line, and in gliding the sole on either side of this line is advanced alternately. Most of the species are strictly littoral in their habits, and seldom wander far below extreme low - water mark ; one of our native species, indeed, is only covered by the sea at the periods of very high tides, and when heavy seas throw their big waves far up the shore. Respira- tion is effected by means of a single gill -plume, which is contained in a chamber formed by the mantle. Their principal food at least is of a vege- table nature, for the rasping of which they are pro- vided with a very long radula. The sexes are distinct; the males smaller than the females. The relative position of the organs will be seen in this diagram of a partial dissection. The Dwarf Winkle (Littorina obtusata) is the yellow, red, brown, purple, or green shell that is so abundant on all our beaches. In the empty condition it is piled up at the base of the rocks after a storm ; in the living state it will be found in profusion on the Bladder Wrack (F'ucus vesiculosus), where it very * , * TCKTON'S WENTLETRAI- ; 2, 3 COMMON NECKLACE-SHELL ; 4 LARGE NECKXACE- SHEI.L ; 5 CUI'-AND-SAUCEK LlMl'ET ; 6 HUNGARIAN CA1' ', 7 NfiRITE WlNKLE J 8, 9 ROUGH WINKLE. ^(ecklace-shells and Winkles 223 closely resembles the bladders of that seaweed. The term dwarf applies to the almost suppression of the spire, a condition also indicated by obtusata, blunted. There are 5 whorls, but the first four form a very small part of the entire shell. Occasionally pure white specimens may be found, and frequently it is banded length- wise with red- brown. It measures about half an inch either way. The Nerite-like Winkle (L. neri- toicles} has a de- cidedly conical shell, and the last whorl only accounts for two-thirds of the whole. The colour is a dark red-brown, paler at the base, where there is sometimes a yellowish zone. In height it is a little more than a quarter of an inch, and in breadth a little less than a quarter. It is usually found clustered on the sides of rocks above ordinary high-water mark, where during the period of neap-tides it must remain dry for days in calm 15 Animal of male Periwinkle, with the shell removed o, mouth; 6, sexual organ; c, reflexed mantle; d, vent; e, kidney;/, slime-gland; g, gill; A, heart; m, shell- muscle; p, foot 224 Shell Life weather; but the gill-chamber holds sufficient moisture to enable respiration to proceed. The Rough Winkle (L. rudis) has a less pointed spire of from 6 to 9 whorls, of which the last whorl occupies in the male one-half, and in the female two-thirds of the whole ; the mouth, too, is much larger in the female than in the male. The colours range from white, yellow, and orange, to red, brown, purple, and black, usually with spiral bands of another tint, and spiral flattened ribs. The female retains her eggs until they are hatched, and this is said to be the reason why this species is not used for food, the minute shells rendering the parent gritty and dangerous to the teeth of the eater. It is every- where plentiful where there are rocks and stony beaches. It is half an inch across, and about five- eighths in height. Experiments made by Professor W. A. Herdman with this species show that it is capable of living out of water for long periods. Marked specimens upon the rocks were found not to have moved within thirty-one consecutive days. It appears to endure life in the water less than life in air, and to be undergoing the change of habit from sea to land that must in past ages have brought about our land mollusks. The Periwinkle or Common Winkle (L. littorea) comes nearest to the Rough Winkle, but differs from it in being twice the size, with flatter whorls, a longer and sharper spire, a much slighter suture or channel between the whorls ; the disproportion in size of the ^{ecklace-shells and Winkles 22$ sexes is not so great in the present species, because the female does not retain her eggs but deposits them in masses upon weeds and rocks. The colour of the shell is yellow- brown, greyish yellow, or olive, with red - brown or dark brown bands, and flat spiral ridges. There are 7 or 8 whorls. The cen- tral pillar round which the spiral is wound is always white. Winkles are exceedingly common below ordinary high- water mark all round our coasts, and thousands of tons are gathered annually and sent into the towns to be sold as a delicacy among the poorer classes. The Chink-shells constitute the genus Lacuna, which is represented by four native species. They are chiefly distinguished from the Winkles by the fact that the lobe to which the operculum is attached is large, and ends in a pair of long tentacle-like fila- ments. The head tentacles are flat and smooth, and the mouth of the umbilicus is a long slit in the pillar, whence the names Chink-shell and Lacuna (a fissure). The shell lacks the stony solidity of the Winkle- shells, though the animal also feeds upon seaweeds, but not so much about rocks. Loven has observed that the animals are coloured to harmonise with the weeds upon which they feed. 226 Shell Life The Thick Chink-shell (L. crassior) is rather solid, opaque, brownish yellow, turreted, with thick epider- mis ; the spire raised, with blunt tip ; whorls 6 or 7, suture deep ; mouth expanded below, with thin lip. The fissure is not always present. The animal is very active, and moves along with a jerking of opposite sides of the foot alternately. Like the Winkles it is fond of getting out of the water into the air. It is rather a local species ; but is widely distributed, and may be found on small weeds below Banded Chink-shed, Lacuna, divaricata (enlarged) ordinary low-water mark where the bottom is sandy. The shell is half an inch long, and less than a third in breadth. The Banded Chink-shell (L. divaricata) is conical, thin, semi - transparent, with slight spiral lines (also present in L. crassior, but there hidden by the epidermis). The colour varies from white to pale brown, usually