MANUAL OF THE MOLLUSCA; OR, RUDIMENTARY TREATISE OF RECENT AND FOSSIL SHELLS. S. P. WOODWARD, P.G.S. M ASSOCIATE OF THE LINNJEAN SOCIETY ; ASSISTANT IN THE DEPARTMENT OF MINERALOGY AND GEOLOGY IN THE BRITISH MUSEUM; AND MEMBER OF THE C.OTTESWOLDE NATURALISTS' CLUB. ILLUSTRATED BY A. N. WATERHOUSE AND JOSEPH WILSON LOWRY. PA.RT II. LONDON. JOHN WEALE, 59, HIGH HOLBOEN. BIO fc- - •' LONDON : 'HINTED BY WILLIAM OSTELL, HART STREET, BLOOMSBURY. EBRATA AND ADDENDA. 7 line 5 for " pterpoda" read " pteropoda." — "13 for " brachiapoda" read " brachiopoda." 11 " 16 for " pector" read " pecten." 15 " 30 for "Mr. Robert" read "Mr. George Roberts;" the statement is undoubtedly correct. 22 " 16 for " slerotic" read " sclerotic." 25 Note. Striped muscular fibre has been observed in Salpa, (Huxley.) 28 line 8 erase the words " when withdrawn." 28 Fig. 16 a, anterior; p, posterior; I, lateral; r, rachidian. 30 line 27 erase " and by four in the brachiopoda." 39 " 22 the " tubular structure" of pinna is probably occasioned by the growth of a confervoid sponge between the laminse. (Quekett.) 46 " 13 erase the word " cyiindrella." 50 " 7 for " brachiopoda" read " opistho-branches." 52 erase lines 20—23, and see p. 245. 54 line 12 see Supplement. 65 M. Verany and H. Miiller have shown that the Hectocotyle is developed in place of the right arm of the third pair of the male cephalopod, and spontaneously detached. See SUPPLE- MENT. 67 line 8 from bottom, for " dorsal" read " ventral." 68 Tremoctopus is a sub-genus of Octopus, not of Philonex-is, 70 line 16 add " Type, Loligo Aalensis, Schubler." 71 " 14 for "Fidenas ? Gray" read (p R. palpebrosa." 79 Note, for " the apocryphal genus spongarium was founded on" read " most of the so-called spongaria are." 89 Sub-genus 6, Diploceras (Salter). The shell is supposed to have resembled Gonioceras, and the external tube to be a simple cavity formed by the approximation of the lateral angles. 94 line 15 (and PL III. fig. 4) for "Rhothomagensis"^?^ "Rotho- magensis, from Rothomagum, Rouen." 1 00 " 6 for " riam" read " rima." 105 " 8 for " Strombidia, Sw." read " Rimella, Ag=" 106 erase line 3. 108 Admete (viridula) is a boreal form of Cancellaria, without plaits. 252013 I Page 108 Cuma (angulifera) and Rapana (p. 109) are Purpurse. 115 Cithara, Schum. belongs to Jam. Conida. 127 line 15 add Syn. Polyphemopsis, Portlock. 128 " 2 for " Triphoris," read " Triforis." — "9 for " eidos, facies" read " ides, patronymic termination.' 129 Fastigiella; Fossil, Eocene. Paris (Cerithium rugosum. Lam.) 131 /or " Paehystoma, Gray" read " Chilostoma, Desh." 132 Remove Aclis to the Pyramidellida. — line 3 from bottom, (and PL IX. fig. 4) for " A. perforata, Mont, MS." read " A. supranitida, Wood." 135 line 4 erase " Nina, Gray." — "6 for " many-whirled" read " few- whirled." 136 (and PI. IX. fig. 24) for " Litiopa bombix" read " L. bombyx." 142 Navicella inhabits freshwaters, adhering to stones and plants. 145 line 30 for " Maclurea, Les." read " Straparollus, D'Orb." 154 line 6 from bottom, for " Pattison" read " R- Patterson,." 155 Metoptoma is a sub-genus of Pileopsis, not Patella. Exp. Plates. PI. V. fig. 5, fcr " California" read " W. Indies." — fig. 7, for " China" read " W. Indies." VII. fig. 15, for " Philippines" read " Tahiti." XII. fig. 13,/or "Australian Ids." read " Tahiti." — fig. 43, for " Sby. Philippines" read " Gray, i Jamaica. Page 165 (rtandina; the Lusitanian Bulimus Algirus belongs to this genus. 168 line 15 insert " devour" before "animal substances." 16 for " Megaloma" read 'c Lomastoma." 3 from bottom, erase " ^Etheria has a large foot." 25 erase " Aucella, Keyserling ;" it is a pearly shell, distinct from Monotis of Minister. NOTICE. IN the long interval since the publication of the first part of this Manual, materials have so accumulated on the writer's hands, that it has been found impracticable to condense them within the space at first contemplated. The illustrations also have been more numerous than was originally expected, and occupy considerably more room. But although a SUPPLEMENT has become inevitable, the publisher has allowed an extra number of pages, in order to render the present part complete in itself. The writer hopes to make the Appendix more valuable by figures and descriptions of the animals of many hitherto un- described Bivalve genera, the materials for which have already been placed at his disposal by Dr. J. E. Gray. The present part owes much to the assistance of Mr. Albany Hancock, of Newcastle; Mr. Thos. Davidson, E.Gr.S., and Mr. T. H. Huxley, F.K.S. CONTENTS. IX PAGE. CLASS II. GASTEROPODA. ORDER II. PULMONIFERA ... 159 SECTION A. INOPERCULATA 159 Fam. I. Helicidce. — Helix, Vitrina, Succinea, Buli- mus, Aehatina, Pupa, Cylindrella, Balea, Tornatel- lina, Paxillus, Clausilia ,... 162 Jam. II. Limacidce. — Limax, Iiicilaria, Arion, Par- macella, TestaceUa .'. 167 Jam. III. Oncidiadce. — Oncidium, Vaginulus 169 Fam. IV. LlmncBidce. — Limrisea, Chilinia, Pliysa, Ancylus, Planorbis 170 Fam. V. Auriculidce. — Auricula, Conovulus, Cary- chium, (Siplionaria) 172 SECTIONS. OPERCULATA f 174 Fam. VI. Cyclostomidce. — Cyclostoma, Ferussina ? Cyclopliorus, Pupina, Helicdna, Stoastoma 175 Jam. VII. Adculida. — Acicula, Geomelania 178 ORDER III. OPISTHO-BRANCHIATA 179 SECTION A. TECTIBRANCHIATA 179 Fam. I. Tornatellidae. — Tornatella, Cinulia, Ringi- cula, Globiconcha, Yarigera, Tylostoma, Ptero- donta? Tornatina ? 179 Fam. II. Bullidce. — Bulla, Accra, Cyliclina, Amphis* phyra, Aplustrum, Scaphander, Bullsea, Doridium, Gastropteron 181 Fam. III. Aplysiada. — Aplysia, Dolabella, N^tar- chus, Icarus, Lobiger 185 Fam. IV. Pleurolranchidtf . — Pleurobranchus, Pos- terobranchaea, Euncina, Umbrella, Tylodina 187 Fam. V. Pliyllidiada— Phyllidia, Dipliyllidia 188 SECTIONS. NUDIBRANCHIATA 188 Fam. VI. Doridce. — Doris, Goniodoris, Triopa, CONTENTS. PAGE s, Thecacera, Polycera, Idalia, Ancula, Cera- tosoma , 190 Fam. VII. Tritoniadae. — Tritonia, Scyllasa, Tethys, Bornella, Dendronotus, Doto, Melibaea, Lomanotus 192 Fam. VIII. JEolida. — JSolis, Glaucus, Fiona, Em- bletonia, Proctonotus, Antiopa, Herrna3a, Alderia... 194 Fam. IX. PhylUrhoidce.— Phyllirhoe 196 Fam. X. Elysiadce. — Elysia, Acteonia, Cenia, Lima- pontia 196 ORDER IV. NUCLEOBRANCHIATA 197 Fam. I. Jirolida. — Firola, Carinaria, Cardiapoda... 199 Fam. II. Atlantida. — Atlanta, Porcellia, Bellero- phon, Cyrtolites, Macl urea 200 CLASS III. PTEROPODA 202 SECTION A. THECOSOMATA 204 Fam. I. HyaleidcB. — Hyalea, Cleodora, Cuvieria, Theca, Pterotheca, Conularia, Eurybia, Cymbulia, Tiedemannia « „ 204 Fam. II. Limacinida. — Lirnacina, Spirialis 207 SECTION B. GYMNOSOMA A 208 Fam. III. Cliida. — Clio, Pneumodermon, Pelagia, Cymodocea 208 CLASS IV. BRACHIOPODA 209 Fam. I. Terebratulidae. — Terebratula, Terebratella, \rgiope, Thecidium, Stringocephalus 215 Fam. II. Spiriferida. — Spirifera, Athyris, Eetzia, Uncites Fam. III. Rhynchonellidtf . — Rhynchonella, Cama- rophoria, Pentamerus, Atrypa 225 Fam. IV. Qrthida. — Orthis, Strophornena, Leptssna, Koniuckia, Davidsonia, Calceola 229 CONTENTS. XI PAGE Fam. V. Productida \ — Producta, Aulosteges, Stro- phalosia, Choneies 233 Fam. VI. Craniadfs. — Crania 235 Fam. VII. Discinidee. — Discina, Siphonotreta 237 VIII. Z/;;y«^.--Lingiila, Obolus 238 S V. CONCHIFEKA . 240 ION A. ASIPHONIDA 253 Fam. I. Ostreida. — Ostrea, Anomia/Placuna, Pectcn, Lima, Spoudylus, Peclum, Plicatula 253 Fam. II, Aviculidtf. — Avicula, Posidonomya, Avi- culo-pecten, Gervillia, Perna, Inoceramus, Pinna ... 260 Fam. III. Mytilida. — ^1 '! \alina, Modiola, Lithodomus, Crenella, Dreisseua 264 Fam. IV. Arcadcc. — Area, Cuculhoa, Pectunculus, Limopsis, Nucula, Isoarca, Leda, Solenella, Solemya 267 Fam. V. Triyoniada. — Trigonia, Myopboria, Axinus, I.yrodesma 271 Fam. VI. Unionida. — Unio, Castalia, Anodon, Iridina, Mycetopus, Liberia, Miilleria... 273 ONE. SIPHONJDA; Integro-pallialia Fam. VII. Chamida. — Cbama, Monopleura, Diceras, llequicnia 276 Fam. VIII. IJlppuritida. — Hippurites, Radiolites, Caprinella, Caprina, Caprotiua .. 279 Fam. IX. Tridacnida. — Tridacna. Hippopus 289 V. Cardiadte. — Cardiuin, Hemicardium, Li- tbocardium, Serripes, Adacna, Conocardium 290 Fam. XI. Lucinidtf. — Lucina, Oryptodon, Corbis, Tancredia, Diplodonta, I'ngulina, Kellia, Monta- outa, Lepton, Galcoinnm 292 Xll CONTENTS. PAGE Fam. XII. Oycladidce. — Cyclas, Cyrenoides, Cyrena 296 Fam. XIII. Cyprinidce. — Cyprina, Circe, Astarte, Crassatella, Isocardia, Cypricardia, Pleui'ophorus, Cardilia, Megalodon, Pachydomus, Pachyrisma, Opis, Cardinia, Myoconcha, Hippopodium, Car- • dita, Venericardia, Yerticordia . . 298 SECTION C. SIPHONIDA; sinu-pallialia 304 Fam. XIV. Yeneridce. — Yenus, Cytherea, Meroe, Trigona, Grateloupia, Artemis, Lucinopsis, Tapes, Yenerupis, Petricola, Glaucomya 304 Fam. XF. Mactridce. — Mactra, Gnathodon, Lu- traria, Anatinella 308 Fam. XFI. Tellinidce.—Teftma, Diodonta, Capsula, Psammobia, Sanguinolaria, Semele, Syndosmya, Scrobicularia, Mesodesma, Ervilia, Donax, Galatea 309 Fam. XFII. Solenida. — Solen, Cultellus, Cerati- solen, Machaera, Solecurtus, Novaculina 314 Fam. XVIII. MyacidcB. — Mya, Corbula, Sphenia, Neaera, Thetis. Panopsea, Saxicava, Glycimeris 317 Fam. XIX. Anatinida. — Anatiria, Cochlodesma, Thracia, Pholadomya, Myacites, Goniomya, Ce- romya, Cardiomorpha, Edmondia, Lyonsia, Pan- dora, Myadora, Myocliama, Chamostrea 320 Fam. XX. GastrocJianidce. — Gastrochsena, Chsena, Clavagella, Aspergillum 325 Fam. XXI. Pholadidce. — Pholas, Pholadidea, Jouan- netia, Xylophaga, Teredo, Teredina 327 MANUAL OF THE MOLLUSCA. PART II. CLASS II. GASTEROPODA.— ORDER II. PULMONIFERA. THIS order embraces all the land-snails and other mollusca which breathe air. They are normal gasteropods, having a broad foot, and usually a large spiral. shell; their breathing-organ is the simplest form of lung, and is like the branchial chamber of the sea-snails, but lined with a network of respiratory vessels. One large division of the land-snails is furnished with an operculated shell ; the rest are in-operculate, and sometimes shell-less. The pulmonifera are closely related to the plant-eating sea-snails (holo- stomata), through Cyclostoma, and to the nudibranches by Oncidium. As a group, they are generally inferior to the sea-snails, on account of the com- parative imperfection of their senses, and the union of the functions of both sexes in each individual. SECTION A. IN-OPERCULATA. The typical pulmonifera vary much in appearance and habits, but agree essentially in structure. Most of them have sufficiently large shells ; in the slugs, however, the shell is small and concealed, or rarely quite wanting. Snail-shells contain a larger proportion of animal matter than sea-shells, and their structure is less distinctly stratified (p. 40). In form, these shells repre- sent many marine genera. The greater part are terrestrial, only some of the smaller families inhabit fresh-waters, or damp places near the sea. The res- piratory orifice is small and valve-like,* to prevent too rapid desiccation in the land-snails, and to guard against the entry of water in the aquatic tribes. Land-snails are universally distributed ; but the necessity for moist air, and the vegetable nature of their food, favour their multiplication in warm and humid regions ; they are especially abundant in islands, whilst in hot and desert countries they appear only in the season of rain or dews. Their geological history is less complete than that of the purely marine orders j but * Hence they are called Adelo-pnenmona (concealed-lunged) by Gray. I 160 ."•*.;:•': /;M4"Nt/Ai. CCF.\XHE MOLLUSC A. their antiquity might be inferred from the distribution of peculiar genera in remote islands, associated with the living representatives of the ancient fauna of Europe. Fresh-water snails (Limnaidte) occur in the English Weald, but fossil land-snails have not been found in strata older than the Tertiary in Europe, and then under forms generically, and even in one in- stance specifically, identical with living types of the new world (Megaspira, Proserpina, Glandina, and Helix labyrinthica). In the coal-strata of Nova Scotia, Sir Chas. Lyell has discovered a single specimen of a reversed and striated shell, apparently a Clausilia. The lingual dentition of the pulmonifera confirms, in a remarkable manner, those views, respecting the affinities of the order, and its zoological value, which have been deduced from the more obvious characters afforded by the animal and shell. The operculated land-snails have seven-ranked teeth, like Paludina and Litorina. The in-operculated air-breathers have, without known exception, rows of very numerous, similar teeth, with broad bases, resembling tessellated pavement. Their crowns are recurved, and either aculeate or dentated. The lingual ribbon is very broad, often nearly as wide as it is long ; and the number of teeth in a row (though usually a third less) is sometimes as great, or even greater, than the number of rows. The rows of teeth are straight or curved or angulated ; when the rows are straight the teeth are similar in shape ; curves indicate gradual changes, and angles ac- company sudden alterations of form. S^5g5|535 M5is!si!-!-i«!«!«!i»!-!«ial«! -f ---:• ' - ' -• ti>f!5b£!i! iy,jhjlyKJ!y|v|j|w|v)vj|~'~'~ J^i^lvWSL-l"^^1-'"^''-'"^ 2 c I Fig. 90. Lingual teeth of Achatina.* The absolute number of teeth is only a specific character, and is usually greatest in the larger species ; but the Helicella have fewer teeth in propor- tion than the Helices, and Velletia has fewer than Ancylus. The anomalous genus Amphibola (p. 139) has an unusually broad tongue, armed with teeth similar to those of the snail. Fig, 91. Lingual teeth of Amphibola.^ About one-third the lingual membrane is spread over the tongue ; the rest ha£ its margins rolled together, and is lodged in a sac or dental canal, which * Fragment of the lingual membrane of Achatina fulica, with central and lateral teeth more enlarged, from a specimen communicated by J. W. Laidlay, Esq. t Part of the tongue of Amphibola avellana, from a preparation by J. W. Wilton, Esq., of Gloucester. GASTEROPODA. 161 diverges downwards from the posterior part of the mouth, and terminates outside the buccal mass of muscles.* The mode in which the tongue is used, may be seen by placing a Limn&a or Planorbis in a glass of water, inside which the green conferva has begun to grow ; they will be observed incessantly cleaning off this film. The upper lip with its mandible is raised, the lower lip — which is horse- shoe shaped — expands, the tongue is protruded and applied to the surface for an instant, and then withdrawn ; its teeth glitter like glass-paper, and in Limnaa it is so flexible, that frequently it will catch against projecting points, and be drawn out of shape slightly as it vibrates over the surface. " The development of the (in-operculate) Pulmonifera has been worked out by Van Beneden and Windischmann,f by Oscar Schmidt,! and by Gegen- ur^ the memoir, by the last named author, contains fall information respecting Limax and Clausilia, and some important notices with regard to Helix. " The yelk undergoes complete division. The first stage of development consists in the separation of the embryo into mantle and foot. The anterior part of the body, in front of the mantle, dilates and forms a contractile sac — the homologue of the velum of marine gasteropoda — which in Doris , Poly- cera, and JEolis, has been seen to exhibit similar contractions. (Gegen- baur.} To this contractile vesicle the name of Yelk-sac was given by Van Beneden and Windischmann, but it is a very different organ from the true Yelk-sac, which exists in the Cephalopoda alone among molluscs. " A similar contractile dilatation exists at the end of the foot — and the contractions of this ' caudal' vesicle and of the ' vitellary' vesicle alternate, so as to produce a kind of circulation before the development of the heart. " The oral tentacles and parts about the mouth are the last to be com- pleted. " A peculiar gland exists during the embryonic period, attached to the parietes of the ' vitellary' vesicle, which Gegenbaur and Schmidt compare to a Wolffian body. " Gegenbaur draws attention to the fact, that the first rudiment of the shell in Limax, Clausilia and probably Helix, is not secreted on the exterior of the mantle, as in other gasteropoda ; but is deposited, in the form o calcarious granules, within its substance. " Besides, therefore, the possession of Wolffian bodies, and of especial contractile organs, which subserve respiration and circulation during em- bryonic life— the terrestrial, gasteropoda are further distinguished by the * Thomson, An. Nat. Hist. Feb. 1851. f Recherches sur I'embryogeme des Limaces. Miiller's Archiv. 1841. t Ueber die Entwickelung von Limax agrestis Miiller's Archiv, 1851. § Beitrage zur Entwickelungs geschichte der Land-gasteropoden. Siebold and Kblliker'* Zeitschrift, 1852. I 2 162 MANUAL OF THE MOLLUSCA. peculiar mode of development of their shells— if the observations upon Clau- silia and Helix may be extended to the rest. The first development of the shell within the substance of the mantle (a relation found hitherto only in the Cephalopoda) is up to the present time a solitary fact, without parallel among the other gasteropodous families." (Huxley.) FAMILY I. HELICULE.* Land-snails. Shell external, usually well developed, and capable of containing the entire animal ; aperture closed by an epiphragm during hybernation.f Animal, with a short retractile head, with four cylindrical, retractile ten- tacles, the upper pair longest and bearing eye-specks at their summits. Body spiral, distinct from the foot ; respiratory orifice on the right side, beneath the margin of the shell ; reproductive orifice near the base of the right ocular tentacle ; mouth armed with a horny, dentated, crescent-shaped upper man- dible ; lingual membrane oblong, central teeth in- conspicuous, laterals numer- ous, similar. (See Intr. p. 17.) HELIX, L. \ Type, H. pomatia, L. Roman snail. Etym. Helix, a coil. Shell umbilicated, perforated or imperforate; discoidal, globosely-de- pressed or conoidal ; aperture transverse, oblique, lunar or roundish ; margins distinct, remote or united by callus. Animal with a long foot, pointed behind; lingual teeth usually in straight rows, edge-teeth dentated. Distr. including the sub-genera, above 1,200 sp. (several hundred sp. are undescribed). World- wide ; ranging northward as far as the limit of trees, and southward to Tierra-del-fuego, but most abundant by far in warm and humid climates. M. D'Orbigny observed 6 sp. at elevations exceeding 11,000 feet, in S. America, and Layard found H. gardeneri at the height of 8,000 feet in Ceylon. The species of tropical and southern islands are mostly peculiar. Several of the smaller British species, and even the large garden- snail (H. aspersa\ have been naturalised in the most remote colonies. The Neapolitans and Brazilians eat snails. Fossil (extinct) sp. about 50. Eocene — . Europe. Sections; Acavus, Montf. Shell imperforate. H. ha3mastoma, PL XII. fig.L Geotrochus (lonchostoma) Hasselt, Trochiform, flat beneath. Polygyra, Say. Depressed, many- whirled. H. polygyrata, PI. XII. fig. 2. * The account of this family is chiefly taken from Dr. L. Pfeiffer's Monographia Jfeliceorum. t The epiphragm is a layer of hardened mucus, sometimes strengthened with car- bonate of lime ; it is always minutely perforated opposite the respiratory orifice. J The synonomy of the genus would fill several pages. See Intr. 1, p. 59. GASTEROPODA. 163 Tridopsis, Raf. Aperture contracted by tooth -like projections. H. hir- suta, PI. XII. fig. 5. Carocolla, Lam. Peristome continuous. H. lapicida, PI. XII. fig. 3. Sub-genera. Anastoma, Fischer. (Tomigerus, Spix.) H. globulosa PI. XII. fig. 4. Aperture of adult turned upwards, ringent; 4 sp. Brazil. Hypostoma (Boysii) Albers, is a minute Indian snail, in which the aperture is similarly distorted. Lychnus (Matheroni, Req.) has a similar shell, but no apertural teeth ; 3 sp. occur in the Eocene Tertiary of the S. France. Streptaxis, Gray. H. contusa, PI. XII. fig. 6. Sub-globose, lower whirls receding from the axis of the upper ; 24 sp. Brazil, W. Africa, Mas- carene Ids. S. Asia. Sag da, Beck. H. epistylium, PI. XII. fig. 7. Imperf orate, globosely conoid, close- whirled, aperture lamellate within, lip sharp ; 3 sp. Jamaica. Proserpina (nitida) Guilding. Shell depressed, shining, callous beneath ; aperture toothed inside; peristome sharp. Distr. 6 sp. Jamaica, Cuba, .Mexico. Fossil, Eocene — . I. Wight (F. Edwards). Helicella, Lam.* Type, H. cellaria, PL XII. fig. 8. Shell thin, de- pressed ; peristome sharp, not reflected. Lingual edge-teeth aculeate. 90 sp. Stenopus (cruentatus) Guild. Syn. Nanina (citrina) Gray ; Ariophanta (laevipes, PI. XII. fig. 9) Desm. Shell thin, polished; peristome thin, not reflected. Animal with the tail truncated and glandular, like Arion ; mantle- margin produced, partly covering the shell. Distr. 70 sp. S. Asia and Ids, N. Zealand, Pacific Ids. W. Indies. VITRINA, Draparnaud, Glass-snail. Type, V. Draparnaldi, PI. XII. fig. 28. Syn. Helicolimax, Per. Shell imperforate, very thin, depressed ; spire short, last whirl large ; aperture large, lunate or rounded, columellar margin slightly inflected, peris* tome often membranous. Animal elongated, too large for complete retraction into the shell ; tail very short; mantle reflected over the shell-margin, and furnished with a posterior lobe on the right side. Lingual teeth (of type) 100 rows of 75 each; marginal teeth with a single, long, recurved apex (Thomson}. Occa- sionally animal-feeders, like the slugs. V. Cuvieri and Freycineti (Helicarion Per.) tail longer, more abruptly truncated, with a caudal gland like anon, mantle more developed. Distr. 64 sp. Old World, 58; Greenland, 1; Brazil, 5. Sub-genera. Daudebardia, Hartm. (Helicophanta, Per.) V. brevipes, PL XII. fig. 29. Shell perforated, horizontally involute ; aperture oblique, ample ; 3 sp. Central Europe. Simpulopsis (sulculosa) Beck ; shell succinea-shaped. 5 sp. Brazil. * For this group Mr. Gray formerly employed the name Zonites, given originally by Montfort to Helix Algira; in his later works be adopts Helicella. 164 MANUAL OF THE MOLLUSC A. SUCCINEA, Draparnaud. Amber- snail. Type, S. putris, PI. XII. fig. 23. Syn. Cochlohydra, Per. Helisiga (S. Helenae) Less. Amphibulima (patula) Beck ; Pelta (Cumingii) Beck. Shell imperforate, thin, ovate or oblong; spire small; aperture large, obliquely oval ; columella and peristome simple, acute. Animal large, tentacles short and thick, foot broad ; lingual teeth like helix ; S. putris has 50 rows, of 65 teeth each (Thomson}. Inhabits damp places, but rarely enters the water. Listr. 68 sp. Europe 5, Africa 3, India ], Australia 1 ; Pacific Ids. 17, N. America 14, S. America 11, W. Indies 11. Fossil. Eocene, Brit. Sub-genus. Omalomjx, D'Orb. 0. unguis. PI. XII. fig. 24. Shell oval, convex, translucent, spire nearly obsolete, margins sharp. Animal large, slug-like ; shell placed on the middle of the back, with the mantle slightly reflected upon it all round. Dist. 2 sp. Bolivia ; Juan Fernandez. BULIMUS, Scopoli. Etym. ? Boulimos, extreme hunger (in allusion to its voracity !) Syn. Bulinus, Brod. (not Adans). Type. B. oblongus. PL XII. fig. 10. Shell oblong or turreted ; aperture with the longitudinal margins unequal, toothless or dentate ; columella entire, revolute externally or nearly simple ; peristome simple or expanded. Animal like Helix. B. ovatus attains a length of 6 inches, and is sold in the market of Rio ; it oviposits amongst dead leaves, the eggs have a brittle shell, and the young when hatched are an inch long. (See p. 54, fig. 31.) Sections. Odontoslomus (gargantuus) Beck, aperture toothed, 13 sp. Brazil. Pachyotis, Beck (Caprella, Guild.) fig. 91.* Partula, Fe'r. P. faba. PI. XII. fig. 13, Tahiti. 26 sp. Asiatic, Australian and Pacific Ids. 24 ; S. America 2. The animal is ovo- viviparous. Gibbus (Lt/onnetianus)^I.outL Shell hump- backed ; Mauritius, 2 sp. Bulimulus, Leacli. B. decollatus. PI. XII. figs. 11, 12. Shell small, lip acute. Above 300 sp. England 3 sp. Zua, Leach. Z. lubrica. PI. XII. fig. 14. Shell polished, columella slightly truncated. Azeca, Leach. A. tridens. PL XII. fig. 15. Shell polished, peristome thickened and toothed. Fig. 91* B. auris-vulpina. '* Fig. 91. Bullmus auris-vulpina, Chemn. The great extinct land-snail of St. GASTEROPODA. 165 Distr. 650 sp. Europe 30, Asia 130, Australia and Pacific Ids. 46, Africa 50, S. States 3, Tropical and S. American 330. Fossil. 30 sp. Eocene — . Europe, S. Helena, Australia, W. Indies. B. Guadalupensis occurs in modern limestone, with human remains. ACHATINA, Lamarck. Agate-shell. Type, A. variegata, PI. XII. fig. 22. Syn. Cochlitoma, Fer. Columna, Perry. Subulina (octona) Beck. Li- guus (virgineus) Montf. Cionella (acicula) Jeffr. Shell imperforate, bulimiform ; columella twisted, and truncated in front ; aperture oval, angular above ; peristome simple, acute. Animal snail-like. The great African Achatinae are the largest of all land-snails, attaining a length of 8 inches ; their eggs exceed an inch in length, and have a calcarious shell. Distr. 120 sp. Europe 9, Africa 38, Asia 8, tropical America 29. Fossil. 14 sp. Eocene — . Europe ; St. Helena. Sub-genera. Glaridina (voluta) Scham. (Oleacina, Bolten; Polyphe- mus, Montf.) Shell oblong, fusiform ; aperture narrow, elliptical. Animal twice as long as the shell ; eye tentacles deflected at the tips, beyond the eyes; vibracula much shorter, also deflected ; lips elongated, tentacular. Frequents low and moist situations ; in confinement one refused vegetable food, but at another snail. (Say.) 40 sp. W. Indies, Central America, Mexico, Florida. Fossil. Eocene — . Glandina costellata. I. Wight. (F. Edwards) Achatinella (vulpina) Sw. (Helicteres, Fer.) Columella twisted into a strong, tooth-like fold. Sandwich Ids. 25, Mariannes 2, Ceylon 1. PUPA, Lamarck. Chrysalis-shell. Type, P. uva. PL XII. fig. 16. Syn. Torquilla (juniperi) Studer. Shell rimate or perforate, cylindrical or oblong; aperture rounded, often toothed ;* margins distant, mostly united by a callous lamina. Animal with a short foot, pointed behind ; lower tentacles short. Distr. 160 sp. Greenland 1, Europe 76, Africa 23, India 12, Pacific Ids. 2, N. America 30, S. America 5. Fossil. 40 sp. Eocene — . Europe. Sub-genus. Vertigo, Mull. V. Venetzii. PI. XII. fig. 1?. Shell mi- nute, sometimes sinistral. Animal with the oral tentacles rudimentary or obsolete. 12 sp. Old World. CYLINDRELLA, L. Pfeiffer. Cylinder-snail. Type, C. cylindrus. PL XII. fig. 20.f Helena ; from a specimen presented by Chas. Darwin, Esq. See " Journal of a Voyage round the World." * Dr. Pfeiffer terms those teeth parietal which are situated on the body-whirl those on the outer lip palatal, and on the inner lip columellar. t The figure is taken from a sp. in Mr. Cuming's cabinet, in which the empty apex, usually decollated, remains attached to the adult shell. 166 MANUAL OF THE MOLLUSCA. Syn. Brachypus, Guild. Siphonostoma, Sw. Shell cylindrical or pupiform, sometimes sinistral, many- whirled, apex of the adult truncated, aperture round, peristome continuous, expanded. Animal similar to clausilia ; foot short, oral tentacles minute. Distr. 50 sp. W. Indies 35, Mexico 5, Texas 2, S. America 1. BALE A, Prideaux. Type, B. perversa. PL XII. fig. 21. Syn. Fusulus, Fitz. Shell slender, usually sinistral, fusiform, multispiral, aperture ovate ; pe- ristome acute, margins unequal, wall of the aperture with one slight plait ; columella simple. Animal snail-like ; teeth 20.20; rows 130 (Thomson). Distr. 8 sp. Norway, Hungary, New Granada, Tristan d'Acunha. The British sp. is found, very rarely, in Porto Santo, only on the highest peak, at an elevation of 1,665 feet. (Wollaston.) Sub-genus. Megaspira (elatior) Lea. PI. XII. fig. 18. Shell dextral, with the columella transversely plaited. Distr. 1 sp. Brazil. Fossil, 1 sp. Eocene — , Rheims. TOENATELLINA, Beck. Etym. Diminutive (or patronymic termination) of tornatella. Type, T. bilamellata, Ant. Syn. Strobilus, Anton. Elasmatina, Petit. Shell imperforate, ovate or elongated ; aperture semi-lunar, margins un- equal, disunited ; columella twisted, truncated ; inner lip 1 -plaited. Distr. 11 sp. Cuba 1, S. America 2, Juan Fernandez 2, Pacific Ids. 5, N. Zealand 1. PAXILLUS, A. Adams. . Type, P. adversus, Ad. Borneo. Shell small, pupiform, sinistral, rimate; spire pointed; aperture semi- ovate, ascending on the body- whirl; inner lip spreading, 1 -plaited, outer lip expanded, notched in front. CLAUSILIA, Draparnaud. Etym. Dimin. of clausum a closed place. Syn. Cochlodina, Fer. Eat. C. plicatula, Drap. (=C. Rolphii, Leach). PI. XII. fig. 19. Shell fusiform, sinistral; aperture elliptical or pyriform, contracted by lamellae, and closed when adult by a moveable shelly plate (clausium) in the neck. Animal with a short, obtuse foot; upper tentacles short, lower very small. C. bidens has 320 rows of 50 teeth; C. nigricans 90 rows of 40 teeth each. Distr. Above 200 sp. Europe 146, Asia 48, Africa 4, S. America 3. Fossil, 20 sp. Eocene — . Brit. France. Coal-strata, N. Scotia. (Lyell.) C. maxima, Grat. Miocene, Dax is two inches in length. GASTEROPODA. 16? FAMILY II. LIMACID^. Slugs. Shell small or rudimentary, usually internal, or partly concealed by the mantle, and placed over the respiratory cavity. Animal elongated ; body not distinct from the foot ; head and tentacles retractile ; tentacles 4, cylindrical, the upper pair supporting eyes ; mantle small, shieldshaped ; respiratory and excretory orifices on the right side. Fig. 92. Limax Sowerbii F6r. Brit. LlMAX, L. Slug. Type, L. maximus. PI. XII. fig. 25. (L. cinereus, Mull.) Shell internal, oblong, flat, or slightly concave beneath, nucleus* posterior ; margin membranous ; epidermis distinct. Animal, foot pointed and keeled behind; mantle shieldshaped, on the front of the back, granulated or marked with concentric striae ; respiratory orifice on the right side, near the posterior margin of the mantle ; repro- ductive orifice near the base of the right ocular tentacle; lingual teeth tricuspid, those near the margin simple, aculeate. The slugs are connected with the snails by Vitrina ; their teeth are similar, but have more elongated cusps. The creeping-disk, or sole of the foot, extends the whole length of the animal ; but they frequently lift up their heads, like the snails, and move their tentacles in search of objects above them. They often climb trees, and some can lower themselves to the ground by a mucous thread. When alarmed they withdraw their heads beneath the mantle, as in fig, 92. Slugs feed chiefly on decaying vegetable and animal substances ; they oviposit at any time of the spring and summer when the weather is moist, and bury themselves in drought and frost. Limax nocti- lucus, Per. (Phosphorax, Webb.) found in Teneriffe, has a luminous pore in the posterior border of the mantle. Distr. 22 sp. Europe, Canaries, Sandwich Ids. Fossil. Eocene — . Brit. The Ancylus ? latus, Edw. of the I. Wight appears to be a Limax. Sub-genus. Geomalacus (maculosus] Allman. Ireland. Shell ungui- form. Animal with a mucus gland at the extremity of the tail ; respiratory orifice near the right anterior border of the mantle. INCILARIA, Benson. e, I. bilineata, Cantor, Chusan. Syn. ? Meghimatium, Hasselt. I 3 168 MANUAL OF THE MOLLUSCA. Animal elongated, tapering behind, entirely covered by a mantle ; tenta- cles 4, the upper bearing eyes, the lower entire ; respiratory orifice on the right side, near the front of the mantle. Lon. 1| inches. Philomycus (Raf.) Fer. = Tebennophorus, Binney, 1842, Bost. Soc. Jottrn. (Helix Carolinensis, Bosc) is also a slug^with a long mantle. AKION, Ferussac. Land-sole. Type, A. empiricorum, Fer. Syn. Limacella, Brard. Shell oval, concave; or represented by numerous irregular calcarious gra- nules. Animal, slug-like ; respiratory orifice on the right side, towards the front of the mantle ; reproductive orifice immediately below it ; tail rounded, slightly truncated, terminated by a mucus-gland. Lingual teeth, as in Umax; A. empiricorum has 160 rows of 101 teeth each. The land-soles occasionally , animal substances, such as dead worms, or injured individuals of their own species. They lay 70-100 eggs, between May and September, are 26-40 days hatching, and attain their full growth in a year; they begin to oviposit a month of two before that period. The eggs of A. hortensis are very phos- phorescent for the first 15 days. (Bouchard.) Distr. 6 sp. Europe. Norway, Brit. Spain, S. Africa. Fossil. Newer Pliocene, Maidstone. (Morris.) Plectrophorus (corninus, Bosc) Fer. 3 sp. Teneriffe ; represented as having a small conical shell on the tail ; probably an erroneous observation. PARMACELLA, Cuvier. Type, P. Olivieri, Cuv. Etym. parma, a small shield. Syn. ? Peltella (Americana), Van Beneden. Shell concealed, oblong, nearly flat, apex sub-spiral. Animal vitrina-like, with an ample foot, pointed behind, and furnished with a mucus-pore ; mantle small, shield-like, in the middle of the back, partly or entirely concealing the shell. P. calyculata, Sby. (Cryptella, Webbf) PL 12, fig. 27, is patelliform, with an exposed papillary spire. Distr. 7 sp. S. Europe; Canary Ids. N. India. Fig. 93. Testacella haliotoides, Fer. * TESTACELLA, Cuvier. Shell small, ear-shaped, situated on the posterior extremity of the body. Animal, slug-like, elongated and tapering towards the head ; back with * Back view of a half-grown individual ; side-view of shell on the tail, and front view of the head. From specimens communicated by Arthur Mackie, ESQ., of Norwich. GASTEROPODA. 169 2 principal lateral furrows, from which numerous vein-like grooves ramify ; mantle not larger than the shell ; respiratory orifice on the right side, beneath sub-spiral apex of the shell ; reproductive orifice behind the right tentacle. The Testacella is subterranean in its habits, feeding on earth-worms, and visiting the surface only at night. Its lingual membrane is very large and wide, with about 50 rows of 20.20 teeth, which diminish rapidly in size to- wards the centre ; each tooth is slender, barbed at the point, and slightly thickened at the base, and furnished with a projection on the middle of the posterior side. Fig. 94.* Distr. 3 sp. S. Europe ; Canary Ids. Brit, (introduced.) FAMILY III. ONCIDIAD^E. Animal, slug-like, destitute of any shell, completely covered by a coriace- ous mantle ; tentacles cylindrical, retractile, with eyes at their extremities ; foot much narrower than the mantle. ONCIDIUM, Buchanan. Type, 0. Typhse, Buch. Etym. Diminutive of Onkos, a tubercle. Animal oblong, convex, usually tuberculated ; head with 2 retractile ten- tacles, bearing the eyes ; mouth covered by a notched veil ; no horny jaws ; tongue broad, with above 70 rows of lingual teeth (in 0. celticum}, teeth 54.1.54 ;f the central teeth minute, triangular, with a single obtuse spine ; laterals, slightly curved ; heart opistho-branchiate ; respiratory orifice poste- rior, distinct from the vent ; sexes combined, $ organ under the right ten- tacle, $ at the posterior extremity of the body. Distr. 16 sp. Brit. Medit. Red Sea, Mauritius, Australia, Pacific. The typical Onddia live on aquatic plants, in the marshes of the warmer parts ot the old world. Those which frequent sea-shores have been separated under the name Peronia, Bl. (Onchis, Fer). One species (0. celticum) is found * Part of the lingual membrane of T. halio tides, from a preparation by Fisher Cocken, Esq. , of Botesdale. The dentition resembles that of lanthina. t This is a convenient mode of stating the number of lingual teeth in each row; it means that there is a single (symmetrical) tooth in the centre, and 54 lateral (un- - symmetrical) teeth on each side. If the number of rows of teeth on the dental mem- brane is known, it may be added below, thus — Peronia Mauritiana, -- 170 MANUAL OF THE MOLLUSCA. on the coast of Cornwall, congregated in little groups, about a foot or two from the surface of the sea, where the waves break over them. They ascend and descend, so as to maintain their distance as the tides rise and fall ; but will not bear long immersion in sea-water. (Couch.) ? Buchanania (oncidioides) Lesson. Named after Dr. F. Hamilton (Buchanan), the Zoologist of India. Animal oval, entirely covered by a simple mantle ; respiratory orifice in the centre of the back ; head with 4 ten- tacles, retractile beneath the mantle; foot oval, much smaller than the mantle; length 3^ inches. Coast of Chile. (Requires confirmation.) VAGINULUS, Ferussac. Type, V. Taunaisii, Fer. Syn. Veronicella, Bl. Animal elongated, slug-like, entirely covered by thick coriaceous mantle, smooth or granulated; head retractile under mantle; tentacles 4, upper pair slender, cylindrical, inflated at the tips and bearing eyes, lower pair short, bifid ; foot linear, pointed behind ; sexes united ; $ orifice behind the right tentacle, ? midway on the right side, beneath the mantle : respiratory and excretory orifices at posterior extremity, between mantle and foot. In- habits forests, in decayed wood and under leaves. Distr. 6 sp. W. Indies, S. America, India, Philippines. FAMILY IV. LIMN^ID^:. Shell thin, horn-coloured ; capable of containing the whole animal when retracted ; aperture simple, lip sharp ; apex sometimes eroded. Animal with a short dilated muzzle ; tentacles 2, eyes sessile at their inner bases; mouth armed with an upper mandible, tongue with teeth similar to Helix. The Limnseids inhabit fresh-waters, in all parts of the world ; they feed chiefly on decaying leaves, and deposit their spawn in the form of oblong transparent masses, on aquatic plants and stones. They frequently glide be- neath the surface of the water, shell downwards, and hybernate or restivate in the mud. Fig. 95. Lamarck. Pond-snail. Etym. Limnaios, marshy. Type, L. stagnalis, fig. 95. PI. XII. fig. 30. * Adjectives employed as names for shells should have the feminine termination. GASTEROPODA. 171 Shell spiral, more or less elongated, thin, translucent ; body-whirl large, aperture rounded in front ; columella obliquely twisted. Animal with a short, broad head; tentacles triangular, compressed; lin- gual teeth (L. stagnates] 55.1.55, about 110 rows, central teeth minute, laterals bicuspid, the inner cusp largest. L. peregra feeds on the green fresh- water algae; L. stacjnalis prefers animal substances. Dislr. 50 sp. Europe, Madeira, India, China, N. America. Fossil, 70 sp, Wealden — . Brit. France. Sub-genus, Amphipeplea, Nilsson. A. glutinosa, PI XII. fig. 31. Shell globular, hyaline. Animal with a lobed mantle, capable of expansion over the shell. Europe ; Philippines. Fig. 96. CHILINIA, Gray. Chilian-snail. Ex. C. pulchra, D'Orb. fig. 96. Syn. Dombeya, D'Orb. Shell oval, thin, ornamented with dark spots or wavy bands ; columella thickened, with 1 or 2 strong prominent folds. Distr. 14 sp. S. America ; in clear running streams. Fossil, 1 sp. Miocene, Rio Negro, Patagonia (D'Orb.) PHTSA, Draparnaud. Type, P. fontinalis, PI. XII. fig. 32. Etym* Physa, a pouch. Syn. Bulin, Adans. Eivicola, Fitz. Isidora, Ehr. Shell ovate, sinistrally spiral, thin, polished ; aperture rounded in front. Animal with long slender tentacles; the eyes at their bases; mantle margin expanded and fringed with long filaments. P. hypnomm (Aplexa, Fleming) has an elongated spire, and the mantle margin is plain. Physopsis, Krauss, S. Africa, has the base of the colu- mella truncated. Camptoceras (terebra), Benson, India, has the whirls dis- united, and the peristome continuous. Distr. 20 sp. N. America, Europe, S. Africa, India, Philippines. Fossil, 14 sp. Wealden — . Brit. France. The largest living sp. (P. Maugeree, California) is 15 lines in length. A fossil sp. found at Grignon measures 26 lines, and another equally large occurs in India. ANCYLUS, Geoffroy. River-limpet. Etym. Ancylus (agkulos) a small round shield. 172 MANUAL OF THE MOLLUSCA. Type, A. fiuviatilis, Mull. PI. XII. fig. 33 (Patella lacustris, L.) Shell conical, limpet-shaped, thin ; apex posterior, sinistral ; interior with a sub-spiral muscular scar. Animal like Limnsea ; tentacles triangular, with eyes at their bases ; lin- gual teeth 37.1.37, in 120 rows, centrals small, laterals with long recurved hooks. Distr. 