with four bands of reddish brown ; whorls 6, suture not deep. Fissure wide. The animal is shy and restless, and has the same awkward mode of progression as L. crassior. * i TO 7 DWARF Wi PA u.i n CHINK- S^ecklace-shells and 'Winkles 227 The shell is about three-quarters of an inch in length and one-third in breadth. It is quite abundant on the weeds at low- water mark and below, on all our shores. The Globular Chink -shell (L. puteolus) is rather solid, glossy, and opaque, the whorls not rounded but rather angular in the centre (periphery) ; yellowish white, with or without three reddish bands, sometimes uniformly dull reddish brown. Spire scarcely raised chink-sheii above the body whorl, which includes four-fifths of the entire bulk of the 3 or 4 whorls. Mouth expanded, with a somewhat angular base ; fissure wide and deep. It may be found in numbers feeding on small weeds, such as Carrageen (Chondrus crispus), about low - water mark. The Pallid Chink-shell (L. pallidula) is almost triangular, greatly ex- panded in front, thin but opaque, glossy, of a yellow-green colour ; epidermis somewhat thick ; mouth very large. The fissure in this species is exceedingly Eggs an c d j n k u . n s ^ e f Pallid large and funnel-shaped, exposing nearly all the hollow spire. Although widely dis- tributed along our shores, this species is found chiefly on the south and west, at low water and for a few fathoms below it. The eggs are deposited in oval patches on seaweeds, as shown in our figure, where also are depicted some aspects of the fry. HE mollusks considered in the previous chapter were marine, many of them lit- toral species, living on the rocks that are uncovered for hours each day when the tide has receded. To protect some from the evaporation of their fluids in such a situation, and to preserve others from enemies when swept off the rocks by rough seas, all those that had distinct whorled shells had the orifice closed by a door or operculum. It can be clearly seen how such an adjunct to the open shell made a transition from marine to terrestrial life easy. Such a form as Littorina rudis, that spends weeks above high water, and is believed to be in the process of changing to a land-snail, was probably the ancestor of the Kound- mouthed Snail (Cyclostoma elegans), which is clearly a marine snail that has been so modified that it lives Spire-shells and Marsh-snails 229 far inland on the dry chalk-downs as well as keeping up its connections by living along the coast-lands. A glance at the figure will show that so far as externals go it makes out a good case for being classified not very far from the Winkles. There is the long proboscis, the same contractile tentacles with eyes at their base, the longitudinal division of the foot, and an operculum, only this has become shelly instead of horny. If we inspected the radula we should find the number and arrangement of the teeth to agree with that of the Winkles. But there is one great difference : instead of the gill-plumes of the Winkles, aeration of the blood in Cyclostoma takes place in a chamber formed under the mantle behind the head, the blood circu- lating about the living tissues of this chamber and taking up oxygen from the air. This arrangement led to th&Cyclostoma being grouped until lately with the land and fresh-water snails that have a closed branchial chamber or lung ; but it is now recognised that there is a great difference in the two. It is an exceedingly interesting case, for it gives a distinct clue to the probable origin of other land-forms that have got much more modified. It must not be assumed that Cyclostoma originated in this country from a Littorina. The genus is a tropical one, and the probability is that C. elegans had a southern origin, for it is found in the Canaries, in Portugal, France, Italy, and Central Germany. It extends no farther north than Yorkshire and Donegal. Its habits are rather singular. A vegetable feeder, 230 Shell Life its favourite resort is on dry hedge-banks, especially on chalky soil. In dry weather, also in winter, it partially buries itself, and in excavating a hole it uses its proboscis for the removal of earth. When climbing it is said to use this same organ as a hand to take hold by. It is very shy, and withdraws into its shell on the slightest alarm, closing its door and dropping to the ground. This species and the next are the only native land - snails that possess the operculum, and its retention in so highly developed a condition by the present species may be explained not only by the nature of its breathing apparatus, but by reference to its enemies. There is a small beetle known as Drilus flavescens, and its larva or grub devotes itself to the destruction of the Round- mouthed Snail. This is how it effects its fell purpose in spite of the stony door that shuts out most enemies. The Drilus-larva waits patiently at the mouth of the snail's shell until the door opens and the mollusk comes forth ; then it contrives to cut the muscular attachment of the operculum, so that when the snail withdraws the door of its fortress will not close properly. The Drilus can now complete its work at leisure ; it enters the shell and consumes the body of the snail, then changes into the pupal condition and waits within the shell until it has attained to its final form as a complete beetle. There is one other native species included in the same family, though it forms another genus. This is the Point-shell (Acicula lineata), whose name indicates, though it does not accurately describe, its dimensions. Its form is cylindrical, with a slight tapering to the upper end ; the whorls 6 or 7, Spire-shells and Marsh-snails 2 3 i pale brown, glossy, and semi - transparent. The animal is much like the Round - mouth, but its tentacles have not the enlarged tips of that species, the operculum is horny instead of stony, and fits into an oval mouth. It is an active little creature, and may be detected by sharp eyes