14 sp. N. and S. America, Europe, Madeira. On stones and aquatic plants in running streams. Fossil, 8 sp. Eocene, Belgium. Sub-genera, Velletia (oblonga, Lightf.) Gray. (Acroloxus, Beck) Shell and animal dextral; lingual teeth 40, in 75 rows. 3 sp. West Indies, Europe. Fossil, 2 sp. Eocene. Brit. France. Latia (neritoides) Gray; shell limpet-like, interior with a transverse plate, turned up and notched on one side. N. Zealand. PLANORBIS, Miiller. Syn. " Coret," Adans. Type, P. corneus, PL XII. fig. 34. Shell discoidal, dextral, many- whirled ; aperture crescentic, peristome thin, incomplete, upper margin projecting. Animal with, a short, round foot ; head short, tentacles slender, the eyes at their inner bases ; lingual teeth sub-quadrate, central and marginal bi- cuspid, laterals tricuspid ; excretory orifices on left side of the neck. Some species of Planorbis have the sutures and spire deeply sunk, and the umbilicus flattened ; specimens occur with the spire elevated (fig. 97*). P. contortus, a minute species, has above 6,000 teeth, (Cocken}. P. corneus secretes a purple fluid j (Lister). P. lacustris (Segmentina, Fleming) has the whirls contracted, internally, by periodic septa, 3 in a whirl, with tri- radiate openings. Distr. 60 sp. N. America, Europe, India, China. Fossil, 60 sp. Wealder — . Brit. France. FAMILY V. AURICULID^E. Shell spiral, covered with horny epidermis, spire short, body-whirl large ; aperture elongated, denticulated ; internal septum progressively absorbed. Animal with a broad and short muzzle, tentacles 2, cylindrical, the eyes sessile behind them; mantle-margin thickened; orifices as in the snails; foot oblong ; sexes united ; mouth with a horny upper jaw ; lingual teeth numer- ous, central series distinct, hooked, tricuspid. A. livida has about 31 laterals (Loven) ; another species examined by Mr. Wilton has 11 large laterals and about 100 smaller (uncini) on each side, gradually diminishing towards the edge, fig. 98, c. central teeth, /. laterals. * P. marginatus, var. Rochdale, communicated by J. S. Gaskoin, Esq. GASTEROPODA. 173 Fig. 98 The Auricula frequent salt-marshes, damp hollows, and places overflowed by the sea ; they were long regarded as marine animals, and their shells con- fused with those of Tornatella and Ringicula. AURICULA, Lamarck. Type. A. Judsc. PI. XII. fig. 35. Etym. Auricula, a little ear. Syn. Cassidula, Per (not Lam.) Marinula (pepita) King. Geovula, Sw. Shell oblong, with thick, dark epidermis ; spire obtuse ; aperture long, narrow, rounded in front, with 2 or 3 strong folds on the inner lip ; outer lip expanded and thickened. Distr. 50sp. Philippines, Celebes, Peejees, Australia, Peru. Fossil, 20 sp. ? Neocomian — . Prance. Fig. 99. A. auris-felis. (From Eyd. and Soul). A. JudcB has truncated tentacles ; the typical species are met with in the brackish-water swamps of tropical islands, on the roots of mangroves, and by small streams within the influence of the tide. One species has been observed by Mr. Adams in nearly 2 fathoms water. Sub-genera, Polydonta, Pischer, P. scarabceus, PI. XII. fig. 36. (Sca- rabus imbrium, Montf.) Shell oval, compressed; spire pointed many- whirled, with lateral varices ; aperture toothed on both sides. Distr. 20 sp. India, Borneo, Celebes, Pacific Ids. Inhabits moist spots in woods near the sea, and is wholly terrestrial, feeding on decayed vegetables. (Adams.) Pedipes (afra) Adans. Shell ovate, spirally striated, aperture denticu- lated on both sides ; the animal loops in walking, like truncatella. Distr. W. Indies, Africa, Philippines, Pacific Ids. Under stones on the sea-shore. Fossil, 5 sp. Eocene — . Brit. Prance. CONOVULUS, Lamarck. Type, C. coniformis, Brug. PL XII. fig. 37. ( = Voluta coffea, L. ?) Syn. Melampus, Montf. Rhodostoma, Sw. Shell obtusely cone-shaped, smooth ; spire short, flat-whirled : aperture long, narrow ; lip sharp, denticulated within ; columella twisted in front ; wall of the aperture with 1 or 2 spiral plaits. 174 MANUAL OF THE MOLLUSCA. Animal with short, tapering and. rather compressed tentacles ; foot di- vided transversely into two portions, advanced successively in walking. Distr. W. Indies, Europe. In salt-marshes and on the sea-shore. The British species have thin ovate shells, with the spire moderately produced, and the aperture oval. They form the sub-genus Alexia. (denticulata) Leach. Fossil. Eocene. Brit. France. CAEYCHIUM, Miiller. Type, C. minimum, PI. XII. fig. 39. Syn. Auricella, Hartm. Shell minute, oblong, finely striated transversely ; aperture oval, toothed, margins thickened, united by callus. Animal with 2 blunt, cylindrical tentacles ; eyes black, sessile, near to- gether, behind the tentacles. Distr. 3 sp. Europe; N. America. At the roots of grass in damp places, especially near the sea. Fossil. Miocene — . Europe. The genus Siphonaria, described at p. 155, is supposed to be pulmoni- ferous, and to bear somewhat the same relation to Auricula, that Ancylus does to Limnaea. The lingual dentition is similar to Auricula ; the centre teeth are distinct, the laterals numerous and hooked. Fig. 100.* SECTION B. OPERCULATA.* The Operculated land-snails are exceedingly like periwinkles (litorinai), and chiefly differ from them in the situations they inhabit, and the medium respired. They have a long truncated muzzle, 2 slender contractile tentacles, and the eyes are sessile on the sides of the head.J The mantle-margin is simple, and the pulmonary cavity is situated on the back of the neck, and quite open in front. Lingual ribbon narrow; teeth 7 -ranked. * Siphonaria sp. from the Cape; three rows of teeth, c central, / laterals, from a preparation by J. W. Wilton, Esq , of Gloucester t Phanero-pnewmona (open-lunged), Gray. The account of this group is chiefly taken from the Catalogue prepared by my friend Dr. Baird. J The tentacles of the helicida are retractile, by inversion (p. 25) those of the cyclostomidce are contractile only. GASTEROPODA 175 Fig. 101. Lingual teeth of Cyclophorus.* The sexes are distinct ; the shell is spiral, and closed by an operculum, presenting many beautiful modifications of structure, characteristic of the smaller groups, which are often peculiar to limited regions, as in the HeliddcE, The oldest fossil species are found in the Eocene Tertiary. FAMILY VI. CYCLOSTOMID/E. Shell spiral, rarely much elongated, often depressed, spirally striated; aperture nearly circular ; peristome simple. Operculum distinctly spiral. Animal with the eyes on slight prominences at the outer bases of the tentacles ; tentacles contractile only ; foot rather elongated. CYCLOSTOMA, Lamarck. Etym. Cyclos circle, stoma mouth. Type, C. elegans, PI. XII. fig. 40. Syn. Leonia (mammillaris) and Lithidion, Gray. Shell turbinated, thin, axis perforated ; aperture oval ; peristome conti- nuous, simple, straight or expanded ; epidermis very thin. Operculum shelly, pauci-spiral. Animal with clavate tentacles ; sole of the foot divided by a longitudinal groove, the sides moved alternately in walking ; the end of the long muzzle is also frequently applied, as by the looping-snails (Truncatellae), and used to assist in climbing. » Fig. 102. Cyclostoma elegans, from Charlton, Kent. Distr. Above 80 sp. S. Europe ; Africa, Madagascar. The only British * C. aquilum, Sby. (original). From a specimen gathered by J. W. Laidlay, Esq. on the steps of the great idol-temple of Maulmein, Birmah. 176 MANUAL OF THE MOLLUSGA. sp. C. elegans, is found on calcarious soils ; it ranges to the Canaries and Algeria, and occurs fossil in the newer Tertiaries. Nearly half the species have the whirls spirally keeled, and have heen distinguished under the name Tropidophora, by Troschel. They are found in Madagascar and the adjacent islands and coast of Africa. Fossil, 20 sp. Eocene, Europe. Sub-genera. Otopoma (foliaceum), Gray. Shell sub-globose, umbili- cated ; peristome with an ear-like process covering part of the perforation. Distr. 15 sp. Arabia, Madagascar, China, New Ireland. Choanopoma (lincina) Pfr. Shell often a little decollated; peristome usually double, the outer edge angularly expanded. Lincina (labeo) Br. has the last whirl produced. Jamaida (anomala) C. B. Adams, has the oper- culum convex. Distr. 70 sp. W. Indies, and a few in Tropical America. Cistula, (fascia), Gray. = Tudora (megacheila), Gray. Shell ovate or elongated, apex usually decollated, peristome free; operculum with a thin shelly outer coat. Chondropoma (semilabre) Pfr. differs in the operculum being "sub-cartilaginous." Distr* About 70 sp. W. Indies; Tropical America, 8 sp. Realia (hieroglyphica), Gray. = Hydrocsena (part) Parreyss, Ompha- lotropis, Pfr. Liarea (Egea), Gray. Bourciera (helicinseformis) Pfr. Shell turrited or turbinate, perforated; peristome simple, straight or expanded; operculum pauci-spiral, horny. Distr. 17 sp. Canaries,? Mauritius, Pacific Ids. (Ecuador, Bourciera.} Pomatias (maculatum), Studer. Shell slender, transversely striated; peristome reflected; operculum cartilaginous, concamerated within. Distr. 10 sp. S. Europe ; Corfu. ? FERUSSINA, Grateloup. Etym. named in honour of Baron Ferussac. Type, F. anastomseformis, Gr. Syn. Strophostoma, Desh. Shell rounded, depressed, umbilicated ; whirls transversely striated above, spirally keeled below ; aperture turned obliquely upwards, peristome simple, Operculum. ? Fossil, I sp. Miocene — . Dax ; Turin. CYCLOPHORUS, Montfort. Etym. Cyclos, circle, phoreus, bearer. Type, C. involutus, PL XII. fig. 41. Shell depressed, openly umbilicated ; aperture circular; peristome con- tinuous, straight or expanded; epidermis thick; operculum horny, many- whirled. Animal with long, slender pointed tentacles ; foot broadly expanded, not grooved. Distr. About 90 sp. India, Philippines, New Zealand, Pacific Ids. Tro- pical America. C. gibbns, Fer. (Alycaeus, Gray) has the last whirl distorted. GASTEROPODA. 177 C. cornu-venatorium, Sby. (Aulopoma, Troschel) Ceylon, has the peristome free when adult ; the operculum is larger than the aperture, and reflected over it. Sub-genera. Pterocyclos (rupestris), Benson. Myxostoma and Steganos- toma, Troschel. Shell depressed, nearly discoidal, widely umbilicated ; pe- ristome expanded, produced into a little wing at the suture ; operc. sub-carti- laginous, spirally lamellated. Distr. 16 sp. India, Ceylon, Birmah, Borneo? Cyclotus (fuscescens) Guilding (Aperostoma, Troschel). Shell depressed, widely umbilicated ; operculum shelly, whirls numerous, with raised margins. Distr. 44 sp. W. Indies, Tropical America, India, Asiatic Ids. Fossil. Eocene, I. Wight (F. Edwards). Leptopoma (perlucidum) Pfr. /S^^turbinated, peristome simple, reflected ; operc. membranous. Distr. 29 sp. Philippines, India, New Guinea, N. Zealand, Pacific Ids. Megaloma* (cylindraceum) Guild. (Farcimen, Troschel.) Shell oblong or pupa-shaped, scarcely perforated, aperture circular ; operc. thin, horny, many- whirled, flat. Distr. 19 sp. West Indies, Tropical America, Canaries, India, Mauritius. Fossil. Eocene — . Paris and I. of Wight (E. Forbes.) Craspedopoma (lucidum) Pfr. Shell turbinate, rimate, a little contracted near the aperture ; operc. round, horny, many -whirled. Distr. 3 sp. Ma- deira, Palma. Fossil. Eocene — . I. Wight, Madeira. Cataulus (tortuosus) Pfr. Shell pupa-shaped, with the base keeled, pro- ducing a channel in the front of the aperture ; operc. circular, horny, the whirls easily separable. Distr. 6 sp. Ceylon. Diplommatina (folliculus) Benson. Shell minute, (1 sp. sinistral) conical, with costulated whirls ; peristome double ; operc. horny, multispiral. Distr. 3 sp. India. PUPINA, Vignard. Type, P. bicanaliculata, Sby. PL XII. fig. 42. Australian Ids. Shell sub-cylindrical, usually polished; aperture circular, peristome thickened, notched in front and at the suture ; operc. membranous, narrow- whirled. P. grandis, Forbes, has a dull epidermis. Distr. 8 sp. Philippines, New Guinea, New Ireland, Louisiades. Sub-genus, Ehegostoma (nunezii) Hasselt. Aperture with a narrow channel in the middle of the columellar side. 6 sp. Philippines. Nicobar. In 72. lubricum (Callia, Gray) the sinus is obsolete. R. pupiniforme (Pupi- nella, Gray) is perforated, and has a dull epidermis. HELICINA, Lamarck. Type, H. Neritella, Lam. Syn. Oligyra, Say. Pachytoma, Sw. Ampullina, Bl. Pitonillus, Montf. * Abridged from Megaloma-stoma ; Swainson, who judiciously curtailed several preposterously long names, allowed this to remain. 178 MANUAL OF THE MOLLUSCA. Shell globose, depressed or keeled, callous beneath ; aperture squarish or semi-lunar ; columella flattened ; peristome simple, expanded ; operc. shelly or membraneous, squarish or semi-ovate, lamellar. Animallike Cyclophorus ; lingual teeth 3.1.3. (Gray.) Distr. 150 sp. W. Indies, 50 ; Tropical America, 44 ; Pacific Ids., 26 ; Australian Ids. 3 ; Philippines, 7. Sub-genera. Lucidella, (aureola) Gray. Peristome more or less toothed internally ; 8 sp. W. Indies, Tropical America. Trochatella (pulchella), Sw. Shell not callous beneath; peristome simple, expanded, W. Indies 16 sp. Venezuela 1. Alcadia, Gray. A. Brownei, PI. XII. fig. 43. Jamaica. Shell helix- shaped, often velvety, callous beneath ; columella flattened, straight ; peris- tome slit in front; operc. shelly, semi-ovate, with a tooth-like process adapted to the slit in the peristome. Distr. 17 sp. Cuba, Jamaica and Haiti. STOASTOMA, C. B. Adams. Etym. Stoa pillared, stoma, month. Type, S. pisum, Ad. Shell minute, globose-conic or depressed, spirally striated; aperture semi-oval ; peristome continuous ; inner margin straight, forming a small spiral keel round the umbilicus ; operc. shelly, lamellar. Distr. 19 sp. Jamaica. S. succineum (Electrina, Gray) has smooth whirls. I. Opara, Polynesia. FAMILY VII. ACICULID.E. Shell elongated, cylindrical ; operculum thin, sub-spiral. Animal with the muzzle rather produced, slender and truncated ; eyes sessile on the upper part of the head, behind the base of the slender tentacles ; foot oblong, short, pointed behind. ACICULA, Hartmann. Type, A. fusca, PI. XII. fig. 44. Syn. Acme and Acmaea, Hartm.* Shell minute, slender, nearly imperforate ; peristome slightly thickened, margins sub-parallel, joined by a thin callus ; operc. hyaline. Distr. 5 sp. Brit. Germany, Trance; Vanicoro (on leaves). A. fusca is found in low, marshy situations, at the roots of grass ; it occurs fossil in the Newer PI eiocene of Essex (J. Brown). GEOMELANIA. Pfeiffer. Type. G. Jamaicensis. Pfr. Etym. Ge, the ground (i.e. terrestrial). ^^imperforate, turreted; aperture entire, effused; peristome simple, expanded; margins joined, basal produced into a tongue-shaped process: operc. oval, pellucid, whirls few, rapidly enlarging. Distr, 21 sp. Jamaica. * All given in the same year, 1821; the name Acmaea having been employed by Eschscholtz for a genus of limpets, Acicula has been retained by Pfeifier and Gray for this land-shell. GASTEROPODA. 179 ORDER III. OPISTHO-BRANCHIATA. Shell rudimentary or wanting. Branchiae arborescent or fasciculated, not contained in a special cavity, but more or less completely exposed on the back and sides, towards the rear (opisthen) of the body. Sexes united. (M. Edwards}. The molluscs of this order may be termed sea-slugs, since the shell, when it exists, is usually small and thin, and wholly or partially concealed by the animal. When alarmed or removed from their native element, they retract their gills and tentacles, and present such a questionable shape that the in- experienced naturalist will be likely enough to return them, with the refuse of the dredge, into the sea. Their internal structure presents many points of interest ; in some the gizzard is armed with horny spines, or large shelly plates ; in others the stomach is extremely complicated, its ramifications and those of the liver being prolonged into the branches of the respiratory organ. The tongue is always armed, but the number and arrangement of the lingual teeth is exceedingly variable, even in the same family ; usually the dental membrane is broad and short, with many similar teeth in each row. The alimentary canal terminates more in the rear of the body than in the other univalve shell-fish.* The gills are behind the heart, and the auricle behind the ventricle; conditions which characterize the embryonic state of the mollusca generally. Comparatively little is known of the geographical distribution of these animals ; they have been found wherever the requisite search has been made, and are probably much more numerous than at present estimated. The shell-bearing genera flourished in the period when the secondary strata were deposited. The living species are chiefly animal-feeders, preying on other shell-fish and on zoophytes. SECTION A. TECTI-BRANCHIATA.f Animal usually provided with a shell, both in the larval and adult state ; branchiae covered by the shell or mantle ; sexes united. FAMILY I. TORNATELLID^. Shell external, solid, spiral or convoluted, sub-cylindrical ; aperture long and narrow ; columella plaited ; sometimes operculated. Animal with a flattened, disk-like head, and broad obtuse tentacles ; foot ample, furnished with lateral and operculigerous lobes. * In the cuttle-fishes and pteropods it is hent upon itself ventrally, in the sea- snails dorsally, terminating in front, near its origin; the vascular system partakes of this flexure, and the gills are in advance of the heart. (Huxley.} t Mono-pluuro-branchiata. SI. Pomato-branchia, (from poma, a lid). Wiegm. The orderTecti-branchiata of Cuvier included only the family Bullidce ; it is here made to comprise the Infero-branches also; no object being gained by the multipli- cation of descriptive epithets. 180 MANUAL OF THE MOLLUSCA. The shells of this family are chiefly extinct, ranging from the period of the coal strata, and attaining their greatest development in the cretaceous age. Tornatella is essentially related to Bulla, but presents some resem- blance to the Pyramidettida in its plaited and operculated aperture; in Tornatina the nucleus, or apex, is sinistral. The spiral striae which orna- ment many of the species, are punctate, as in the Bullidse ; and the outer lip often remarkably thickened, as in Auricula. TORNATELLA, Lamarck. Type. T. tornatilis, PL XIV. fig. 1. Syn. Action, Montf. (not Oken), Dactylus (solidulus) Schum. ? Monoptygma (elegans) Lea, Shell solid, ovate, with a conical, many- whirled spire ; spirally grooved or punctate-striate ; aperture long, narrow, rounded in front ; outer lip sharp . columella with a strong, tortuous fold ; operculum horny, elliptical, lamellar. Animal white ; head truncated and slightly notched in front, furnished posteriorly with recumbent tentacular lobes, and small eyes behind them, near their inner bases; foot oblong, lateral lobes slightly reflected on the shell. Lingual teeth 12.12, similar, with long simple hooks. Fig. 103. Distr. 16 sp. U. States, Brit. Senegal, Red Sea, Philippines, Japan, Peru. T. tornatilis inhabits deep water, ( — 60 fms. Forbes). Fossil, 70 sp. Trias — Lias — . N. America, Europe, S. India. Sub-genera, Cylindrites (Llhwyd) Lycett. C. acutus, Shy. PI. XIV. fig. 2. (A.) Shell smooth, slender, sub-cylindrical, spire small, aperture long and narrow, columella rounded, twisted, and directed slightly outwards. (B.) Shell oval, spire sunk, whirls with acute margins. Bath Oolite, Brit. Acteonina, D'Orb. Tornatellse "without columella plaits," 30 sp. Garb. — Portlandian, (including Cylindrites). Acteonella, D'Orb. A. Renauxiana, PI. XIV. fig. 3. Shell thick, cone- like or convoluted, spire short or concealed, aperture long and narrow, colu- mella with 3 strong and regular spiral plaits in front. Distr. 11 sp. Chalk; Brit. France. Acteon Cabanetiana, D'Orb. (Itieria, Matheron, 1842) Coral-rag, France, belongs to the genus Nerinea (D'Orb.) p. 129. CINULTA. Gray. Type, C. avellana, PL XIV. fig. 4. Syn. Avellana and Ringinella, D'Orb. Shell globular, thick, spirally groved and punctate, spire small ; aperture GASTEROPODA. 181 narrow, rounded and sinuated in front ; outer lip thickened and reflected ; crenulated inside, columella with several tooth-like folds. Fossil, 20 sp. Neocomian — Chalk. Brit. France. RINGICTJLA, v. p. 112, PI, V. fig. 21. GLOBICONCHA, D'Orbigny. Type, G. rotundata, D'Orb. Fossil, 6 sp. Chalk. France. Shell ventricose, smooth, aperture crescent-shaped, simple, not toothed or thickened on the columellar side. VARIGERA, D'Orbigny. 1850.* Type, V. Guerangeri, D'Orb. Fossil, 8 sp. Neoc:— . Chalk. France. Shell like Gloliconcha, but with lateral varices. TYLOSTOMA, Sharp. 1849. Type, T. Torrubiee, Sh. Etym. Tulos, a callosity, stoma, mouth. Shell ventricose, smooth or punctate-striate, spire moderate, aperture ovate-lunate, pointed above, rounded in front ; outer lip periodically (once or twice in a whirl) thickened inside and expanded, rising slightly ; inner lip callous, spread over body- whirl. Distr. 4 sp. L. Cretaceous rocks, Portugal. ? PTERODONTA, D'Orbigny. Type, P. inflata, D'Orb. Fossil, 8 sp. Chalk. France. Shell oblong, ventricose, spire elongated ; aperture oval, lip slightly ex- panded, notched in front, and with a tooth-like ridge internally, remote from the margin. ? TORNATINA, A. Adams. Type, T. voluta. PL XIV. fig. 5. Shell cylindrical or fusiform, spire conspicuous, apex sinistral, suture channelled, columella callous, 1- plaited. Animal with a broad, trigonal head, rounded in front ; tentacular lobes triangular, with eyes at their outer bases ; foot short, truncated in front. Distr. 15 sp. W. Indies, TL States, Medit. Philippines, China, Australia. On sandy bottoms, ranging to 35 fms. (Adams). Volvula, Adams (Bulla acuminata, Brug.) is a small convoluted shell, with the spire concealed, and the columella obsoletely folded; it is referred to Cylichna by Loven, to Ovulum by Forbes. Distr. Brit. Medit. Fossil. Miocene — . Suffolk. FAMILY II. BULLION. Shell globular or cylindrical, convoluted, thin, often punctate-striated ; * The dates of M. D'Orbigny's genera, given in the Prodrome de Paleontologie. are dates of invention ; the names were not published, in many instances, until years afterwards. 182 MANUAL OF THE MOLLUSC A. spire small or concealed ; aperture long, rounded and sinuated in front ; lip sharp. No operculum. Animal more or less investing the shell ; head a flattened disk,* with tentacular lobes, often united ; eyes immersed in the centre of the disk, or wanting ; foot oblong, furnished with a posterior lobe (meta-podium], and side-lobes (epipodia) ; gill single on the right side of the back, covered by the shell; mantle-margin simple or expanded, and enveloping the shell. Lingual dentition very various ; central teeth often wanting, laterals single or numerous. Gizzard armed with calcarious plates. Sexes united. The BullidfE are animal-feeders ; they are said to use their lateral lobes for swimming. About 1.50 recent species have been described by Mr. A. Adams in Sowerby's Thesaurus Conchyliorum. Fossil species date from the lower Oolites ; one is found in the Arab-Caspian formation. BULLA, Lamarck. Bubble-shell. Type, B. ampulla, PL XIV. fig. 6. Syn. Haminea (hydatis) Leach. Shell oval, ventricose, convoluted, external or only partially invested by the animal; apex perforated; aperture longer than the shell, rounded at each end ; lip sharp. Animal with a large cephalic disk, truncated in front, bilobed behind, the lobes laminated beneath; eyes sub-central, immersed or wanting; lateral lobes very large, reflected on the sides of the shell, posterior lobe covering the spire ; foot quadrate ; gizzard furnished with 3 chiton-like plates ; teeth. ? Bulla naucum (Atys, Montf. Alicula, Ehr. Roxania, Leach). PI. XIV. fig. 7 ; has the columella twisted, and the spire entirely concealed. Distr. 60 sp. In all temperate and tropical seas, especially on sandy bottoms, ranging from low water to 25 or 30 fms. Fossil, 70 sp. Ool. — . S. America, U.S. Europe. Sub-genera ? Crypt-opthalmus (smaragdinus) Ehr. Red sea. Shell scarcely convolute, fragile, oval, convex, without spire or columella. Anima semi-cylindrical, head with short tentacular lobes, eyes small, concealed unde the lateral margins of the head, mantle and lateral lobes enveloping the shell Phaneropthalmus, A. Adams. (Xanthonella, Gray) B. lutea, Quoy, New Guinea. Shell oval, convex, pointed behind, columella margin with a curvec process. Animal long, cylindrical, head with short tentacular lobes, eyes in middle of disk, lateral lobes enveloping. Linteria, A. Adams (Glauconella, Gray), Bulla viridis, Rang. PL XIV fig. 7. Shell oval, widely open, showing the rudimentary internal spire * The cephalic expansion of the Bullidae is formed by the fusion of the dorsal and oral tentacles. (Cuvier.) The tentacular lobes, or posterior part of the disk is sup plied with nerves from the olfactory ganglia; the anterior portion of the disk re ceives branches' from the labial nerve, which comes from the front margin of the cerebroid. (Hancock.} GASTEROPODA. 183 Animal with a squarish, disk-like head, eyes sessile in the centre ; mantle not investing; a posterior lobe; lateral lobes enveloping. (Pl.XIV. lig. 8, not 7)» ACERA, Miiller. Type, A. bullata, Pi. XIV. fig. 9. Etym. Akeros, hornless. Shell thin, flexible, globosely* cylindrical, spire truncated, whirls chan- nelled ; aperture long, expanded and deeply sinuated in front, outer margin disunited at the suture ; columella open, exposing the whirls. Animal with a short and simple head-lobe, truncated in front and eyeless ; lateral lobes nearly concealing the shell ; lingual teeth hooked and serrulate, laterals about 40, narrow, claw-shaped ; gizzard armed with horny teeth. Distr. 7 sp. Greenland, Brit. Medit. Zanzibar, India, New Zealand. A. bullata is found amongst weed, in 1 — 15 fms. water (Forbes). CYLICHNA, Loven. Type, C. cylindracea, PL XIV. fig. 10. Syn. Bullina, Risso. Shell strong, cylindrical, smooth or punctate- str iate ; spire minute or truncated ; aperture narrow, rounded in front ; columella callous, with one plait. Animal short and broad, not investing the shell ; head flattened, truncated in front, with sub -centrally immersed eyes, tentacular lobes more or less united ; foot oblong, posterior and lateral lobes not much developed ; gizzard armed; lingual teeth squarish, recurved and serrated, with 1 large and 5 or 6 small hooked laterals. Distr. 20 sp. U. States, Greenland, Brit. Red Sea, Australia. Fossil. Miocene — . Brit. 184 MANUAL OF THE MOLLUSCA. small, black, sessile at the inner bases of the tentacles ; lingual teeth (B. physis) 13.0.13, serrated. Distr. 10 sp. U. States, W. Indies, Mauritius, Ceylon, China, Australia. SCAPHANDER, Montfort. Type, S. lignarius, PI. XIV. fig. 12. Etym. Scaphe boat, aner, man. Shell oblong, convolute ; spirally striated; aperture much expanded in front; spire concealed; epidermis thick; lingual teeth 1.0.1. crested. Animal with a large oblong head, destitute of eyes ; foot short and broad; lateral lobes reflected, but not enveloping the shell ; gizzard of two large trigonal plates and a small narrow transverse plate (fig. 17). Distr. 5 sp. U. States, Norway, Brit. Medit. on sandy ground ; 50 fins. Fossil, 8 sp. Eocene — . Brit. France. z Fig. 104. Bullcea aperta.* BULL^A, Lamarck. f Type, B. aperta, PL XIV. fig. 13. Shell internal, white, translucent, oval, slightly convoluted, spire rudi- mentary. Animal pale, slug-like ; mantle investing the shell ; head oblong ; eye- less ; foot broad ; lateral lobes large, but not enveloping ; tongue with 2 or 4 series of sickle-shaped uncini ; gizzard with 3 longitudinal shelly plates. Egg capsules ovate, in single series on a long spiral thread ; fry with a ciliated head- veil and an operculated, spiral shell, (Lov'eri}. Distr. 10 sp. W. Indies, Greenland, Norway, Britain, Medit. Corea, Borneo. Fossil, Eocene — . France. Sub-genus, Chelidonura, A. Adams, (Hirundella, Gray) B. hirundinaria, Quoy, Mauritius. Shell concealed; outer lip produced posteriorly into a spur; columellar border inflected. Animal with enveloping side lobes; mantle with two appendages behind, like the lateral processes of Hyalaea. DORIDITJM, Meckel. Etym. diminutive of Doris. Syn. Accra, Cuv. Eidothea, Kisso. * From a specimen dredged at Folkstone; o, mouth, c, head, or cephalic disk, t, side-lobes of the foot, ra, mantle, The shell s, and gizzard g, are indistinctly seen through the translucent integuments. t Gray adopts the pre-Linnean name Philine (Ascanius, 1762), and D'Orhigny the still older Lobaria, (Miiller, 1741), names given to particular species, and not to genera as now understood. GASTEROPODA. 185 Type, D. membranaceum, Meek. Medit. Animal oblong, truncated behind, the angles produced and dilated or filiform ; head ovate-oblong, retuse in front ; side-lobes expanded, wing-like ; mantle investing a rudimentary, membranous shell. GASTROPTERON, Meckel. Type, G. Meckelii, Bl. (Clio amate, Chiaje) Medit. Animal shell-less, oval, with side-lobes developed into wing-like expan- sions meeting and uniting behind ; cephalic disk triangular, obtuse in front, pointed behind, eyes centrally immersed; lingual teeth 5.1.5.; mantle? branchial plume exposed on the right side ; reproductive orifice in front of the gill, excretory opening behind it. Lon. 1, lat. 2 inches. Sormetus Adansonii, Bl. is described as semi-cylindrical, with sides grooved, head indistinct ; shell unguiform, thin, and transparent. Atlas (Peronii, Bl.) Lesueur. Head with 2 small tentacular lobes; body con- tracted in the middle ; foot dilated circularly, and fringed at the margin. FAMILY III. APLYSIAD^. Shell wanting, or rudimentary and covered by the mantle, oblong, tri- % gonal, or slightly convoluted. Animal slug-like, with distinct head, tentacles and eyes; foot long, drawn out into a tail behind ; sides with extensive lobes, reflected over the back and shell ; branchial plume concealed. Sexes united. APLYSIA, Gmelin. Sea Hare. Type. A. depilans, PI. XIV. fig. 14. Syn. Siphonotus (geographicus) Ad. Shell oblong, convex, flexible and translucent, with a posterior slightly incurved apex. Animal oval, with a long neck and prominent back ; head with 4 ten- tacles, dorsal pair ear -like with eyes at anterior lateral bases ; mouth probos- cidiform, with horny jaws, lingual teeth 13.1.13, hooked and serrated, about 30 rows ; gizzard armed with horny spines ; sides with ample lobes folding over the back, and capable of being used for swimming ; gill in the middle of the back, covered by the shell, and by a lobe of the mantle which is folded posteriorly to form an excretory siphon. Distr. 40 sp. W. Indies, Norway, Brit. Medit. Mauritius, China. The Sea-hares are mixed feeders, living chiefly on sea- weed, but also de- vouring animal substances ; they inhabit the laminarian zone, and oviposit amongst the weed in spring, at which time they are frequently gregarious (Forbes}. They are perfectly harmless animals and may be handled with im- punity. When molested they discharge a violet fluid from the edge of the internal surface of the mantle, which does not injure the skin, has but a faint smell, and changes to wine-red (Goodsir). ' In old times they were K 2 186 MANUAL OF THE MOLLUSCA. objects of superstitious dread, on account of their grotesque forms, and the imaginary properties of their fluid, which was held to he poisonous and to produce indelible stains.* Fossil : one or two shells of the newest tertiary in Sicily have been doubt- fully referred to this genus. Sub-genus, Aclesia (dolabrifera) Rang. Shell trapeziform. Side-lobes closely enveloping the body, leaving only a small dorsal respiratory opening, surface ornamented with filaments. W. Indies. DOLABELLA, Lamarck. Type. D. Rumphii, PI. XIV. fig. 15. Etym. Volabella, a small hatchet. Shell hard, calcarious, trigonal, with a curved and callous apex. Animal like Aplysia, with gill near posterior extremity of the body and lateral crests closely appressed, leaving only a narrow opening ; ornamented with branching filaments. Distr. 12 sp. Medit. Mauritius, Ceylon, Society Ids. Sandwich Ids. NOTARCHUS, Cuvier. Type, N. Cuvieri, Bl. Etym. Notos, the back, arcJios vent. Syn. Busiris (griseus) Risso, ? Bursatella (Leachii) BI. Animal shell-less, ornamented with filaments, sometimes dendritic, foot narrow, linear, lateral crests united, leaving only a narrow branchial slit ;. gills not covered by an opercular mantle lobe. Distr. 4 sp. Medit. Red Sea. ICARUS, Forbes, 1843. * Type. I. Gravesii, F. Syn. Lophocercus (Sieboldtii) Krohn, 1847. Shell like Bullsea ; convoluted, thin, ovate, covered with epidermis, outer lip separated at the suture, posterior angle inflected and rounded. Animal slender, papillose ; tentacles 2, ear-shaped ; eyes sessile on sides of head; side-lobes reflected and partly covering the shell, united behind ; tail long and pointed. LOBIGER, Krohn. Type, L. Philippii, PL XIV. fig. 16. Sicily. Shell oval, transparent, flexible/ slightly convoluted ; covered with epidermis. Animal slender, papillose, with 2 flattened, oval tentacles, and minute sessile eyes on the sides of the head ; shell exposed on the middle of the back, covering the plume-like gill ; sides with two pairs of rounded, dilated lobes, or natatory appendages, foot linear, tail long and slender. * Aplysia, (from a and piuo) un-washable ; the Aplysia of the Greek Fishermen cvvere sponges unfit for washing ! GASTEROPODA. 187 FAMILY IV. PLEUROBRANCHID.E. Shell limpet-like or concealed, rarely wanting ; mantle or shell covering the back of the animal ; gill lateral, between the mantle-margin and foot ; food vegetable, stomach extremely complicated. PLEUROBRANCHUS, Cuvier. Ex. P. membranaceus, PI. XIV. fig. 17. Etym. Pleura side, branchia gill. Syn. Berthella (plumula) Bl. Oscanius (membr.) Gray. Shell internal, large, oblong, flexible, slightly convex, lamellar, with a posterior, subspiral nucleus. Animal oblong, convex ; mantle covering the back and sides, papillated, containing spicula ; foot large, separated from the mantle by a groove; gill single, free at the end, placed on the right side between the mantle and foot ; orifices near the base of the gill ; head with 2 grooved tentacles, eyes at their outer bases ; mouth armed with horny jaws and covered by a broad veil with tentacular lobes. Distr. 20 sp. S. America, Norway, Brit. Medit. Red Sea. Sub-genus ? Pleurobranchaea Meckel; P. Meckelii, Leve, Medit. Syn. Pleurobranchidium (maculaturn) , Uuoy, S. Australia. Mantle-margin very narrow, not concealing the gill ; dorsal tentacles ear -like, oral veil tentaculi- form. POSTEROBRANCH.EA, D'Orbigny. Type, P. maculata, D'Orb. Coast of Chile. Animal shell-less ; oval, depressed, covered by a mantle broader than the foot ; foot oblong, bi-lobed behind ; branchial plume on the left side, pro- jecting posteriorly ; reproductive orifice in front of gill, excretory behind ; proboscis covered by a broad bi-lobed veil ; no dorsal tentacles. RUNCINA, (Forbes) Hancock. Type, R. Hancocki, Forbes. Syn. ? Pelta, Quatr. (not Beck.) Animal minute, slug-like, with a distinct mantle; eyes sessile on the front part of the mantle ; no tentacles ; gills 3, slightly plumose, placed with the vent on the right side, at the hinder part of the back, beneath the mantle ; gizzard armed ; reproductive organs on the right side. Distr. on Conferva near high-water mark, Torbay. UMBRELLA, Chemnitz. Chinese-umbrella shell. Type, U. umbellata, PL XIV. fig. 18. Syn. Acardo, Lam. Gastroplax, Bl. Shell limpet-like, orbicular, depressed, marked by concentric lines of growth; apex sub-central, oblique, scarcely raised; margins acute; inner surface with a central coloured and striated disk, surrounded by a continuous irregular muscular impression. Animal with a very large tuberculated foot, deeply notched in front ; mouth small, proboscidiform, retractile into the pedal notch, covered by a 188 MANUAL OF THE MOLLUSCA. small lobed veil ; dorsal tentacles ear-shaped, with large plicated cavities at their bases ; eyes small, sessile between the tentacles ; mantle not extending beyond the shell ; gill forming a series of plumes beneath the shell in front and on the right side; reproductive organ in front of the dorsal tentacles; excretory orifice posterior, tubular. Distr. 3 sp. Canaries, Medit. India, China, Sandwich Ids. Fossil 2 sp. Eocene — . U. States, Sicily. TYLODINA, Rafinesque. Type, T. punctulata, Raf. ( = citrina, Joannis) 3 sp. Medit. Norway. Shell limpet-like, depressed, apex sub-central, with a minute spiral nucleus. Animal oblong, foot truncated in front, rather pointed behind; dorsal tentacles ear-like, with eyes sessile at their inner bases ; oral tentacles broad ; branchial plume projecting posteriorly on the right side. FAMILY V. PHYLLIDIAD^E. Animal shell-less, covered by a mantle, branchial laminse arranged in series on both sides of the body, between the foot and mantle. Sexes united. PHYLLIDIA, Cuvier. Type, P. pustulosa, Cuv. Etym. Diminutive of Phyllon, a leaf. Animal oblong, covered with a coriaceous tuberculated mantle ; dorsal tentacles clavate, retractile into cavities near the front of the mantle ; mouth with two tentacles ; foot broadly oval ; gills forming a series of laminse ex- tending the entire length of both sides ; excretory orifice in the middle line, near the posterior end of the back, or between the mantle and foot ; repro- ductive organs on the right side ; stomach simple, membranous. Distr. 4 sp. Medit. Red Sea, India. DTPHYLLIDIA, Cuvier. Type, D. Brugmansii, Cuv. Syn. Pleurophyllidia, Chiaje. Linguella, Bl. Animal oblong, fleshy ; mantle ample ; gills limited to the hinder two- thirds of the body ; head with minute tentacles and a lobe-like veil ; vent at the right side, behind the reproductive orifices; lingual teeth 30.1.30. Distr. 4 sp. Norway, Brit. (D. lineata, Otto) Medit. SECTION B. NUDIBEANCHIATA. Animal destitute of a shell except in the embryo state ; branchiae always external, on the back or sides of the body ; sexes united. The Nudibranchiate sea- slugs are found on all coasts where the bottom is firm or rocky, from, between tide-marks to a depth of 50 fathoms; a few species are pelagic, crawling on the stems and fronds of floating sea-weed. They have been found by MiddendorflP, in the Icy Sea, at Sitka, and in the sea of Ochotsk ; in the tropical and southern seas they are abundant. No GASTEROPODA. 189 satisfactory account, however, has been published of any except the European, and especially the British species, which form the subject of an admirable monograph by Messrs. Alder and Hancock, in the transactions of the Ray Society. They require to be watched and drawn whilst living and active, since after immersion in spirits they lose both their form and colour. In some the back is covered with a cloak or mantle ( ?,) which contains calcari- ous spicula of various forms, sometimes so abundant as to form a hard shield- like crust.