as it ranges over the moss, dead leaves, and decaying trees in damp woods or dry ditches. The Spire-shells (Rissoa) form one of the most largely represented genera of British shells, something like a quarter of a hundred native species being in- cluded in it. Like Acme they have an elongated shell, but here the shape is distinctly conical, the last or body-whorl constituting one- half to two-thirds of the whole. A The mouth of the shell is more or rajL less round, fitted with a horny ^^ ^ * Latticed Thick-lipped operculum ; there is rarely an Spire-sheii Spire-sheii umbilicus. The animals are very ca ( ^ a) (B ' an like Winkles ; the body is slender, the head produced into a bilobed snout, and the mouth armed with a pair of jaws and a short radula. The blunt-tipped tentacles are more or less hairy, and bear the eyes on small prominences near their base. The foot is divided down the middle as in the Winkles, but only half-way. From the hinder extremity of the lobe to which the operculum is attached, an appendage like a tentacle is given off from each side, thus showing a relationship with the Chink-shells (Lacuna). The shells are all very small, but their forms are beautiful. The Spire-shells may be found on seaweeds and Zostera at all depths between high water and 100 fathoms, according to species. The 232 Shell Life mollusk has the faculty for spinning invisible threads, and by this means suspending itself from the weeds or from the surface of the water. It is impossible here to give descriptions of the numerous species, whose names will be found in the list at the end of the work. The Red Spire-shell (Barleeia rubra) is distinct from the Rissoce only in that the opercular lobe is without appendages and the operculum more solid. The genus Hydrobia, too, is but little removed from Rissoa, and less so from Barleeia, with which it agrees in the absence of tails to the operculum lobe. The shells are smooth, and just beyond the mouth there is a chink which appears like the approach to an umbilicus. We have four species, of which one, the Laver Spire-shell (H. ulvce), is partially marine. It feeds in g re at numbers on the Laver or Sea Lettuce (Ulva latissima), whether this be between tide-marks on the seashore, in rock-pools, or in estuaries, and as far up tidal rivers as the salt water extends. The other species (H. similis, H. ventrosa, H. jenkinsii) have taken themselves up the rivers where the fresh water greatly predominates over the salt, H. similis being found in the muddy ditches of the Thames marshes between Greenwich and Wool- wich, where it has for company so distinctly fresh- water a form as Bithynia tentaculata and the more marine Assiminia yrayana. In the small genus Jeffreysia the minute shells are thin and glossy, and the operculum has a slight projection from the straight inner side. J. diaphana occurs on Delesseria and other seaweeds at low water ; /. S fire-shells and Marsh-snails 233 opalina on Corallina officinalis and Laminaria ; J. globularis on Laminaria at Croulin Island, Skye. In the genus Bithynia again we come upon two fresh-water species that have obviously been derived from marine forms. The name is badly chosen, for it might indicate that the species inhabit deep water, whereas streams, ponds, and ditches are their usual habitat. The figure represents the Common Bithynia (B. tentaculata) of the natural size. The pale brown shell is a symmetrical spiral of conic-oval outline, fairly solid ; the oval mouth closed by a thick shelly operculum ; umbilicus a narrow chink. The animal is dark brown or black above, paling to a dirty grey below, with a long deeply cleft snout, one branchial plume, and thread-like diverging tentacles. The prominent black eyes are not stalked. Leach's Bithynia (B. Icachii) is a much smaller species (a quarter of an inch long), with a thinner, semi- transparent shell, swollen whorls, and a more distinct umbilicus. The mouth of the shell is nearly round, and the operculum almost circular. Both species frequent sluggish rivers and still waters, but whereas the larger form is widely distributed everywhere in England, Ireland, and Wales, the smaller is more local and less abundant. They feed indifferently on animal and vegetable substances ; and lay their eggs in bands on stones and water-plants. The Sentinel-shells (Assiminea) have been so-called because their eyes are borne upon long stalks which give them the power of elevation 234 Shell Life possessed by some of the Crabs, and are therefore supposed to be able to keep a sharp look-out as a sentinel should. These eyestalks are of the same length as the tentacles, to which they are united. The shell is very like that of Hydrobia. The Dun Sentinel (A. grayana) lives in brackish water, coming up the Thames as far as Greenwich. Another of these small-sized mollusks is the Skenea planorbis, whose reddish or tawny shell at first sight looks like one of the small fresh- water Flat-coiled Shells (Planorbis), whence its specific name. The spire is flattened, the four rounded whorls loosely coiled, the mouth round, and the spiral operculum horny. In habit it is very like the Winkles, for though it has been dredged from a depth of 40 fathoms, and may be taken from Confervce in the rock-pools, it also feeds upon Lichina pygmcea, which spends half the day submerged and the other half dried and shrivelled in the air. A somewhat similar but less depressed shell is the White Belted-shell (Adeorbis subcarinatus), which makes up for small dimensions by having a long scientific name, as many other small creatures do. There are only 4 whorls, and these have 6 strong narrow ridges or keels. The large mouth does not show quite so even an outline as in our figure, the ridges usually producing corresponding indentations of the mouth. The operculum is thin. There is a large umbilicus. It is a local species, occurring at various places on the south and west coasts, and at a few places in Scotland and Ireland. The