* The dorsal tentacles and gills pass through holes in the cloak somewhat like the " key-hole " in Flssurella. In others there is no trace of a mantle whatever. The eyes appear as minute black dots, immersed in the skin, behind the tentacles ; they are well organized, and conspicuous in the young, but often invisible in the adult. The dorsal tentacles are laminated, like the antennse of many insects (fig. 11, p. 23) ; they are never used as organs of touch, and are supplied with nerves from the olfactory ganglia. The nervous centres are often conspicuous by their bright orange colour ; they are concentrated above the oesophagus ; three pairs are larger than the rest, the cerebroid in front, the branchial behind, and the pedal ganglia at the sides. The cerebroid supplies nerves to the tentacles, mouth, and lips. The olfactory ganglia are sessile on the front of the cerebroid (in Doris) or situated at the base of the tentacles (mjEolis). The optic ganglia are placed on the posterior border of the cerebroid; the auditory capsules are sessile on the cerebroid, immediately behind the eyes, they contain an ag- glomeration of minute otolites which are continually oscillating.f The luc- cal ganglia are below the oesophagus, united to the cerebroid by commissures, forming a ring ; anterior to this a small ring is sometimes formed by the union of the 5th pair of nerves. The pedal ganglia (properly infra- cesopha- geal) are united laterally to the cerebroid and rarely meet below, but are united by commissures which form (together with those of the branchial centres) the 3rd ring, or great nervous collar. The branchial ganglia are united behind to the cerebroid, and sometimes blend with them ; they supply the skin of the back, the rudimentary mantle, and the gills ; beneath, and sessile on their front border is the single visceral ganglion. Besides this excito-motory system, (which includes the great centres, or brain, and the nerves of sensation and voluntary motion), the nudibranches possess a sym- pathetic system, consisting of innumerable minute ganglia, dotted over all the viscera, united by nerves forming plexuses, and connected in front with the buccal and branchial centres.:}: * According to Mr. Huxley, the " cloak" of the Dorids is not the equivalent of the mantle, but " has more relation to the epipodium." t The auditory capsules of other Mollusca (excepting the Nucleobranches) are attached to the posterior side of the pedal (sub-cesophageal) ganglia. J The sympathetic system supplies nerves to the heart and other organs which are independent of the will, and not ordinarily susceptible of pain ; they are called " or- ganic " nerves, as all the vegetative functions depend on them. Its existence in the 190 MANUAL OF THE MOLLUSCA. The digestive organs of the Nudibranches present two remarkable modi- fications : in Doris and Tritonia the liver is compact and the stomach a sim- ple membranous sac; whilst in JEolis the liver is disintegrated, and its canals so large that the process of digestion must be chiefly carried on in them, and they are regarded as ccecal prolongations of the stomach; the cceca extend into a series of gill-like processes, arranged upon the back of the ani- mal, which also contain part or the whole of the true liver ; the gastric rami- fications vary exceedingly in amount of complexity. The vascular system and circulation of the nndibranchiate molluscs is in- complete. In Doris veins can be traced only in the liver and skin; the greater part of the blood from the arteries escapes into the visceral sinus and into a net-work of sinuses in the skin, from which it returns to the auricle by two lateral veins, without having circulated through the gills. The heart is contained in a pericardium to which is attached a small ventricle, or portal heart, for impelling blood to the liver ; the hepatic veins run side by side with the arteries and open into a circular vein, surrounding the vent, and supplying the gills. Only hepatic blood, therefore, circulates through the gills. In JEolis there are no special gills, but the gastro -hepatic papilla? are accompanied by veins which transmit blood to the auricle. The skin acts as an accessory breathing-organ ; it performs the function entirely in the Elysiadte. and in the other families when by accident the branchiae are des- troyed. The water on the gills is renewed by ciliary action. The fry is provided with a transparent, nautiloid shell, closed by an operculum, and swims with a lobed head- veil fringed with cilia, like the young of most other gasteropods. — Hancock and Embleton, Phil. Trans. 1852. An. Nat. Hist. 1843. FAMILY VI. DORID^E.* Sea-lemons. Animal oblong ; gills plume-like, placed in a circle on the middle of the back ; tentacles two ; eye-specks immersed, behind the tentacles, not always visible in the adult ; lingual membrane with usually numerous lateral teeth, rachis often edentulous ; stomach simple ; liver compact ; skin strengthened with spicula, more or less definitely arranged. DORIS, L. Etym. Doris, a sea- nymph. Ex. D. Johnstoni, PL XIII. fig. 1. Animal oval, depressed ; mantle large, simple, covering the head and foot; dorsal tentacles 2, clavate or conical, lamellated, retractile within Mollusca was first clearly demonstrated by M.M. Hancock and Embleton. The excito-motory system of the Mollusca corresponds with the cerebro-spinal system of the vertebrata. * Contracted from Dorididce; as the Greeks used Deucalides for Dencaliontiades. Ehrenberg divided the genus Doris into sections, by the number and form of the gills, characters of only specific importance. GASTEROPODA. 191 cavities ; gills surrounding the vent on the posterior part of the back, retrac- tile into a cavity ; head with an oral veil, sometimes produced into labial tentacles ; mouth with a lower mandible, consisting of two horny plates, united near the front, and having 2 projecting points ; lingual teeth numer- ous, central small, laterals similar, hooked and sometimes serrated (24-68 rows; 37-141 in a row; nidamental ribbon rather wide, forming a spiral coil of few volutions (p. 50, fig. 29.) Sub-genus, Oncidoris (Bl. ?). D. bilameData, Johnst. Back elevated, tuberculose; gills non-retractile; oral tentacles fused into a veil; buccal mass with a gizzard-like appendage ; lingual teeth 2 in each row. (A. and H.) D. scutigera (Villiersia) D'Orb. Rochelle; has the mantle more than usually strengthened with calcarious spicula. The Dorids vary in length from 3 lines to more than 3 inches ; they feed on zoophytes and sponges, and are most plentiful on rocky coasts, near low-water, but range as low as 25 fms. They occur in all seas, from Nor- way to the Pacific. GONIODORIS, Forbes. Etym. Gonia, an angle. Type, Gr. nodosa, PL XIII. fig. 2. Animal oblong; tentacles clavate, laminated, non -retractile; mantle small, simple, exposing the head and foot. Spawn coiled irregularly. Distr. Norway, Brit. (2 sp.) Medit. China. Between tide-marks. TRIOPA, Johnston. Type, T. clavigera, PI. XIII. fig, 3. Syn. Psiloceros, Menke. Animal oblong; tentacles clavate, retractile within sheaths; mantle margined with filaments ; gills few, pinnate, around or in front of the dorsal vent. (A. and H.) Lingual teeth 8.1.8, or 8.0.8. Distr. Norway, Brit. Low- water — 20 fms. Pamirs, Loven. Type, A. punctilucens, PI. XIII. fig. 4. Etym. ? Aix (aigos) a goat. Animal oblong or elongated, covered with very large tubercles ; no dis- tinct mantle ; tentacles linear, retractile within prominent lobed sheaths ; gills dendritic, placed around the dorsal vent. (A. and H.) Lingual teeth 17.0.17. Distr. Norway, Brit. (2 sp.) France. Literal zone. THECACERA, Fleming. Etym. Theke a sheath, ceras a horn. Type, T. pennigerum, Mont. Animal oblong, smooth ; tentacles clavate, laminated, retractile within sheaths ; head with a simple frontal veil ; gills pinnate, placed round the dorsal vent, and surrounded by a row of tubercles. (A. and H.) Distr. Brit. 2 sp, Lon. i— | inch. Found at low-water. POLYCERA, Cuvier. Etym. Polycera, many horns. Type, P. quadrilineata, PI. XIII. fig. 5, K 3 192 MANUAL OF THE MOLLUSC A. Animal oblong or elongated ; tentacles laminated, non-retractile, sheath- less ; head-veil bordered with tubercles or tentacular processes ; gills with 2 or more lateral appendages. (A. and H.) Distr. Norway, 5 sp. Brit. Red Sea. Within tide-marks and in deep water on corallines. The spawn is strap -shaped, and coiled on stones, in July and August. P. ocellata (Plocamophoms, Riippell) has the cephalic tentacles branched. ID ALIA, Leuckart. Etym. Idalia, Venus, from Mt. Idalium in Cyprus. Syn. Euplocamus, Phil. Peplidium (Maderse) Lowe. Ex. I. aspersa, PL XIII. fig. 6. Coralline zone. Animal broadly oblong, nearly smooth, tentacles clavate or linear, with filaments at their base ; head slightly lobed at the sides ; mantle very small, margined with filaments; lingual teeth 2.0.2. Distr. Norway, Brit. (4 sp.) Medit. Madeira. ANCULA, Loven. Syn. Miranda, A. and H. Type, A. cristata, Alder. Animal slender, elongated; mantle entirely adnate, ornamented with simple filaments ; tentacles clavate, laminated ; with filiform appendages at their base ; labial veil produced on each side. Distr. Norway, Brit. Lon. ^ inch. CERATOSOMA (Gray), A. Adams. Etym. Ceratois, horned, soma, body. Type, C. cornigerum, Ad. Animal oblong, narrow, with two large and prominent horn-like pro- cesses on the posterior part of the back, behind the gills ; gills 5, bipinnate ; dorsal tentacles clavate, laminated, rising from rounded tubercles, non- retractile ; head with short lateral processes : foot narrow. Distr. Sooloo sea. (A. Adams.) FAMILY VII. TRITONIAD.E. Animal with laminated, plumose, or papillose gills, arranged along the sides of the back ; tentacles retractile into sheaths ; lingual membrane with 1 central and numerous lateral teeth ; orifices on the right side. TRITONIA, Cuvier. Ex. T. plebeia, PL XIII. fig. 7. Animal elongated ; tentacles with branched filaments ; veil tuberculated or digitated ; gills in single series on a ridge down each side of the back ; mouth armed with horny jaws; stomach simple; liver compact. Listr. Norway, Brit. Under stones at low-water, — ^5 fm. F. Hom- bergii, Cuv. found on the scallop -banks, attains a length exceeding 6 inches. GASTEROPODA. 193 SCYLL^A, L. Type, S. pelagica, PI. XIII. fig. 8. Etym. Scyllaea, a sea-nymph. Animal elongated, compressed; foot long, narrow and channelled, adapted for clasping sea-weed ; back with 2 pairs of wing-like lateral lobes, bearing small tufted branchiae on their inner surfaces; tentacles dorsal, slender, with lamellated tips, retractile into long sheaths; lingual teeth 24.1.24, denticulated; gizzard armed with horny, knife-like plates ; orifices on the right side. Distr. Atlantic, S. Brit. Medit. On floating sea- weed. Nerea (punctata) Lesson, New Guinea; 10 lines long, with ear-shaped tentacles, and 3 pairs of dorsal lobes. TETHYS, L. Etym. Tethys, the sea (personified.) Syn. Timbria, Bohadsch. Type, T. fimbriata, L. PL XIII. fig. 9. Animal elliptical, depressed; head covered by a broadly expanded, fringed disk, with 2 conical tentacles, retractile into foliaceous sheaths ; gills slightly branched, a single row down each side of the back ; reproductive orifices be- hind first gills, vent on right side, behind second gill ; stomach simple. Distr. 1 sp. Medit. Attains a foot in length, and feeds on other mol- luscs and crustaceans. (Cuvier.) ? BORNELLA (Gray), A. Adams. Type, A. Adamsii, Gray. Lon. 4 inches. Animal elongated ; dorsal tentacles retractile into branched sheaths ; head with stellate processes; back with two rows of cylindrical, branched, gastric processes, to which small dendritic gills are attached;* foot very narrow. Distr. 2 sp. Straits of Sunda, on floating weed ; Borneo, ? DENDRONOTUS, A. and H.f Etym. Dendron, a tree, notos, the back. Type, D. arborescens, PL XIII. fig. 10. Animal elongated ; tentacles laminated ; front of the head with branched appendages ; gills arborescent, in single series down each side of the back ; foot narrow ; lingual teeth 10.1.10 ; stomach and liver ramified. Distr. Icy sea; Norway, Brit. On sea-weed and corallines; low-water — coralline zone. ?DOTO, Oken. Etym. Doto, a sea-nymph. Ex. D. coronata, PL XIII. fig. 11* * This observation deserves further enquiry. f This and the following genera are placed by Alder and Hancock in the family JEolidce ; they have a ramified stomach, but their external (zoological) characters agree better with Tritonia than Molls. 194 MANUAL OF THE MOLLUSC A. Animal slender, elongated; tentacles linear, retractile into trumpet- shaped sheaths ; veil small, simple ; gills ovate, muricated, in single series down each side of the back; lingual membrane slender, with above 100 recurved, denticulated teeth, in single series ; foot very narrow. The stomach is ramified, and the liver is entirely contained in the dorsal processes, which fall off readily when the animal is handled, and are soon renewed. Distr. Norway, Brit. On corallines in deep water — 50 fms. ? MELIBCEA, Rang. Type, M. rosea, Rang ; on floating weed, off the Cape. Animal elongated, with a narrow, channelled foot and long slender tail ; sides of the back with 6 pairs of tuberculated lobes, easily deciduous ; tenta- cles cylindrical, retractile into long trumpet-shaped sheaths ; head covered by a lobe-like veil ; sexual orifices behind right tentacle, excretory behind first gill on the right side. ? LOMANOTUS, Verany. Hx. L. marmoratus, PL XIII. fig. 12. Syn. Eumenis, A. and H. Animal elongated, smooth ; head covered with a veil ; tentacles clavate, laminated, retractile into sheaths ; gills filamentose, arranged along the sides of the back, on the wavy margins of the mantle; foot narrow, with tenta- cular processes in front ; stomach ramified. Distr. Brit. Medit. On corallines. FAMILY VIII. Animal with papillose gills, arranged along the sides of the back ; ten- tacles sheath-less, non-retractile ; lingual teeth 0.1.0.; ramifications of the stomach and liver extending into the dorsal papilla ; excretory orifices on the right side ; skin smooth, without spicula ; no distinct mantle. 2EoLis, Cuvier. Syn. Psiloceros, Menke. Eubranchus, Forbes. Amphorina, Quatref. Type, M. papillosa, L. Elym. JZolis, daughter of JEolus. Animal ovate; dorsal tentacles smooth, oval, slender; gills simple, cylindrical, numerous, depressed and imbricated ; mouth with a horny upper jaw, consisting of two lateral plates, united above by a ligament; foot narrow ; tongue with a single series of curved, pectinated teeth ; spawn of numerous waved coils. Sub-genera. Fladellina, Cuv. (Phyllodesmium, Ehr.) Body slender; dorsal tentacles laminated, buccal long; papillae clustered; spawn multi- spiral. Ex. E. coronata, PI. XIII. fig, 13. (also fig. 11, p. 23.) Cavolina> Brug. (Montagua, Flem.) C. peregrina. Body lanceolate ; ten- tacles smooth or wrinkled ; papillae in transverse, rather distant rows ; spawn of 1 or 2 coils. GASTEROPODA. 195 TergipeS) Cuv. T. lacinulata. Body linear; tentacles smooth; papillae in a single row on each side ; spawn kidney-shaped. Distr. Norway, Brit. (33 sp.) U. States, Medit. S. Atlantic, Pacific. Found amongst rocks, at low- water ; they are active animals, moving their tentacles continually, and extending and contracting their papillae; they swim readily at the surface, inverted. They feed chiefly on sertularian zoophytes, and if kept fasting will devour each other ; when irritated they discharge a milky fluid from their papillse, which are very liable to fall* off. GLAUCUS, Forster. Etijm. Glaucus, a sea-deity. Syn. Laiiiogerus, Bl. Pleuropus, Eaf. Ex. G. Atlanticus, PL XIII. fig. 14. Animal elongated, slender : foot linear, channelled ; tentacles 4, conical ; jaws horny ; teeth in single series, arched and pectinated ; gills slender, cylindrical, supported on 3 pairs of lateral lobes ; stomach giving off large cceca to the tail and side lobes ; liver contained in the branchial papillae ; sexual orifice beneath first dextral gill, vent behind second gill ; spawn in a close spiral coil. Distr. 6 sp. Atlantic, Pacific. Found on floating sea- weed; devours small sea-jellies, Porpita and Velellce. (Bennet.) FIONA, Alder and Hancock. Type, F. nobilis, A. and H. Syn. Oithona, A. and H. (not Baird). Animal elongated ; oral and dorsal tentacles linear ; mouth armed with horny jaws ; gills papillary, clothing inegularly a sub-pallial expansion on the sides of the back, each with a membranous fringe running down its inner side. Distr. Falmouth. Under stones at low-water. (Dr. Cocks.) EMBLETONIA, A. and H. Etym. Dedicated to Dr. Embleton, of Newcastle. Syn. Pterochilus, A. and H. ? Clcelia (formosa) Loven. Type, E. pulchra, PI. XIII. fig. 15. Animal slender ; tentacles 2, simple ; head produced into a flat lobe on each side ; papillae simple, subcylindrical, in a single row down each side of the back. Distr. Scotland (2 sp.) In the litoral and laminarian zones. Calliopaa (bellula) D'Orb. Brest; has 2 rows of papillee down each side of the back ; cephalic lobes subulate ; vent dextral. Lon. 3 lines. PHOCTONOTUS, A. and H. Type, P. mucroniferus, PI. XIII. fig. 16. Dublin, shallow water. Syn. Venilia, A. and H. Zephrina, Quatref. Animal oblong, depressed, pointed behind; dorsal tentacles 2, linear, simple, with eyes at their base, behind ; oral tentacles short ; head covered 196 MANUAL OF THE MOLLUSCA. by a small semilunar veil ; mouth with horny jaws ; gills papillose, on ridges down the sides of the back, and round the head in front ; vent dorsal. ANTIOPA, A. and H. Type, A. splendida, A. and H. Syn. Janus, Verany. Animal ovate-oblong, pointed behind ; dorsal tentacles lamellated, united at the base by an arched crest ; head with a small veil and two labial tenta- cles ; gills ovate, placed along the lateral ridges of the back and continuous above the head ; vent central, posterior, sexual orifice at the right side ; lin- gual teeth numerous. ? Distr. Brit. Medit HERM.EA, Loven. Type, H. bifida, PL XIII. fig. 17. Norway, Brit. Animal elongated, tentacles folded longitudinally; giDs numerous, papil- lose, arranged down the sides of the back ; sexual orifice below right tenta- cles ; vent dorsal, or sub-lateral, anterior. ALDERIA, Allman. Etym. Named after Joshua Alder, one of the authors of the Monograph on the British Nudibranchiate Mollusca. Type, A. modesta, PL XIII. fig. 18. Norway, S. Ireland and S. Wales. Animal oblong, without tentacles ; head lobed at the sides ; gills papil- lose, arranged down the sides of the back ; vent dorsal, posterior, ? Stiliger (ornatus) Ehrenberg ; Red Sea. Vent dorsal, anterior. FAMILY IX. PHYLLIRHOIDJS. Animal pelagic, foot-less (apodal), compressed, swimming freely with a fin-like tail ; tentacles 2, dorsal ; no branchiae ; lingual teeth in a single series ; stomach furnished with elongated co3ca ; orifices on the right side ; sexes united. PHYLLIRHOE, Peron and Lesueur. Etym. Phyllon, a leaf, rhoe, the wave. Syn. Eurydice, Esch. Type, P. bucephala, Peron. Distr. 6 sp. Medit. Moluccas, Pacific. Animal translucent, fusiform, with a lobed tail ; muzzle round, truncated ; jaws horny; lingual teeth 3.0. 3.; tentacles long and slender, with short sheaths ; intromittent organ long, bifid. FAMILY X Animal shell-less, limaciform, with no distinct mantle or breathing organ ; respiration performed by the ciliated surface of the body ; mouth armed with a single series of lingual teeth ; stomach central, vent median, sub-central ; hepatic organs branched, extending the length of the body and opening into the sides of the stomach ; sexes united ; male and ovarian orifices below the GASTEROPODA. 197 right eye ; female orifice in the middle of the right side ; heart with an auricle behind, and traces of an arterial and venous system, eyes sessile on the sides of the head, tentacles simple or obsolete.* ELYSIA, Risso. Type, E. viridis, PL XIII. fig. 19. Syn. Action, Oken. Animal elliptical, depressed, with wing-like lateral expansions ; tentacles simple, with sessile eyes behind them ; foot narrow. Distr. Brit. Medit. On Zostera and sea-weed, in the laminarian zone. Placo-branchus (ocellatus, Rang.) Hasselt, Java; described as 2 inches long, with four small tentacles ; the lateral expansions much developed and meeting behind, the upper surface longitudinally plaited, and forming, when the side-lobes are rolled together, a sort of branchial chamber. ACTEONIA, _Quatrefages. Ex. A. corrugata, PL XIII. fig. 20. British channel. Animal minute, leach-like; head obtuse, with lateral crests proceeding from two short conical tentacles, behind which are the eyes. CENIA, Alder and Hancock. Type, C. Cocksii, PL XIII. fig. 21. Etym. Cenia, Falmouth. Syn. ? Fucola (rubra) (Quoy). Animal limaciform, back elevated, head slightly angulated, bearing two linear dorsal tentacles, with eyes at their outer bases behind. LIMAPONTIA, Johnston. Type, L. nigra, PL XIII. fig. 22. Syn. Chalidis, Qu. Pontolimax, Cr. Animal minute, leach-like ; head truncated in front, with arched lateral ridges on which are the eyes ; foot linear. Distr. Norway, England and France, between half-tide and high-water, feeding on Conferva, in the spring and summer ; spawn in small pear-shaped masses, each with 50-150 eggs; fry with a transparent nautiloid shell, closed by an operculum. ORDER IV. NUCLEOBRANCHIATA. Bl.f The present order consists entirely of pelagic animals, which swim at the surface, instead of creeping on the bed of the sea. Their rank and ain- * Order Dermi-branchiata, Quatref. (Pelli-branchiata, A. and H.) M. Quatre- fages erroneously described the Elysiadce as wanting both heart and blood vessels, like the Ascidian zoophytes ; with them he associated the family JEolidce, which he described as having a heart and arteries, but no veins, their office being performed by lacunae of the areolar tissue. In both families the product of digestion (chyle) was supposed to be aerated in the gastric ramifications, by the direct influence of the sur- rounding water. To this group, which has been since abandoned, he applied the name Phlebenterata, (phlebs, a vein, entera, the intestines). t So called because the respiratory and digestive organs form a sort of nucleus on the posterior part of the back. See fig. 105, s. b., and PI. XIV. fig. 24. 198 MANUAL OF THE MOLLUSCA. nities entitle them to the first place in the class ; but their extremely aber- rant form, and unusual mode of progression, have caused us to postpone their description till after that of the ordinary and typical gasteropoda. There are two families of nucleobranchiate mollusks ; the firolas and carinarias, with large bodies and small or no shells, and the Atlantas, which can retire into their shells and close them with an operculum. Both animal and shell are symmetrical, or nearly so ; the nucleus of the shell is minute and dextrally spiral. The nucleobranches swim rapidly by the vigorous movements of their fin-like tails, or by a fan-shaped ventral fin ; and adhere to sea-weed by a small sucker placed on the margin of the latter. Mr. Huxley has shown that these organs represent the three essential parts of the foot in the most highly developed sea-snails. The sucker represents the central part of the foot, or creeping disk (meso-podium] of the snail and whelk; the ventral fin is homologous with the anterior division of the foot, (pro-podium} which is very distinct in Natica (p. 123), and in Harpa and Oliva\ but is only marked by a groove in Paludina and Dollum (fig. 71.) The terminal fin (or tail of Carinaria) which carries the operculum of Atlanta, is the equivalent of the operculigerous lobe (meta-podium] of the ordinary gasteropods, such as Strombus (fig. 69). The abdomen, or visceral mass, is small, whilst the anterior part of the body (or cephalo -thorax, M. Edw.) is enormously developed. The proboscis is large and cylindrical, and the tongue armed with recurved spines. The alimentary canal of Firola is bent up at a right angle posteriorly on the dorsal side ; in Atlanta it is recurved, and ends in the branchial cham- ber. The heart is proso-branchiate, although in Firola the auricle is rather above than in front of the ventricle, owing to the small amount of the dorsal flexure. The nucleobranches, and especially those without shells, " afford the most complete ocular demonstration of the truth of MILNE EDWARDS' views with regard to the nature of the circulation in the mollusca. Their transparency allows the blood-corpuscles to be seen floating in the general cavity of the body — between the viscera and the outer integument— and drifting back- wards to the heart ; having reached the wall of the auricle they make their way through its meshes as they best can, sometimes getting entangled therein, if the force of the heart has become feeble. From the auricle they may be followed to the ventricle, and thence to the aorta and pedal artery, through whose open ends they pour into the tissues of the head and fin." (Huxley.} Such delicate and transparent creatures would hardly seem to need any special breathing-organ, and in fact it is present or absent in species of the same genus, and even in specimens of the same species. Carinaria has fully-formed branchiae; in Atlanta they are sometimes distinct, and GASTEROPODA. 199 wanting in others ; in liroloides they are only indicated hy a ciliated sub- spiral band. The larvae are furnished with a shell, and with ciliated vela. (Gegenbaur.) The nucleobrauches are dioecious ; some individuals (of Jirola) have a leaf-like appendage, others a long slender egg-tube depending from the oviduct, and regularly annulated.* The larvae are furnished with a shell, and with ciliated vela. (Gegeubaur.) The nervous system is remarkable for the wide separation of the centres. The buccal ganglia are situated considerably in front of the cephalic, arid the pedal ganglia are far behind, so that the commissures which unite them are nearly parallel with the oesophagus. The branchial ganglia are at the pos- terior extremity of the body, as in the bivalves. The eyes are hour-glass shaped, and very perfectly organized ; the auditory vesicles are placed behind, and connected with the cephalic ganglia, they each contain a round otolite, which sometimes seems to oscillate. (Huxley.} FAMILY I. Animal elongated, cylindrical, translucent, furnished with a ventral fin, and a tail fin used in swimming; gills exposed on the posterior part of the back, or covered by a small hyaline shell. Mouth with a circular lip ; lingual membrane with few rows of teeth: central teeth transversely elongated, with 3 recurved cusps ; laterals 3 on each side, the first a transverse plate with a hooked apex, 2 and 3 sickle-shaped.f FIROLA, Peron and Lesueur. Type, F. Coronata, Forsk. Medit. Syn. Pterotrachsea, Forsk. Animal fusiform, elongated, with a long, slender, proboscidiform head ; fin narrowed -at the base, furnished with a small sucker; tail elongated, keeled, sometimes pinnate ; nucleus prominent ; branchial processes numerous, conical, slender ; tentacles 4, short and conical ; eyes black and distinct, pro- tected by a rudimentary eyelid ; lingual ribbon oblong. The female firola have a long moniliform oviduct. Anops Peronii, D'Orb. described and figured as having no head (!) was probably a mutilated Firola. " Such speci- mens are very common, and seem just as lively as the rest." (Huxley.) Distr. 8 sp. Atlantic, Medit. Pacific. Sub-genus, Firoloides, Lesueur. ( Cerophora, D'Orb.) F. Desmarestii, Les. Body cylindrical ; head tapering, furnished with two slender tentacles ; nucleus at the posterior extremity of the body, with or without small bran- chial filaments; egg-tube regularly annulated; tail fin small and slender, ventral fin without a sucker. Distr. 6 sp. Atlantic. * We can only call to mind one other example of a segmented organ in the mol~ lusca ; viz. the penniform styles of Teredo bipalmulata.. t The genus Sagitta, Q. and G. sometimes referred to this family, is an articulate animal. (HuxleyO 200 MANUAL OF THE MOLLUSCA. CARINARIA, Lamarck. Fig. 105.* Eym. Carina, a keel (or keeled vessel.) Type. C. cymbium, L. fig. 105, PI. XIV. fig. ]9. Shell hyaline, symmetrical, limpet-shaped, with a posterior sub-spiral apex and a fimbriated dorsal keel ; nucleus minute, dextrally spiral. Animal large, translucent, granulated; head thick, cylindrical; lingual ribbon triangular, teeth increasing rapidly in size, from the front backwards'; tentacles long and slender, eyes near their base : ventral fin rounded, broadly attached, with a small marginal sucker; tail large, laterally compressed; nucleus pedunculated, covered by the shell, gills numerous, pinnate, project- ing from beneath the shell. Distr. 5 sp. Medit. and warmer parts of the Atlantic and Indian Oceans. They feed on small Acalepha, and probably on the pteropoda ; Mr. Wilton found in the stomach of a Carinaria two fragments of quartz rock, weighing together nearly 3 gr. Fossil, 1 sp. Miocene. Turin. CARDIAPODA, D'Orbigny. Ex. C. placenta, PL XIV. fig. 20. Etym. Cardia, heart, pous, foot. Syn. Carinaroides, Eyd. and Souleyet. Animal like Carinaria. Distr. 5 sp. Atlantic. Shell minute, cartilaginous ; peristome expanded and bi-lobed in front, enveloping the spire behind. FAMILY II. ATLANTIC. Animal furnished with a well- developed shell, into which it can retire; gills contained in a dorsal mantle-cavity ; lingual teeth similar to Carinaria. Shell symmetrical, discoidal, sometimes closed by an operculum. ATLANTA, Lesueur. Type, A. Peronii, PL XIV. fig. 21-23. Syn. Steira, Esch. Shell minute, glassy, compressed and prominently keeled ; nucleus dex- * Fig. 105. p. proboscis; t, tentacles; 6, branchias ; s, shell; /, foot; d, disk. GASTEROPODA. 201 trally spiral ; aperture narrow, deeply notched at the keel ; operculum ovate, pointed, lamellar, with a minute, apical, dextrally spiral nucleus. Animal 3-lobed; head large, sub-cylindrical; tentacles conical, with con- spicuous eyes behind them ; ventral fin flattened, fan-shaped, furnished with a small fringed sucker ; tail pointed, operculigerous. Distr. 15 sp. Warmer parts of the Atlautic, Canary Ids. Sub-genus. Oxygyrus, Benson. Syn. Ladas, Cantraine ; Helieo-phlegma, D'Orb. 0. Keraudrenii, PL XIII. figs. 24, 25. Shell milky, narrowly um- bilicated on both sides ; nucleus not visible ; back rounded, keeled only near the aperture; body whirl, near the aperture, and keel cartilaginous; no aper- tural slit ; operculum trigonal, lamellar." 2 sp. Atlantic. Medit. The Atlanta was discovered by Lamanon, who supposed it to be the living analogue of the Ammonite. The operculum of Oxygyrus (PI. XIII. fig. 25) is singularly like the Trigonellites (p. 80) ; that of Atlanta (fig. 22) is the only example of a dextral operculum to a dextral shell (p. 102). PORCELLIA, Leveille. Ex. P. Puzosi, PI. XIV. fig. 29. Shell discoidal, many whirled ; whirls keeled or coronated ; nucleus spiral ; aperture with a narrow dorsal slit. Fossil, 10 sp. Devonian — Trias. Brit. Belgium. BELLEROPHON, Monfort. Ex. B. bi-carinatus, Lev. PL XIV. fig. 27. Syn. Euphemus, M'Coy. Shell symmetrically convoluted, globular, or discoidal, strong, few- whirled; whirls often sculptured; dorsally keeled; aperture sinuated and deeply notched on the dorsal side. Fossil, 70 sp. L. Silurian — Garb. N. America, Europe, Australia. The name Bucania was given by Hall to the species with exposed whirls ; in B. expansus, PL XIV. fig. 28, the aperture of the adult shell is much ex- panded, and the dorsal slit filled up. (Salter.} JBellerophina, D'Orb (not Forbes) is founded on the Nautilus minutus. Shy. PL XIV. fig. 26, a small globular shell, spirally striated, and devoid of septa. It is found in the gault of England and Trance. CYRTOLITES, Conrad. type, C. ornatus, PL XIV. fig. 30. Etym. Kurtos, curved, lithos, stone. Shell thin, symmetrical, horn-shaped or discoidal, with whirls more or less separate, keeled and sculptured. Fossil, 13 sp. L. Silurian — Garb, N. America, Europe. ? Ecculiomphalus (Bucklandi) Portlock, PL XIV. fig. 31. L. Silurian, Brit. U. States. Shell thin, curved, or discoidal with few widely separate whirls, slightly unsymmetrical, keeled. 202 MANUAL OF THE MOLLUSCA. Fig. 106. Maclurea Logani, ( S alter) L. Silurian. Canada. ? MACLUKEA, Lesueur. Named after Wm. Maclure, the first American geologist. Shell discoidal, few whirled, longitudinally grooved at the hack, and slightly rugose with lines of growth; dextral side convex, deeply and narrowly perforated ; left side flat, exposing the inner whirls ; operculum sinistrally sub-spiral, solid, with two internal projections (t t] one of them beneath the nucleus, very thick and rugose. Fossil, 5 sp. L. Silurian. N. America ; Scotland (Ayrshire, McCoy). This singular shell abounds in the " Chazy " limestone of the U. States and Canada ; sections of it may be seen even in the pavement of New York; but specimens are very difficult to obtain. We are indebted to W. E. Logan, Esq., Geological Surveyor of Canada, for the opportunity of examining a large series of silicified specimens, and of figuring a perfect shell, with its operculum in situ. It has more the aspect of a bivalve, such as Requienia Lonsdalii (PI. XVIII. fig. 12) than of a spiral univalve, but has no hinge. Many of the specimens are overgrown with a zoophyte, generally on the convex side only, rarely on both sides. The Maclurea has been described as sinistral ; but its operculum is that of a dextral shell ; so that the spire must be regarded as deeply sunk and the umbilicus expanded, as in certain species of Planorbis : unless it is a case conversely parallel to Atlanta, in which both shell and operculum have dex- tral nuclei. The affinities of Maclurea can only be determined by careful examination and comparison with allied, but less abnormal forms, associated with it in the oldest fossiliferous rocks ; its relation to Euomphalus (p. 145) is not supported by the evidence of Mr. Logan's spetimens. CLASS III. PTEROPODA. This little group consists of animals whose entire life is passed in the open sea, far away from any shelter, save what is afforded by the floating gulf-weed, and whose organization is specially adapted to that sphere of existence. In appearance and habits they strikingly resemble the fry of the ordinary sea-snails, swimming like them by the vigorous flapping of a pair of fins. To the naturalist ashore they are almost unknown ; but the voyager on the great ocean meets with them where there is little else to arrest his attention, and marvels at their delicate forms, and almost incredible numbers. They swarm in the tropics, and no less in arctic seas, where by their myriads PTEROPODA. 203 the water is discoloured for leagues (Scoresby). They are seen swimming at the surface in the heat of the day, as well as in the cool of the evening. Some of the larger kinds have prehensile tentacles, and their mouths armed with lingual teeth, so that, fragile as they are, they probably feed upon still smaller and feebler creatures, (e. g. entomostraca). In high latitudes they are the principal food of the whale, and of many sea-birds. Their shells are rarely drifted on shore, but abound in the fine sediment brought up by the dredge from great depths. A few species occur in the tertiary strata of Eng- land and the continent ; in the older rocks they are unknown, unless some comparatively gigantic forms (comilaria and theca] have been rightly referred to this order. In structure, the Pteropoda are most nearly related to the marine uni- valves, but much inferior to them. Their nervous ganglia are concentrated into a mass below the oesophagus ; they have auditory vesicles, containing otolites ; and are sensible of light and heat and probably of odours, although at most they possess very imperfect eyes and tentacles. The true foot is small or obsolete ; in chodora it is combined with the fins, but in Clio it is sufficiently distinct, and consists of two elements ; in Spirialis the posterior portion of the foot supports an operculum. The fins are developed from the sides of the mouth or neck, and are the equivalents of the side-lappets (epipodia] of the sea-snails. The mouth ot Pneumodermon is furnished with two tentacles supporting miniature suckers ; these organs have been compared with the dorsal arms of the cuttle-fishes, but it is doubtful whether their nature is the same.* A more certain point of resemblance is the ventral flexure of the alimentary canal, which terminates on the under surface, near the right side of the neck. The pteropods have a muscular gizzard, armed with gastric teeth ; a liver ; a pyloric ccecum ; and a contractile renal organ opening into the cavity of the mantle. The heart consists of an auricle and a ventricle, and is essentially opistho-branchiate, although sometimes affected by the general flexure of the body. The venous system is extremely incom- plete. The respiratory organ, which is little more than a ciliated surface, is either situated at. the extremity of the body and unprotected by a mantle, or included in a branchial chamber with an opening in front. The shell, when present, is symmetrical, glassy, and translucent, consisting of a dorsal and a ventral plate united, with an anterior opening for the head, lateral slits for long filiform processes of the mantle, and terminated behind in one or three points ; in other cases it is conical, or spirally coiled and closed by a spiral operculum. The sexes are united, and the orifices situated on the right side of the neck. According to Vogt, the embryo Pteropod has deciduous vela, * The figures of Eydoux and Souleyet represent them as being supplied -vrith nerves from the cephalic ganglia ; \vhereasthearms of the cuttle-fish, and all other parts or modifications of the foot, in the mollusca, derive their nerves from the pedal ganglia (Huxley). 204 MANUAL OP THE MOLLUSCA. like the sea-snails, before the proper locomotive organs are developed (Huxley). From this it would appear that while the Pteropoda present some analo- gical resemblances to the Cephalopoda, and permanently represent the larval stage of the sea-snails, they are developed on a type sufficiently peculiar to entitle them to rank as a distinct group ; not indeed of equal value with the Gasteropoda, but with one of its orders. This group, the lowest of the univalve or encephalous orders, makes no approach towards the bivalves or acephala. Forskahl and Lamarck indeed compared Hyalaa with Terebratula ; but they made the ventral plate of one answer to the dorsal valve of the other, and the anterior cephalic orifice of the pteropodous shell, correspond with the posterior, byssal foramen of the bivalve ! SECTION A. THECOSOMATA, Bl.* Animal, furnished with an external shell ; head indistinct : foot and ten- tacles rudimentary, combined with the fins; mouth situated in a cavity formed by the union of the locomotive organs ; respiratory organ contained within a mantle-cavity. FAMILY I. HYALEID^ Shell straight or curved, globular or needle-shaped, symmetrical. Animal with two large fins, attached by a columellar muscle passing from the apex of the shell to the base of the fins ; body inclosed in a mantle ; gill represented by a transversely plaited and ciliated surface, within the mantle cavity, on the ventral side; lingual teeth (of Hyalea) 1.1.1, each with a strong recurved hook. H YALE A, Lamarck. Etym. Hyaleos, glassy. Syn. Cavolina, Gioeni not Brug. Type, H. tridentata, fig. 107. PL XIV. fig. 32. Shell globular, translucent; dorsal plate rather flat, produced into a hood ; aperture contracted, with a slit on each side ; posterior extremity tri- dentate. In H. trispinosa (Diacria, Gray) the lateral slits ojen into the cervical aperture. Animal, with long appendages to the mantle, passing through the lateral slits of the shell ; tentacles indistinct ; fins united by a semicircular ventral lobe, the equivalent of the posterior element of the foot. Distr. 19. sp. Atlantic, Medit. Indian Ocean. Fossil, 5 sp. Miocene — . Sicily, Tu- rin, Dax. Fig. 107. H. tridentata. * Theke a case, soma a body ; several of the genera have no shells. PTEROPODA. 205 CLEODORA, Peron and Lesueur. Syn. Clio, L. (part) not Miiller. Balantium, Leach MS. Type, C. pyramidata, PL XIV. fig. 33. Shell pyramidal, 3 sided, striated transversely ; ventral side flat, dorsal keeled; aperture simple, triangular, with the angles produced ; apex acute. Animal with rudimentary eyes ; tentacles obsolete ; mantle-margin with a siphonal (?) process; fins ample, united ventrally by a' rounded lobe; lingual teeth 1.1.1. The transverse bars of the gill, the heart, and other organs are visible through the pellucid shell. In C. curvata and pellucida (Pleuropus, Esch.) the mantle is furnished with two long filaments on each side. Distr. 12 sp. Atlantic, Medit. Indian Ocean, Pacific, C. Horn. Fossil. Miocene — . Brit. (C. infundibulum, Crag.) Sub-genus. Creseis, Rang. (Styliola, Lesueur). C. aciculata, PI. XIV. fig. 34. Slender, conical, pointed, straight or curved. Fins rather narrow, truncate, with small tentacles projecting from their dorsal edges, and rudi- ments of the mesopodium on their surface; mantle -margin with a spiral process on the left side. M. Rang states that he has seen these pteropods clustering round floating seaweed. Distr. 5 sp. (like Cleodora.) CUVIERIA, Rang.* Dedicated to Baron Cuvier. Type, C. columnella, Rang, PI. XIV. fig. 35. Shell cylindrical, transparent ; aperture simple, transversely ovate ; apex acute in the young, afterwards partitioned off, and usually deciduous. Animal with simple narrow fins, united ventrally by two small lobes ; lingual teeth 1.1.1. Distr. 4 sp. Atlantic, India, Australia. Fossil 1 sp. (C. Astesana, Rang.) Pliocene, Turin. Sub-genus, Vaginella, Baud. V. depressa, PI. XIV. fig. 36. Shell oblong, with a pointed apex; aperture contracted, transverse. Fossil, 1 sp. Miocene. Bordeaux, Turin. THECA, Morris. 