obvious natural relationships of the species Spire-shells and Marsh-snails 235 considered in this chapter causes us to jump fre- quently from the seashore to the estuary and the inland waters. So, also, from considering some of the smallest of our native species we have now to mention the largest of the fresh-water gill-bearing River Snails, ViM\po.ro, ; male on left, fe ght, young ( mollusks the River Snails ( Vivipara). Like many others that have been under notice the animal has a prominent snout, the eyes are placed outside the base of the tentacles (in this case on short stalks), the shell has a symmetrical spire, and an oval mouth, closed by a horny concentric operculum. They are 236 Shell Life Common River Sna (one-half nat. size) herbivorous mollusks. The males are smaller than the females, because the latter retain their eggs until they are hatched, and, therefore, require more roomy whorls for their accommodation. The two native species are much alike superficially, but nature has been kind to the tyro in giving them marks that serve to distinguish them readily. The Common River Snail (F. vivi- para) has a thicker and longer shell, a blunter apex, less swollen whorls, a less circular mouth, arid the umbilicus is reduced to a small narrow chink. Lister's River Snail ( F. contecta) is a little larger than the other, has a more circular mouth, and a distinct and deep though small um- bilicus. It is a much more local species than the other. They are both fairly active animals, and tolerably hardy, for V. contecta ranges from Finland to the Pyrenees, and V. vivipara has been known to produce a batch of young shortly after having been thawed out from a temperature of 23 F. The last of these operculate fresh- water species we have to glance at are the so-called Valve-shells (Valvata), of which we have two so distinct in form that there is no difficulty in identifying them. The animals are built much on the same plan as the foregoing the head drawn out into a long snout, and the eyes at the base of the tentacles, but in this case on the Lister's River Sna (one-half nat. size) Spire-shells and Marsh-snails 237 inner side. When gliding through the waters the branchial plume is exserted from beneath the mantle, and with it a long tentacle-like outgrowth from the mantle, which is regarded as also employed in respiration, and thought by some as the other branchial plume aborted. The sexes are united in each individual, but only one sex is functionally active at one time. They inhabit slow and still fresh waters all over these islands. The Common Valve-shell (F. piscinalis) has a blunt spire, and the general form of the shell is globular, brownish yellow in colour, V a h e n || and marked with spiral ridges. The um- bilicus, though round and deep, is not large. The Flat Valve-shell (V. cristata) differs in the form of its greyish shell, which is always flat, like that of a Planorbis, and the animal has a smaller snout and stouter tentacles. The umbilicus, too, is proportion- ately larger and more open. 'E are back again upon the seashore seeking for what Borlase nearly one hundred and fifty years ago called the Small Needle -whelk (Bittium retwulatuni), a name we believe not in use among the folks along our coasts, who usually lump a large number of species together under a kind of generic title, according to size or habit. Thus these Horn-shells (Bittium, and Ceritkium), small Nassas, Pheasant-shells, Necklace-shells, and others, are all known along the Cornish coast as " Shillifillies." In the Horn - shells there is a long pyramidal spire of many whorls ornamented with little bosses in spiral lines, a small mouth with a little groove on its lower margin, a horny operculum, and no umbilicus. The animal is much like those last described in the previous chapter, but the branchial siphon is merely a short fold of the mantle, J i' }) 4 4 5 13 J 14 2 EUROPEAN COWRY ; 3 SHALL NEEDLE-WHEI.K ; 4 POLISHED EULIMA ; 5 DISTORTED EUI.I.MA ; 6 AWL-SHAVED EULIMA; 7 AUGER-SHELL; 8 PRICKLY SPINDLE; 9 LEAST WHELK; 10 RIBBED SPINDLE; n SMALL STING-WINKLE; 12 NETTED DOG-WHELK ; 13, 14 THICK-LIPPED DOG-WHELK. Cowry and Pyramid-shells 239 the tentacles are awl-shaped, and the eyes are placed on little prominences at their outer base. The sexes are distinct. The Common species, B. reticulatum, figured here, is about half an inch long, of a reddish-brown colour. It feeds upon decaying animal and vegetable matter, and abounds on all our coasts between half-tide and about 15 fathoms. The Reversed Horn-shell (Triforis per- versa) is a smaller shell with the spiral turned in the opposite direction. B. reticulatum, like most spiral shells, has the open mouth on the right hand of the observer when the shell is held with the spire upwards ; in T. perversa the mouth is to the left hand. It is by no means so plentiful as B. reticulatum, and is found chiefly on our southern and western shores, in the Channel Islands, and all round Ireland. It is found sparingly in Scotland, the Orkneys, and Shet- land. Its range is from low water to about 20 fathoms. The Obelisk-shell (Lovenella metula) is a third species, of whitish hue, about three-quarters of an inch long, found rarely on the Shetland fishing banks in from 45 to 96 fathoms. Another group of Horn-shells is placed in a separate genus Cerithiopsis, that is having a likeness to Cerithium, and these are chiefly distinguished by the groove at the base of the mouth being developed into a distinct though short canal, which is lined by the mantle tube or branchial siphon. The British species are C. tubercularis, G. barleei, C. pulchella, G. metaxce, G. concatenata, and G. costnlcAca. The only example we have of the Screw-shells 16 2 4 Shell Life Auger-shell (two-thirds nat : (Turritella) is the one to which Pennant gave the name of the Auger (T. communis), on account of its resemblance to that boring implement. It is a giant compared with the little Horn- shells. The whorls