1845. Type, T. lanceolata. Syn. Creseis, Forbes.f Pugiunculus, Ban*. Shell straight, conical, tapering to a point, back flattened, aperture trigonal. Lon. 1-8 inches. Fossil, 6 sp. Silurian. N. America, Brit., New South Wales. PTEROTHECA, Salter. Type, P. transversa, Portlock, 3 sp. L. Silurian ; Ireland, Wales, Canada. Shell bi-lobed, transversely oval, with a dorsal keel projecting slightly at each end ; ventral plate small triangular. * Under the name of " triptere," M.M. Quoy and Gaimard described the fragment of a pteropod, since ascertained to have been a Cuvieria. f Creseis Sedgwicki, Forbes, is an orthoceras with very thin septa, belonging to the same group with (Conularia) teres, Sby. Tentaculites, Schl. is anellidous. (Salter.) 206 MANUAL OF THE MOLLUSC A. ? CONULARIA, Miller. Etym. Conulus, a little cone. Type, C. quadrisulcata, fig. 108. Shell four-sided, straight, and tapering, the angles grooved, sides striated transversely, apex partitioned off. Fossil, 15 sp. Silurian — Garb. N. America, Europe, Australia. Sub-genus, Coleoprion (gracilis) Sandberger; Devonian? Germany. Shell round, tapering, sides obliquely striated, striee alternating along the dorsal line. EURYBIA, Rang. 1827.f Etym. Eurybia, a sea-nymph. Fig. 108.* Ex. E. Gaudichaudi, PI. XIV. fig. 3?. (after Huxley.) Animal globular ; fins narrow, truncated and notched at the ends, united ventrally by a small lobe (metapodium) ; mouth with two elongated ten- tacles, behind which are minute eye-peduncles and a two-lobed rudimentary foot (mesopodium) ; body inclosed in a cartilaginous integument, with a cleft in front, into which the locomotive organs can be retracted. Lingual teeth 1.0.1. The animal has no proper gill, but Mr. Huxley has observed two ciliated circles surrounding the body, as in the larva of Pueumodermon. Distr. 3 sp. Atlantic, Pacific. Sub-genus, Psyche, Rang. P. globulosa, PI. XIV. fig. 38. Animal globular, with two simple oval fins. Distr. 1 sp. Off Newfoundland. \ CYMBULIA, Peron and Lesueur. Etym. Diminutive of cymba, a boat. Type, C. proboscidea, PI. XIV. fig. 39. (after Adams). Shell cartilaginous, slipper-shaped, pointed in front, truncated posteriorly ; aperture elongated, ventral. Animal with large rounded fins connected ventrally by an elongated lobe ; mouth furnished with minute tentacles; lingual teeth 1.1.1 ; stomach muscular, armed with two sharp plates. Distr. 3 sp. Atlantic, Medit. India Ocean. lann. d disk; TIEDEMANNIA, Chiaje. Type, T. Neapolitana, PI. XIV. fig. 40. Named after Fr. Tiedemann. Animal naked, transparent, fins united, forming a large rounded mouth central ; tentacles elongated, connate ; eye-tubercles minute. Larv shell-bearing. Distr. 2 sp. Medit. Australia. * Carboniferous limestone, Brit. Belgium, t This name had been previously employed for four different genera of plants an animals. PTEROPODA. 207 FAMILY II. Shell minute, spiral, sometimes operculate. Animal with fins attached to the sides of the mouth, and united ventrally by an operculigerous lobe ; mantle-cavity opening dorsally ; excretory orifices on the right side. The shells of the true limacimda are sinistral, by which they may be known from the fry of Atlanta, Carinaria, and most other Gasteropods. LIMACINA, Cuvier. Etym, Limacina, snail-like. Syn. Spiratella, Bl. Ex. L. antarctica (drawn by Dr. Joseph Hooker), PL XIV. fig. 41. Shell sub-globose, sinistrally spiral, umbilicated; whirls transversely striated ; umbilicus margined ; no operculum. Animal with expanded fins, notched on their ventral margins ; operc. lobe divided; lingual teeth 1.1.1. Distr, 2 sp. Arctic and Antarctic Seas ; gregarious. SPIRIALIS, Eydoux and Souleyet. Ex. S. bulimoides, PL XIV. fig. 42. Syn. Heterofusus, Mem. Heliconoides, D'Orb. Peracle, Forbes. Scaea, Ph. Shell minute, hyaline, sinistrally spiral, globose or turrited, smooth or reticulated ; operculum thin, glassy, semilunar, slightly spiral, with a central muscular scar. Animal with narrow, simple fins, united by a simple, transverse operculi- gerous lobe ; mouth central, with prominent lips. Distr. 12 sp. Greenland and Norway to C. Horn, Indian Ocean, Pacific. ? CHELETROPIS, Forbes. Etym. Chele, a claw, tropis, a keel. Syn. Sinusigera, D'Orb. Type, C. Huxleyi, PL XIV. fig. 43. Shell dextrally spiral, imperforate, double-keeled; nucleus sinistral; aperture channelled in front; peristome thickened, reflected, with two clavv- like lobes. Animal pteropodous ? gregarious in the open sea. Distr. 2 sp. S. America, S. E. Australia. Another minute spiral shell, recently discovered, may be noticed here : MACGILLIVRAYIA. Forbes. Named after its discoverer, the Naturalist to H. M. S. Rattlesnake. Type, M. pelagica, PL XIV. fig. 44. Shell minute, dextrally spiral, globular, imperforate, thin, horny, trans- lucent ; spire obtuse ; aperture oblong, entire ; peristome thin, incomplete, operc. thin horny, concentric, nucleus sub-external. JL 208 MANUAL OF THE MOLLUSCA. Animal with 4 long tentacles, mantle with, a siphonal process ; foot ex- panded, truncated in front, furnished with a float after the manner of lanthina ; lingual dentition closely resembling Jeffrey sia. Distr. 2 sp. Taken in the towing-net oif C. Byron, E. coast Australia, 15 miles from shore; floating, and apparently gregarious. (J. Macgillivray.) Mindoro. (Adams.) SECTION B. GYMNOSOMATA, Bl. Animal naked, without mantle or shell ; head distinct ; fins attached to the sides of the neck ; gill indistinct. FAMILY III. Body fusiform; head with tentacles often supporting suckers; foot small, but distinct, consisting of a central and posterior lobe ; heart opistho-bran- chiate ; excretory orifices distant, on the right side ; lingual teeth (in Clio) 12.1.12, central wide, denticulated, unciui strongly hooked and recurved. CLIO (L.)* Miiller. Etijm. Clio, a sea-nymph. Syn. Clione, Pallas. Type, C. borealis, PI. XIV. fig. 45. (C. caudata, L. part.) Head with. 2 eye tubercles and 2 simple tentacula; mouth with lateral lobes, each supporting 3 conical retractile processes, furnished with numerous microscopic suckers ; fins ovate ; foot lobed. In swimming, the Clio brings he ends of its fins almost in contact, first above and then below. (Scoresby.} Distr. 4 sp. Arctic and Antarctic Seas, Norway, India. Sab-genus ? Cliodita (fusiformis), Quoy and Gaimard. Head supported on a narrow neck ; tentacles indistinct. 3 sp. Cape, Amboina. PNEUMODERMON, Cuvier. Etym. Pneumon, lung (or gill), derma, skin. Type, P. violaceum, PI. XIV. fig. 46. Body fusiform; head furnished with ocular tentacles; lingual teeth 4.0.4 ; mouth covered by a large hood supporting two small, simple, and two large acetabuliferous tentacles, suckers numerous, pedicillate, neck rather contracted ; fins rounded ; foot oval, with a pointed posterior lobe ; excretory orifice situated near the posterior extremity of the body, which has small branchial processes and a minute, rudimentary shell. * This name was employed by Linnaeus for all the Pteropoda then known ; his definition is most suited to the "northern clio," probably the only species with which he was personally acquainted. The first species enumerated in the Syst. Nat. is C. caudata, and reference is made to an indeterminable figure in Brown's Jamaica, and to Marten's account of the Spitzbergen mollusk (C. borealis.) In cases like this the rule is to adopt the practice of the next succeeding naturalist who defines the limits of the group more exactly. BRACHIOPODA. 209 In the fry of Pnenmodermon the end of the body is encircled with ciliated bands. (Miiller.) Distr. 4 sp. Atlantic, India, Pacific Ocean. Sub-genus ? Spongiobranchcea, D'Orbigny. S. Australis, PL XIV. fig. 47§ Gill (?) forming a spongy ring at the end of the body; tentacles each wilif 6 rather large suckers. Distr. 2 sp. S. Atlantic (Fry of Pneumodermon ?). Trichocyclus, Eschscholtz, T. Dumerilii, PL XIV. fig. 48. Animal without acetabuliferous tentacles ? mouth proboscidiform; front of the head surrounded with a circle of cilia, and two others round the body. ? PELAGIA, Quoy and Gaimard. Etym. Pelagus, the deep sea: (not = Pelagia, Peron andLes.) Type, P. alba, PL XIV. fig. 49. Amboina, Animal fusiform, truncated in front, rough ; neck slightly contracted ; fins small, fan-shaped. CYMODOCEA, D'Orbigny. Etym. Kumodoke, a Nereid. Type, C. diaphana, PI. XIV. fig. 50. Animal fusiform, truncated in front, pointed behind ; neck slightly con- tracted ; fins 2 on each side, first pair large and rounded, lower pair ligulate ; foot elongated ; mouth proboscidiform. Distr. I sp. Atlantic. CLASS IV. BRACHIOPODA, Cuvier, 1805, (= Order Pallio-branchiata, Blainville, Prodr. 1814.) The Brachiopoda are bivalve shell-fish which differ from the ordinary mussels, cockles, &c. in being always equal-sided, and never quite equivalve. Their forms are symmetrical, and so commonly resemble antique lamps, that they were called lampades, or " lamp-shells," by the old naturalists (Meuschen, 1787, Humphreys, 1797); the hole which in a lamp admits the wick, serves in the lampshell for the passage of the pedicle by which it is attached to submarine objects.* The valves of the Brachiopoda are respectively dorsal and ventral ; the ventral valve is usually largest, and has a prominent beak, by which it is attached, or through which the organ of adhesion passes. The dorsal, or smaller valve, is always free and imperforate. The valves are articulated by two curved teeth, developed from the margin of the ventral valve, and re- ceived by sockets in the other ; this hinge is so complete that the valves cannot be separated without injury.f A few, abnormal genera, have no 210 MANUAL OF THE MOLLUSCA. hinge ; in Crania and Discina the lower valve is flat, the upper like a limpet ; the valves of Lingula are nearly equal, and have been compared to a duck's bill. (Petiver). Ventral valve. Dorsal valve. Fig. 109. Muscular system of Terebratula * a. a. adductor-muscles; r. cardinal-muscles; x. accessory cardinals; p. ventral pedicle-muscles ; p.' dorsal pedicle-muscles ; z.capsular-muscles; o. mouth; v. vent; /. loop ; t. dental socket. The valves are both opened and closed by muscles ; those which open the shell (cardinales) originate on each side the centre of the ventral valve, and converge towards the hinge-margin of the free valve, behind the dental sockets, where there is usually a prominent cardinal process.^ The teeth form the fulcrum on which the dorsal valve turns. The adductor muscles are four in number, and quite distinct in Crania and Discina ; in Linyula the posterior pair are combined, and in Terebratula the four muscles are separate at their dorsal terminations, but united at their insertion in the centre of the larger valve. The pedicle is fixed by a pair of muscles (each doubly -attached) to the dorsal hinge-plate, and by another pair to the ventra valve, outside the cardinal muscles.J In the hinge-less genera the contrac- tion of the cardinal muscles must tend to slide the free valve forwards, and in Crania and Discina these muscles are attached to a prominent ventral * Waldheimia Australia, Quoy. f . From a drawing by Albany Hancock, Esq. t The term " retractors' used at p. 8 is relinquished for the more appropriate term " cardinal muscles,'" given by Prof. King. They are particularly interesting from their function, as antagonists of the adductor muscles, like the ligament of ordinary bivalves. J The muscular system of Terebratula presents a considerable amount of resem- blance to that of Modiola (fig. 177); the anterior and posterior pedal muscles may be compared to the dorsal and ventral pedicle muscles. BRACHIOPODA. 211 process, which renders them less oblique ; the upper valve is restored to its place by two pairs of retractor sliding-muscles, which are perhaps the equi- valents of the dorsal pedicle muscles of Terebratula* The muscles are remarkably glistening and tendinous, except at their expanded ends, which are soft and fleshy ; their impressions are often dee]), and always character- istic ; but difficult of interpretation from their complexity, their change of position, and the occasional suppression of some and combination of others. f On separating the valves of a recent Terebmtula, the digestive organs and muscles are seen to occupy only a very small space near the beak of the shell, partitioned off from the general cavity by a strong membrane, in the centre of which is placed the animal's mouth. The large cavity is occu- pied by the fringed arms, which have been already alluded to (page 8) as the characteristic organs of the class. Their nature will be better understood by comparing them with the lips and labial tentacles of the ordinary bivalves (pp. 24, 27, fig- 171, P-P-] ) they are in fact lateral prolongations of the lips supported on muscular stalks, and are so long as to require being folded or coiled up. In Ehynchonella and Lingula the arms are spiral and separate ; in Terebratula and Discina they are only spiral at the tips, and are united together by a membrane, so as to form a lobed disk. It has been conjec- tured that the living animals have the power of protruding their arms in search of food ; but this supposition is rendered less probable by the fact that in many genera they are supported by a brittle skeleton of shell. The internal skeleton consists of two spiral processes in the Spiri/enda (fig. 132), whilst in Terebralula and Thecidlum it takes the form of a loop, which sup- ports the brachial membrane, but does not strictly follow the course of the arms. The mode in which the arms are folded is highly characteristic of the genera of Brachiopoda ; the extent to which they are supported by a calca- rious skeleton is of less importance, and liable to be modified by age. That margin of the oral arms which answers to the lower lip of an ordinary bivalve, is fringed with long filaments («mj), as may be seen even in dry specimens of recent Terebratulce. In some fossil examples the cirri them- selves were supported by slender processes of shell ; § they cannot therefore be vibratile organs, but are probably themselves covered with microscopic cilia, like the oral tentacles of the ascidian polypes (cilio-brachiata of Farre). The anterior lip and inner margin of the oral arms is plain, and forms a * In Discina one pair of the retractor muscles seems to be actually inserted in the pedicle. Mr. Hancock compares the pedicle muscles with the retractors of the Bryozoa ; he objects to the hypothesis of the sliding movement of the valves. t Prof. King has shown that the compound nature of a muscular impression is often indicated by the mode in which the vascular markings proceed from it (as in figs. HO, 145.) J Called cilia at p. 8, but this term should be restricted to the microscopic organs which clothe the cirri. § Spiriferarostrata and Terebratula pectunculo ides, in the British Museum. 212 MANUAL OF THE MOLLUSCA. narrow gutter along which the particles collected by the ciliary currents ma> be conveyed to the mouth. The object of the folding of tBfe arms is obvi- ously to give increased surface for the disposition of the cirri. The month conducts by a narrow oesophagus to a simple stomach, which is surrounded by the large and granulated liver ; the intestine of Lingula is reflected dorsally, slightly convoluted, and terminates between the mantle lobes on the right side (fig. 165). In Orbicula it is reflected ventrally, and passes straight to the right, ending as in Lingula. In Terebratula, Rhyncho- nella, and probably all the normal Brachiopoda, the intestine is simple and reflected ventrally, passing through a notch or foramen in the hinge-plate, and ending behind the ventral insertion of the adductor muscle (fig. 109, v.) * The interior of the valves is lined by the two lobes of the mantle, which are often fringed with fine horny bristles (seta] ; these are quite straight, brittle, and deeply implanted between the laminae of the mantle ; they serve to guard the opening of the valves. The mantle-lobes of the Brachiopoda are not only organs by which the shell is formed, they are also provided with large veins by which respiration is effected ; in the Terebratulidte there are two great venous trunks in the dorsal mantle- lobe, four in the ventral ; in Rhynchonella and Dlscina the lobes are similar, and the Orthidce have four large veins in the dorsal lobe and only two in the ventral. The first indica- tion of a special breathing organ is presented by Lingula, in which the veins develope parallel rows of small vascular processes. (Cuvier.) The veins open into the visceral cavity, f which is itself a great vascular sinus. There are two organs which Prof. Owen regards as hearts, each consisting of an auricle and a ventricle, situated near the sides of the mouth in Terebratula ; but in Lingula (fig. 165, h.} they are more posterior, and quite at the sides. The ventricles propel the blood into the visceral and pallial arteries, and are therefore both branchial and systemic. The pallial arteries are very slender, and accompany the veins on their outer surfaces, forming linear impressions along the centre of the vascular markings in some fossil shells (fig. 141). The ova of Terebratula are developed within the large veins, which they accompany as far as the secondary branches. In the Rhynchonellida, anc probably in the extinct Orthidte, the ovaria do not extend into the venous trunks, but occupy large sinuses on each side of the body ; and in Discina and Lingula they (or the testes) fill the interstices of all the viscera, but do not appear to extend into the mantle. The ova are supposed to escape by two orifices, situated at the sides of the mouth in Terebratula. (Hancock.) * The position at which the intestine terminates in the Terebratulce and Rhyn- chonellce, seems to necessitate the escape of the farces by the umbonal opening ; in those extinct genera which have the foramen closed at an early age, there is still an opening between the valves (e. g. in Uncites) which has been mistaken for a byssal notch. t The veins do not terminate in hearts as formerly supposed \. the statement at p. 30, line 27, should be erased. BRACHIOPODA. 213 Recent Discince often have minute fry attached to their valves, and Mr. Suess, of Vienna, has noticed a specimen of the fossil String ocephalus, which contained numerous embryo shells. Nothing is yet known respecting the development of the Brachiopoda., but there can be no doubt that in their first stage they are free and able to swim about, until they meet with a suitable position. It is probable that in the second stage they all adhere by a byssus, which in most instances becomes consolidated, and forms a permanent organ of attachment. Some of the extinct genera (e. g. Spirifera and Strophomena) appear to have become free when adult, or to have fixed themselves by some other means. Four genera, belonging to very distinct families, cement themselves to foreign objects by the substance of the ventral valve. The Lamp -shells are all natives of the sea. They are found hanging from the branches of corals, the under sides of shelving rocks, and the cavities of other shells. Specimens obtained from rocky situations are frequently distorted, and those from stony and gravelly beds, where there is motion in the waters, have the beak worn, the foramen large, and the ornamental sculpturing of the valves less sharply finished. On clay beds, as in the deep clay strata, they are seldom found ; but where the bottom con- sists of calcarious mud they appear to be very abundant, mooring themselves to every hard substance on the sea-bed, and clustering one upon the other. Some of the Brachiopoda appear to attain their full growth in a single season, and all, probably, live many years after becoming adult. The growth of the valves takes place chiefly at the margin; adult shells are more globular than the young, and aged specimens still more so. The shell is also thickened by the deposit of internal layers, which sometimes entirely fill the beak, and every portion of the cavity of the interior which is not oc- cupied by the animal, suggesting the notion that the creature must have died from the plethoric exercise of the calcifying function, converting its shell into a mausoleum, like many of the ascidian zoophytes. The intimate structure of the shell of the Brachiopoda has been investigated by Mr. Morris, Prof. King, and more recently by Dr. Carpenter ; according to the last observer, it consists of flat- tened prisms of considerable length, arranged parallel to each other with great regularity, and obliquely to the surfaces of the shell, the interior of which is imbricated by their out-crop (fig. 110.) This struc- tructure only is found in the Rhynchonellidee; but in most — perhaps all the other Brachiopoda* — pjgt HQ Ttrebratula. the shell is traversed by canals, from one surface * The fossil shells of the older rocks are so generally pseudomorphous, or par- take of the raetamorphic character of the rock ttself, that it is difficult to obtain sped mens in a state fit for microscopic examination. 214 MANUAL OF THE MOLLUSCA. to the other, nearly vertically, and regularly, the distance and size of the perforations varying with the species. Their external orifices are trumpet-shaped, the inner often very small; sometimes they bifurcate towards the exterior, and in Crania they become arborescent. The canals are occupied by ccecal processes of the outer mantle-layer,* and are covered ex- ternally by a thickening of the epidermis. Mr. Huxley has suggested that these co3ca are analogous to the vascular processes by which in many asci- dians the tunic adheres to the test ; the extent of which adhesion varies in closely allied genera. The large tubular spines of the Productida must have been also lined by prolongations of the mantle ; but their development was more probably related to the maintenance of the shell in a fixed position, than to the internal economy of the animal. (King.} Dr. Carpenter states that the shell of the Brachiopoda generally contains less animal matter than other bivalves ; but that Discina and Lingula consist almost entirely of a horny animal substance, which is laminar, and penetrated by oblique tubuli of ex- treme minuteness. He has also shown that there is not in these shells that distinction between the outer and inner layers, either in structure or mode of growth, which prevails among the ordinary bivalves ; the inner layers only differ in the minute size of the perforations, and the whole thickness corres- ponds with the outer layer only in the Lamellibranchiata. The loop, or brachial processes, are always impunctate. Of all shell-fish the Brachiopoda enjoy the greatest range both of climate, and depth, and time; they are found in tropical and polar seas ; in pools left by the ebbing tide, and at the greatest depths hitherto explored by the dredge. At present only 70 recent species are known ; but many more will probably be found in the deep-sea, which these shells mostly inhabit. The number of living species is already greater than has been discovered in any secondary stratum, but the vast abundance of fossil specimens has made them seem more important than the living types, which are still rare in the cabinets of collectors, though far from being so in the sea. Above 1,000 extinct species of Brachiopoda have been described, of which more than half are found in England. They are distributed throughout all the sedimentary rocks of marine origin from the Cambrian strata upwards, and appear to have attained their maximum, both of generic and specific development, in the Devonian age.* The oldest form of organic life at present known, both in the old and new world, is a Lingula. Some species (like Atrypa reticularis} * Called the " lining membrane of the shell," by Dr. Carpenter. (Davidson Intr. Mon. Brach.) Mr. Quekett states that the perforations are closed externally by disks, surrounded by radiating lines, supposed to indicate the existence of vibratile cilia in the living specimens. t The number of Devonian species amounts to 300; but these were not all living at one time, they are obtained from a whole series of deposits, representing a succession of periods. BBACHIOPODA. 215 jxteud through a whole " system" of rocks, and abound equally in both lemispheres ; others (like Spirifera striata) range from the Cordillera to the Ural mountains. One recent Terebratula (caput-serpentis] made its appear- ince in the Miocene Tertiary ; whilst others, scarcely distinguishable from it, ire found in the Upper Oolite, and throughout the Chalk series and London FAMILY I. TEREBRATULID^E. Shell minutely punctate; usually round or oval, smooth or striated; central valve with a prominent beak, and two curved hinge-teeth ; dorsal ralve with a depressed umbo, a prominent cardinal process between the dental ockets, and a slender shelly loop. Animal attached by a pedicle, or by the ventral valve : oral arms united o each other by a membrane, variously folded ; sometimes spiral at their extremities. Fig. 111. Terebratula vitrea, Born. TEREBRATULA, (Llhwyd.) Brug. Lamp-shell. Eiym. Diminutive of terebratus, perforated. Syn. Lampas, Humph. Gryphus, Muhlfeldt. Epithyris, Phil. Types, T. maxillata, PI. XV. fig. 1, (= Ter. minor-subrubra, Llhwyd. Anomia terebratula, L.) T. vitrea, fig. 3. Shell smooth, convex ; beak truncated and perforated ; foramen circular ; leltidium of two pieces, frequently blended ; loop very short, simple, attached y its crura to the hinge- plate. (Tig. Ill, A.) Animal attached by a pedicle ; brachial disk tri-lobed, centre lobe elon- 'ated and spirally convoluted. (Pig. Ill, B.) The young of T. diphya Pygope of Link) has bi-lobed valves, (PI. XV. fig. 2.) ; when adult the obes unite, leaving a round hole through the centre of the shell. Distr. 1 sp. Medit. 90—250 fathoms on nullipore mud. (Forbes.} Fossil, 100 sp. Devonian — . World-wide. 216 MANUAL OF THE MOLLUSCA. Sub-genera. Terebratulina (caput-serpentis) D'Orb. PI. XV. fig. 3. Fig. 112. Shell finely striated, auriculate, deltidium usually rudimental ; Fig. 112. Dorsal valve: Animc foramen incomplete ; loop short, rendered annular in the adult by the union of the oral processes. List. 7 sp. U. States, Norway, Cape, Japan. 10 — 1 20 fms. Fossil, 20 sp. Oxfordian — . U. S. Europe. WaW.heim.ia (australis) King. PI. XV. fig. 4 (p. 8, figs. 4, 5.) figs. 109, 113, 114. Fig. 113. Dorsal valve. Fig. 114. Ventral valve. Fig. 113. j, cardinal process; t', dental sockets ; p, hinge-plate; s, septum; c, crura of the loop ; I, reflected portion of the loop ; m, quadruple adductor-impression. Fig. 114. /, foramen; d, deltidium; t, teeth; o; single adductor-impression; r, cardinal muscles; x, accessory muscles ; p, pedicle muscles; v, position of the vent ; z, attachment of 'pedicle-sheath. Shell smooth or plaited, dorsal valve frequently impressed ; foramen com plete ; loop elongated and reflected ; septum (s) of smaller valve elongated Distr. 9 sp. Norway, Java, Australia, California, Cape Horn. Low- water — 100 fms. Fossil, 60 sp. Trias — . S. America, Europe. Eudesia (car dium) King, includes 1 recent, and 6 fossil species which are sharply plaited T. impressa (PL XV. fig. 5) is the type of a group which has the externa shape of Terebratella. BRACHIOPODA. 217 Fig. 116. Ter: Evansii. Dav. TEREBRATELLA, D'Orbigny. Type, T. dorsata, Gmel. (= Magellanica, Chemn.) PI. XV. fig. 7. Kg. 115. Shell smooth or radiately plaited ; dorsal valve longitudinally impressed; hinge-line straight, or not much curved ; beak with a flattened area on each side of the deltidium; foramen large; deltidium incomplete ; loop attached to the septum (*). Animal like Terelratula ; the spiral lobe of the brachial disk becomes very diminutive in some species, and is obsolete in Morrisia , and T. Cumingii. Distr. excluding sub- genera, 16 sp. Cape Horn, Valparaiso (90 ' fins.), New Zealand, Japan, Ochotsk, Spits- bergen, Labrador. Fossil, 16 sp. Lias — . U.S. Europe. In T. crenulata and Evansii (fig. 116) the dorsal septum sometimes projects so far as to touch the oppo- site valve, but in other examples it remains undeveloped. (Davidson.} Sub-genera. Trigonosemus (elegans) Konig. Syn. Delthyridaea (pecti- niformis) M'Coy. Fissirostra, D'Orb. Ex. T. Palissii, PI. XV. fig. 8. Shell finely plaited, beak prominent, curved, with a narrow apical foramen ; cardinal area large, triangular ; deltidium solid, flat ; cardinal process very prominent. Distr. 5 sp. Chalk, Europe. Lyra (Meadi) Cumberland, Min. Con. 1816. PI. XV. fig. 6. Syn. Te- rebrirostra, D'Orb. Rhynchora, Dalman.* Shell ornamented with rounded ribs ; beak very long, divided lengthwise internally, by the dental plates ; loop doubly attached ? Distr. 4 sp. cretaceous : Europe. Three species of similar form are found in the Trias of St. Cassian. Magas (pumila) Sby. Pig. 117. Shell smooth, conspicuously punctate, dorsal valve impressed, foramen angular, deltidium ru- dimentary; internal septum (s) promi- nent, touching the ventral valve; re- flected portions of the loop disunited (I). 2 sp. IT. Green-sand — Chalk. Europe. The recent Ter. Cumingii, of New Zealand, Fig. 117. M. pumila. * The name Rhynchora was given by Dalman to the Ter. costata. Wahl. (= T. pectinata, L.) on the supposition that it was identical with Sowerby's T. Lyra ? and as no specimen could be found with a long beak, an artificial one was manufactured for it, of which there is a cast in the Brit, M. The second species of" Rhynchora," Ter. spatulata, Wahl. has no beak whatever : in shape it is.. like an Argiopf. but measures an inch each way. The ventral valve is a simple bent plate with the teeth at the angles; the dorsal valve is flat, with a very wide hinge-plate, and sockets at the angles, whilst a single septum projects from the centre, with portions of a loop attached, 218 MANUAL OF THE MOLLUSCA. resembles Bouchardia externally, but has tlie diverging processes of the loop as in 7 " Fig. 118. B.tulipa,Bl* Bouchardia (tulipa) Davidson, fig. 118. Beak prominent, with a minute apical foramen (/) deltidium blended with the shell (d) apophysis anchor- shaped, the septum (s) being furnished with two short lamellae, Brazil, 13 fms. Fig. 119. Animal. *£• Dorsal vatoc.t Morrisia (anomioides, Scacchi) Davidson. Eig. 119. Shell minute, conspicuously punctate ; foramen large, encroaching equally on both valves ; hinge area small, straight ; loop not reflected, attached to a small forked process in the centre of the valve. Animal with sigmoid arms, destitute of spiral terminations ; cirri in pairs. Distr. 2 sp. Medit. 95 fms. (lories.) ? Fossil. 1 sp. Pliocene, Palermo. Fig. 120. Dorsal valve with animal, f Fig. 121. Dorsal valve. * The muscular [impressions in Bouchardia have been compared with those of Ter. Cumingii, of \rhich the animal is known. The large impressions (r)in the disk of the ventral valve appear to be formed by the cardinal muscles; a. by the adductor; p. by the pedicle muscles. t Fig. 119. c. loop; /. pedicle notch ; o. the ovaries. From the originals in Mr. Davidson's collection ; magnified ten diameters. BKACH10PODA. 219 Kraussia (rubra) Dav. Cape. Fig. 121. K. Lamarckiana, Dav. Aus- tralia. Fig. 120. Shell transversely oblong; hinge-line nearly straight; beak truncated, laterally keeled ; area flat ; foramen large, deltidium rudi- mentary; dorsal valve longitudinally impressed, furnished inside with a forked process rising nearly centrally from the septum; interior often strongly tuberculated. The apophysis is sometimes a little branched, indi- cating a tendency towards the form it attains in fig. 122. Animal with rather small oral arms, the spiral lobe very diminutive. Distr. 6 sp. S, Africa, Sydney, N. Zealand; low-water to 120 fms. Fig. 122. Animal. Dorsal valve. ? Megerlia (truncata) King, 1850. PI. XV. fig. 9. Fig. 122. Loop trebly attached ; to the hinge-plate by its crura, and to the septum by pro- cesses from the diverging and reflected portions of the loop. Distr. 2 sp. Medit. Philippines. These species belong to the same natural group with Kraussia. ? Kingena (lima) Dav. Cretaceous, Europe, Guadaloupe. Valves spinu- lose; loop trebly attached. Fig. 123. Ter. (Kingena) lima-, (after Davidson.) /. dental sockets rj, cardinal process, c. crura; d. diverging processes of loop ; r, reflected portion ; e. third attachment of loop ; *. dorsal septum. 220 MANUAL OF THE MOLLUSCA. ? Ismenia (pectunculus) King. Coral rag, Europe. Valves ornamented with corresponding ribs ; loop trebly attached. ? Waltonia (Valenciennei) Dav. New Zealand. Perhaps the fry of Ter . rubicunda, with the reflected part of the loop wanting. Fig. 124. Argiope decollata. Fig. 125. A. Neapolitan^ Sc. ARGIOPE, Eudes Deslongchamps. Etym. Argiope, a nymph. Syn. Megathyris, D'Orb. Type, A. decollata, PI. XV. %. 10. Fig. 124—126. Shell minute, transversely oblong or semi-ovate, smooth or with corre- sponding ribs; hinge line wide and straight, with a narrow area to each valve ; foramen large, deltidium rudimentary ; interior of dorsal valve with one or more prominent, sub-marginal septa ; loop two or four-lobed, adhering to the septa, and more or less confluent with the valve. Fig. 126. A. decollata, ^p ; dorsal valve with the animal, from a specimen dredged by Prof. Forbes in the ./Egean. The oral aperture is seen in the centre of the disk. Animal with oral arms folded into two or four lobes, united by mem- brane, forming a brachial disk fringed with long cirri : mantle extending to the margins of the valves, closely adherent. Distr, 4 sp. N. Brit. Madeira, Canaries, Medit. 40 — 105 fathoms. Fossil. 5 sp. U. Greensand — . Europe. Interiors of dorsal valves magnified, from the originals in Coll. Davidson. BRACHIOPODA. 221 Fig. 127. T. radians. THECIDIUM, Defrance. Etym. TheUdion, a small pouch. Type, T. radians, PI. XV. fig. 11. Shell small, thick, punctate, attached by the beak ; hinge-area (ft) flat ; deltidium (d) triangular, indistinct : dorsal valve (fig. 127) rounded, de- pressed ; interior with a broad granulated margin ; cardinal process promi- nent, between the dental sockets ; oral processes united, forming a bridge over the small and deep visceral cavity ; disk grooved for the reception of the loop, the grooves separated by branches from a central septum ; loop often unsym- metrical, lobed, and united more or less intimately with the sides of the grooves: ventral valve (fig. 129) deeply excavated , hinge-teeth prominent ; cavities for the adductor (a) and pedicle muscles (p) small ; disk occupied by two large smooth impressions of the cardinal muscles, bor- dered by a vascular line. Animal (fig. 128) with elongated oral arms, folded on them- selves and fringed with long cirri ; mantle extending to the margin of the valves and closely adherent ; epidermis distinct. T. radians is the only un-attached spe- cies, it is supposed to be fixed by a pedicle when young (D'Orb.) . T. hierofflyphicum, Pi. XV. fig. 12, has a very complicated interior ; whilst in seve- ral others there are but two brachial lobes. The Liassic species form the subject of a monograph by M. Eugene Deslong- champs; they are often minute, and attached in numbers to sea-urchins, corals, and terebratulse. Distr. 1 sp. Medit. Fossil, 27 sp. Trias — . Europe. * Dorsal valve with the animal, magnified. Coll. Davidson. Fig. 129. T. radians, y. 222 MANUAL OP THE MOLLUSCA. I Fig. 130. Dorsal valve. Profile* a, adductor; c, crura; /, loop; .;", cardinal process; p, hinge-plate; s, dorsal septum ; v. s. ventral septum; t, dental sockets. ? STRINGOCEPHALUS, Defiance. Etym. Strinx (stringos) an owl, cephale the head.f S. Burtini, PI. XV. fig. 13. Fig. 130, 131. Devonian, Europe. Shell punctate; sub -orbicular, with a prominent beak: ventral valve with a longitudinal septum (v.s.} in the middle; hinge-area distinct ; foramen large and angular in the young shell, gradually surrounded by the deltidium and rendered small and oval in the adult; deltidium composed of three elements; teeth prominent; dorsal valve depressed, cardinal process (/) very prominent, some- times touching the opposite valve, its extremity forked to receive the ventral septum (v.s.}; hinge-plate (p) sup- porting a shelly loop, after the manner of Argiope. Fig. 131.1 FAMILY II. SPIRIFERIDJS. Shell furnished internally with two calcarious spiral processes (apophyses) directed outwards, towards the sides of the shell, and destined for the support of the oral arms ; which must have been fixed immoveably; the spiral lamellae * The loop (which was discovered by Prof. King) has a distinct suture in the middle ; the dotted lines proceeding from its inner edge are added from a drawing by Mr. Suess, and represent what he regards as shelly processes for supporting a mem- branous disk. They may be portions of spirals, whose outer whirls are confluent. t Internal casts of Producta gigantea are called " owl-heads" by quarrymen in the North of England. (Sowerby). I Fig. 131. Young shell, magnified 4 diameters; h, hinge area; b, deltidium: p, pseudo-deltidium. BRACH10PODA. 223 are sometimes spinulose, indicating the existence of rigid cirri, especially on the front of the whirls ; valves articulated by teeth and sockets. Fig. 132. Dorsal; Ventral valve. % SPIRIFERA, Sowerby. Type, S. striata, Sby. fig. 132. Syn. Trigonotreta, Ko'nig. Choristites. Fischer. Delthyris, Dalman. Martinia &c. M'Coy. Shell impunctate,* transversely oval or elongated, tri-lobed, beaked, bi- convex, with a dorsal ridge and ventral furrow ; hinge-line wide and straight ; area moderate, striated across ; foramen angular, open in the young, after- wards progressively closed ; ventral valve with prominent hinge-teeth, and a central muscular scar, consisting of the single adductor flanked by two cardi- nal impressions : dorsal valve with a small cardinal process, a divided hinge- plate, and two conical spires directed outwards and nearly filling the cavity of the shell ; crura united by an oral loop. The shell and spires are some- times silicified, in limestone, and may be developed by means of acid. In S. mosquensis the dental plates are prolonged nearly to the front of the ventral valve. Distr. 200 sp. L. Sil. — Trias. Arctic America — Chile, Falkland Ids, Europe ; China ; Thibet ; Australia ; Tasmania. In China these and other fossils are used as medicine. Sub-genera. Spiriferina, D'Orb. S. Walcotti, PI. 15, f.14. Shell punc- tate, external surface spinulose ; foramen covered by a pseudo-deltidium ; in- terior of ventral valve with a prominent septum, rising from the adductor scar. Distr. 6 sp. Trias — L. Oolites. Brit. France, Germany, S. America. Cyrtia, Dalman. C. exporrecta, PL XV. fig. 15. Shell impunctate, pyra- midal, beak prominent, area equiangular, deltidium with a small tubular foramen. Fossil, 7 sp. Silur. — Trias. Europe. In C. BucUi, heteroclyta, calceola, &c. the shell is punctate. ATHYRIS, M'Coy. Etym, A, without, thuris, a door.f (i. e. deltidium). Syn. Spirigera, D'Orb. Cleiothyris, King (not Phil.) * Prof. King attributes this to metamorphism ; S. Demarlii. Bouch. from the Devonian limestone, is punctate. (Carpenter). t Sometimes employed, incorrectly, in the sense of a door -way or foramen. 224 MANUAL OF THE MOLLUSCA. Types, A. concentrica, Buch. A. Roissyi, fig. 133, 134. A. lamellosa, PI. XV. fig. 16. Shell impunctate, transversely oval, or sub -orbicular, bi-convex, smooth, or ornamented with squamose lines of growth, sometimes developed into wing-like expansions, (fig. 134*) ; hinge-line curved, area obsolete, foramen Fig. 133. Interior of dorsal valve. Fig. 134. Specimen with fringe. round, truncating the beak, deltidium obsolete ; hinge-plate of dorsal valve with four muscular cavities, perforated by a small round foramen, and supporting a small complicated loop (?) between the spires ; spires directed outwards, crura united by a prominent oral loop. The foramen in the jiinge-plate occupies the situation of the notch through which the intestine passes in the recent Rhynchonella ; in A. con- centrica a slender curved tube is sometimes attached to the foramen, beneath the hinge-plate. A. tumida has the hinge-plate merely grooved, and the byssal foramen is angular. Fossil, about 20 sp. Silurian — Lias. N. and S. America ; Europe. Sub-genus? Merista, Suess. Ter. scalprum, Rcemer^ (A. cassidea, Quenst. Sp. plebeia. Ph.) Silurian — Devonian; Europe. Shell impunctate, dental plates (v) and dorsal septum (d] supported by arched plates (" shoe-lifter" processes, of King) which readily det- ach, leaving cavities (as in fig. 135) ; spiral arms have been observed in all the species. RETZIA, King. Dedicated to the distinguished Swedish naturalist, Retzius. Type,Ter. Adrieni, Vern. Ex. R. serpentina, Carb. L. Belgium. Fig. 136- Shell punctate, terebratula-shaped ; beak truncated by a round foramen rendered complete by a distinct deltidium: hinge-area small, triangular, sharply defined ; interior with diverging shelly spires. Fossil, about 20 species. Silurian — Trias. S. America. U. S. Europe- * The spurious genus Actinoconchus (M'Coy) was founded on this character; similar expansions are formed by species of Atrypa, Camarophoria, and Producta. Fig. 135. Merista. BKACH10PODA. 225 Prof. King first pointed out the existence of calcarions spires in several Tere- bratulce of the older rocks, and others have been discovered by MM. Quen- stedt, De Koninck, and Barrande. In form they resemble Terebratulina, Eudesia, and Lyra. Fig 136. Retzia serpentina, D. K. Fig, 137, Uncites gryphus. UNCITES, Defrance. Type, U. gryphus, PL XV. fig. 17. Fig 137. Fossil, Devonian. Europe. Shell impunctate ; oval, bi-convex, with a long incurved beak ; foramen apical, closed at an early age; deltidium, large, concave; spiral processes directed outwards ; no hinge- area. The large, concave deltidium of Uncites so much resembles the channel formed by the dental plates of Pentamerus, that Dalman mistook the shell for a member of that genus. The discovery of internal spires, by Prof. Bey- rich, shows that it only differs from Retzia in being impunctate and destitute of hinge-area. Some of the specimens have corresponding depressions in the sides of the valves (fig. 137, p) forming pouches which do not communicate with the interior. FAMILY III. RHYNCHONELLID.E. Shell impunctate, oblong, or trigonal, beaked; hinge-line curved ; no area; valves articulated, convex, often sharply plaited ; foramen beneath the beak, usually completed by a deltidium, sometimes concealed; hinge.teeth supported Fig. 138. R. nigricans. Fig. 139. Ventral: Dorsal. Fig. 138. Dorsal valve with the animal; a, adductor muscles : i, intestine. Fig. 139. R. psittacea, interiors, s, septum ; /, foramen ; d, deltidium; t, teeth; t, sockets'; c, oral lamellse; a, adductor impressions ; r, cardinal; p, pedicle muscles ; o, ovarian spaces. 226 MANUAL OF THE MOLLUSCA. by dental plates ; hinge-plate deeply divided, supporting oral lamellse, r; provided with spiral processes ; muscular impressions grouped as in Terebra tula ; vascular" impressions consisting of two principal trunks in each valvi narrow, dichotomising, angular, the principal posterior branches inclosing ovarian spaces. Animal (of Rhynchonella} with elongated spiral arms, directed inwards* towards the concavity of the dorsal valve; alimentary canal terminating behind the insertion of the adductor in the ventral valve ; mantle not adhering, its margin fringed with a few short setse. Ven- Ventral aspect. Umbonal aspect. Fig. 140. Rh. acuminata, internal casts. Fig. 140! Umbonal aspect, with the dorsal valve above (Coll. Prof. King), tral aspect (Coll. Prof. Morris). A, adductor; R, cardinal; P, pedicle; V, vascular O, ovarian impressions. RHYNCHONELLA.. Fischer. Syn. Hypothyris, Phil. Hemithyris (psittacea) D'Orb. Acanthothyris (spinosa) D'Orb. Cyclothyris (latissima) M'Coy. Trigonella (part) Fische (not L. nor Da Costa). Types, R. acuta, PI. XV. fig. 18 : furcillata, fig. 19 : spinosa, fig. 20 : acu minata, fig. 140 : nigricans, fig. 138; psittacea, fig. 139 (p. 8, fig. 3). Shell trigonal, acutely beaked, usually plaited ; dorsal valve elevated in front, depressed at the sides ; ventral valve flattened, or hollowed along the centre, hinge plates supporting two slender curved lamellae ; dental plates diverging. The foramen is at first only an angular notch in the hinge-line of the ven tral valve, but the growth of tbe deltidium usually renders it complete in th adult shell ; in the cretaceous species it is tubular. In R. acuminata an many other palaeozoic examples, the beak is so closely incurved as to allow no space for a pedicle. Both the recent Rhynchonella are black ; R. ocfo plicata of the Chalk sometimes retains six dark spots. BRACHIOPODA. 227 Distr. 2 sp. E. psittacea, Labrador (low water?) Hudson's Bay, 100 fms. : Melville Id. Sitka ; Icy Sea. R. nigricans, New Zealand, 19 fms. Fossil, 250 sp. L. Silurian — . N, and S. America, Europe, Thibet, China. Sub-genera, ? Porambonites, Pander. P. sequirostris, Schl. Shell im- punctate ; surface minutely pitted ; each valve with a minute hinge-area and indications. of two septa; foramen angular, usually concealed. Distr. 4 sp. L. Silurian. Russia, Portugal. Camarophoria, King. T. Schlotheimi, Buch. Tigs. 141, 142. Ventral valve with converging dental plates (d) supported on a low septal ridge (s) ; dorsal valve with a prominent septum (s) supporting a spoon-shaped central process (v) ; oral lamellae long and slender (o). Foramen angular, cardinal process distinct (f). Fossil., 9 sp. ? Garb. — Permian (Magnesian limestone). Germany; England. ' t Fig. 141. Internal cast.* Fig. 142. Section. PENTAMERUS, Sowerby. Etym. Pentameres, 5 -partite. Syn. Gypidia (conchydium) Dalman. Type, P. Knightii, PI. XV. fig. 22. Fig. 143. Shell impunctate, ovate, ventricose, with a large incurved beak ; valves usually plaited; foramen angular ; no area or deltidium; dental plates (d) converging, trough-like, supported on a prominent septum (s) ; dorsal valve with two contiguous longitudinal septa (s s) opposed to the plates of the other valve. Oral lamellse have been detected by Mr. Salter in P. liratus ; in P. ? Ire- virostris (Devonian, Newton) the dorsal valve has a long trough-like process supported by a single low septum. Fossil, 20 sp. Arctic America, U. S. Europe. *. Ventral side of cast, showing the V shaped cavity of the dental plates, and the impressions of branchial veins, accompanied by arteries; (after King.) 228 MANUAL OF THE MOLLUSCA. Fig. 143. Longitudinal; Transverse section. The relations of the animal to the shell, in such a species as P. Knightii can only be inferred by comparison with other species in which the internal plates are less developed, a*hd with other genera, such as Cyrtia and Camaro- phoria. In fig. 143, the small central chamber (v) must have been occupied by the digestive organs, the large lateral spaces (d s) by the spiral arms : it is doubtful whether any muscles were attached to these plates ; in Porambo- nites the adductor impression is situated beyond the point to which the dental plates converge, and in Camarophoria the muscular impressions occupy the same position as in Rhynchonella. ATRTPA, Dalman. Syn. Cleiothyris, Phillips. Spirigerina, D'Orb.* Hipparionyx, Vanuxem. Type, A. reticularis, PL XV. fig. 17. Pigs. 144, 145. Fig. I'M, Dor sal valve. Fig. 145, Ventral valve; interiors, p, hinge-plate; a, impressions of adductor muscle; c, cardinal muscle p, pedicle muscle ; o, ovarian sinus ; d, deltidium. Shell impunctate : oval, usually plaited and ornamented with squamose lines of growth; dorsal valve gibbose; ventral depressed in front; beak * The term Atrypa (a, without, trupa, foramen) is objectionable, like all Dalman's names; but M. D'Orbigny has made no improvement by proposing Spirigerina, in addition to Spirifera, Spirigera, and Spiriferina ! BRACHIOPODA. 229 small, often closely incurved: foramen round, sometimes completed by a deltidium, often concealed : dorsal valve with a divided hinge-plate, support- ing two broad spirally coiled lamellae ; spires vertical, closely appressed, and directed towards the centre of the valve ; teeth and impressions like Rhyn- chonella. The shells of this genus differ from Rhynchonella chiefly in the calcifi- cation of the oral supports, a character of uncertain value. Fossil, 15 sp. L. Silurian — Trias. America (Wellington Channel ! Falkland Ids.), Europe, Thibet. FAMILY IV. ORTHID^.* Shell transversely oblong, depressed, rarely foraminated; hinge-line wide and straight; beaks inconspicuous; valves plano-convex, or concavo- convex, each with a hinge-area (h) notched in the centre ; ventral valve with prominent teeth (f) ; muscular impressions occupying a saucer-shaped cavity with a raised margin ; adductor (a) central ; cardinal and pedicle impressions (r) conjoined, lateral, fan-like : dorsal valve with a tooth-like cardinal-pro- cess between two curved brachial processes (c) ; adductor impression (a) quadruple: vascular impressions consisting of six principal trunks in the dorsal valve, two in the ventral, the external branches turned outwards and backwards inclosing wide ovarian spaces (0). Indications have been observed, in several genera, of horizontally-coiled spiral arms ; the space between the valves is often very small. The shell- structure is punctate, except in a few instances, where the original texture is probably obliterated. Dorsal valve.\ Ventral valve. Fig: 147. Orthis, striatula. Devonian, EifeL ORTHIS, Dalman. Etym. Orthos, straight. Type, 0. rustica, PI. XV. fig. 23. Syn. Dicoelosia (biloba) King. Platystrophia (biforata) King. Gonam- bonites (inflexa) Pander. Orthambonites (calligramma) Pander. * The names of the Families are formed from those of the typical genera, by sub- stituting ides for the last syllable of the genitive case. f From a specimen presented by M. De Koninck to the British Museum; internal casts of this fossil were called hysterolites by old authors. 230 MANUAL OF THE MOLLUSCA. Shell transversely oblong, radiately striated or plaited, bi-convex, hinj line narrower than the shell, cardinal process simple, brachial pn tooth-like, prominent and curved. Fossil, 100 sp. L. Silurian — Garb. Arctic America, U.S. S. America Falkland Ids. Europe, Thibet. ? Sub-genera, Orthisina, D'Orb. 0. anomala, Schl. Fig. 148 Pronites (ascendens) and Hemipronites, Pander. Shell impunctate ? wii at the hinge-line ; cardinal notch closed, byssal notch (fissure) covered by a convex pseudo- deltidium, sometimes perforated by a small round foramen. Fossil. L. Silurian, Europe. 0. pelargonatus (Streptorhynchus, King) from the Magnesian limestone, 0. senilis, Garb limestone, and some Devonian species, have the beak twisted, as it if had been attached ; there is no foramen. STROPHOMENA, Blainville.* Etym. Strophos bent, mene crescent. Ex. S. rhomboidalis, PI. XV. fig. 24. (= Leptaena depressa, Sby.) Syn. Leptsena (depressa) Dalnian. Leptagonia, M'Coy. Enteletes, ] Shell semi-circular, widest at the hinge-line, concavo-convex, depn radiately striated; area double; ventral valve with an angular notch, pro- gressively covered by a convex pseudo-deltidium ; umbo depressed, rarely $] perforated, in young shells, by a minute foramen (fig. 149, e) ; musculai depressions 4, central pair narrow, formed by the adductor: external paii (m) fan-like, left by the cardinal and pedicle muscles ; dorsal valve with E bi-lobed cardinal process, between the dental sockets, and four depressions foi the add actor muscle. Fig. 148, Orthisina. Fig. 149. Ventral valve. Dorsal valve. Interior of S. analoga, Garb, limestone (after King). e, foramen ; t, teeth ; o, ovarian spaces ; b, brachial pits ? * The name Strophomena (rugosa) was originally given by Rafinesque to sonn unknown or imaginary fossil ; it has, however, been adopted both in America an< Europe for the group typified by S. alternata and planumbona. BllACHIOPODA. 231 There are no apparent brachial processes in the dorsal valve of Stro- pkomena, and it is possible that the spiral arms may have been supported at some point near the centre of the shell (£) as in Producta ; S. rhomb oidalis occasionally exhibits traces of spiral arms, in the ventral valve. S, latlssima Bouch. has plain areas, like Calceola. The valves of the Strophomenas are nearly flat until they approach their full growth, they then bend abruptly to one side ; the dorsal valve becomes concave in S. alternata and rhomboidalis, whilst in S. planumbona and euglypha it be. comes convex; these distinctions are not even sub-generic. Fossil, 100 sp. L. Silurian — Garb, _T Fig. 150. Lepttena. f N. America, Europe, Thibet. A§ hlnge areas. V) ventral> B> interior S. demissa, Conr. (Stropheodonta, of dorsal valve. ' Hall). S. Dutertrii, and several other species have a denticulated hinge-line. Sub-genera ? Leptana (part) Dalman. L. transversalis, fig. 150. (Plec- tambonites, Pander.) Valves regularly curved; dorsal concave, thickened, muscular impressions elongated. Fossil, L. Silurian — Lias. N. America, Europe. The lias Leptseiias resemble Thecidia internally ; they are free shells, with sometimes a minute foramen at the apex of the triangular delti- dium ; L. liassma, PI. XV. fig. 25. Fig, 145. Producta ? Leonhardi, Koninclda, Suess. Producta Leonhardi, AVissm. (P, alpina, Schl.) fig. 145. Trias, St. Cassian. Shell orbicular, concavo-convex, smooth; valves articu- lated ? closely appressed ; ventral valve convex, dorsal concave ; beak in- curved, no hinge-area* nor foramen ? interior of each valve furrowed by two spiral lines of four volutions, directed inwards, and crossing the vascular impressions ; umbo with 3 diverging ridges. The small spiral cavities, once occupied by the arms, and now filled with spar, may be seen in specimens with both valves, by holding them to the light. Mr. Suess of Vienna states A, Translucent specimen; B, interior of dorsal valve. M 232 MANUAL OF THE MOLLUSCA. that he has found traces of very slender spiral lamellae occupying the furrows. This curious little shell most resembles the Triassic Leptana dubia (Pro ducta) Minister (= Crania Murc/dsoni, Klipst. !) DAVIDSONIA, Bouchard. Dedicated to the author of the Monograph of British Fossil Brachiopoda Type, D. Verneuili, Bouch. Fig. 151. Devonian, Eifel. Fig. 151. Dorsal valve. Ventral valve, Shell solid, attached by outer surface of the ventral valve to rocks, shells, and corals ; valves plain, articulated ; ventral valve with a wide area (K) ; foramen angular, covered by a convex deltidium (d] : disk occupied by two < nical elevations, obscurely grooved by a spiral furrow of 5-6 volutions ; dorsa valve with two shallow lateral cavities ; vascular impressions consisting of two principal sub -marginal trunks, in each valve, with diverging branches ; cardinal and adductor impressions distinct. The furrowed cones undoubtedly indicate the existence of spiral arms, similar to those of Atrypa (fig. 144), but destitute of calcified supports. The mantle-lobes seem to have conti- nued depositing shell until the internal cavity was reduced to the smallest possible limit. Fig. 152. Dorsal valve. Ventral valve. ? CALCEOLA, Lamarck. Etf/m. Calceola, a slipper. Type, C. sandalina, PL XV. fig. 26. Fig. 152. Shell thick, triangular ; valves plain, not articulated : ventral valve pyra- midal ; area large, flat, triangular, with an obscure central line ; hinge-lin? straight, crenulated, dorsal valve flat, semi-circular, with a narrow area (h), a small cardinal process (j), and two lateral groups of small apophysary (?) ridges (b) ; internal surface punctate-striate. Fossil, Devonian, Eifel, Brit. BRACHIOPODA. 233 ^he supposed Carboniferous species (Hypodema, D.K.) is, perhaps, related o Pileopsis. Calceola is shaped like Cyrtia., and its hinge-area resembles hat of some Strophomenas. FAMILY V. PRODUCTION. Shell concavo-convex, with a straight hinge-line; valves rarely articu- ated by teeth ; closely appressed, furnished with tubular spines ; ventral 'alve convex; dorsal concave; internal surface dotted with conspicuous, unnel-shaped punctures; dorsal valve with a prominent cardinal process; irachial processes (?) sub-central; vascular markings lateral, broad and imple ; adductor impressions dendritic, separated by a narrow central ridge ; Central valve with a slightly notched hinge-line ; adductor scar central, near he umbo ; cardinal impressions lateral, striated. Fig. 153. Producta gigantea, % Carl, limestone. A, interior of dorsal valve ; B, interior of ventral valve, with the umbo removed; ), ideal section of both valves ; D, hinge-line of A ; .;', cardinal process; a, adductor; cardinal muscles; b, oral processes?; *, hollows occupied by the spiral arms ; v , 'ascular impressions ; h, hinge-area. 234 MANUAL OF THE MOLLUSCA. by a pedicle when young, the impressions of the pedicle-muscle blending with those of the hinge-muscles (c) in the ventral valve. A few species appear to have been permanently fixed. P. striatais irregular in its growth, elongated and tapering towards the beak, and occurs in numbers packed closely to- gether. P. proboscidea seems to have lived habitually in cavities, or half- buried in mud, as suggested by M. D'Orbigny ; its ventral valve is prolonged several inches beyond the other, and has its edges rolled together and united, forming a large permanently open tube for the brachial currents. The large spines are most usually situated on the ears of the ventral valve, and may have served to moor the shell ; being tubular they were permanently suscep- tible of growth and repair. Although edentulous, the dorsal valve must have turned on its long hinge- line with as much precision as in those genera which are regularly articulated by teeth. Fossil, 60 sp. Devonian — Permian. N. and S. America, Europe., Spitzbergen, Thibet, Australia. Fig. 154. Exterior. Interior, S/ib-genus, Aulosteges, Helmersen. A. Wangenheimii, Vern. fig. 154. Permian, Russia. Shell like Producta ; ventral valve with a large flat trian- gular hinge-area (h}% with a narrow convex pseudo-deltidium (d) in the centre: beak a little distorted, as if attached when young; dorsal valve slightly convex near the umbo ; interior as in Producta (longi-spina.) STROPHALOSU, King. Ex. S. Morrisii, King. fig. 155. Syn. Orthothrix, Geinitz. Shell attached by the umbo of the ventral valve ; sub-quadrate ; covered with long slen- der spines; valves articulated, dorsal mode- rately concave, ventral convex, each with a small area ; fissure covered ; vascular impres- sions conjoined, reniform. Fossil, 8 sp. Devonian — Trias. Europe; Himalaya (Gerard), Fig. 1 55. S. Morrisii. BRACHIOPODA. 235 CHONETES, Fischer. Ex. C. striatella, PL XV. fig. 29. Etym. Chone, a cup. Shell transversely oblong, with a wide and straight hinge-line ; area double ; valves radiately striated, articulated ; hinge-margin of ventral valve with a series of tubular spines; fissure covered; interior punctate-striate ; vascular impressions (#) very small. (Davidson) . Fossil, 24 sp. Silurian — Carboniferous. Europe, N. America, Falk- land Ids. Fig. 156. Dorsal valve. Ventral valve.* FAMILY VI. CRANIAM. Shell orbicular, calcarious, hinge-less ; attached by the umbo, or whole "breadth of the ventral valve, rarely free ; dorsal valve limpet-like ; interior of each valve with a broad granulated border ; disk with four large muscular Impressions, and digitated vascular impressions ; structure punctate. Animal with free spiral arms, directed towards the concavity of the dorsal valve, and supported by a nose-like prominence in the middle of the lower valve; mantle extending to the edges of the valves, and closely adhering, its margins plain. (Fig. 159.) Fig. 157. Ventral valve. Fig. 158. Dorsal valve. Crania anomala, Muller. y Zetland. a, anterior adductors; a', posterior adductors ; c, protractor sliding muscles; c', cardi- nal muscle, r , o, retractor sliding muscles. * Interiors of two sp. of Chonetes from Nehou and the Eifel, after Davidson; a, adductor : c, cardinals. 236 MANUAL OF THE MOLLUSCA. CRANIA, Retzius. Etym. Kraneia, capitate. Type, Anomia craniolaris, L. Ex, C. Iguabergensis, PL XV. fig. 30. C. anomala, figs. 157—159. Syn. Criopus, Poll. Orbicula {anomala) Cuvier, = O. Norvegica, Lara, Shell smooth or radiately striated ; umbo of dorsal valve sub-central : of ventral valve sub-central, marginal, or prominent and cap-like, with an ob- scure triangular area traversed by a central line. The large muscular impressions of the attached valve are sometimes convex, in other species deeply excavated; those of the upper valve are usually convex, but in C. Parisiensis the anterior (central) pair are deve- loped as prominent diverging apophyses. In C. tripartita, Minister, the nasal process divides the fixed valve into three cells.* C. Ignabergensis is equivalve, and either quite free or very slightly attached. C. anomala is gregarious on rocks and stones in deep water, both in the North Sea and Mediterranean (40—90 fathoms, living ; 150 fms. dead ; Forbes) : the animal is orange- coloured, and its ]abial arms are thick, fringed with cirri, and disposed in a few horizontal gyrations (fig. 159.) Distr. 5 sp. Spitzbergen, Brit. Medit. India, New S. Wales. — 150 fms> Fossil, 28 sp. L. Silurian — . Europe. C. antiquissima, Eichw. (Pseudo-crania M'Coy) is free, and has the inter- nal border of the valves smooth ; the branchial impressions blend in front. Spondylobolus craniolans, M'Coy, is a small and obscure fossil, from the L. Silurian shale of Builth. The upper valve appears to have been like Crania, the lower to have had a small grooved beak, with blunt, tooth-like processes at the hinge-line. Fig. 159. Crania.^ Fig. 160. Discina.% * M. Quenstedt has placed the Oolitic Cranias in Siphonaria! t Dorsal valve with the animal, seen hy removing the mantle. J The animal as seen on the removal of part of the lower mantle-lobe, the ex- tremities of the labial arms are displaced forwards, in order to show their spiral terminations: p, is the expanded surface of the pedicle; the mouth is concealed by the overhanging cirri. The mantle-fringe is not represented. BllACHIOPODA. 237 FAMILY VII. DISCINIDJS. Shell attached by a pedicle, passing through a foramen in the ventral valve ; valves not articulated ; minutely punctate. Animal with a highly vascular mantle, fringed with long horny setae : oral arms curved backwards, returning upon themselves, and ending in small spires directed downwards, towards the ventral valve. Fig. 161. Dorsal. Fig. 162. Ventral lobe. Discina lamellosa, Brod. y. M, umbo; /, foramen; d, disk; a, anterior adductors; a', posterior adductors; c,c', protractor sliding muscles; r, retractor muscles. The mantle-fringe is not represented in fig. 162. DISCINA, Lamarck. Syn. Orbicula, Sby (not Cuvier*). Orbiculoidea (elliptica) D'Orb. Type, D. lamellosa, PL XV. fig. 31. (= D. ostreoides, Lam.) Shell orbicular, horny ; upper valve limpet-like, smooth or concentrically lamellose, apex behind the centre ; lower valve flat or conical, with a sunk aud perforated disk on the posterior side; interior polished ; lower valve with a central prominence in front of the foramen. Animal transparent ; mantle lobes distinct all round ; labial folds united, not extensile ; alimentary canal simple, bent upon itself ventrally, and termi- nating between the mantle-lobes on the right side. There are four distinct adductor muscles, as in Crania • and the same number of sliding muscles, viz. two pairs for the protraction and two for the retraction of the dorsal valve, but some of these are probably inserted in the pedicle. The oral cirri are extremely tender and flexible, contrasting with the stiff and brittle setse of the mantle, which are themselves more like the bristles of certain anne- * The Orbicula of Cuvier was the Patella anomala, Mull (= Crania) as pointed out by Dr. Fleming, in the " History of British Animals," 1828. 238 MANUAL OF THE MOLLUSCA. lides (e. g. the sea-mouse, Aphrodite], The relation of the animal to the perforate and imperforate valves is shown to be the same as in Terebratula, by the labial fringe ; but the only process which can possibly have afforded support to the oral arms, is developed from the centre of the ventral valve, as in Crania. Baron Ryckholt has represented a Devonian fossil from Bel- gium, with a fringed border; but if this shell is the Crania obsoleta of Goldfuss, the fringe must belong to the shell, and not to the mantle. Distr. 7 sp. W. Africa, Malacca, Peru, Panama. Fossil, 29 sp. Silurian — . Europe, U. States, Falkland Ids. The (27) Palaeozoic and secondary species constitute the genus Orbiculoidea, D'Orb. (Schizotreta, Kutorga.) In some species the valves are equally convex, and the foramen occupies the end of a narrow groove. Sub-genus, Trematis, Sharpe. (= Orbicella, D'Orb.) T. terminalis, Emmons. Valves convex, superficially punctate ; dorsal valve with a thick- ened hinge-margin (and three diverging plates, indicated on casts ; Sharpe.} Fossil, 14 sp. L. and U. Silurian. N. America, Europe. Fig. 163. Fig. 164. Exterior. Fig. 163, a, Interior, SIPHONOTRETA, Vemeuil. Etym. Siphon a tube, tretos perforated. Types, S. unguiculata, Eichw. fig. 163, ]63, a. S. verrueosa, fig. 164. Shell oval, bi-convex, slightly beaked, conspicuously punctate, or spiny ; beak perforated by a tubular foramen; hinge-margins thickened; ventral valve with four close adductor scars surrounding the foramen. The spines are tubular, and open into the interior of the shell by prominent orifices. ( Carpenter.} S. anglica, Morris, has moniliform spines. Fossil, 6 sp. L. and U. Silurian. Brit. Bohemia, Russia. ? Acrotreta (sub-conica) Kutorga, L. Silurian, Russia. Shaped like Cyrtia, with an apical foramen ; no hinge. FAMILY VIII. LINGULIDJS. Shell oblong or orbicular, sub-equivalve, attached by a pedicle passing out between the valves ; texture horny, minutely tubular. BRACHIOPODA. 239 Animal with a highly vascular mantle, fringed with horny setae ; oral irms thick, fleshy, spiral, the spires directed inwards, towards each other; -alves opened and closed by sliding muscles. Fig. 165. Dorsal* 166. Ventral. 167. Ventral. Lingula anatina, Lam (original). Syn. Patella unguis, L. (part.) a a, anterior adductors ; a', posterior adductor; p p, external protractors ; p'p', cen- ral proti actors; r r, anterior retractors; r'r'r', posterior retractors; c, capsule of pedicle; tin, visceral sheath; o, oesophagus; s, stomach; /, liver; i, intestine; v, vent ; hh, auricles ; h\ left ventricle ; b, branchial vessels ; m\ mantle margin ; m, inner amina of mantle-margin retracted, showing bases of setae; s, setae. LINGULA, Bruguiere. Eiym,. Lingula, a little tongue. Type, L. anatina, PI. XV. fig. 32. Shell oblong, compressed, slightly gaping at each end, truncated in front, •ather pointed at the umbones ; dorsal valve rather shorter, with a thickened linge -margin, and a raised central ridge inside. Animal with the mantle-lobes firmly adhering to the shell, and united to the epidermis, their margins distinct, and fringed all round ; branchial veins giving off numerous free, elongated, narrow loops from their inner surfaces ; visceral cavity occupying the posterior half of the shell, and surrounded by a strong muscular sheath ; pedicle elongated, thick ; adductor muscles 3, the posterior pair combined ; two pairs of retractors, the posterior pair unsym- * In fig 165 a small portion of the liver and visceral sheath have been removed, to show the course of the stomach and intestine. In some specimens the whole of the viscera, except a portion of the liver, are concealed by the ovaries. In fig. 167, the front half of the ventral mantle-lobe is raised, to show the spiral arms; the black spot in the centre is the mouth, with its upper and lower lips, one fringed, the other plain. The mantle-fringe has been omitted in figs. 165-7. M 3 240 MANUAL OF THE MOLLUSCA. metrical, one of them dividing; protractor sliding muscles, two pairs; stomach long and straight, sustained by inflections of the visceral sheath ; intestine convoluted dorsally, terminating between the mantle-lobes on the right side; oral arms disposed in about six close whirls, their cavities opening into the prolongation of the visceral sheath in front of the adductors. Observations on the living Lingula are much wanted; the oral arms probably extended as far as the margins of the shell ; and the pedicle, which is often nine inches long in preserved specimens, is doubtless much longer, and contractile when alive. The shell is horny and flexible, and always of a greenish colour. Distr. 1 sp. India, Philippines, Moluccas, Australia, Feejees, Sandwich Ids. W. America. Fossil, 34 sp. L. Silurian — . N. America, Europe, Thibet. Lingula existed in the British Seas as late as the period of the Coralline Crag. The recent species have been found at small depths, and even at low- water half buried in sand. L. Davisii, L. Silurian, Tremadoc, has a pedicle- groove like Obolus, fig. 168. (Salter). Fig. 168. Ventral valve. Fig. 169. Dorsal valve. Obolus Davidsoni (Salter). Wenlock limestone, Dudley. A, posterior adductors ; B, sliding muscles ; C, Anterior adductors. . The pedicle-scar in the centre of fig. 168 has no letter. OBOLUS, Eichwald. Syn. Ungula, Pander ; Aulonotreta, Kutorga. Etym. Obolus, a small Greek coin. Type, 0. Apolliuis, Eichw. Shell orbicular, calcario-corneous, depressed, sub-equivalve, smoot ; hinge-margin thickened inside, and slightly grooved in the ventral valve , posterior adductor impressions separate ; anterior pair sub-central ; impres- sions of sliding-rnuscles lateral. Fig. 168, 169 (after Davidson.) Fossil, 4 sp. L, and U. Silurian. Sweden, Russia, England, U. States. CLASS V. CONCHIFERA, LAMARCK. (Lamelli-oranchiata, Blainville.) The bivalve shell-fish, or Conchifera, are familiar to every one, under the CONCHIFERA. 241 form of oysters, scallops, mussels, and cockles.* They come next to the univalves (gasteropoda) in variety and importance, and though less numerous specifically, are far more abundant individually.! The bivalves are all aquatic, and excepting a few widely-dispersed and prolific genera, are all inhabitants of the sea ; they are found on every coast, and in every climate, ranging from low -water mark to a depth of more than 200 fathoms. In their native element the Oyster and Scallop lie on one side, and the lower valve is deeper and more capacious than the upper ; in these the foot is wanting, or else small, and not used for locomotion. Most other bivalves live in an erect position, resting on the edges of their shells, which are of equal size. Those which move about much, like the river-mussel, maintain themselves nearly horizontally^ and their keel-shaped foot is adapted for ploughing through sand or mud. The position of those bivalves which live half-buried in river-beds or at the bottom of the sea, is often indicated by the darker colour of the part exposed ; or by deposits of tufa, or the growth of sea-weed on the projecting ends of the valves. In Nucula and some others the foot is deeply cleft, and capable of ex- panding into a disk, like that on which the snails glide : whilst in the mussel, pearl-oyster, and others which habitually spin a byssus, the foot is finger-like and grooved. The burrowing species have a strong and stout foot with which they bore vertically into the sea- bed, often to a depth far exceeding the length of their valves ; these never voluntarily quit their abodes, and often become buried and fossilized in them. They most usually burrow in soft ground, but also in coarse gravel, and firm sands and clays ; one small modiola makes its hole in the cellulose tunic of Ascidians, and another in floating blubber. The boring shell-fish have been distinguished from the mere burro wers, perhaps without sufficient reason, for they are found in substances of every degree of hardness, from soft mud to compact limestone, and the method employed is probably the same. § The means by which bivalves perforate stone and timber has been the subject of much inquiry, both on account of its physiological interest, and the desire to obtain some remedy for the injuries done to ships and piers and breakwaters. The ship-worm (teredo) and some allied genera, perforate timber only ; whilst the pJiolas bores into a variety of materials, such as * They are the Dithyra of Aristotle and Swainson, and constitute the second or sub-typical group in the quinary system. t It has been stated that the predatory mollu&ca are more numerous than the vegetable-feeders; but it is not so with the individuals constituting the species. I This is the position in which they are always figured in English books, being best suited for the comparison of one shell with another. § See the admirable memoir by Mr, Albany Hancock, in the An. Nat. Hist, for October, 1848. 242 MANUAL OF THE MOLLUSCA. chalk, shale, clay, soft sandstone and sandy marl, and decomposing gneiss ;* it has also been found boring in the peat of submarine forests, in wax, and in amber. f It is obvious that these substances can only be perforated alike by mechanical means ; either by the foot or by the valves, or both together, as in the burrowing shellfish. The pholas shell is rough, like a file, and sufficiently hard to abrade limestone ; and the animal is able to turn from side to side, or even quite round in its cell, the interior of which is often annulated with furrows made by the spines on the front of the valves. The foot of the pholas is very large, filling the great anterior opening of the valves ; that of the ship-worm is smaller, but surrounded with a thick collar, formed by the edges of the mantle, and both are armed with a strong epithe- lium. The foot appears to be a more efficient instrument than the shell in one respect, inasmuch as its surface may be renewed as fast as it is worn away.j; (Hancock.) The mechanical explanation becomes more difficult in the case of another set of shells, lithodomus, gastrockana, saxicava, and ungulina, which bore only into calcarious rocks, and attack the hardest marble, and still harder shells (fig. 25, p. 42). In these the valves can render no assistance, as they are smooth, and covered with epidermis ; neither does the foot help, being small and finger-like, and not applied to the end of the burrow. Their power of movement also is extremely limited, their cells not being cylindrical, whilst one of them, saxicava, is fixed in its crypt by a byssus. These shell fish have been supposed to dissolve the rock by chemical means (Deshayes), or else to wear it away with the thickened anterior margins of the mantle. (Hancock.) § The holes of the lithodomi often serve to shelter other animals after the * There is a specimen from the coast of France, in the Brit. Museum. t Highgate resin, in the cabinet of Mr. Bowerbank. I The final polish to some steel goods is said to be given by the hands of work- women. In Carlisle Castle they point to the rude impression of a hand on the dungeon wall, as the work of FERGUS M'lvon, in the two years of his solitary im- prisonment. § All attempts to detect the presence of an acid secretion have hitherto failed, as might be expected ; for the hypothesis of an acid solvent supposes only a very feeble but continuous action, such as in nature always works out the greatest results in the end. See Liebig's Organic Chemistry, and Dumas and Boussingault on the " Balance of Organic Nature." Intimately connected with this question are several other phenomena; the removal of portions of the interior of univalves, by the animal itself, as in the genera Conus, Auricula, and Nerita (fig. 24, p. 40); the perforation of shells by the tongues of the carnivorous gasteropods and the formation of holes in wood and limestone by limpets. Some facts in surgery also illustrate this subject, (1) dead bone is removed when granulations grow into contact with it : (2) if a hole is bored in a bone, and an ivory peg driven into it, and covered up, so much of the peg as is imbedded in the bone will be removed. (Paget.) The " absorption" of the fangs of milk-teeth, previous to shedding, is well-known. In these cases the removal of the bone earth is effected without the development of an acid, or other disturbance of the neutral condition of the circulating fluid. CONCHIFERA. 243 death of the rightful owners ; species of Modiola, Area, Venerupis, and Co- ralliophaga, both recent and fossil, have been found in such situations, and mistaken for the real miners.* The boring shellfish have been called " stone-eaters" (lilhophagi) and " wood-eaters" (xylophagi) t and some of them at least are obliged to swallow the material produced by their operations, although they may derive no sustenance from it. The ship-worm is often filled with pulpy, impalpable sawdust, of the colour of the timber in which it worked. (Hancock.} No shellfish deepens or enlarges its burrow after attaining the full-growth usual to its species (p. 43). The bivalves live by filtering water through their gills.f Whatever particles the current brings, whether organic or inorganic, animal or vege- table, are collected on the surface of the breathing- organ and conveyed to the mouth. In this manner they help to remove the impurities of turbid water.;}; The mechanism by which this is effected may be most conveniently examined in a bivalve with a closed mantle, like the great My a (fig. 170), which lives in the mud of tidal rivers, with only the ends of its long combined siphons exposed at the surface. § The siphons can be extended twice the length of the shell, or drawn completely within it ; they are separated, internally, by a thick muscular wall. The branchial siphon («?) has its orifice surrounded by a double fringe ; the exhalent siphon (s') has but a single row of tentacles ; these organs are very sensitive, and if rudely touched the orifices close and the siphon itself is rapidly withdrawn. When unmolested, a current flows steadily into the orifice of the branchial siphon, whilst another current rises up from the exhalent tube. There is no other opening in the mantle except a small slit in front (p] through which the foot is protruded. The body of the animal occupies the centre of the shell (b), and in front of it is the mouth (0) furnished with an upper and a lower lip, which are prolonged on each side into a pair of large membranous palpi (^). The gills (g) are placed two on each side of the body, and are attached along tbeir upper, or dorsal margins ; behind the body they are united to each other and to the siphonal partition. Each gill is composed of two laminse, divided internally into a series * Fossil univalves (trochi) occupying the burrows of apholas, were discovered by Mr. Bensted in the Kentish-rag of Maidstone. See Mantell's Medals of Creation. M. Buvignier has found several species of Area fossilized in the burrows of lithodomi. t It seems scarcely necessary to remark that the bivalves do not feed upon prey caught 'between their valves. Microscopists are well aware that sediment taken from the alimentary canal of bivalve shellfish contains the skeletons of animalcules and minute vegetable organisms, whose geometrical forms are remarkably varied and beautiful; they have also been obtained (in greater abundance than ordinary) from mud filling the interior of fossil oyster-shells. J When placed in water coloured with indigo, they will in a short time render it clear, by collecting the minute particles and condensing them into a solid form. § Alder and Hancock on the branchial currents of Pholas and Mya. An. Nat. Hist. Nov. 1851. 244 MANUAL OF THE MOLLU' of parallel tubes, indicated outside by transverse lines; these tubes open into longitudinal channels at the base of the gills, which unite behind the posterior adductor muscle at the commencement of the exhalent siphon (c). Examined by the microscope, the gill laminee ap- pear to be a network of blood-vessels whose pores opening into the gill-tubes, are fringed with vibratile cilia. These microscopic organs perform most impor- tant offices ; they create the currents of water, arrest the floating particles, and mould them, mixed with the viscid secre- tion of the surface, into threads, in the furrows of the gill, and propel them along the grooved edge of its free margin, in the direction of the mouth; they are then received between the palpi in the form of ravelled threads. (Alder and Han- cock.