are spirally ridged, the mouth comparatively small and round, though with a suggestion of squarishness, and without a canal or groove. The operculum is round and horny. The mantle is fringed with a triple row of fine filaments. As the new whorls increase in size to accommodate the growing animal the older whorls at the top of the spire, being too narrow for occupation, are partitioned off by the deposit of shell internally. It occurs on all our shores above sand and mud in from 3 to 100 fathoms. We have just mentioned how the owner of an old house shuts off the rooms that are no longer large enough for use, more spacious apartments having been erected. Some other species having thus partitioned off the old from the new, deliberately knock the older portion against stones in order to break it off; in other cases the making of the dividing wall appears to cause the older part to perish. Shells that have undergone this process are said to be decollated. Perhaps the case of the Blind-shell (Ccecum trachea) is still more remarkable, as the entire appearance of the shell is altered by the conduct of the animal. It begins life with a shell coiled Cowry and Pyramid-shells 241 flat (discoid), but after a time the new portions are added in almost a straight line ; then the animal constructs a conical division across the interior to separate the straight portion from the spiral, which soon falls off. Later another division is made in order to get rid of a portion that is too narrow. So that we have here a creature beginning life with a spiral shell, and arriving at maturity with one of a cylindrical character like a Tooth-shell (Dentalium}, except that the exterior of this is marked off into rings whilst that is plain. The ringed appearance accounts for its specific name trachea as recalling the structure of the windpipe. The round opening of the brown shell is closed by a flat brown operculum. It may be found in fair abundance in water from 15 to 50 fathoms deep on the coasts of Dorset, Devon, Cornwall, Wales, Guernsey, the Clyde district, Bantry, and Galway. The animal is extremely active, but not so agile as that of the minute Smooth Blind-shell (C. glabrum), which has a thin, smooth transparent white shell closed by a convex operculum. It is found all round these islands between the depths of 15 and 50 fathoms. The Pelican's-foot (Clienopus pes-pelicani) when fully developed brings to mind the Strombs and Wing-shells of the tropics, and it is interesting to note how easily this form may be produced from a shell of entirely different appear- ance. In earlier life the shell is shaped like the Auger-shell (Turritella), but by successive additions 2 4 2 Shell Life made to the lip the latter expands into a broad flap with five triangular processes, each grooved beneath. There are three thick spiral ribs which are more or less broken into tubercles. The colour is yellowish - white tinged with brown, and the mouth is closed by a pointed operculum. The animal is of similar structure to those we have been recently considering : the foot continued for- ward in advance of the head ; the long snout and awl-shaped tentacles, with the small black eyes on little footstalks at their base. It is cream coloured, mottled with purplish brown and flecked with yellow and white, the whole effect being that of the sand upon which it glides awkwardly in the coralline zone (15 to 50 fathoms), as though its shell were an encumbrance to it. The Shetland Pelican's - foot Cowry and Pyramid-shells 243 (C. macandreai) is a much smaller and more delicate species, found only on muddy sand off Shetland in from 60 to 80 fathoms of water. The five points from the mouth of the shell are relatively longer and more distinct, the one that is nearest the spire often exceeding it in length and running parallel with it. The colour is paler, so is that of the animal. A more striking object-lesson in the evolution of shell - structure is afforded by the three British members of the Cowry family (Cyprceidce), each of them representing a separate genus. In all of them the mantle is furnished with a pair of large side-lobes which fold over the shell and almost meet above it. The mouth of the shell is mostly as long as the shell, and is not closed by an operculum. The animal has a short muzzle, a broad foot with a squarish front, and a long siphon. They are carnivorous, feeding upon zoophytes, etc. Of these three forms the Smooth Margin-shell (Erato lew is) best illustrates our meaning. It will be seen that the body-whorl is three or four times longer than the remainder of the shell, and that the mouth is almost as long as this whorl. The lip of . Ma k rgin -' he "T, & . * from above and below this is at first quite thin and sharp- edged ; then it is turned in a little but still has a plain edge, but after- wards it is considerably thickened and becomes toothed on the inner margin. Now the animal which Margin-shell and anima! o is of a lively disposition does not permit us to see much of this white shell when he is on active service, for the mantle-lobes are 244 Shell Life thrown well up over it, and only a narrow streak of the shell shows between. The shell is little less than half an inch in length, and occurs locally all round our islands on sandy ground in from 12 to 85 fathoms. The white foot is speckled with orange, pink, and black, to harmonise with this ground, whilst the mantle-lobes are dotted with purple-brown marks and studded with pale yellow tubercles in imitation of the zoophytes on which it feeds. The Poached Egg (Ovula patula) has a mouth that is much longer than the shell-proper, and it appears to be all body-whorl. But if we look again at the Margin-shell and imagine ^ the outer lip extended to a Poached Egg . ., greater length than the spire, the result would be spindle-shaped, much like the shell of the Poached Egg when freed from the mantle-lobes. This shell is thin, glossy, and almost transparent, whitish with a