} In Mf/a, therefore (and in other bur- rowers), the cavity of the shell forms a closed branchial chamber, and the water which enters it by the respiratory siphon can only escape by passing through the gills into the dorsal channels, and so into the exhalent siphon. In the river- mussel the gills are not united to the body, but a slit is left by which water might pass into the dorsal channel, were it not for the close apposition of the parts under ordinary circumstances (fig. 171, b). The gills of the oyster are united Fig. 170. throughout, by their bases, to each other and to the mantle, completely separating the branchial cavity from the cloaca. In Pecten the gills and mantle are free, but the " dorsal channels" still exist, and carry out the filtered water. * Mya arenaria, L. (original, from specimens obtained at Southend, and commu- nicated by Miss Hume). The left valve and mantle lobe and half the siphons are re- moved, a, a', adductor muscles; b, body; c, cloaca; /, foot; g, branchiae; h, heart; m, cut edge of the mantle; o, mouth; s, s', siphons; t, labial tentacles; v, vent. The arrows indicate the direction of the currents ; the four rows of dots at the base of the gills are the orifices of the branchial tubes, opening into the dorsal channels. CONCHIFERA. 245 In some genera the gills subserve a third purpose ; the oviducts open into the dorsal channels, and the eggs are received into the gill-tubes and retained there until they are hatched. In the river-mussel the outer gills only receive the eggs, with which they are completely distended in the winter months (Fig. 171, 0,0}. In Cyclas the inner gills form the mar- supium, and only from 10 to 20 of the fry are found in them at one time ; these remain until they are nearly a quarter the length of the parent.* Fig. 171. River-mussel. (Anodon cygneus ? )t The valves of the Conchifera are bound together by an elastic ligament, and articulated by a hinge furnished with interlocking teeth. The shell is closed by powerful adductor muscles, but opens spontaneously by the action of the ligament, when the animal relaxes, and after it is dead. Each valve is a hollow cone, with the apex turned more or less to one side ; the apex is the point from which the growth of the valve commences, and is termed the beak, or umlo (p. 37.) The beaks (umbones} are near the hinge, because that side grows least rapidly, sometimes they are quite mar- ginal ; but they always tend to become wider apart with age. The beaks are either straight, as in Pecten ; curved as in Venus ; or spiral, as in Isocardia and Dicer as. In the latter case each valve is like a spiral univalve, especially those with a large aperture and small spire, such as Concholepas ; it is the left valve which resembles the ordinary univalve, the right valve being a left-handed spiral like the reversed gasteropods. When one valve is spiral and the other flat, as in Chama ammonia (fig. 185), the resemblance to an operculated spiral univalve becomes very striking (see p. 47). * Some other particular respecting the organization and development of bivalve shell-fish are given in the introductory chapter. For an account of their vascular system see Milne-Edwards, An. Sc. Nat. 1847, Tom. VIII. p. 77. t The valves are forcibly opened and the foot (/) contracted ; a, anterior adductor- muscle, much stretched ; p, p, palpi; g, inner gills; o, o, outer gills distended with spawn ; 6, b, a bristle passed through one of the dorsal channels. 246 MANUAL OF THE MOLLUSCA. The relation of the shell to the animal may be readily determined, in most instances, by the direction of the umbones, and the position of the liga- ment. The umbones are turned towards the front, and the ligament is pos- terior; both are situated on the back, or dorsal side of the shell. The length of a bivalve is measured from the anterior to the posterior side, its breadth from the dorsal margin to the base, and its thickness from the centres of the closed valves.* Dorsal margin. Ventral margin, or base. Fig. 172. Unio pictorum, L. (original) with the right valve and mantle-lobe re- moved; a, a, adductor muscles ; p. p, pedal muscles; x, accessory pedal muscle; u, umbo; I, ligament ; b, branchial orifice; v, anal opening; /, foot; o, mouth; t, palpi. The Conchifera are mostly equivalve, the right and left valves being of the same size and shape, except in the Qstreida and a few others. In Ostrea, Pandora and Lyonsia the right valve is smallest; in Chamostrea and Cor- bula, the left ; whilst the Chamacea follow no rule in this respect. The bivalves are all more or less inequilateral, the anterior being usually much shorter than the posterior side. Pectunculus is nearly equilateral, and in Glycimeris and Solemya, the anterior is much longer than the posterior side The front of the smaller Pectens is shewn by the byssal notch ; but in the large scallops, oysters and Spondyli, the only indication of the position of the animal is afforded by the large internal muscular impression, which is on the posterior side. The ligament is sometimes between the umbones, but is never anterior to them. The siphonal impression, inside the shell, is always posterior. Bivalves are said to be close, when the valves fit accurately, and gaping * Linnaeus and the naturalists of his school, described the front of the shell as the back, the left valve as the right, and vice versa. In those works which have been compiled from "original descriptions" (instead of specimens) sometimes one end, sometimes the other, is called anterior; and the length of the shell is sometimes estimated in the direction of the length of the animal, but just as frequently in a line at right angles to it. CONCHIFERA. 24? when they cannot be completely shut. In Gaslrochana (PI. XXIII, fig. 15,) the opening is anterior, and serves for the passage of the foot ; in My a it is posterior and siphonal; in Solen and Glycimeris both ends are open. In Bysso-arca (PL XVII. fig, 13,) there is a ventral opening formed by corres- ponding notches in the margin of the valves, which serves for the passage of the byssus ; in Pecten, Avicula, and Anomia, (fig. 176 s) the byssal notch (or sinus) is confined to the right valve. The surface of bivalve shells is often ornamented with ribs which radiate from the umbones to the margin, or with concentric ridges, which coincide with the lines of growth. Sometimes the sculpturing is oblique, or wavy ; in Tellina fabula it is confined to the right valve. In many species of Pholas, Teredo and Cardium the surface is divided into two areas by a trans- verse furrow, or by a change in the direction of the ribs. The lunule (see fig. 14, p. 26,) is an oval space in front of the beaks; it is deeply im- pressed in Cardium retusum, L. Astarte excavata and the genus Opts. When a similar impression exists behind the beaks it is termed the escut- cheon* The ligament of the Conchifera forms a substitute for the muscles by which the valves of the Brachiopoda are opened. It consists of two parts, the ligament properly so called, and the cartilage ; they exist either combined or distinct, and sometimes one is developed and not the other. The external ligament is a horny substance, similar to the epidermis which clothes the valves; it is usually attached to ridges on the posterior hinge-margins, behind the umbones, and is consequently stretched by the closing of the valves. The ligament is large in the river-mussels, and small in the Mactras and Myas, which have a large internal cartilage ; in Area and Pectunculus the ligament is spread over a flat, lozenge- shaped area, situated between the umbones, and furrowed with cartilage grooves. In Chama and Isocardia the ligament splits in front, and forms a spiral round each umbo. The Pholades have no ligament, but the anterior adductor is shifted to such a position on the hinge-margin that it acts as a hinge -muscle. (PL XXIII, fig. 13.) The internal ligament, or cartilage, is lodged in furrows formed by the ligamental plates, or in pits along the hinge-line ; in Mya and Nucula it is contained in a spoon- shaped process of one or both valves. It is composed of elastic fibres placed perpendicularly to the surfaces between which it is contained, and is slightly iridescent when broken ; it is compressed by the closing of the valves, and tends forcibly to open them as soon as the pressure of the muscles is removed. The name Amphidesma (double ligament) was given to certain bivalves, on the supposition that the separation of the carti- * Only those technical terms which are used in a. peculiar sense are here referred to; for the rest, any Dictionary may be consulted, especially Roberta's Etymological Dictionary of Geology, by Longman and Co. 248 MANUAL OF THE MOLLUSCA. laa:e from the ligament was peculiar to them. The cartilage-pit of many of the Anatinidtn is furnished internally with a moveable ossicle. The ligament is frequently preserved in fossil shells, such as the great Cyprinas and Carditas of the London Clay, the Unios of the Wealden, and even in some lower Silurian bivalves. All bivalves are clothed with an epidermis (v. p. 40) which is organi- cally connected with the margin of the mantle. It is developed to a remark- able extent in Solemya and Glycimeris (PL XXII. fig. 13, 17), and in My a it is continued over the siphons and closed mantle -lobes, making the shell appear internal. The interior of bivalves is inscribed with characters borrowed directly from the shell-fish, and affording a surer clue to its affinities than those which, the exterior presents. The structure of the hinge characterizes both families and genera, whilst the condition of the respiratory and locomotive organs may be to some extent inferred from the muscular markings. The margin of the shell on which the ligament and teeth are situated, is termed the hinge-line. It is very long and straight in Avicula and Area, very short in Vulsella, and curved in most genera. The locomotive bivalves have generally the strongest hinges, but the most perfect examples are pre- sented by Area and Spondylus. The central teeth, those immediately beneath the umbo, are called hinge (or cardinal) teeth; those on each side are lateral teeth. Sometimes lateral teeth are developed, and not cardinal teeth (Alasmodon ; Kellia) \ more frequently the hinge- teeth alone are present. In young shells the teeth are sharp and well-defined; in aged specimens they are often thickened> or even obliterated by irregular growth (Hippopodium) or the encroachment of the hinge-line (Pectunculus}. Many of the fixed and boring shells are edentulous.* The muscular impressions are those of the adductors, the foot and byssus, the siphons, and the mantle (see p. 26.) The adductor impressions are usually simple, although the muscles themselves may be composed of two elements,! as in Cytherea chione (fig. 14, p. 26) and the common oyster. The impression of the posterior adductor in Spondylus is double (PL XVI. fig. 15). In Pecten varius (fig. 173, a, a,} large independent impressions are formed by the two por- tions of the adductor, and in the left valve there is a third impression (p) produced by the foot, which in the byssiferous pectens is a simple conical muscle with a broad base. * The dentition of bivalve shells may be stated thus :— cardinal teeth, 2.3 or f —meaning 2 in the right valve, 3 in the left; lateral teeth 1—1, 2—2, or 1 anterior and 1 posterior in the right valve, 2 anterior and 2 posterior lateral teeth in the left valve. t Compare the shell of modiola, PI. XVII. fig. 5, with the woodcut, fig. 177. CONCHIFERA. 249 Fig. 173. Left valve. (Pecten varius) : Right valve. a, a, adductor; p, pedal impression; m, pallial line: I. ligamental margin; c, c, car- tilage ; e, e, anterior ears ; b. byssal sinus. In the left valve of Anomia there are four distinct muscular impressions (fig. 175). Of these, the small posterior spot alone is produced by the ad- ductor, and corresponds with the solitary impression in the right valve. Fig. 176. Right valve. Fig. 174. Fig. 175. Left valve.* The adductor itself (fig. 174 #') is double. The large central impression (p) is produced by the muscle of the plug (the equivalent of the byssal muscle in Pinna and Jlfodiola). The small impression within the umbo (u) and the third impression in the disk (jp') (wanting in Placunomia] are caused by the retractors of the foot. The term monomyary, employed by Lamarck to distinguish the bivalves with one adductor, applies only to the Ostreida, part of the Avicididee, and to the genera Tridacna and Mulleria. The dimyary bivalves have a second adductor, near the anterior margin, * Fig. 176. Right valve of Anomia ephippium,L. I, ligamental process; *, sinus. Fig. 175, Left valve; 2, .-ligament pit. Fig. 174. Muscular system, from a drawing communicated by A. Hancock, Esq. /, the foot; pi, the plug. The muscle pis generally described as a portion of the adductor; but it is certain, from a comparison of this shell with Carolia and Placuna, that a' represents the entire adductor, andp the byssal muscle. 250 MANUAL OF THE MOLLUSCA. which is small in Mytilus (fig. 30), but large in Pinna. The retractor muscles of the foot (already alluded to at p. 26) have their fixed points near those of the adductors ; the anterior pair are attached within the umbones (fig. 177, «, «,) or nearer the adductor, as in Astarte, and JJnio (fig. 172). The posterior pair (p1 p') are often close to the adductor, and leave no separate impression. The Unionidce have two additional retractors of the foot, attached laterally behind the anterior adductors ; in Leda, Solenellay and a few others, this lateral attachment forms a line extending from the anterior adductor backwards into the umbonal region of the shell. (See PI. XVII. fig. 21, 22.) In those shellfish like Pinna and the mussel, which are permanently moored by a strong bt/ssus, the foot (/) serves only to mould and fix the threads of which it is formed. The fibres of the foot-muscles pass chiefly to the byssus (d), and besides these two additional muscles (p,p) are developed. In Pinna, Modiola and Dreissena the byssal muscles are equal to the great adductors in size. Fig. 177. Muscles of Modiola.* In a few rare instances the muscles are fixed to prominent apophyses. The falciform processes of Pholas and Teredo (PL XXIII. fig. 19, 26) are developed for the attachment of the foot-muscle; the posterior muscular * Fig, 177. Muscular system of Modiola modiolus, L. from a drawing communi- cated by A. Hancock, Esq. aa, anterior, a* a1 posterior adductors; uu and p'p', pedal muscles; pp, byssal muscles ; /, foot; b, byssus; m, pallial line. CONCH1FERA. 251 ridge of Diceras and Cardilia resembles a lateral tooth, and in the extinct genus Eadiolites both adductors were attached to large tooth -like processes of the opercular valve ; but, as a rule, the muscles deposit less shell than the mantle, and their impressions deepen with age. The pallial line (fig. 177, m) is produced by the muscular fibres of the mantle-margin; it is broken up into irregular spots in the monomyary bivalves, and in Saxicava and Panopaa Norveyica. The siphonal impression, or pallial sinus (fig. 14, p. 26,) only exists in those shells which have retractile siphons ; its depth is an index to their length. The large combined siphons of Mya (fig. 170) are much longer than the shell ; and those of some Tellinidce three or four times its length, yet they are completely retractile. The small siphons of Cyclas and Dreissena cause no inflection of the pallial line. The form of the sinus is characteristic of genera and species. In the umbonal area (within the pallial line) there are sometimes fur- rows produced by the viscera, which may be distinguished from the mus- cular markings by absence of polish and outline. (See Lucina, PL XIX. % 6.) Fossil bivalves are of constant occurrence in all sedimentary rocks ; they are somewhat rare in the oldest formations, but increase steadily in number and variety through the secondary and tertiary strata, and attain a maximum of development in existing seas. Some families, like the Cyprinidce and Lucinida are more abundant fossil than recent; whilst many genera, and one whole family (the Hippuri- tidce], have become extinct. The determination of the affinities of fossil bivalves is often exceedingly difficult, owing to the conditions under which they occur. Sometimes they are found in pairs, filled up with hard stone ; and frequently as casts, or moulds of the interior, giving no trace of the hinge, and very obscure indications of the muscular markings. Casts of single valves are more instructive, as they afford impressions of the hinge.* Another difficulty arises from the frequent destruction of the nacreous or lamellar portion of the fossil bivalves, whilst the cellular layers remain. The Aviculidce of the chalk have entirely lost their pearly interiors ; the SpondyU, Chamas, and Eadiolites are in the same condition, their inner layers are gone and no vacancy left, the whole interior being filled with chalk. As it is the inner layer alone which forms the hinge, and alone receives the impressions of the soft parts, the true characters of the shells could not be de- termined from such specimens. Our knowledge of the extinct Radiolite is derived from natural moulds of the interior, formed before the dissolution of * These impressions may be conveniently moulded with gutta-percha. M. Agassiz published a set of plaster-casts of the interiors of the genera of recent shells, which may be seen in the Brit. Museum. [Memoire sur les monies des Mollusques, vivans etfossiles, par L. Agassiz, Mem. Soc. Sc. Nat. Neuchatel, t 2.]. 252 MANUAL OF THE MOLLUSCA. the inner layer of shell, or from specimens in which this layer is replaced by spar. The necessities of geologists have compelled them to pay very minute attention to the markings in the interior of shells, to their microscopic texture, and every other available source of comparison and distinction. It must not, however, be expected that the entire structure and affinities of molluscous animals can be predicated from the examination of an internal mould or a morsel of shell, any more than that the form and habits of an extinct quad- ruped can be inferred from a solitary tooth or the fragment of a bone.* The systematic arrangement of the bivalves now employed is essentially that of Lamarck, modified, however, by many recent observations. The families follow each other according to relationship, and not according to absolute rank; the Venerida are the highest organized, and from this culmi- nating point the stream of affinities takes two courses, one towards the Myas, the other in the direction of the oysters ; groups analogically related to the Tunicaries and Brachiopoda. SECTION A. ASIPHONIDA. a. Pallial line simple : Integro-pallialia. Fam. 1. Ostreidse. 2. Aviculidae. 3. Mytilidae. 4. Arcadse. 5. Trigoniadse. 6. UnionidEe. SECTION B. SIPHONIDA. 7. Chamidee. 8. Hippnritidse. 9. Tridacnidse. 11. Lucinidse. 12. Cycladida?. 13. Cyprinidse. 10. Cardiadse. b. Pallial line sinuated: Sinu-pallialia. 14. Veneridse. 15. Mactridse. 16. TellinidEe. 17. Solenida?. 18. Myacidse. 19. Anatmidse. 20. Gastrochaenidae. 21. Pholadidse. The characters which have been most relied on for distinguishing these groups and the genera of bivalves are the following, stated nearly in the order of their value: — 1. Extent to which the mantle-lobes are united. 2. Number and position of muscular impressions. 3. Presence or absence of zpallial sinus. 4. Form of the foot. 5. Structure of the branckiee. * Etudes Critiques sur les Mollusques Fossiles, par L. Agassiz, Neuchatel, 1840. CONCHIFERA. 253 6. Microscopic structure of the shell, (v. p, 38.) 7. Position of the ligament, internal or external. 8. Dentition of the hinge. 9. Equality or inequality of the valves. 10. Regularity or irregularity of form. 11. Habit; — free, burrowing or fixed. 12. Medium of respiration, fresh or salt-water. A few exceptions may be found, in which one or other of these characters loes not possess its usual value.* Such instances serve to warn us against coo implicit reliance on single characters. Groups, to be natural, must be based on the consideration of all these particulars — on " the totality of the inimal organization." (Owen). SECTION A. ASIPHONIDA. Animal unprovided with respiratory siphons ; mantle-lobes free, or united at only one point which divides the branchial from the exhalent chamber (cloaca) ; pallia! impression simple. Shell usually pearly or sub-nacreous inside; cellular externally; pallial line simple or obsolete. FAMILY I. OSTREID^. Shell inequivalve, slightly inequilatural, free or adherent, resting on one valve ; beaks central, straight ; ligament internal ; epidermis thin ; adductor mpression single, behind the centre; pallial line obscure; hinge usually edentulous. Animal marine ; mantle quite open ; very slightly adherent to the edge * 1. Cardita and Crassatella (Fam. 13) have the mantle more open,^whilst in Iridina (6), and especially in Dreissena (3) it is more closed than in the most nearly allied genera. 2. Mulleria (6) and Tridacna (9) are monomyary. 3. Leda (4) and Adacna (10) have a pallial sinus ; Anapa (16) has none. 4. The form of the foot is usually characteristic of the families ; but sometimes it is adaptively modified. 5. Diplodonta (11) has four gills. 6. Pearly structure is variable even in species of the same genus. 7. Crassatella (13) and Semele (16) have an internal ligament; in Solenella and Isoarca (4) it is external. , 8. Anodon (16), Adacna, Serripes (10), and Cryptodon (11) are edentulous. 9. Corbula (18) and Pandora (19) are more inequivalve than their allies; Chama arcinella (7) is equivalve. )0. Hinnites (1), JEtheria ((5), Myochama and Chamostrea (19) are irregular. 11. Pecten is free, byssiferous, or fixed : Area free or byssiferous. This character varies with age and locality in the same species. It does not always depend on the form of the foot, as JEiher.ia, though fixed, Jias akn?ge. foot, and Lithodomus and Un- gulina — boring shells — have the foot like Mytilus and Lucina. 12. Novaculina is a river Solen, and Scaphula a fresh-water Area. 254 MANUAL OF THE MOLLUSC A. of the shell ; foot small and byssiferous, or obsolete ; gills crescent-shaped, 2 on each side ; adductor musele composed of two elements, but representing only the posterior shell -muscle of other bivalves. OSTREA, L. Oyster. Syn. Amphidonta and Pycnodonta, Fischer. Peloris, Poli. Type, O. edulis, L. Ex. 0. diluviana, PL XVI. fig. 1. Shell irregular, attached by the left valve ; upper valve flat or concave, often plain ; lower convex, often plaited or foliaceous, and with a prominent beak ; ligamental cavity triangular or elongated ; hinge toothless ; structure sub -nacreous, laminated, with prismatic cellular substance between the margins of the laminae. Animal with the mantle-margin double, finely fringed; gills nearly equal, united posteriorly to each other and the mantle-lobes, forming a com- plete branchial chamber; lips plain; palpi triangular, attached; sexes distinct.* Distr. 60 sp. Tropical and temperate seas. Norway, Black Sea, &c. Fossil, 200 sp. Carb. — . U. States, Europe, India. The interior of recent oyster-shells has a slightly nacreous lustre; in fossil specimens an irregular cellular structure is often very apparent on de- composed or fractured surfaces. Fossil oysters which have grown upon Ammonites, Trigoniee, &c. frequently take the form of those shells. In the " cock's-comb" oysters both valves are plaited; 0-. diluviana sends out long root-like processes from its lower valve. The " Tree oyster" (Dendrostrea, Sw.) grows on the root of the mangrove. Oyster shells become very thick with age, especially in rough water ; the fossil oyster of the Tagus (0. longirostris] attains a length of two feet. The greatest enemy of oyster- banks is a sponge (Cliona), which eats into the valves, both of dead and living shells; at first only small round holes, at irregular intervals, and often dis- posed in regular patterns, are visible ; but ultimately the shell is completely mined and falls to pieces. Natural oyster-banks usually occur in water several fathoms deep ; the oysters spawn in May and June, and the fry ("spats") are extensively collected and removed to artificial grounds, or tanks, where the water is very shallow ; they are then called " natives," and do not attain their full growth in less than 5 or 7 years, whilst the " sea- oysters" are full-grown in 4 years. Native oysters do not breed freely, and many sometimes die in the spawning season; they are also liable to be killed by frost. The season is from August 4 to May 12. From 20 to 30,000 bushels of " natives" and 100,000 bushels of sea-oysters are annually sent to the London market. Many other species of oysters are eaten in India, China, Australia, &c. " Green oysters" are those which have fed on con- * The course of the alimentary canal in the common oyster is incorrectly repre- sented by Poli, and copied in the Crochaid ed. of Cuvier. CONCHIFERA. feri^m the tanks. Sub-genera. Qryphaa, Lamarck. G. incurva, Sby (section) fig. < 178. Tree, or very slightly attached ; left valve with a prominent, incurved umbo ; right valve small, concave. Fossil, 30 sp. Lias — Chalk. Europe, India. Exogyra, Sby. E. conica, PI. XVI. fig. 2. Shell chama- shaped, attached by the left valve ; umbones sub-spiral, turned Fig. 178. Grypha to the posterior side (i. e. reversed); right valve opercular. Fossil, 40 sp. L. Oolite — Chalk. U. States ; Europe. ANOMIA, L. 3ob MANUAL OF THE MOLLUSC A. in the lower valve, and its muscle becomes (functionally) an adductor. Distr. 12 sp. W. Indies, Brit. (P. patelliformis], New Zealand, California, Behring's sea, Ochotsk. — 50 fms. Limanomia (Grayana) Bouchard. Shell eared like Lima. Fossil, 4 sp. Devonian ; Boulonnais, China ? PLACUNA, Solander. Window-shell. Etijm. Plakous a thin cake. Ex. P. sella, PI. XVI. fig. 5. Shell sub -orbicular, compressed, translucent, free, resting on the righ valve ; hinge area narrow and obscure ; cartilage supported by two diverging ridges in the right valve and corresponding grooves in the left ; muscular impressions double, the larger element round and central, the smaller distinc' and crescent shaped, in front of it. The Placunse are very closely allied to Anomia ; and many intermediate forms may be traced. The shell of each consists entirely of sub-nacreous plicated laminse, peculiarly separable, and occasionally penetrated by minute tubuli. (Carpenter.) P. sella, called, from its shape, the "saddle-oyster,3 is remarkably striated. In P. placenta, PL XVI. fig. 6, the anterior carti lage ridge is only half so long as the other, which appears to be connecte< with the economy of the shell when young ; in specimens 1 inch across there is a pedal impression below the cartilage grooves of the upper valve and a shallow sinus in the margin of the lower valve, indicating a slight byssal attachment at that age. Distr. 4 sp. Scinde, N. Australia, China. Sub-genera. Carolia, Cantraine 1835, (after Prince Charles Bonaparte.) Syn. Hemiplacuna, G. Shy. Type, C. placunoides, PL XVI. fig. 7- Shell like Placuna ; hinge, when young, like Anomia, with a byssal plug passing through a small deep sinus in front of the cartilage process, which is closed in the adult. Distr. 3 sp. (Brit. Mus.) Tertiary, Egypt, America ? Placunopsis, Morris and Lycett. P. Jurensis, Rcemer. Sub -orbicular, upper valve convex, radiately striated, or taking the form of the surface to which it adheres ; lower valve flat ; ligamental groove sub-marginal, trans- verse ; muscular impression large, sub-central. Fossil, 4 sp. Lower Oolites, Europe. PECTEN, 0. F. Miffler. Scallop. Etym. Pecten, a comb. Type, P. maximus (Janira, Schum.) Syn. Argus, Poli. Discites, Schl. Amusium, Muhlfeldt. Shell sub-orbicular, regular, resting on the right valve, usually orna- mented with radiating ribs; beaks approximate, eared; anterior ears most prominent; posterior side a little oblique; right valve most convex, with a notch below the front ear; hinge-margins straight, united by a narrow ligament; cartilage internal, in a central pit; adductor impres- CONCHIFERA. 257 don double, obscure ; pedal impression only in the left valve, or obsolete :% ITS). Animal with the mantle quite open, its margins double, the inner pen- lent like a curtain (m) finely fringed; it its base a row of conspicuous round )lack eyes (ocelli) surrounded by :entacular filaments; gills (/br) ex- ceedingly delicate, crescent-shaped, [uite disconnected posteriorly having "' ;eparate excurrent canals ; lips foli- iceous ; palpi truncated, plain out- >ide, striated within ; foot finger-like, grooved, byssiferous in the young. JFig. 179. Pecten varius.* The Scallop (P. maximus] and " quin" (P. opercularis) are esteemed lelicacies ; the latter covers extensive banks, especially on the N. and W. of Ireland, in 15 to 25 fin. water. The scallop ranges from 3 — 40 fms. : its body is bright orange, or scarlet, the mantle fawn-colour, marbled with )rown ; the shell is used for " scalloping" oysters, formerly it was employed is a drinking cup, and celebrated as such in Ossian's " hall of shells." An illied species has received the name of " St. James's shell" (P. Jacoboeus) ; t was worn by pilgrims to the Holy -land, and became the badge of several Drders of kmghthood.f Most of the Pectens spin a byssus when young, and some, like P. varius, o so habitually ; P. niveus moors itself to the fronds of the tangle (La- ninaria.} The Rev. D. Landsborough observed the fry of P. opercularis, when less tian the size of a sixpence, swimming in a pool of sea- water left by the ebbing f the tide. "Their motion was rapid and zig-zag; they seemed, by the udden opening and closing of their valves, to have the power of darting like n arrow through the water. One jerk carried them some yards, and then y another sudden jerk they were off in a moment on a different tack." The shell of Pecten and the succeeding genera consists almost exclusively f membranous laminse, coarsely or finely corrugated. It is composed of wo very distinct layers, differing in colour (and also in texture and destruc- ibility), but having essentially the same structure. Traces of cellularity re sometimes discoverable on the external surface ; P. nolilis has a distinct rismatic-cellular layer externally. (Carpenter.} 258 MANUAL OF THE MOLLUSCA. Sub-genera, Neithea, Dronet. P. quinque -costatus and other fossil sp. with concavo-convex valves and distinct hinge-teeth; the inner layers of these shells are wanting in all specimens from the English chalk. Pallium, Schum. P. plica, PI. XVI. fig. 8. Hinge obscurely toothed. Hinnites (Cortesii) Defr. P. pusio, PL XVI. fig. 10. Shell legular and byssiferous when young ; afterwards cementing its lower valve and becoming more or less irregular. Distr. 2 sp. Fossil, Trias ? Miocene — , Europe. Hemipecten, A. Adams. H. Forbesianus, PI. XVI. fig. 9. Shel] hyaline, posterior ears obsolete, anterior prominent ; right valve flat, byssal sinus deep ; structure permeated by microscopic tubuli, as in Lima. Distr. 120 sp. World-wide; Nova-Zembla — C. Horn; — 200 fms. Fossil, 450 sp. (including Aviculo-pecten). Carb. — . World-wide. LIMA, Bruguiere. Etym. Lima, a file. Ex. L. squamosa, PI. XVI. fig. 11. (Ostrea lima, L.] Syn. Plagiostoma (Llhwyd) Sby. P. cardiiforme, PI. XVI. fig. 12. Shell equivalve, compressed, obliquely oval; anterior side straight, gaping, posterior rounded, usually close; umbones apart, eared; valves smooth, punctate-striate, or radiately ribbed and imbricated; hinge area triangular, cartilage pit central ; adductor impression lateral, large, double ; pedal scars 2, small. Animal, mantle-magins separate, inner pendent, fringed with long ten- tacular filaments, ocelli inconspicuous ; foot finger-like, grooved ; lips with tentacular filaments, palpi small, striated inside ; gills equal on each side? distinct. The shell is always white ; its outer layer consists of coarsely-plicated membranous lamellae ; the inner layer is perforated by minute tubuli, form- ing a complete network. (Carpenter?) The Limas are either free or spin a byssus ; some make an artificial burrow when adult, by spinning together sand or coral-fragments and shells, but the habit is not constant. (Forbes.) The burrows of L. hians are several times longer than the shell, and closed at each end. (Charlesworth.) " This species is pale or deep crimson, with an orange mantle ; when taken out of its nest it is one of the most beautiful marine animals to look upon, it swims with great vigour, like the scallop, by opening and closing its valves, so that it is impelled onwards or upwards in a succession of jumps. The filaments of the fringe are easily broken off, and seem to live many hours after they are detached, twisting themselves like worms." (Landsborouyh.) .L. spinosa has conspicuous ocelli, and short filaments. Sub-genera, Limatula, S. Wood. L. sub-auriculata, PI. XVI. fig. 13. Valves equilateral ; 8 sp. Greenland — Brit. Fossil, Miocene — .Europe. Limcea, Bronn. L. strigilata, PI. XVI. fig. 14.* Hinge minutely * After Bronn; the figure in Brocchi does not show the teeth. 259 toothed. Fossil, 4 sp. Lias — Pliocene. The recent Limaa ? Sarsii (Loven) Norway (= L. crassa of the JEgean ?) has the mantle-border plain. Some of the larger recent sp. have obscure lateral teeth. Distr. 20 sp. Norway, Brit. W. Indies, Canaries, India, Australia; 1 — 150 fms. The largest living sp. (L. excavata, Chemu.) is found on the coast of Norway. Fossil, 200 sp. Garb. ? Trias — . U. States, Europe, India. The so- called Plagiostoma spinosum is a Spondylus. SPONDYLUS, (Pliny) L. Thorny-oyster. Type, S. gsedaropus, L. Ex. S. princeps, PL XVI. fig. 15. Si/n. Dianchora, Sby. Podopsis, Lam. Pachytes, Defr. Shell irregular, attached by the right valve, radiately ribbed, spiny or foliaceous ; umbones remote, eared ; lower valve with a triangular hinge- area, cartilage in a central groove, nearly or quite covered ; hinge of 2 curved interlocking teeth in each valve ; adductor impression double. Animal, with the mantle open and gills separate, as in Pecten ; lips foliaceous, palpi short ; foot small, cylindrical, truncated. In aged specimens the circular portion of the muscular scar exhibits den- dritic vascular markings. The lower valve is always most spiny and least coloured; in some sp. (like S. imperialis] the shell is scarcely, if at all, attached by its beak or spines. The inner shell-layer is very distinct from the outer, and always wanting in fossil specimens from calcarious rocks, then called Dianchora. Specimens from the Miocene of St. Domingo, which have lost this layer, contain a loose mould of the original interior. Water-cavities are common in the inner layer, the border of the mantle having deposited shell more rapidly than the umboual portion. ( Owen, Mag. Nat. Hist. 1 838, p. 409.) Distr. 30 sp. W. Indies, Canaries, Medit. India, Torres Straits, Pacific, W. America: — 105 fms. Fossil, 45 sp. Inf. Oolite ? Neocomian — . Europe, U. States, India. Sub-genus, Pedum, Brug. P. spondyloides, PI. XVI. fig. 16. Shell thin, smooth, compressed, attached by a byssus passing through a deep notch in the right valve. Inhabits coral-reefs, where it is found half-imbeded :, Red Sea, Indian Ocean, Mauritius, Chinese Seas. PLICATULA, Lamarck. Etym. Plicatus, plaited. Type, P. cristata, PL XVI. fig. 17. Shell irregular, attached by the umbo of the right valve ; valves smooth or plaited ; hinge-area obscure ; cartilage quite internal ; hinge-teeth, 2 ID each valve ; adductor scar simple. Distr. 6 sp. W. Indies, India, Philippines, Australia, W. America. Fossil, 40 sp. Trias — . U. S. Europe, Algeria, India. P. Mantelli (Lea) Alabama, has the valves eared. 260 / M ; \\ [ - ^ J / 01 'T H P 1\1 ?M -US C A . FAMILY II. AYICULID^. "Wing-shells. Shell inequivalve, very oblique, resting on the smaller (right) valve, and attached by a byssus ; epidermis indistinct : outer layer prismatic-cellular, (fig. 180) interior nacreous; posterior muscular impression large, sub-central, anterior small, within the umbo ; pallial line, irregularly dotted ; hinge- line straight, elongated; umbones anterior, eared, the posterior ear wing-like ; cartilage contained in one or several grooves; hinge edentulous, or ob- Fig. 180, Pinna.* scurely toothed. Animal with the mantle-lobes free, their margins fringed ; foot small spinning a byssus; gills 2 on each side, crescent-shaped, entirely free (Desk. or united to each other posteriorly, and to the mantle (as in the Oyster, and not as in Pecteri) . The wing-shells, or pearl-oysters, are natives of tropical and tempe rate seas ; there are no living species in northern latitudes, where fossil forms are very numerous. AVICULA (Klein) Bruguiere. Etym. Amcula, a little bird. Type, A. hirundo, PI. XVI. fig. 18. Shell obliquely oval, very inequivalve ; right valve with a byssal sinu beneath the anterior ear ; cartilage pit single, oblique ; hinge with 1 or 2 small cardinal teeth, and an elongated posterior tooth, often obsolete ; pos- terior muscular impression (adductor and pedal) large, sub-central ; anterior (pedal scar) small, umbonal. Animal (of meleagrina) with mantle-lobes united at one point by the gills, their margins fringed and furnished with a pendent curtain; curtains fringed in the branchial region, plain behind; foot finger-like, grooved byssus often solid, cylindrical, with an expanded termination ; pedal muscles 4, posterior large in front of the adductor ; adductor composed of 2 elements ; retractors of the mantle forming a series of dots, and a large spot near the adductor; lips simple : palpi truncated; gills equal, crescentic, united behinc the foot. (Brit. M.) Distr. 25 sp. Mexico, S. Brit. Medit. India, Pacific:— 20 fms. Fossil, 300 sp. L. Silurian — . World-wide. Sub-genera, Meleagrina, Lam. M. margaritifera, PI. XVI. fig. 19 The " pearl-oysters" are less oblique than the other ainculce, and their valves are flatter and nearly equal ; the posterior pedal impression is blended with that of the great adductor. They are found at Madagascar, Ceylon, Swan * The cellular structure may be seen with a hand-lens, in the thin margin of the shell, by holding it up to the light; or on the edges of broken fragments. CONCHIFERA. 261 R. Panama, &c. Manilla is the chief port to which they are taken. There are three principal kinds, which are worth from £2 to £4 per cwt. : 1 . the silver-lipped, from the Society Ids. of which about 20 tons are annually imported to Liverpool ; 2. the black-lipped, from Manilla, of which 30 tons were imported in 1851 ; 3. a smaller sort from Panama, 200 tons of which are annually imported; in 1851 a single vessel brought 340 tons. (T. C. Archer.) These shells afford the " mother- o'-pearl" used for ornamental purposes; and the "oriental" pearls of commerce (p. 38). Mr. Hope's pearl, said to be the largest known, measures 2 inches long, 4 round, and weighs 1800 grains.* Pearl-oysters are found in about 12 fathom water; the fisheries of the Persian Gulf and Ceylon have been celebrated from the time of Pliny. Malleus, Lam. M. vulgaris, PI. XVI. fig. 20. The " hammer-oyster" is remarkable for its form, which becomes extremely elongated with age ; both ears are long, and the umbones central. When young it is like an ordinary Avicula, with a deep byssal notch in the right valve. 6 sp. China, Australia. Vulsella, Lam. V. lingulata, PI. XVI. fig. 21. Syn. Reniella, Sw. Shell oblong, striated, sub-equivalve ; umbones straight, earless. Often found imbedded in living sponges. Distr. 3 sp. Red Sea, India, Australia, Tasmania. Fossil, 4 sp. U. Chalk — . Brit. France. Pteroperna, Lycett, 1852. P. costatula, Desl. Shell with a long pos- terior wing; hinge-line bordered by a groove; anterior teeth numerous, minute; posterior 1 or 2, long, nearly parallel with the hinge-margin. fossil, 3 sp. Bath oolite ; Brit. France. ?-3fowa?fo (Pallasii) J&gsss&Rg, 1846. (Monotis, Minister, not Bronn.) Very inequivalve ; left umbo prominent, earless ; right valve small and flat, vdth a deep sinus beneath the small anterior ear. Fossil, Permian — Gault. Europe. " In A. cygnipes we find no trace of prismatic cellular structure or nacre, but the coarsely corrugated and somewhat tubular structure of the Pectens." (Carpenter?) Ambonychia (bellistriata) Hall, 1847. Nearly equivalve, gibbose, oblique, obtusely winged. A. vetusta (Inoceramus, Sby.) is concentrically fur- rowed ; the right valve has a small anterior ear (usually concealed) separated by a deep and narrow sinus. Fossil, 12 sp. L. Silurian — Carb. TJ. S. Europe. ? Cardiola (interrupta) Broderip, 1844. Equivalve, gibbose, obliquely oval, radiately ribbed ; beaks prominent ; hinge-area short and flat. Fossil, 17 sp. U. Silurian — Dev. TJ. S. Europe. ? Eurydesma, (cordata) Morris ; Devonian ? N. S. Wales. Shell equivalve, * Sections of oriental pearls exhibit very fine concentric laminae surrounding a grain of sand, or some such extraneous matter ; the nacreous lustre has been attri- bited to the diffraction of light from the out-cropping edges of the laminae, but Dr. Carpenter has shown that it may result from the minute plication of a single lamina. (Stefig. 23, p. 38.) 262 MANUAL OF THE MOLLUSCA. sub-orbicular, ventricose, very thick near the beaks; ligamental area long, wide sub-internal ; byssal groove close to the limbo ; right valve with a large, blunt hinge-tooth ; adductor impression single, placed anteriorly; pallial line dotted. Pterinea (Isevis) Goldf. 1832. Shell thick, rather inequivalve, very oblique and broadly winged ; beaks anterior ; sinus shallow ; hinge-area long, straight, narrow, striated lengthwise; anterior teeth few, radiating; poste- rior teeth laminar, elongated ; anterior (pedal) scar deep, posterior (adductor) impression large, very eccentric. Fossil, 25 sp. L. Sil. — Garb. U. S. Europe, Australia. Pteronites (angustatus) M'Coy, 1844, is thinner and has the teeth, &c. less developed/ Monotis, Bronn, 1830, M. salinaria, Schl. Trias, Hallein. Obliquely oval, compressed, radiated ; anterior side short, rounded ; posterior slightly eared. Syn. ? Halobia (salinarum) Br. 1830. Trias, Hallstadt. Semi-oval, ra- diated, compressed, with a shallow sinus in front , hinge-line long and straight, POSIDONOMYA, Bronn. Syn. Posidonia, Br. 1828. (not Kouig). Poseidon, Neptune. Type, P. Becheri, PL XVI. fig. 22. Shell thin, equivalve, compressed, earless, concentrically furrowed ; hinge-line short and straight, edentulous. Fossil, 50 sp. L. Silurian — Trias. U. S. Europe. ? AVICULO-PECTEN, M'Coy, 1852 Type, Pecten granosus, Sby. Min. Con. t. 574. Shell inequivalve, sub -orbicular, eared; hinge-areas flat, with several long, narrow cartilage furrows, slightly oblique on each side of the umbones; right valve with a deep and narrow byssal sinus beneath the anterior ear ; adductor impression large, simple, sub-central; pedal scar small and deep, beneath the umbo. Fossil (see Pecten). L. Silurian — Carb. Spitzbergen — Australia. GERVILLIA, Defrance. Etym. Dedicated to M. Gerville, a French naturalist. Ex. G. anceps, PI. XVII. fig. 1. Shell like Avicula ; elongated: anterior ear small, posterior wing-like: area long and flat, cartilage pits several, wide apart ; hinge-teeth obscure, diverging posteriorly. Fossil, 30 sp. Carb. — Chalk. Europe. Sub-genus ? Bakewellia, King. B. ceratophaga, Schl. Fossil, 5 sp. Permian, Brit. Germany, Russia. Shell small, inequivalve, cartilage pits 2 — 5 ; hinge with anterior and posterior teeth ; anterior muscular impres- sion and pallial line distinct. PERN A, Bruguiere. Etym. Perna, a shell-fish (resembling a gammon) Pliny. CONCHIFEEA. 263 Syn. Melina, Retz. Isognomon, Klein. Pedalion, Solander. Type, P. ephippium, L. PL XVII. fig. 2. Shell nearly equivalve, compressed, sub-quadrate; area wide, cartilage pits numerous, elongated, close-set ; right valve with a byssal sinus ; mus- cular impression double. The Pernas vary in form like the Avicula ; some are very oblique, some very inequivalve, and many fossil sp. have the posterior side produced and wing-like. In some Tertiary Pernas the pearly layer is an inch thick. Distr. 16 sp. Tropical seas ; W. Indies — India — W. America. Fossil, 30 sp. Trias — . U. States, Chile, Europe. Sub-genera, CrenaMa, Lamk. C. viridis, PI. XVI. fig. 24. Shell thin, oblong,' compressed; byssal sinus obsolete; cartilage pits shallow, crescent-shaped. Distr. 5 sp. N. Africa, Red Sea — China ; in sponges. Hypotrema, D'Orb. 1853. H. rupellensis (=? Pulvinites Adansonii, Defr. 1826); Coral-rag, Rochelle. Shell oblong, inequivalve ; right valve flat or concave, with a round byssal foramen near the hinge; left valve convex, with a muscular impression near the umbo ; hinge-margin broad, curved, with about 12 close-set transverse cartilage grooves. INOCERAMUS, Sowerby (1834). Etym. Is (inos) fibre, Keramos shell. Ex. I. sulcatus, PI. XVII. fig. 3. Syn. Catillus, Brongn. Shell inequivalve, ventricose, radiately or concentrically furrowed, um- bones prominent; hinge-line straight, elongated; cartilage pits transverse, numerous, close-set. This genus diifers from Perna chiefly in form. /. involutus has the left valve spiral, the right opercular. I. Cuvieri attains the length of a yard. Large flat fragments are common both in the chalk and flints, and are often perforated by the Cliona. Hemispherical pearls have been found developed Tom their inner surface, and spherical pearls of the same prismatic-cellular structure occur detached, in the chalk. ( Welherell.} The Inocerami of the gault are nacreous. Fossil, 40 sp. Lias — Chalk. S. America, U.S. Europe, Algeria, Thibet. PINNA, L. Etym. Pinna, a fin or wing. Type, P. squamosa, PI. XVI. fig. 23. Shell equivalve, wedge-shaped ; umbones quite anterior; posterior side truncated and gaping ; ligamental groove linear, elongated ; hinge edentu- lous ; anterior adductor scar apical, posterior sub -central, large, ill-defined ; pedal scar in front of posterior adductor. Animal with the mantle margin doubly fringed ; foot elongated, grooved, spinning a powerful byssus, attached by large triple muscles to the centre of each valve; adductors both large; palpi elongated; gills long, N 3 264 MANUAL OF THE MOLLUSCA. Distr. 30 sp. TJ. States, S. Brit. Medit. Australia, Pacific, Panama. Fossil, 50 sp. Devonian — . U. S. Europe, S. India. The shell of the Pinna attains a length of two feet ; when young it i thin, brittle, and translucent, consisting almost entirely of prismatic eel] layers ; the pearly lining is thin, divided, and extends less than halfway from the beak. Some fossil Piunas crumble under the touch into their componen fibres. The living sp. range from extreme low- water to 60 fms ; they ar moored vertically, and often nearly buried in sand, with knife -like edges ered The byssus has sometimes been mixed with silk, spun, and knitted int gloves, &c. (Brit. Mus.) A little crab which nestles in the mantle and gill of the Pinna, was anciently believed to have formed an alliance with the blint shellfish, and received the name of Pinna-guardian (Pinnoteres] from Aris totle ; similar species infest the Mussels and Anomice of the British coast. Sub-genus, Trichites, (Plott) Lycett. T. Plottii, Llhwyd. ("Pinni gene,3' Saussure.) Shell thick, inequi valve, somewhat irregular, margin undulated. Fossil, 5 sp. Oolitic strata of England and France. Fragment an inch or more in thickness are common in the Cotteswolde-hills ; full grown individuals are supposed to have measured a yard across. FAMILY III. MYTILID^. Mussels. Shell equivalve, oval or elongated, closed, umbones anterior, epidermi thick and dark, often filameutose ; ligament internal, sub-marginal, very long hinge edentulous ; outer shell layer obscurely prismatic-cellular ;* inner mor or less nacreous ; pallia! line simple ; anterior muscular impression small an< narrow, posterior large, obscure. Animal marine or fluviatile, attached by a byssus ; mantle-lobes unitec between the siphonal openings ; gills two on each side, elongated, and unitec behind to each other and to the mantle, dorsal margins of the outer and inner most laminae free ; foot cylindrical, grooved. The shells of this family exhibit a propensity for concealment, frequently spinning a nest of sand and shell-fragments, burrowing in soft substances, 01 secreting themselves in the burrows of other shells. MYTILUS, L. Sea-mussel. Ex. M. smaragdinus, PI. XVII. fig. 4. Shell wedge-shaped, rounded behind ; umbones terminal, pointed ; hinge teeth minute or obsolete ; pedal muscular impressions two in each valve small, simple, close to the adductors. Animal with the mantle-margins plain in the anal region, and projecting slightly ; branchial margins fringed ; byssus strong and coarse ; gills nearl; equal ; palpi long and pointed, free. * A thin layer of minute cells may frequently be detected immediately under the epidermis. (Carpenter.) CONCHIFERA. 265 The common edible mussel frequents mud-banks which are uncovered at low-water ; the fry abound in water a few fathoms deep ; they are full-grown in a single year. From some unknown cause they are, at times, extremely deleterious. The consumption of mussels in Edinburgh and Leith is esti- mated at 400 bushels ( = 400,000 mussels) annually; enormous quantities are also used for bait, especially in the deep sea fishery, for which purpose 30 or 40 millions are collected yearly in the Frith of Forth alone. (Dr. Knapp.) Mussels produce small and inferior pearls. At Port Stanley, Falkland Ids. Mr. Macgillivray noticed beds of mussels which were chiefly dead, being frozen at low- water. M. bilocularis (Septifer, Recluz) has an umbonal shelf for the support of the anterior adductor, like Dreissena ; it is found at Mauritius and Australia. M. exustus (Brachydontes, Sw.) has the hinge - margin denticulated continuously, Distr. 50 sp. World-wide. Ochotsk, Behring's Sea, Russian Ice-meer; Black Sea, C. Horn, Cape, New Zealand, Fossil, 80 sp. Permian — . U. S. Europe, S. India. ? MYALINA, Koninck, 1842. Types, M. Goldfussiana, Kon. Carb, M. acuminata, Sby. Permian. Shell equivalve, mytili-form ; beaks nearly terminal, septiferous inter- nally; hinge-margin thickened, flat, with several longitudinal cartilage- grooves ; muscular impressions 2 ; pallia! line simple. Fossil 6 sp. Carb. — Permian. Europe. The ligamental area resem- bles that of the recent Area obliquata, Chemn. India. MODIOLA, Lam. Horse-mussel. Etym. Modi&lus^ a small measure, or drinking- vessel. Ex. M. tulipa, PI. XVII. fig. 5. M. modiolus, p. 250, fig. 177. Shell oblong, inflated in front : umbones anterior, obtuse : hinge tooth- less ; pedal impressions 3 in each valve, the central elongated ; epidermis often produced into long beard-like fringes. Animal with the mantle-margin simple, protruding in the branchial region; byssus ample, fine; palpi triangular, pointed. The Modiola are distinguished from the Mussels by their habit of bur- rowing, or spinning a nest. Low- water — 100 fms. Distr. 50 sp. chiefly tropical ; M. modiolus, Arctic seas — Brit. fossil, 130 sp. Silurian ? Lias — , U. S. Europe, Thibet, S. India. Sub-genera. Lithodomus, Cuv. M. lithophaga, PL XVII. fig. 7. Shell cylindrical, inflated in front, wedge-shaped, behind; epidermis thick and dark; interior nacreous.* Distr. 12 sp. W.Indies — New Zealand, Fossil, * The outer shell-layer has a- tubular structure; the tubes are excessivaly minute ., seldom branching, oblique and parallel, (Carpenter.) 266 MANUAL OF THE MOLLUSCA. 16 sp. Bath oolite — . Europe, TL S. The " date-shell" bores into corals, shells, and the hardest limestone rocks (fig. 25, p. 42) ; its burrows are shaped like the shell, and do not admit of free rotatory motion. The animal, which is eaten in the Medit, is like a common mussel ; in L. patagonicus the siphons are produced. Like other burrowing shellfish, they are luminous. Perforations of LWwdomi in limestone cliffs, and in the columns of the Temple of Serapis at Puteoli, have afforded conclusive evidence of changes in the level of sea- coasts in modern times. (Ly ell's Principles of Geology.) Crenella, Brown. C. discors, PL XVII. fig. 8. (Lanistes, Sw. Modio- laria, Beck.) Shell short and tumid, partly smooth, and partly orna- mented with radiating striae ; hinge-margin crenulated behind the ligament ; interior brilliantly nacreous. Animal with the anal tube and branchial margins prominent. Distr. Temperate and arctic seas; Nova Zembla, Ochotsk, Brit. New Zealand. Low-water — 40 fms. Spinning a nest, or hiding amongst the roots of sea-weed and corallines. M. marmorata, Forbes, burrows in the test of Ascidia. Fossil, U. Green-sand — , Europe. Modiolarca (trapezina) Gray ; Falkland Ids. — Kerguelen, attached to floating sea- weed ; mantle-lobes united, pedal opening small, foot with an expanded sole, front adductor round. M. ? pelagica, PL XVII. fig. 6. is found burrowing in floating blubber, off the Cape. (Forbes?) ? Mytilimeria (Nuttallii) Conrad. Shell irregularly oval, thin, edentulous, gaping posteriorly; umbones sub-spiral; ligament short, semi -internal. Distr. California ; animal gregarious, forming a nest. Modiolopsis (mytiloides) Hall, 1847 (= Cypricardites, part, Conrad. Lyonsia, part, D'Orb.) Shell like modiola, thin and smooth, front end some- what lobed ; anterior adductor scar large and oval. Fossil, Silurian, U. S. Europe. ? Orthonotus (pholadis) Courad. L. Silurian, New York. Shell elon- gated, margins parallel, umboues anterior, back plaited.* DRETSSENA, Van Beneden. Etijm. Dedicated to Dreyssen, a Belgian physician. Syn. Mytilomya, Cantr. Congeria, Partsch. Tichogonia, Rossm. Type, D. polymorpha, PL XVII. fig. 9. (Mytilus Volga, Chemn.) Shell like Mytilus., without its pearly lining ; inner layer composed of large prismatic cells; umbones terminal; valves obtusely keeled; right valve with a slight byssal sinus ; anterior adductor supported on a shelf within the beak ; pedal impression single, posterior. * Hall and Salter employ the name Orthonotus for such shells as Solen constrictus, Sandb, Devonian, Germany ; Sanguinolites anguliferus, M'Coy, U. Silurian, Kendal; and Solenopsis minor, M'Coy, Carb. limestone, Ireland. M. D'Orbigny has mistaken the plaits for teeth, and placed the genus with Nucula. The recent M. plicata, Lam. from Nicobar Ids. has the same long straight back and plaited dorsal region. CONCHIFERA. 267 Animal with the mantle closed ; byssal orifice small; anal siphon very small, conical, plain, branchial prominent, fringed inside ; palpi small, triangular ; foot-muscles short and thick, close in front of the posterior adductor. D. polymorpha is a native of the Aralo- Cas- pian rivers; in 1824 it was observed by Mr. J. Sowerby in the Surrey docks, to which it appears to have been brought with foreign timber, in the Fi&- 18]- Breissena. holds of vessels. It has since spread into the canals and docks of many parts of the country, and has been noticed in the iron water-pipes of London, incrusted with a ferruginous deposit. (Cunnington.} Fossil. 10 sp. Eocene — . Brit. Germany. FAMILY IV. ARCADE. Shell regular, equivalve, with strong epidermis ; hinge with a long row of similar, comb-like teeth ; pallial line distinct ; muscular impressions sub- equal. Structure corrugated, with vertical tubuli in rays between the ribs or striae. (Carpenter.} Animal with the mantle open ; foot large, bent, and deeply grooved ; gills very oblique, united posteriorly to a membranous septum. ARCA, L. Etym. Area, a chest. Type, A. Note, PL XVII. fig. 12. Ex. A. granosa, PI. XVII. fig. 10. A. pexata, fig. 11. A. zebra, fig. 13- Shell equivalve or nearly so, thick, sub-quadrate, ventricose, strongly ribbed or cancellated ; margins smooth or dentated, close or sinuated ventrally ; hinge straight, teeth very numerous, transverse ; umbones anterior, separated by a flat, lozenge-shaped ligamental area, with numerous cartilage-grooves ; pallial line simple ; posterior adductor impression double ; pedal scars 2, the posterior elongated. Animal with a long pointed foot, heeled and deeply grooved ; mantle furnished with ocelli ; palpi 0 ; gills long, narrow, less striated externally, continuous with the lips : hearts two, each with an auricle. The name Bysso-arca was chosen unfortunately, by Swainson, for the typical species of the genus, in which the byssal orifice is sometimes very large (PL XVII. fig. 13). The byssus is a horny cone, composed of nume- rous thin plates, occasionally becoming solid and calcarious ; it can be cast off and re-formed with great rapidity. (Forbes.} The Areas with close valves have the left valve a little larger than the right, and more ornate. The Bysso-arks secrete themselves under stones at low-water, in crevices of rocks, and the empty burrows of boring mollusks ; they are often much worn and distorted. Listr. 130 sp. World-wide, most abundant in warm sea ; low water — 268 MANUAL OF THE MOLLUSCA. 230 fms. (A. imbricata, Poll). Prince- Regent Inlet (A. glacialis] A. sca- phula, Benson, is found in the Ganges and its branches, from Calcutta to Humeerpoor on the Jumna, 1000 miles from the sea. Fossil, 200 sp. L. Silurian — . U. S. Europe; S. India. CUCULLJSA, Lamarck. Etym. Cucullus, a cowl. Type, C. concamerata, PI. XVII. fig. 14. Shell sub-quadrate, ventricose; valves close, striated; hinge-teeth few and oblique, parallel with the hinge-line at each end ; posterior muscular impression bounded by an elevated ridge. Distr. 1 sp. Mauritius, Nicobar, China. Fossil, 100 sp. L. Silurian — . N. America, Patagonia, Europe. Sub-genus, Macrodon, Lycett. M. Hirsonensis, PI. XVII. fig. 15. Shell with a few oblique anterior teeth and one or more long laminar posterior teeth. The Ark-shells of the Palaeozoic and secondary strata have their anterior teeth more or less oblique, like Area, the posterior teeth parallel with the hinge-line like Citculfaa ; their valves are close or gaping below ; their umbones frequently sub-spiral ; and the hinge-area is often very narrow, and in some species only the posterior moiety is visible. PECTUNCULUS, Lam. Type, P. pectiniformis, PL XVII. fig. 16. (Area pectunculus, L.) Shell orbicular, nearly equilateral, smooth or radiately striated ; umbones central, divided by a striated ligamental area; hinge with a semicircular row of transverse teeth ; adductors sub-equal ; pallial line simple ; margins crenated inside. Animal with a large crescent- shaped foot, margins of the sole undulated ; mantle open, margins simple, with minute ocelli ; gills equal, lips continuous with the gills. Distr. 50 sp. W. Indies, Brit. India, N. Zealand, W. America: ranging from 8 to 60, rarely 120 fathoms. Fossil, 70 sp. Neocomian — . U. S. Europe: S. India. The teeth of Pectunculus and Area increase in number with age^ by additions to each end of the hinge-line, but sometimes the central teeth are obliterated by encroachments of the ligament. LIMOPSIS, Sassi, 1827. Type, L. aurita, PL XVII. fig. 17. Syn. Trigonocoelia, Nyst. Shell orbicular, convex, slightly oblique ; ligamental area with a triangular cartilage-pit in the centre ; hinge with 2 equal, curved series of transverse teeth. Distr. 1 sp. Red Sea (Nyst.) Fossil, 17 sp. Bath-oolite — . U. States; Europe. CONCHIFERA. 269 NUCULA, Lam. Etym. Diminutive of nux, a nut. Ex. N. Cobboldise, PI. XVII. fig. 18. Shell trigonal, with the umbones turned towards the short posterior side ; smooth or sculptured, epidermis olive, interior pearly, margins crenulated ; hinge with prominent internal cartilage -pit, and a series of sharp teeth on each side ; pallial line simple. Animal with the mantle open, its margins plain; foot large, deeply fissured in front, forming when expanded a disk with serrated margins; mouth and lips minute, palpi very large, rounded, strongly plaited inside and furnished with a long convoluted appendage ; gills small, plume-like, united behind the foot to the branchial septum. The Nucula uses its foot for burrowing, and Prof. Forbes has seen it creep up the side of a glass of sea-water. The labial appendages protrude from the shell at the same time with the foot. N. mirabilis, Adams, from Japan, is sculptured like the extinct N. Cobboldite. Distr. 70 sp. U. S. Norway, Cape, Japan, Sitka, Chile. On coarse bottoms, from 5—100 fms. Fossil, 100 sp. L. Silurian ? — . Trias — . America, Europe, India. Sub-genera. Nuculina, D'Orb.* 1847. N. miliaris, PI. XVII. fig. 19. Shell minute ; teeth few, in one series, with a posterior lateral tooth. Eocene, France. Nucinella (ovalis) Searles-Wood, 1850 (=Pleurodon, Wood, 1840) a minute shell from the Coralline crag of Suffolk, is described as having an external ligament. ? Stalaymium (margaritaceum) Conrad, 1833 = Myoparo costatus, Lea, Eocene, Alabama. ? S. Nystii, Galeotti (Nucunella, D'Orb. Eocene, Bel- gium. Shell like Limopsis ; ligamental area narrow, wholly posterior. ISOARCA, Miinster, 1842. Type, I. subspirata, M. Oxford Clay ; France, Germany. Shell ventricose ; beaks large, anterior, often sub-spiral ; ligament entirely external ; hinge-line Curved, with two series of transverse teeth, smallest in the centre ; pallial line simple. I. Logani (Ctenodonta) Salter, L. Silurian, Canada, is 3 inches-long and has the ligament preserved. Fossil, 14 sp. L. Silurian — Chalk. N. America ; Europe. Sub-genus. Cucullella, M'Coy. C. antiqua, Sby. U. Silurian, Hereford- shire. Shell elliptical, with a strong rib behind the anterior adductor impression. LEDA, Schumacher. Etym. Leda, in Greek myth, mother of Castor and Pollux. Syn. Lembulus (Leach) Bisso. Ex. L. caudata, PI. XVII. fig. 20. Shell resembling Nucula ; oblong, rounded in front, produced and pointed * N. donaciformis, Parreyss, from the White Nile, is a crustacean ! (Eatheria). 270 MANUAL OF THE MOLLUSCA. behind ; margins even ; pallial line with a small sinus ; umbonal area with a linear impression joining the anterior adductor. Animal furnished with two partially-united, slender, unequal, siphonal tubes (Forbes} ; gills narrow, plume-like, deeply laminated, attached through- out ; mantle-margin with small ventral lobes forming by their apposition a third siphon. Distr. 30 sp. Northern and Arctic Seas , 10—180 fms. Siberia, Mel- ville Id. Mass. Brit. Medit. Cape, Japan, Australia. Fossil, 110 sp. U. S. Europe; S. India. Fig. 182. Yoldian. sp. -f- Antarctic Expedition. fFrom a drawing by Albany Hancock, Esq.) The internal organs are represented as seen, through the mantle, on the removal of the right valve. a, a, adductors; p,p, pedal muscles; I, ligament; g, gills; s, siphons (much con. tracted); t. c, labial palpi and appendages; i, intestine; /, foot; x,x, lateral muscles of the foot; m, pallial line. Sub-genus, Yoldia, Holier (dedicated to the Countess Yoldi). Y. myalis, PI. XVII. fig. 21. Shell oblong, slightly attenuated behind, compressed, smooth or obliquely sculptured, with dark olive shining epidermis ; external ligament. slight ; cartilage as in Leda ; pallial sinus deep. Animal with the branchial and anal siphons united, retractile ; palpi very large, appendiculate ; gills narrow, posterior ; foot slightly heeled, deeply grooved, its margins crenulated ; intestine lying partly close to the right side of the body, and producing an impression in the shell ; mantle-margin plain in front, fringed behind ; destitute of ventral lobes. Distr. Arctic and Antarctic Seas ; Green- land, Mass. Brazil; Norway, Kamtschatka. Fossil, Miocene — . (Crag and Glacial deposits.) England, Belgium. SOLENELLA, Sowerby. Type, S. Norrisii, PL XVII. fig. 22. S. ornata, fig. 23. Syn. Malletia, Desm. Ctenoconeha, Gray. Neilo, Adams. CONCHIFERA. 2?1 Shell oval or ark-shaped, compressed, smooth or concentrically furrowed, epidermis olive; ligament external, elongated, prominent: hinge with an anterior and posterior series of fine sharp teeth ; interior sub-nacreous ; pal- lia! sinus large and deep ; anterior adductor giving off a long oblique pedal line. Animal like Toldia ; mantle-margins slightly fringed and furnished with ventral lobes ; siphonal tubes united, long and slender, completely retractile ; palpi appendiculate, convoluted, as long as the shell ; gills narrow, posterior ; foot deeply cleft, forming an oval disk, even-margined and striated across. Distr. 2 sp. Valparaiso; New Zealand (shell like S. ornata). Fossil, 1 sp. Miocene. Pt. Desire, Patagonia. ? SOLEMYA, Lamarck. Type, S. togata, PL XXII. fig. 1?. Syn. Solenomya, Menke. Shell elongated, cylindrical, gaping at each end ; epidermis dark, horny, extending beyond the margins ; umbones posterior ; hinge edentulous ; liga- ment concealed ; pallial line obscure. Outer layer of long prismatic cells, nearly parallel with the surface, and mingled with dark cells, as in Pinna ; inner layer also cellular. Animal with the mantle lobes united behind, with a single siphonal orifice, hour-glass shaped , and cirrated ; foot proboscidiform, truncated and fringed at the end ; gills forming a single plume on each side, with the laminae free to the base ; palpi long and narrow, nearly free. The shell resembles Glycimeris in the shortness of its posterior side, and the extraordinary development of its epidermis ; the animal most resembles Leda in the structure of its foot and gills. Distr. 4 sp. TL States, Canaries, W. Africa (Gaboon ft.), Medit, Aus- tralia, New Zealand. Burrowing in mud ; 2 fins. Fossil, 4 sp. Garb. — . Brit. Belgium. FAMILY V. TJUGONIAD.E. Shell equivalve, close, trigonal, with the umbones directed posteriorly ; ligament external ; interior nacreous ; hinge-teeth few, diverging ; pallial line simple. Animal with the mantle open ; foot long and bent ; gills two on each side, recumbent ; palpi simple. TRIGONIA, Bruguiere (not Aublet) Etym. Trigonos, three-angled. Syn. Lyriodon, G. Sby. Ex. T. costata, PL XVII. fig. 24. T. pectiuata, fig. 183. Shell thick, tuberculated, or ornamented with radiating or concentric ribs ; posterior side angular; ligament small and prominent; hinge-teeth 2. 3, diverging, transversely striated ; centre tooth of left valve divided ; pedal impressions in front ^)f the posterior adductor, and one in the umbo of the left valve ; anterior adductor impression close to the umbo. 272 MANUAL OF THE MOLLUSCA. Animal with a long and pointed foot, bent sharply, heel prominent, sole bordered by two crenulated ridges; palpi small and pointed ; gills ample, the outer smallest, united behind the body to each other and to the mantle.^ The shell of Trigonia is almost en- tirely nacreous, and usually wanting or metamorphic in limestone strata; casts of the interior are called "horse-heads" by the Portland quarry-men;* they spoil the stone. SHicified casts have Fig- 183. Trigonia pectinata.% been found at Tisbury, in which the animal itself, with its gills, was preserved. f The species with the posterior angle of the shell elongated, have a siphonal ridge inside. The epidermal layer of the recent shell consists of nucleated cells, forming a beautiful microscopic object. A Trigonia placed by Mr. S. Stutchbury on the gunwale of his boat leapt overboard, clearing a ledge of four inches ; they are supposed to be migratory, as dredging for them is ver uncertain, though they abound in some parts of Sydney Harbour. Distr. 3 sp. (or varieties ?) Australia. Fossil, 100 sp. Trias — Chalk; (not known in Tertiaries). Europe U. S. Chile, Algeria, Cape, S. India. MTOPHORTA, Bronn, 1830. Type, M. vulgaris, Schl. Syn. Cryptina (Kefersteinii) Boue. Shell trigonal, umbones turned forwards ; obliquely keeled ; smooth o sculptured ; teeth 2.3, striated obscurely , centre tooth of left valve simple anterior of right valve prominent; mould like Trigonia. M. decussata PI. XVII. fig. 25, has a lateral tooth at the dorsal angle of the left valve. Fossil, 13 sp, Trias : Germany, Tyrol. i AXINUS, Sowerby, 1821. Type, A. obscurus, Sby. Syn. Schizodus, King (not Waterhouse). Shell trigonal, rounded in front, attenuated behind ; rather thin, smooth with an obscure oblique ridge ; ligament external ; hinge-teeth 2.3, smooth rather small ; anterior adductor slightly impressed, removed from the hinge with a pedal scar close to it ; pallial line simple. Fossil, 20 sp. U. Silurian — Muschelkalk. U. States, Europe. Mactra tri * See Plott's Oxfordshire, T. vii. fig. 1. t In the collection of the late Miss Benett of Warminster, now in Philadelphia. J Fig. 183. From a specimen in alcohol ; the gills slightly curled and contracted they should terminate near the margin, between the arrows winch indicate th inhalentand exhalent currents : a,a ', adductors ; hi, ligament; 1. t', dental sockets o, mouth; It, labial tentacles or palpi; p, pallial line; m, margin; /, foot; v, cloaca. CONCH1FERA. 273 gona, Goldf. Isocardia axiniformis. Ph. Anodontopsis securiformis, Anatina attenuata and Doldbra securiformis, M'Coy, probably belong to this genus. Dolalra equilateralis, Amphidesma subtruncatum, Anodontopsis angusti- frons, M'Coy, with many others from the Palaeozoic rocks, may constitute a distinct genus, but their generic character has yet to be discovered. LYRODESMA, Conrad, 1841. Type, L. plan a, New York. Syn. Actinodonta, Phil. Shell trigonia-shaped, rather elongated, with a striated posterior area; hinge with several (5 — 9) radiating teeth, striated across; ligament external. Fossil, 3 sp. L. Silurian : Canada, U. States, Brit. FAMILY VI. UNIONS. Naides. Shell usually regular, equivalve, closed ; structure nacreous, with a very thin prismatic-cellular layer beneath the epidermis; epidermis thick and dark ; ligament external, large and prominent ; margins even ; anterior hinge- teeth thick and striated, posterior laminar, sometimes wanting; adductor scars deeply impressed ; pedal scars 3, distinct, 2 behind the anterior ad- ductor, one in front of the posterior. Animal with the mantle-margins united between the siphonal orifices and, rarely, in front of the branchial opening; anal orifice plain, branchial fringed ; foot very large, tongue-shaped, compressed, byssiferous in the fry ; gills elon- gated, sub-equal, united posteriorly to each other and to the mantle, but not to the body ; palpi moderate, laterally attached, striated inside : lips plain. Sexes distinct. The river-mussels are found in the ponds and streams of all parts of the world. In Europe the species are few, though specimens are abundant ; in . America both species and individuals abound. All the remarkable generic forms are peculiar to S. America and Africa. Two of these are fixed, and irregular when adult, and have been placed with the chamas and oysters by the admirers of artificial systems ; fortunately, however, M. D'Orbigny has ascertained that the Mulleria, which is fixed and mono-myary when adult, is locomotive and di-myary when young ! * Like other fresh-water shells, the na'ids are often extensively eroded by the carbonic acid dissolved in the water they inhabit (p. 41).f This condi- tion of the umbones is conspicuous in the great fossil Uniones of the Wealden, * In the synopsis at p. 252 it will be seen that each of the principal groups of bivalves contains members which are fixed and irregular, and others which are byssi- ferous, or burrowing, or locomotive. f Probably many of the organic acids, produced by the decay of vegetable matter, assist in the process. It has been suggested that sulphuric acid may sometimes be set free in river-water, by the decomposition of iron-pyrites in the banks : but Prof. Boye of Philadelphia states that it has not been detected in any river of the United States, where the phenomenon of erosion is most notorious. 274 MANUAL OF THE MOLLUSCA. but cannot be detected in the Cardinifs, and some other fossils formerly re ferred to this family. The outer gills of the female unionidee are filled with spawn in the winte and early spring ; the fry spins a delicate, ravelled byssus, and flaps its trian gular valves with the posterior shell-muscle, which is largely developed, whils the other is yet inconspicuous. The shells of the female river-mussels ar rather shorter and more ventricose than the others. (See pp. 18, 34,) UNIO, Retz. River-mussel. Etym. Unio a pearl (Pliny). Ex. U. litoralis, PL XVIII. fig. 1. Shell oval or elongated, smooth, corrugated, or spiny, becoming very solid with age ; anterior teeth 1.2 or 2.2, short, irregular; posterior teeth 1.2, elongated, laminar. Animal with the mantle-margins only united between the siphonal open ings ; palpi long, pointed, laterally attached. (Fig. 1?2, p. 246.) U. plicatus (Symphynota, Sw. Dipsas, Leach) has the valves produce< into a thin, elastic dorsal wing, as in Syria.* In the Pearl-mussel, U. % garitiferus (Margaritana, Schum. Alasmodon, Say) the posterior teet become obsolete with age. This species, which afforded the once famou British pearls, is found in the mountain streams of Britain, Lapland, am Canada ; it is used for bait in the Aberdeen Cod-fishery. The Scotch pear fishery continued till the end of the last century, especially in the R. Tay where the mussels were collected by the peasantry before harvest- time. Th pearls were usually found in old and deformed specimens ; round pearls abou the size of a pea, perfect in every respect, were worth £3 or £4. (Dr Knapp.) An account of the Irish pearl-fishery was given by Sir R. Reddin in the Phil. Trans. 1693. The mussels were found set up in the sand of th river-beds with their open side turned from the torrent ; about one in 10 might contain a pearl, and one pearl in 100 might be tolerably clear. (Se p. 38.) Listr. 250 sp. N. America, S. America, Europe, Africa, Asia, Australia. Fossil, 50 sp. Wealden — . Europe, India. Sub-genera, Monocondylaa, D'Orb. M. Paraguay ana, PL XVIII. fig. , Shell with a single large, round, obtuse cardinal tooth in each valve ; n lateral teeth. Distr. 6 sp. S. America. Hyria, Lam. H. syrmatophora, PL XVIII. fig. 3. Syn. Pachyodon an Prisodon, Schum. Shell Area-shaped, hinge-line straight, with a dors wing on the posterior side; teeth elongated, transversely striated. Dist 4 sp. S. America. * This is the species in which the Chinese produce artificial pearls by the intr duction of shot, &c., between the mantle of the animal and its shell (p. 38); M Gaskoin has an example containing two strings of pearls, and another in the Bri Mus, has a number of little josses made of bell-metal, now completely coated wi pearl, in its interior. CONCHIFERA. 2?5 CAST ALIA, Lamarck. Type, C. ambigua, PI. XVIII. fig. 4. Syn. Tetraplodon, Spix. Shell ventricose; trigonal; umbones prominent, farrowed; hinge-teeth striated; anterior 2.1, short; posterior 1.2, elongated. Animal with mantle-lobes united behind, forming two distinct siphonal orifices, the branchial cirrated. Distr. Rivers of S. America, Guiana, Brazil. 276 MANUAL OF THE MOLLUSCA. Animal with the mantle-lobes open ; body large, oblong, projecting back wards ; no trace of a foot ; palpi large, semi-oval ; gills sub-equal, plaitec united posteriorly, and to the body and mantle. Distr. R. Nile, from 1st Cataracts to Fazool;* R. Senegal. MULLEUIA, Ferussac. Dedicated to Otto Frid. Miiller, author of the " Zoologia Danica." Type, M. lobata, Fer. Syn. Acostsea (Guaduasana) D'Orb. Shell when ysung free, equivalve, Anodon- shaped, with a long and pro minent ligament, and two adductor impressions : adult irregular, inequivalve attached by the right valve ; umbones elongated, progressively filled up wit shell, and forming an irregular '• talon" in front of the fixed valve ; epider mis thick ; ligament in a marginal groove ; interior pearly, muscular impres sion single, posterior. Distr. R. Magdalena, near Bogota, New Granada. Mr. Isaac Lea has determined the identity of Mulleria and Acostcea b) examination of Ferussac's type, and the suite of specimens, of different ages in the collection of M. D'Orbigny. f SECTION B. SIPHONIDA. Animal with respiratory siphons ; mantle-lobes more or less united. a. Siphons short, pallial line simple ; Integro-pallialia, FAMILY VII. CHAMIP.E. jS/^/Hnequi valve, thick, attached; beaks sub-spiral; ligament external; hinge-teeth 2 in one valve, 1 in the other ; adductor impressions large, culated ; pallial line simple. Animal with the mantle closed ; pedal and siphonal orifices small, sub equal ; foot very small ; gills two on each side, very unequal, united pos teriorly. CHAMA (Pliny) L. Ex. C. macrophylla, PI. XVIII. figs. 8, 9. Syn. Arcinella, Schum. Shell attached usually by the left umbo ; valves foliaceous, the uppei smallest ; hinge-tooth of free valve thick, curved, received between two teeth in the other ; adductor impressions large, oblong, the anterior encroaching on the hinge-tooth. Animal with the mantle-margins united by a curtain, with two rows o: tentacular filaments ; siphonal orifices wide apart, branchial slightly promi- nent, fringed, anal with a simple valve ; foot bent, or heeled ; liver occupying the umbo of the attached valve only ; ovary extending into both mantle- lobes, as far as the pallial line ; lips simple, palpi small and curled ; gills * The " fresh- water oysters" discovered by BRUCE. t The only specimen of Mulleria in England was purchased many years ago by Mr. Thos. Norris, of Bury, for £2Q. CONCHIFERA. 277 leeply plaited, the outer pair much shorter and very narrow, furnished with a 'ree dorsal border, and united behind to each other, and to the mantle ; ad- luctors each composed of two elements. Fig. 184. Right Side. Fig. 185. Leftside. Animal of Chama (from Torres Str. Mr. Jukes.) Fig. 184. Right side, with the umbonal portion of the mantle removed. Fig. 185. Leftside, showing the relative extent of the liver and ovarium. a, a, adductors; m, pallial line; e, excurrent orifice; 6, branchial; /, foot and >edal orifice; p, posterior pedal muscle; t, palpi; g, gills (contracted); I, liver; o, varium ; d, dental lobes. The shell of Chama, consists of three layers ; the external, coloured layer 5 laminated by oblique lines of growth, with corrugations at right angles to the aminae ; the foliaceous spines contain reticulated tubuli : the middle layer is paque white and consists of ill-defined vertical prisms or corrugated struc- ture ; the inner layer, which is translucent and membranous, is penetrated y scattered vertical tubuli; the minute processes that occupy the tubuli ive to the mantle (and to the casts of the shell) a granular appearance (fig. 85, 1, m.) Some Chamas are attached indifferently by either valve ; when fixed by he right valve the dentition is reversed, the left valve having the single ooth. Chama arcinella, which is always attached by the right umbo, has tie normal dentition 1:2; it is nearly regular and equivalve, and has a dis- inct lunule. Distr. 50 sp. Tropical seas, especially amongst coral-reefs ; — 50 fms. V. Indies, Canaries, Medit. India, China. Fossil, 30 sp. Green-sand — . U. States, Europe. Sub-genus ? Monopleura; Matheron (= Dipilidia, Math) M. imdri- ata, Math. Fig. 187. Neocomian, S. France. Shell attached by the 'extral umbo ; valves alike in structure and sculpturing ; fixed valve straight, aversely conical, with a long, straight ligamental groove, and obscure hinge- rea; opercular valve fiat or convex, with an oblique, sub-marginal umbo. 278 MANUAL OP THE MOLLUSCA. Fig. 186. Bi-radiolites,%- Fig. 187. Monopleura, £. p, point of attachment ; /, ligamental groove; a, a, corresponding areas. Fossil, 9 sp. Neocomian — Chalk. France, Texas. They are commonly found in groups, adhering laterally, or rising one above the other ; the casts of such as are known are quite simple and chama-like. a Fig. 188. Diceras arietinum, f. Fig. 189. Requienia ammonia, a, point of attachment; /, I, ligamental grooves ; t, posterior adductor inflection. DICERAS, Lamarck. Type, D. arietinum, PI. XVIII. figs. 10, 11, and fig. 188, 190. Shell sub-equivalve, attached by either umbo ; beaks very prominent spiral, furrowed externally by ligamental grooves ; hinge very thick, teet 2.1, prominent; muscular impressions bounded by long spiral ridges, some times obsolete. Distr. 5 sp. Middle oolite. Germany, Switz. France, Algeria. Diceras differs from Chama in the great prominence of both its umbones in having constantly two hinge-teeth in the right valve and one in the left and in the prominent ridges bordering the muscular impressions. Simila ridges exist in Cucull&a, Megalodon, Cardilia and the Hippurite ; they pro duce deep spiral furrows on the casts, which are of common occurrence in th Coral-oolite of the Alps. One or both the anterior furrows (fig. 190, t, t) ar frequently obsolete. The dental pits are much deeper than the teeth whic CONCH1FERA. 279 hey receive, and are sub-spiral, giving rise to bifid projections (c, c] on the ;asts ; the single tooth in the left valve consists of two elements, and the cavity (fossef) which receives it is divided at the bottom. Fig. 190. Diceras, J. Fig. 191. Requienia, Internal pasts : a, point of attachment ; c, c', casts of dental pits ; t, t't furrows produced by spiral ridges. (Mus. Brit.) REQUIENIA, Matheron. Dedicated to M. Requien, author of a Catalogue of Corsican Mollusca. "Ex. R, Lonsdalii, PI. XVIII. fig. 12 and fig. 191, R. Ammonia, fig. 189. Shell thick, very inequivalve, attached by the left umbo ; ligament ex- ;ernal ; teeth 2:1; left valve spiral, its cavity deep, not camerated ; free valve smaller, sub-spiral ; posterior adductor bordered by a prominent sub- spiral ridge in each valve. The shell-structure of Requienia is like that of Ckama. The relative size of the valves is subject to much variation ; in R. Favri (Sharpe) they are nearly equal. The hinge-teeth are like those of Diceras ; the cavity for the >osterior tooth of the right valve is very deep and sub-spiral (fig. 191, een palliobranchiate ; but they occur on the rim of the shell, and not on the , as in Crania.