tendency towards yellow. Young speci- mens exhibit a brief spire within the canal formed by the extension of the outer lip above, but the adult shell is of the form shown in this figure. The animal is yellow- ish white tinged with brown ; the mantle- lobes, which sometimes completely cover the shell, are marked with brown transverse lines and small spots. It feeds upon the zoophyte Tubu- laria indivisa, and lives among the colonies of its victims, the brown stripes of the mantle-lobes helping to disguise it from its own enemies by assimilation to the clustered tubes. Its distribution is not general, Cowry and Pyramid-shells Young shell of Cowry but restricted to Dorset, Devon, Cornwall, Guernsey, Sark, and a few places on the Irish coast, in the coralline zone. The shell of the beautiful though common European Cowry (Cyprcea europcea) undergoes a similar change. At first it is a spired shell, though the spire ^^ is very short ; the outer lip is thin and sharp- edged, but as it grows this turns in, thickens, and so reduces the opening considerably. The difference between the young and the adult Cowry shells is so great that the naturalists of a few generations back classed them as belonging to distinct species. When the identity of the animals was proved it was believed that the earlier was abandoned when it got too small, and a new one of a different pattern made to shelter the more adult animal. The animal varies in colour from yellow to pink or brown, but most frequently it is orange. The mantle-lobes, which are covered with yellow or white raised points, and red or purple spots, well cover the shell. The ground colour of the shell is white, but in half- grown individuals this is crossed by transverse lines of deep flesh tint. In old specimens the white spaces between these lines become elevated into ridges which are continuous with the ribs that protect the mouth. That part of the shell where the mantle-lobes meet is often marked with three dark brown spots, of which the central one European Cowry from above and belov European Cowry 246 Shell Life is the largest and the least sharply defined, but plain specimens are far more plentiful. The animal is very active, but also shy, for it rapidly withdraws into its shell on very slight alarm. The old English form of the name was Gowry. On some parts of the coast it is the Nun, in others the Stick-farthing. Atlanta peroni (magnified) Between the Cowries and the Naked Tongues (GymnoglosscC) there comes a group of sea-snails who have become specially modified for a free-swimming life in the open ocean. The foot, instead of being Cowry and Pyramid-shells 247 flat for crawling, as in those that crawl upon rocks or weeds, is developed into fin -like expansions. With these they swim in an inverted position at the surface. The shell is not present, or is very small, in one family (Pterotrachceidce) ; in another (Atlantidce) it is spiral, and sufficient to entirely accommodate the animal, which shuts itself in with an operculum. Both shell and animal are perfectly translucent, so that the internal organisation is clear without dissection. These creatures had not been regarded as coming within the British area, though they swarm in the warmer parts of the Atlantic, as well as in the Indian and Pacific Oceans ; but in September 1888 Professor M'Intosh took in the waters of St. Andrews Bay " a small transparent univalve, like a finely fashioned shell of glass, containing its inhabitant." It measured about one-twelfth of an inch, and was probably a young example. It was evidently a species of Atlanta, nearly allied to that figured, but having a flat margin instead of the keel that is present in Atlanta peroni. Such a capture is of great interest, for hitherto these creatures were considered to exist only in more genial seaa EFORE describing the creatures whose names stand as the title of this chapter, we must glance at a couple of orders collectively known as the Gymnoglossa, or Naked Tongues, from the fact that the radula (as well as the jaws) is absent. Their true position in the systems of classification is still a matter of contention among the " doctors who differ," but they appear to be closely allied to forms such as Rissoa and Hydrobia, and to have lost their teeth owing to a very distinct change of habit many of them being parasites. The mouth is developed into a proboscis, used in the parasitic forms for sucking the juices of the host. The Eulima-shells (Eulima) consist of half a dozen native species with polished awl-shaped semi-trans- parent shells that taper to a very fine point, but as the animal in growing has to vacate the older Whelks and Conelets 249 portion the tip of the spire is frequently broken off. The mouth of the shell is oval, closed with a horny operculum, and the outer lip thickened inside. The animal has a foot whose broad front extends far in advance of the head, which is kept under shelter though it shows through the shell, as seen in the figure. The siphonal fold of the mantle is very rudimentary, and the eyes are behind the base of the tentacles, which are united at their origin. The Polished Eulima (E. polita) has a highly polished shell resembling ivory, about three-quarters of an inch in length. The animal is also white, but streaked and tinged with yellow ; the snout marked with a golden V, the black eyes ringed with yellow. Unlike its fellows, this species is not parasitic, yet it lacks a radula just as much as they do. This appears to point to the fact that the original species of Eulima was a parasite who had no use for a radula and exchanged it for a proboscis through which fluids and soft food could be drawn ; but that E. polita on giving up the parasitic ways of its ancestors has not found the need for teeth. The Intermediate Eulima (E. intermedia) is not quite so large, more spindle-shaped, semi-transparent, and less distinctly white ; and the animal is without the V-mark on the snout. The Distorted Eulima (E. philippi) owes its name to the curved spire of the slender, nearly transparent shell, which is less than a quarter-inch in length. The Awl-shaped Eulima (E. siibulata) has an awl-shaped, semi-transparent thin shell, half an inch long, with three pairs of spiral tawny bands. The Two-lined Eulima (E. bilineata) 250 Shell Life is very similar to the last, but little more than a quarter of an inch long and with only two of the spiral bands. Most of these Eulimas attach them- selves to the shells of bivalves, the opercula of gasteropods, or to the interior and exterior of the Sea Cucumbers (Holotliuria). The Urchin Snail (Stilifer turtoni), of which we have but one species, agrees with Eulima in having no teeth. It is, however, housed in a shell of different shape, the body - whorl being large and broad, the greater part of the spire above being so slender and cylindrical that it has suggested the Greek stylus. It differs from Eulima again in having no operculum. The head of the animal is snout-like and ends in a suctorial mouth. The tentacles are cylindrical, and the mantle-edges turn up and overlap the margins of the shell. This creature is found only on and among the spines of Sea Urchins, where it appears to feed upon the excreta of the Eckinis. The Pyramid-shells (Odostomia) are well repre- sented on our shores by a score of species. The shells are all small, conical or awl-shaped, smooth or spirally grooved, with the apex coiled the reverse way (sinistral) to the greater part of the shell, and the mouth with y sh,~ a tooth-like projection on the inner lip hence the name Odostomia = tooth - mouth. The animal is very like Eulima. The proboscis is only protruded for the purpose of feeding, which appears to be at the expense of the jelly-like polyps and sponges whose softer slime-like portions they can obtain by suction. Some of them appear to subsist Whelks and Conelets 251 upon the excreta of other mollusks, the Pallid Pyramid (0. pallida) being frequently found on Pectens near the excretory outlet ; others are found under clusters of mussels, on the opercula of other gasteropods, and at the base of- seaweeds. As in the case of other parasitic mollusks the shell is white or nearly so. Space will not allow of an enumeration of the species in the body of the work, but a list of the British species will be found in the Appendix. Jeffreys included in the genus the species often separated to form the genera Turbonilla and Eulimella. The genus Turbonilla consists of a dozen species distinguished by having the central pillar straight (instead of curved as in Odostomia) and in most cases without the tooth-like projection. The shell, too, is more elongated, and the whorls have ribs running across them,' as shown in the figure of the Staircase Pyramid (T. scalaris). The six species com- prised in the genus Eulimella agree with Turbonilla in the elongated shell with its straight and seldom-toothed pillar, but it is in this case free from ribs of any sort and is polished. The remaining families to be mentioned in this chapter are grouped together under the name of Rachiglossa, on account of an agreement in the disposition of the teeth on the radula. Instead of there being a large number in each row, there are here only three ; but each tooth has its front edge broken into a number of long sharp points, varying with each family. The proboscis is long, but can be completely retracted. In the type family, Muircidcv, the radula is contained in the proboscis, and its 252 Shell Life central teeth have three or more strong cutting points, or cusps, whilst the side teeth are plain. It is to the skilful manipulation of these central teeth that those neat round holes in bivalve shells are due, the members of this family being mostly carnivorous. A further character of these mollusks is seen in the shells, the mouth running off into a spout, as shown more clearly in the figure of the Ribbed Spindle-shell (Trophon truncatus}. This spout is for the accommodation of the siphonal fold of the mantle, and is commonly referred to in handbooks as the anterior canal Through the siphon fresh supplies of water are drawn into the branchiae. It is worthy of note that as a rule (to which there are several notable exceptions) this form of shell and siphon indicates carnivorous propensities, and the reason for its existence may be found in the habits of the creature. Much of the food of these mollusks is tainted, often putrid ; and whilst the mouth is immersed in such a pabulum it would clearly not serve the purpose of respiration to draw in water from the immediate neighbourhood. The long siphon is extended to one side, or over the top of the shell, and the water taken in from as remote a point as possible. The Little Spindle-shells ( Troplto n) are represented by three species, of whelk-like form, all being about two-thirds of an inch long. The Prickly Spindle- shell (T. muricatus) is slender, dull, the whorls Whelks and Conekts 253 crossed by swollen, sometimes prickly ribs, which are broken by a series of spiral channels. The colouring is a flesh tint with touches of reddish brown. The mouth is small and ends in a long anterior canal. The operculum is pear-shaped, with the nucleus at the narrow end. It has been found chiefly on the shores of Devon, Cornwall, and Guernsey, in the Isle of Man, Tenby, Dublin Bay, Cork, etc., in soft ground between 15 and 50 fathoms. The Ribbed Spindle- shell (T. truncatus) is broader, slightly more glossy, and paler, the ribs not broken into tubercles by the spiral grooves. The upper part of the spire is smooth and polished, the mouth oval and the canal short. It affects hard ground from 2 to 50 fathoms deep, on the east coast, around Scotland, south and east Ireland, and the Isle of Man. The Berwick Spindle - shell (T. barvicensis) is more like the Prickly Spindle but broader, much more glossy, the whorls crossed by fewer but more prominent, almost toothed, ribs. The cusps on these ridges are stronger above, so that the top of the whorl appears to be encircled by spires. The colour is white. This is a more northern form, occurring on stony ground from low water to 50 fathoms on our northern coasts, coming only as far south as Yorkshire and North- umberland. The Sting- winkles (Ocinebra) have the same form of shell, but it is disguised by the ribs and great thickening of the lip from time to time. What are known as varices or " growth lines " really represent periods of comparative rest from shell production. At least, the shell is not enlarged internally, but only thickened at its mouth. These are, of course, the 254 Shell Life same as we have described as ribs crossing the whorls in the case of Lachesis, Trophon, and others, but in Ocinebra erinacea they are more varicose. In addition there are several spiral ridges running from the mouth to the apex, and in crossing the varices they produce that rugged appearance so characteristic of the species. A figure is given on page 252. The animal is yellowish, mottled with white. It is found chiefly on the southern and western coasts, including Wales, and all round Ireland. It inhabits rough ground from a little below low-water mark to about 30 fathoms. It is one of the great enemies of the oyster, boring neat round holes in the upper valve of young oysters and so gaining admittance. It is from this nefarious practice that the fishermen interested in oyster-beds have called it the Sting-winkle, its " sting " being the proboscis with its boring implement. Like the Murex trunculus so well known to the ancients, and like Purpura, the Sting- winkle carries about a small quantity of fluid capable of dying fabrics violet or purple, and which is probably ejected in the water for defensive purposes. The shell attains a length of about 2^ inches. The triangular egg-capsules, each containing from a dozen to twenty eggs, are deposited separately but in little groups. The Small Sting - winkle (0. aciculata) is similar in appearance, but of a dark red-brown colour, with more numerous spiral ridges, and only about half an inch in length. The animal is bright red, sometimes flecked with yellow. It has been found only in the Channel Islands, where it is moderately plentiful. The Purple (Purpura lapillus), commonly known Whelks and Conekts 255 as Dog-winkle, and in Ireland as Horse-winkle, is one of the commonest of marine snails. It may be found in abundance high and dry on the rocks after the recess of the tide, where, like the Rough Winkle, it appears to enjoy a prolonged air-bath. Such a habit should expose it to grave dangers from shore-birds, but its shell is thick and stony, and in some places it appears even to have developed something like pro- tective coloration, but whether the cases adduced would be sufficient to deceive birds is open to question. Its colour is a more or less pure white, spirally banded with orange, red-brown, or brown ; but the propor- tions and intensity of these hues, as well as the sculpturing of the shell, varies greatly. The Rev. A. H. Cooke, M.A., in the Cambridge Natural History, remarks that " in many cases the variations may be shown to bear a direct relation to the manner of life. Forms occurring in very exposed situations, e.q. Land's End, outer Purple ' Dog-winkle rocks of the Scilly Islands, coasts of north Devon and Yorkshire, are stunted, with a short spire and relatively large mouth, the latter being developed in order to increase the power of adherence to the rock, and consequently of resistance to wave force. On the other hand, shells occurring in sheltered situations, estuaries, narrow straits, or even on open coasts where there is plenty of shelter from the waves, are comparatively of great size, with a well- developed produced spire, and a mouth small in proportion to the area of shell surface." The same author also thinks that in some places (Newquay, Cornwall, for example) the spiral bands of white and 17 256 Shell Life colour agree with the veined rocks to which the Purple clings. In this connection it is interesting to note that Linnaeus must have been struck by the pebble-like appearance often assumed by this species, for he called it lapillus (a little stone or pebble). As in the case of the Periwinkle, already referred to, this stoniness has relation to the hard knocks littoral species experience in stormy weather, when they may be dashed off the rocks and churned up among actual stones. The animal is of the pattern usual among the family, yellowish in colour, more or less tinged with brown. It attacks limpets in much the same manner as that adopted by the Sting- winkle ; but its favourite food is the Mussel, whose shell can be perforated much more rapidly than that of the Limpet. According to Spence Bate, a mussel-shell keeps the enterprising Purple busy for a couple of days, and then it has the reward of its patience in the succulent flesh of the bivalve. But it must not be supposed that the Purple has its own way entirely in this matter of dainty feeding; it has a Nemesis in the form of a Starfish who is also fond of Mussel. The Starfish may be poetically regarded as taking revenge for the Purple's depredations on the mussel-beds. The Star- fish has no means of forcing open the Purple shell as he does with the Oyster, but silently and slowly he creeps to a spot where several Purples are within reach of his long fingers, and laying hold of them with the delicate suckers of his under-side he brings them all beneath his central mouth. Then his stomach is turned inside out and envelops the Purples, which are dissolved out of their shells, in spite of the Whelks and Conelets 257 protecting operculum, by the powerful digestive fluid of the Star. The yellow egg-capsules of the Purple are very common objects on rock-ledges; each one contains from 20 to 40 embryos. M. Cailliaud declared not only that these are hatched by the parent, but that the father and the mother take turns to pro-