^ The chief peculiarity of the Hippuritidte is the dissimi- arity in the structure of the valves, but even this is deprived of much signi- icance by its inconstancy 4 The free valve of Hippurites is perforated by adiating canals which open round its inner margin, and communicate with MANUAL OF THE MOLLUSCA. the upper surface by numerous pores, as if to supply the interior with filtera water ; possibly, they were closed by the epidermis.* In the closely allied genus Radiolites there is no trace of such canals, no in Caprotina. Those which exist in the upper valve of Caprina, and in bot valves of Caprinella, have no communication with the outer surface of th shell ; they appear to be only of the same character with the tubular ribs < Cardium costatum (PI. XIX. fig. 1 ), and it is highly improbable that the were permanently occupied by processes from the margin of the mantle. The teeth of the left, or upper valve, are so prominent and straight, tha its movement must have been nearly vertical, for which purpose the interna ligament appears to have been exactly suited by its position and magnitude but it is probable that, like other bi-valves, they opened to a very small exten Fig. 194. Interior of lower valve, £. Fig. 195. Upper valve (restored). Hippurites radiosus, Desm. Lower Chalk, St. Mamest, DordogneA a, a, adductor impressions and processes ; c, c, cartilage pits ; /, t\ teeth and dent; sockets ; u, umbonal cavity ; p, orifices of canals ; I, ligamental inflection ; m, mu cular; n> siphonal inflection. HTPPURITES, Lamarck. Name, adopted from old writers, " fossil Hippuris" or Horse-tail. Types, H. bi-ocidatus, Lam. and R. cornu-vaccinum, fig. 198. Shell very inequivalve, inversely conical, or elongated and cylindrical ; fixed valve striated or smooth, with three paraEel furrows (I, m, n,} on the cardinal side, indicating duplicatures of the outer shell layer : internal margin slightly plaited; pallia! line continuous; urabonal cavity moderately deep, ligamental inflection (1} with a small cartilage-pit on each side (c, r pits corresponding to the posterior ridges'in the lower valve; surface »orous, the pores leading to canals in the outer shell -layer, which open round he pallial line upon the inner margin ; anterior cartilage-pit deep and conical, Fig. 196. H. Toucasianus, upper valve, $.* Fig. 197. Lower valve, with mould, •§. I, ligamental ; m, muscular; n, siphonal inflections; a;, fracture, showing canals; ?, cartilage: «, left umbo; the arrows indicate the probable direction of thebranchial currents. posterior shallow ; umbonal cavity turned to the front (u} ; teeth 2, straight, sub-central, the anterior largest, each supporting a crooked muscular apo- physis, the first broad, the hinder prominent, tooth -like ; inflections (m, n) surrounded by deep channels. H. comu-vactinum attains a length of more than a foot, and is curved like a cow's-horn ; the outer layer separates readily from the core, which is furrowed longitudinally, The ligamental inflection (I) is very deep and narrow, and the anterior tooth further removed from the side than in H. bi-oculatus and radiosus (figs. 194, 5) ; the posterior apophysis (#') does not nearly fill the corresponding cavity in the lower valve. In H. bi-oculatus and some other species there is no ligamental ridge inside ; these, when they have lost their inner layer, present a cylindrical cavity with two parallel ridges, extending down one side. The third inflection (n) is possibly a siphonal fold, such as exists in the tube of Teredo, and sometimes in the valves of Pholas, Clavagella, and the caudate species of Trigonia. The development of processes from the upper valve, for the attachment of the adductor muscles harmonizes with the other peculiarities of the Hip- purite. The equal growth of the margins of the valves produces central umbones, and necessitates an internal cartilage; this again causes the removal * This internal mould, representing the form of the animal, was obtained by re- moving the upper valve «piecemeal with the chisel ; a plaster-cast taken from it represents the interior of the upper valve, with the bases of the teeth and apophyses. See originals in Brit. Mus. MANUAL OF THE MOLLUSCA. I, Fig. 198. Longitudinal section; upper half, |. Fig. 199. Transverse section, •§-. Hippurites cornu-vaccinum, JBronn. Salzburg. /, m, n, duplicatures ; u, umbonal cavity of left valve; r, of right valve; c, c', car tilage-pits; t, t', teeth; a,V, muscular apophyses; d, outer shell-layer, Fig. 198 i taken in the line d, b, of fig. 199, cutting only the base of the posterior tooth (f ) Fig. 199, is from a larger specimen, at about the level d, b of fig. 198, cutting the poin of the posterior apophysis (a'), and shewing the peculiar shell-texture deposited by the anterior adductor (a). of the teeth and adductors further from the hinge-margin, to a position in which the muscles must have been unusually long, unless supported in the manner described. Supposing the animal to have had a small foot,* like Fig. 200. Hippurites cornu-vaccinum. Fig. 201. Radiolites cylindraceus, %. Longitudinal sections taken through the teeth (t, f) and apophyses (a, a'). d, outer, r, inner shell-layer ; I, dental plate of lower valve ; u, umbonal cavity of upper valves ; i, intestinal channel. Originals in Brit. M. * This is extremely doubtful ; since p. 253 was printed, we have examined an authentic specimen of Aetheria, and find that Rang and Cailliaud's account is incor- rect : it has no foot. CONCHIFERA. 285 Vicuna, the mantle-opening for that organ would liave been completely ob- ;ructed by the adductor, but that the muscular support was hook-shaped ig. 200, a). The posterior adductor-process is similarly under-cut for the assage of the rectum, which in all bivalves emerges between the hinge and osterior adductor, winds round outside that muscle and terminates in the ne of the exhaleut current. There is a groove (sometimes an inch deep) 3und the second and third duplicatures in the upper valve, which seems in- mded to facilitate the passage of the alimentary canal, and the flow of water •om the gills into the exhalent channel. The smallness of the space for the ranchise may have been compensated by deep plication of those organs, as i Chama and Tridacna. Fossil, 16 sp. Chalk. Bohemia, Tyrol, France, Spain, Turkey, Syria Jgeria, Egypt. Fig. 202. Interior of lower valve. Fig. 203. Interior of upper valve. Radiolitesmammillaris, Math. ^ L. Chalk. S. Mamest, Dordogne. ligamental inflection ; m, pallial line; c, c, cartilage pits ; a, a, adductor impressions and processes; t, teeth and dental sockets. RADIOLITES, Lamarck, 1801. Etym. Radius, a ray. Syn. Spheerulites, De la Metherie, 3805. 286 MANUAL OF THE MOLLUSCA. structure ; internal margins smooth or finely striated, simple, continuous ; ligamental inflection very narrow, dividing the deep and rugose cartilage pits : lower valve with a thick outer layer, often foliaceous ; its cavity deep and straight, with two dental sockets and lateral muscular impressions; upper valve flat or conical, with a central umbo ; outer layer thin, radiated ; um- bonal cavity inclined towards the ligament ; teeth angular, striated, supporting curved and sub-equal muscular processes. The upper valve of R. fleuriausus has an oblique umbo, with a distincl ligamental groove. The foliations of the lower valve are frequently undu- lated ; they are sometimes as thin as paper and several inches wide. The umbonal cavity of the lower valve is partitioned off by very delicate funnel-shaped laminee. Specimens frequently occur in which the outer she! layer is preserved, whilst the inner is wanting, and the mould ("birostrites"^ remains loose in the centre. The interior of the outer shell layer is deepl} grooved with lines of growth, and exhibits a distinct ligamental ridge in each valve. 287 Fig, 207. Caprinella triangularis, Desm. U. Green-sand, Rochelle. § A, portion of the left valve, after D'Orbigny,* the shell-wall is removed byweather- ing, exposing the camerated interior. B, mould of five of the water-chambers. C, mould of the body-chamber ; u, umbo of right valve ; s, of left valve ; t, dental groove : a, surface from which the posterior lobe has been detached. From the originals in the Brit. M. presented by S. P. Pratt, Esq. -> CAPRINELLA, D'Orbigny. Type, C. triangularis, Desm. (Fig 207). Syn. Caprinula (Boissii) D'Orb. Shell fixed by the apex of the right valve, or free ; composed of a thick layer of open tubes, with a thin compact superficial lamina ; cartilage inter- nal, contained in several deep pits ; umbones more or less camerated ; right Fig. Fig. 208. Straight valve. Fig. 209. Spiral valve. Transverse sections of C. Boissii, L. Chalk, Lisbon (Mr. Sharpe). I, position of ligamental inflection; t, teeth; c, cartilage pits; u, umbonal cavity. ig. 209 is from a weathered specimen, which has lost the outer layer. The tubes of the shell-wall are filled with limestone containing small shells. 288 MANUAL OF THE MOLLUSCA. valve conical or elongated, with a ligamental furrow on its convex side, and furnished with one strong hinge-tooth supported by an oblique plate : left valve oblique or spiral, with 2 hinge-teeth, the anterior supported by a plate which divides the umbonal cavity lengthwise. In C. triangularis the umbonal cavity of the spiral valve is partitioned off at regular intervals (Fig. 207, A) ; the length of the water chambers is sometimes 3£ inches, and of the body-chamber from 2 to 7 diameters; speci- mens measuring a yard across may be seen on the cavernous shores of the islets near Rochelle.* (Pratt.} Fossil, 6 sp. Neocomian — L. Chalk. France, Portugal, Texas. -7 Fig. 210. C. Aguilloni, left valve. Fig 211. C. adversa (after D'Orb.) «. a, position of adductors ; I, ligament; u, umbonal cavity; t, tooth of fixed val ve, broken off and remaining in its socket ; c, original point of attachment. CAPRINA, C. D'Orb. Etym. Caprina, pertaining to a goat. Syn. Plagioptychus, Matheron. Type, C. Aguilloni, C. D'Orb. L. Chalk, Tyrol, ( = C. Partschii, Hauer.) Shell with dissimilar valves, cartilage internal; fixed valve conical, marked only by lines of growth and a ligameutal groove ; hinge-margin with several deep cartilage-pits ; and one large and prominent tooth on the posterior side ; free valve oblique or spiral, thick, perforated by one or more rows of flattened canals, radiating from the umbo and opening around the inner margin ; anterior tooth supported by a plate which divides the umbonal cavity lengthwise, posterior tooth obscure ; hinge-margin much thickened, grooved for the cartilage. In C. adversa (fig. 211) the free valve is (b) sinistrally spiral; its cavity is partitioned off by numerous septa, and divided longitudinally by the dental plate. When young it is attached by the apex of the straight valve (c), but afterwards becomes detached, as the large specimens are found imbedded with * These singular fossils were called ichthyosarcolites by Desmarest, from their resemblance to the flaky muscles of fishes. CONCH1FERA. 289 the spire downwards. (Saemann). The lower valve of C. Coquandiana is sub-spiral. Fossil, 5 sp. U. Green-sand and L. Chalk. Bohemia, France, Texas. Fig. 212. Internal mould of Caprotina quadripartita, D'Orb. «, left umbo; r, right umbo; I, ligamental inflection; c, cartilage; t , V, dental sockets ; a, a', position of adductors ; at e, a portion of the third lobe is broken away.* From a specimen collected by Mr. Pratt. CAPROTINA, D'Orbigny. Type, C. semistriata, PI. XIX. fig. 13, 14. Le Mans, Sarthe. Shell composed of two distinct layers ; valves alike in structure, dis- similar in sculpturing ; ligamental groove slight ; cartilage internal ; right valve fixed, striated, or ribbed, with one narrow tooth between two deep pits, cartilage pits several on each side of the ligamental inflection, posterior adductor supported by a plate : free valve flat or convex, with a marginal umbo; teeth 2, very prominent, supported by ridges (apophyses) of the adductor muscles (a, a?}, the anterior tooth connected with a third plate (n), which divides the umbonal cavity. The smaller Caprotinte occur in groups, attached to oyster-shells ; their muscular ridges are much less developed than in the large species (fig. 212), 6'. costata is like a little Radiolite. Fossil, 4 sp. U. Green-sand, France. (The rest are Chamas, &c.) FAMILY IX. Shell regular, equivalve, truncated in front ; ligament external ; valves strongly ribbed, margins toothed ; muscular impressions blended, sub-Qentral, obscure. Animal attached by a byssus, or free; mantle-lobe extensively united ; * The first and fourth lobes, those on each side of the ligamental inflection, appear to be the two divisions of a great internal cartilage, like that of the Radiolite. (Fig. 205, 206, c, c.) 290 MANUAL OF THE MOLLUSCA. pedal opening, large, anterior ; siphonal orifices surrounded by a thickened pallial border ; branchial plain ; anal remote, with a tubular valve : shell- muscle single, large and round, with a smaller pedal muscle close to it behind ; foot finger-like, with a byssal groove ; gills 2 on each side, narrow, strongly plaited, the outer pair composed of a single lamina, the inner thick, with margins conspicuously grooved ; palpi very slender, pointed. The shell of Tridacna is extremely hard, being calcified until almost every trace of organic structure is obliterated. (Carpenter.} TRIDACNA, Bruguiere. Clam-shell. Etym. Tri- three, dakno, to bite ; a kind of oyster. (Pliny.) Ex. T. squamosa, PL XVIII. fig. 15. Shell massive, trigonal, ornamented with radiating ribs and imbricating foliations ; margins deeply indented ; byssal sinus in each valve large, close to the umbo in front; hinge teeth 1.1, posterior laterals 2.1. A pair of valves of T. gig as, weighing upwards of SOOlbs. and measuring above 2 feet across, are used as benitiers in the Church of St. Sulpice, Paris. (Dillwyn.) Capt. Cook states that the animal of this species sometimes weighs 20 Ibs. and is good eating.* Distr. 6 sp. Indian Ocean, China Seas, Pacific. Fossil, T. media. Miocene, Poland (Pusch). Tridacna and Hippopus are found in the raised coral-reefs of Torres Straits, (Macgillivray.) Sub-genus. Hippopus, Lamarck. H. maculatus, PI. XVIII. fig. 16. The "bear's-paw clam" has close valves with 2 hinge-teeth in each. It is found on the reefs in the Coral Sea. The animal spins a small byssus. FAMILY X. Shell regular, equivalve, free, cordate, ornamented with radiating ribs ; posterior slope sculptured differently from the front and sides ; cardinal teeth 2, laterals 1.1 in each valve ; ligament external, short and prominent ; pallia] line simple or slightly sinuated behind; muscular impressions sub-quadrate. Animal with mantle open in front ; siphons usually very short, cirrated externally ; gills 2 on each side, thick, united posteriorly ; palpi narrow and pointed ; foot large, sickle-shaped. CARDIUM, L. Cockle. Etym. Kardia, the heart. Syn. Papyridea, Sw. Types, C. costatum, PI. XIX. fig. 1. C. lyratum, fig. 2. Shell ventricose, close or gaping posteriorly ; umbones prominent, sub- central ; margins crenulated ; pallial line more or less sinuated. * " We staid a long time in the lagoon (of Keeling Id.), examining the fields oi coral and the gigantic clam-shells, into which if a man were to put his hand, he woult not, as long as the animal lived, be able to withdraw it."—-Darwin's Journal, p. 460, CONCHIFEKA. 291 Animal with the mantle-margins plaited ; siphons clothed with tentacular filaments, anal orifice with a tubular valve: branchial fringed; foot long, cylin rical, sickle-shaped, heeled. The cockle (C. edule) frequents sandy bays, near low-water; a small variety lives in the brackish waters of the R. Thames, as high as Graves- end ; it ranges to the Baltic, and is found in the Black Sea and Caspian. C. rusticum extends from the Icy Sea to the Medit. Black Sea, Caspian, and Aral. On the coast of Devon the large prickly cockle (C. aculeatum) is eaten. Sub-genera. Hemicardium (Cardissa) Cuvier. C. hemicardium, PI. XIX. fig. 3. Shell depressed, posterior slope flat, valves prominently keeled. Lithocardium aviculare, PI. XVIII. fig. 17. Shell triangular, keeled ; ante- rior side very short; hinge-teeth 1.2, directed backwards; posterior laterals 2.1 ; anterior muscular pit minute, posterior impression large, remote from the hinge. L. cymbulare, Lam. exhibits slight indications of a byssal sinus in the front margins of the valves. Fossil, Eocene, France. These shells present considerable resemblance to Tridacna. Serripes (groenlandicus) Beck. Hinge edentulous. Arctic Seas, from C. Parry to Sea of Kara ; fossil in the Norwich Crag. Fig. 213. C. laeviusculum, Eichw. (after Middendorff.) Adacna, Eichwald. C. edentulum, PI. XIX. fig. 4. (Acardo, Sw. not Brug, Pholadomya, Ag. and Mid. not Sby.) Shell compressed, gaping behind, thin, nearly edentulous ; pallial line sinuated: Animal with the foot (/) com- pressed ; siphons (s) elongated, united nearly to the end, plain. Distr. 8 sp, Aral, Caspian, Azof, Black Sea, and the embouchures of the Wolga, Dnjestr, Dnjepr, and Don ; burrowing in mud. C. Caspicum (Monodacna, Eichw.) has a single hinge-tooth, and C. trigonoides (Didacna, E.) rudiments of two teeth. The siphonal inflection varies in amount. Distr. 200 sp. World- wide ; from the sea-shore to 140 fathoms. Gre- garious on sands and sandy mud. Fig. 214. Conocardium aliforme, Sby. Carb : Ireland. (Mus. Tennant.) 292 MANUAL OF THE MOLLUSCA. Fossil, 270 sp. U. Silurian — . Patagonia — S. India. C. Hillanum, Sby. (Protocardium, Beyr.) is the type of a small group in which the sides are concentrically furrowed, the posterior slope radiately striated ; the pallial line is slightly sinuated. Jura — Chalk ; Europe; India. CONOCARDIUM, Bronn. Syn. Lychas, Stein. Pleurorhynchus, Ph. Lunulo-cardium, Miinster. Type, C. Hiberuicum, PI. XIX. fig. 5. C. aliforme, fig. 214. Shell, equivalve trigonal, conical and gaping in front, truncated behind, with a long siphonal tube near the umbones ; anterior slope radiately, pos- terior obliquely striated; margins strongly crenulated within; hinge with anterior and posterior laminar teeth : ligament external. The truncated end has usually been considered anterior, a conclusion which seems incompatible with the vertical position and burrowing habits of most free and equivalve shells: if compared with Adacna (fig. 213) the large gape (a) will be for the foot, and the long tube (s) siphonal. C. Hiber- nicum has an expanded keel, like Hemicardium inversum. The shell- struc- ture is prismatic-cellular, as first pointed out by Sowerby ; but the cells are cubical, and much larger than in any of the Aviculada. In Cardium the outer layer is only corrugated or obscurely prismatic-cellular. Fossil, 30 sp. U. Silurian — Garb. N. America, Europe. FAMILY X. LUCINTD^. Shell orbicular, free, closed ; hinge-teeth 1 or 2, laterals 1 — 1 or obso- lete; interior dull, obliquely furrowed; pallial line simple; muscular im- pressions 2, elongated, rugose; ligament inconspicuous or sub-internal.l Animal with mantle-lobes open below, and having one or two siphonal orifices behind ; foot elongated, cylindrical, or strap-shaped (ligulate], pro- truded at the base of the shell : gills one (or two) on each side, large and thick, oval ; mouth and palpi usually minute. The Lucinida are distributed chiefly in the tropical and temperate seas, upon sandy and muddy bottoms, from the sea-shore to the greatest habitable depths. The shell consists of two distinct layers. LUCINA, Bruguiere. Etym. Lucina, a name of Juno. Type, L. Pennsylvanica, PI. XIX. fig. 6. Shell orbicular, white; umbones depressed; lunule distinct; margins smooth or minutely crenulated ; ligament oblique, semi-internal ; hinge-teeth 2.2, laterals 1 — 1 and 2 — 2, or obsolete; muscular impressions rugose, anterior elongated within the pallial line, posterior oblong ; umbonal area with an oblique furrow. Animal with the mantle freely open below ; siphonal orifices simple ; CONCHIFERA. 293 mouth minute, lips thin ; gills single on each side, very large and thick ; foot cylindrical, pointed, slightly heeled at the base. The foot of Lucina is often twice as long as the animal, but is usually folded back on itself and concealed between the gills ; it is hollow throughout. L. lactea (Loripes, Poli.) has a long, contractile anal tube. L. tigrina (Codakia, Scop.) has the ligament concealed between the valves, its lateral teeth are obsolete. Distr. 70 sp. W. Indies, Norway, Black Sea, N, Zealand ;— 120 fms. Fossil, 200 sp. U. Silurian — . U. States — T. del. Fuego ; Europe — S. India. Sub-genus, Cryptodon, Turton. L. flexuosa, PI. XIX. fig. 7. Syn. Ptychina, Phil, Thyatira, Leach. Clausina (ferruginosa) Jeflr. Shell thin, edentulous ; ligament quite internal, oblique, Animal with a long anal tube. Distr. Norway — N. Zealand. Fossil, Eocene — . U. S. Europe. CORBIS, Cuvier. Etym. Corbis, a basket. Type, C. elegans. PI. XIX. fig. 8. Syn. Fimbria, Muhl. not Bohadsch. " Idotsea," Schum. Shell oval, ventricose, sub-equilateral, concentrically sculptured ; margins denticulated within ; hinge-teeth 2, laterals 2, in each valve ; pallial line simple ; umbonal area with an oblique furrow, muscular impressions round and polished ; pedal scars close to adductors. Animal with the mantle open below, doubly fringed ; foot long pointed ; siphonal opening single, with a long retractile tubular valve ; lips narrow ; palpi rudimentary; gills single on each side, thick, quadrangular, plaited, united behind. Distr. 2 sp. India, China, N. Australia, Pacific. Fossil, 80 sp. (including sub-genera). Lias — . U. States, Europe. In C. dubia (Semi-corbis) Desh. Eocene, Paris, the lateral teeth are obsolete. Sub-genera. Sphcera (corrugata) Sby. Shell globular, concentrically furrowed and obscurely radiated ; ligament prominent ; margins crenulated ; hinge-teeth 2.2, obscure ; laterals obsolete. Fossil, Trias — Chalk. Europe. ? Unicardium, D'Orb. (Mactromya, Ag. part) = Corbula cardi- oides, Sby. Shell thin, oval, ventricose, concentrically striated; ligamental plates elongated ; pallial line simple ; hinge with an obscure tooth, or eden- tulous Fossil, 40 sp. ? Lias — Portlandian. Europe. ? TANCREDIA, Lycett, 1850. Dedicated to Sir Thos. Tancred, Bt. founder of the Cotteswolde Natu- ralists Club. Ex. T. extensa, L. PI. XXI. fig. 22. Syn. Hettangia, Turquem. Shell trigonal, smooth; anterior side usually longest; cardinal teeth 294 MANUAL OF THE MOLLUSCA. 2.2, one of them small; a posterior lateral tooth in each valve; ligament external ; muscular impressions oval ; pallial line simple. Fossil, 11 sp. Lias — Bath Oolite. Brit. Trance. DIPLODONTA. Bronn. " Etym. Diplos, twin, odonta, teeth. Syn. Sphserella, Conrad. Type, D. lupinus ( Venus) Brocchi. PI. XIX. fig. 9. Shell sub-orbicular, smooth ; ligament double, rather long, sub-marginal; hinge-teeth 2.2, of which the anterior in the left valve, and posterior in the right, are bifid ; muscular impressions polished, anterior elongated. Animal with the mantle-margins nearly plain, united; pedal opening large, ventral ; foot pointed, hollow ; palpi large, free ; gills 2 on each side, distinct, the outer oval, inner broadest in front, united behind ; branchial orifice small, simple ; anal larger, with a plain valve. Distr. 12 sp. W. Indies, Rio, Brit. Medit. Red Sea, W. Africa, India, Corea, Australia, California. D. diaphana (Felania Recluz) burrows in sand. Fossil, Eocene — . U. States, Europe. ? Scacchia, Philippi, 1844 ; Telliua elliptica, Sc. Shell minute, ovate, posterior side shortest ; hinge-teeth 1 or 2, laterals obsolete ; ligament mi- nute; cartilage internal, in an oblong pit. Animal with mantle widely open ; siphonal orifice single ; foot compressed, linguiform ; palpi moderate, oblong. Distr. 2 sp. Medit. Fossil, 1 sp. Pliocene, Sicily. ? Cyamium, Philippi, 1845, C. antarcticum, PL XIX. fig. 16. Shell oblong, hinge-teeth 2.2 ; ligament double; cartilage in a triangular groove behind the teeth in each valve. Distr. Patagonia. UNGULINA, Daudin. Etym. Ungulina, like a hoof. Type, U. oblonga. PI. XIX. fig. 10. Shell sub-orbicular ; ligament very short ; epidermis thick, wrinkled^ sometimes black; hinge-teeth 2.2 ; muscular impressions long, rugose. Animal with the mantle open below, fringed ; siphonal orifice single ; foot vermi-form, thickened at the end and perforated, projecting from the base of the shell or folded up between the gills ; palpi pointed ; gills 2 on each side, unequal, the external narrower, with a free dorsal border, inner widest in front. Distr. 4 sp. Senegal, Philippines, excavating winding galleries in coral. KELLIA, Turton, 1822. Etym. Named after Mr. O'Kelly of Dublin. Syn. Lasea (Leach) Br. 1827- Cycladina (Adansonii) Cantr. Bornia (sub-orbicularis) Phil. Poronia (rubra) Recluz (not Willd.) Eryciua (cycla- diformis) Desh. (not Lam.) Types, K. sub-orbicularis. Mont. K. rubra. PI. XIX. fig. 12. Shell small, thin, sub -orbicular, closed ; beaks small ; margins smooth ; ligament internal, interrupting the margin (in K. suborbicularis], or on CONCHIFEKA. 295 the thickened margins (in K. rubrd] ; cardinal teeth 1 or 2, laterals 1 — 1 in each valve. Animal with the mantle prolonged in front into a respiratory canal, either complete (in K. suborbicularis} or opening into the pedal slit (in K. rubra) ; foot strap-shaped, grooved ; gills large, two on each side, united posteriorly, the external pair narrower and prolonged dorsally ; palpi triangular ; pos- terior siphonal orifice single, exhalent. The hinges of these little shells are subject to variations, which are not constantly associated with the modifications of the mantle-openings. They creep about freely, and fix themselves by a byssus at pleasure. K. rubra is found in crevices of rocks at high-water mark, and often in situations only reached by the spray, except at spring-tides ; other species range as deep as 200 fms. K. Laperousii (Chironia) Desh. PL XIX. fig. 11, was obtained, burrowing in sandstone, from deep-water, at Monterey, Cali- fornia. Distr. 20 sp. Norway — New Zealaud — California. Fossil, 20 sp. Eocene — . U. States, Europe. Sub-genera. Turtonia (minuta) Hanley. Shell oblong, inequilateral, anterior side very short ; ligament concealed between the valves ; hinge-teeth 2.2. Animal with the mantle open in front ; foot large, heeled ; siphon single, slender, elongated, protruded from the long end of the shell. Distr. Greenland, Norway, Brit. In pools and crevices of rocks between tide-marks, and in the roots of sea -weeds and corallines. Mr. Thompson obtained them from the stomachs of mullets taken on the N.E. coast of Ireland. Pythina (Deshayesiana) Hinds. (Myllita, D'Orb. and Reel.) Shell tri- gonal, divaricately sculptured ; ^ligament internal ; right valve with 2 lateral teeth, left with 1 cardinal and 2 laterals. Distr. 2 sp. New Ireland, Australia, Philippines. Fossil, Eocene — . France. MONTACUTA, Turton. Dedicated to Col. George Montagu, the most distinguished of the earlier English malacologists. Type, M. substriata. PI. XIX. fig. 13. Shell minute, thin, oblong, anterior side longest ; hinge-line notched ; ligament internal, between 2 laminar, diverging teeth (with a minute ossicle. Love'n}. Animal with the mantle open in front ; margins simple ; siphonal orifice single ; foot large and broad, grooved. The Montacutce moor themselves by a byssus, or walk freely ; M. sub- striata has only been found attached to the spines of the purple heart-urchin (Spatangus purpureus] in 5 — 90 fms. M. bidentata burrows in the valves of dead oyster-shells. Distr. 3 sp. U. S. Norway, Brit JSgean. Fossil, 2 sp. Miocene — . Brit. 296 MANUAL OF THE MOLLUSCA. LEPTON, Turton. Etym. Lepton, a minute piece of money (from leptos, thin). Syn. ? Solecardia (eburnea) Conrad, L. California. Type, L. squamosum. PI. XIX. fig. 34. Fig. 215. Shell sub-orbicu]ar, compressed, smooth, or shagreened, a little opened at the ends and longest behind; hinge-teeth 0.1 or 1.1. in front of an angular cartilage notch; lateral teeth 2.2 and 1.1. Animal with the mantle (m] open in front, extending beyond the shell, and bearing a fringe of filaments, of which one in front (£) is very large; siphon (s) single ; gills 2 on each side, separate; foot (f) thick, tapering, heeled and grooved, forming a sole or creeping disk. (Alder.} Fig. 215. Lepton. Distr. 3 sp. U. S. Brit. Spain. Laminarian and Coralline Zones. Fossil, Miocene — . U. S. Brit. GALEOMMA, Turton. Syn. Hiatella, Costa (not Daud.) ; Parthenopea, Scacchi (not Fabr.) Type, G. Turtoni, PI. XIX. fig. 15. (Galee, weasel, omma, eye.) Shell thin, oval, equilateral, gaping widely below ; invested with a thick, fibrous epidermis ; beaks minute; ligament internal ; teeth 0.1. Animal with the mantle-lobes united behind and pierced with 1 siphonal orifice, margins double, the inner with a row of eye-like tubercles ; gills large, sub-equal, united behind; lips large, palpi lanceolate, plaited; foot long compressed, with a narrow flat sole. The Galeomma spins a byssus, but breaks from its mooring at will and creeps about like a snail, spreading out its valves nearly flat. (Clarke.} Distr. 3 sp. Brit. Medit. Mauritius, Pacific. Fossil, Pliocene — . Sicily. FAMILY XI. CYCLADID^E. Shell sub-orbicular, closed ; ligament external ; epidermis thick, horny ; umbones of aged shells eroded ; hinge with cardinal and lateral teeth ; pallial line simple, or with a very small inflection. Animal with mantle open in front, margins plain ; siphons (1 or 2) more or less united, orifices usually plain ; gills 2 on each side, large unequal, united posteriorly ; palpi lanceolate : foot large, tongue-shaped. All the shells of this family were formerly included in the genus Cyclas, a name now retained for the small species inhabiting the rivers of the north temperate zone ; the Cyrena are found in warmer regions, on the shores of creeks and in brackish water, where they are gregarious, burying vertically in the mud, and often associated with members of marine genera. CONCHIFERA. 297 CYCLAS, Bruguiere. Etym. KuJclas, orbicular. Type, C. Cornea. PI. XIX. fig. 17. Syn. SphEerium, Scop. Pisum, Muhlf. (not L.) Musculium, Link. Shell thin, ventricose, nearly equilateral; cardinal teeth 2.1, minute, laterals 1 — 1 : 2 — 2, elongated, compressed. Animal ovo-viviparous ; siphons partly united, anal shortest, orifices plain ; gills very large, the outer smallest, with a dorsal flap ; palpi small and pointed. The fry of Cyclas are hatched in the internal branchiae, they are few in number and very unequal in size ; a full-grown C. cornea has about 6 in each gill; the largest being £ to i the length of the parent. The young Cyclades and Pisidia are very active, climbing about submerged plants and often suspending tnemselves by byssal threads ; the striated gills and pulsat- ing heart are easily seen through the shell. Fig 216. Pisidium amnicum, -f . with its foot protruded. Sub-genus, Pisidium, Pfr. P. amnicum, PI. XIX. fig. 18. SMI ine- quilateral, anterior side longest; teeth stronger than in Cyclas. Animal with a single, small, excurrent siphon; branchial and pedal orifices confluent, Dislr. 30 sp. U. States, S. America, Greenland, Norway, Sicily, Algeria, Cape, India, Caspian. Fossil, 35 sp. Wealden — . Europe. CYEENA, Lamarck. Etym. Cyrene, a nymph. Type, C. cyprinoides, PL XIX. fig. 20. Shell oval, strong, covered with thick, rough epidermis ; ligament thick and prominent; hinge-teeth 3.3, laterals 1 — 1 in each valve; pallial line slightly sinuated. Animal (of type) with the mantle open in front and below, margins plain ; siphons short, orifices fringed ; gills unequal, square in front, plaited, inner lamina free at base ; palpi lanceolate ; foot strong, tongue- shaped. Section, Corbicula, Muhlf. C. consobrina, PI. XIX. fig. 21. Shell orbicular, concentrically furrowed, epidermis polished; lateral teeth elon- gated, striated across. Distr. 25 sp. Tropical America (eastern) ; Egypt, India, China, Australia, 298 MANUAL OF THE MOLLUSCA. Pacific Ids. In the mud of rivers, and in mangrove swamps, usually near the coast. C. consobrina ranges from Egypt to Cashmere and China, and is found fossil in the Pliocene formations of England,* Belgium and Sicily. Fossil, 70 sp. Wealden — . Europe, U. States. ? CYRENOIDES, Joannis. Syn. CyreneUa, Desh. Type, C. Dupontii, PL XIX. fig. 19. Shell orbicular, ventricose, thin, eroded at the beaks ; epidermis dark olive ; ligament external, prominent, elongated ; cardinal teeth 3:2, the central tooth of the right valve bifid ; muscular impressions long, narrow ; pallial line simple. Animal with the mantle open in front and below, margin simple, siphons short, united ; palpi moderate, narrow ; gills very unequal, narrow, united behind ; foot cylindrical elongated. Distr. 1 sp. R. Senegal. The marine sp. are Diplodonfa. FAMILY XII. CYPRINID^. Shell regular, equivalve, oval or elongated ; valves close, solid ; epider- mis thick and dark; ligament external, conspicuous; cardinal teeth 1 — 3 in each valve, and usually a posterior lateral tooth ; pedal scars close to, or confluent with the adductors ; pallial line simple. Animal with the mantle-lobes united posteriorly by a curtain, pierced with two siphonal orifices ; foot thick, tongue-shaped ; gills 2 on each side, large, unequal, united behind, forming a complete partition ; palpi moderate, lanceolate. One half the genera of this family are extinct, and the rest (excepting Circe} were more abundant in former periods than at the present time. Oyprina and Astarte are boreal forms ; Circe and Cardita abound in the Southern seas. CYPRINA, Lamarck. Etym. Kuprinos (from Kupris] related to Venus. Type, C. Islandica, PL XIX. fig. 22. Syn. Arctica, Schum, Shell oval, large and strong, with usually an oblique line or angle on the posterior side of each valve ; epidermis thick and dark ; ligament pro- minent; umbones oblique.; no lunule; cardinal teeth 2:2, laterals 0 — 1, 1 — 0 ; muscular impressions oval, polished ; pallial sinus obsolete. Animal with the mantle open in front and below, margins plain ; siphonal orifices close together, fringed, slightly projecting ; outer . gills semilunar, inner truncated in front. The principal hinge-tooth in the right valve of Cyprina represents the * Associated with the bones of Elephas meridionalis, Rhinoceros leptorhinus, Mastodon Arvernensis, Hippopotamus major, &c. CONCHIFERA. 299 second and third in Venus and Cytherea ; the second tooth of the left valve is consequently obsolete. Distr. C. Islandica ranges from Greenland and the U. S. to the Icy Sea, Norway, and England ; in 5 — 80 fm. water. It occurs fossil in Sicily and Piedmont, but not alive in the Medit. Fossil, 90 sp. (D'Orb.) Muschelkalk — . Europe. CIRCE, Schumacher. Etym. In Greek myth, a celebrated enchantress. Ex. C. corrugata, PL XX. fig. 2. Syn. Paphia (undulata) Lam.* Shell sub-orbicular, compressed, thick, often sculptured with diverging striae ; nmbones flat ; lunule distinct ; ligament nearly concealed ; margins smooth; hinge-teeth 3:3; laterals obscure; pallial line entire. Animal (of C. minima} with the mantle open, margins denticulate, siphonal orifices close together, scarcely projecting, fringed; foot large, heeled; palpi long and narrow. Ranges from 8 — 50 fms. (Forbes.) Distr. 37 sp. Australia, India, Red Sea, Canaries, Brit. ASTARTE, Sowerby, 1816. Syn. Crassina, Lam. Tridonta, Schum. Goodallia, Turton. Ex. A. sulcata, PL XX. fig. 1. (Astarte, the Syrian Venus.) Shell sub-orbicular, compressed, thick, smooth or concentrically fur- rowed; lunule impressed; ligament external; epidermis dark: hinge-teeth 2:2, the anterior tooth of the right valve large and thick ; anterior pedal scar distinct ; pallial line simple. Animal with mantle open ; margins plain or slightly fringed ; siphonal orifices simple ; foot moderate, tongue- shaped ; lips large, palpi lanceolate ; gills nearly equal, united behind, and attached to the siphonal band. Distr. 14 sp. Behrings Sea, Wellington Channel, Kara Sea, Ochotsk, U. S. Norway, Brit. Canaries, ^gean (30—112 fms.) Fossil, 200 sp. (D'Orb.) Lias — . N. and S. America, Europe, Thibet. ? Digitaria, Wood ; Tellina digitaria, L. Medit. Fossil, Crag, Brit. CRASSATELLA, Lamarck. Syn. Ptychomya, Ag. Paphia (Lam. part) Roissy. Type, C. ponderosa, PL XXI. fig. 4. Etym. Crassus thick. Shell solid, ventricose, attenuated behind, smooth or concentrically fur- rowed ; lunule distinct ; ligament internal ; margin smooth or denticulated ; * This name was employed by Bolten, in 1798, for sp. of Veneridae, and by Lamarck, in 1801, for Venus divaricata, Chemn. (= Circe divaricata and Crassatella contraria) and Mesodesma glabratum. In 1808, Fabricius adopted the name fora group of butterflies, in which sense it is now widely employed, having been aban- doned by Lamarck in his later works, and by all succeeding malacologists. 300 MANUAL OF THE MOLLUSCA. pallial line simple ; hinge-teeth 1:2, striated, in front of cartilage pit ; lateral teeth 0 — 1, 1 — 0 ; adductor impressions deep, rounded ; pedal small, distinct. Animal with mantle-lobes united only by the branchial septum ; inhalent margins cirrated; foot moderate, compressed, triangular grooved; gills smooth, unequal, outer semi-lunar, inner widest in front ; palpi triangular. Distr. 30 sp. Australia, N. Zealand, Philippines, India, W. Africa, Canaries, Brazil. Fossil, 50 sp. Neocomian — . Patagonia, U. S. Europe. ISOCARDIA, Lam. Heart-cockle. Etym. Isos, like, cardia, the heart. Type, I. cor. PI. XX. fig. 3. Syn. Glossus, Poli ; Bucardium, Muhlfeldt ; Pecchiolia, Meneghini. Shell cordate, ventricose; umbones distant, sub-spiral; ligament exter- nal; hinge-teeth 2:2; laterals 1 — 1 in each valve, the anterior sometimes obsolete. Animal with the mantle open in front ; foot triangular, pointed, com- pressed ; siphonal orifices close together, fringed ; palpi long and narrow ; gills very large, nearly equal. Fig. 217. Isocardia cor. The heart-cockle burrows in sand, by means of its foot (/), leaving only the siphonal openings exposed. (Bulwer.} Distr. 5 sp. Brit. Medit. China, Japan. Fossil, 70 sp. Trias — . U. S. Europe, S. India. The Isocardia-shaped fossils of the old rocks belong to the genera Car- diomorpha and Iso-arca ; many of those in the Oolites to Ceromya. Casts of true Isocardia have only two transverse dental folds between the beaks, and no longitudinal furrows. CYPRICARDIA, Lam. Ex. C. obesa, PI. XX. fig. 4. Syn. Trapezium, Humph. Libitina, Sch. CONCH1FERA. 301 Shell oblong, with an oblique posterior ridge; umbones anterior de- pressed; ligament external, in deep and narrow grooves; cardinal teeth 2:2, laterals 1 — 1 in each valve, sometimes obscure ; muscular impressions oval, (of two elements) ; pallial line simple. Animal (of C. solenoides) with mantle-lobes united, cirrated behind; pedal opening moderate ; foot small, compressed, with a large byssal pore near the heel ; siphons short, conical, unequal, cirrated externally ; orifices fringed ; palpi small ; gills unequal, the outer narrower and shorter, deeply lamellated, united posteriorly, the inner prolonged between the palpi. Distr. 13 sp. Red Sea, India, Australia. In crevices of rock and coral. Fossil, 60 sp. L. Silurian — . N. America, Europe. ? Sub-genera. Coralliophaga, Bl. C. coralliophaga, Lam. Shell long, cylindrical, thin, slightly gaping behind; hinge-teeth 2:2, and a laminar posterior tooth ; pallial line with a wide and shallow sinus. Distr. 2 sp. Medit. in the burrows of the Lithodomus ; sometimes two or three dead shells are found one within the other, besides the original owner of the cell. ? Cypricardites, Conrad (part). An. Geol. Rep. 1841. (Sanguinolites, M'Coy). Employed for Cypricardia-shaped shells of the palaeozoic rocks; some of them are more nearly related to Modiola (v. Modiolopsis, p. 266) but they bear no resemblance to Sanguinolaria. PLEURornoRus, King, 1848. T^/pe, P. costatus, Brown. Permian, England, (Pal. Trans. 1850. PI. XV. fig. 13—20.) Syn. ? Cleidophorus, Hall (cast only). Unionites, Wissm. ? Mseonia, Dana. Shell oblong ; dorsal area defined by a line, or keel ; umbones anterior, depressed; hinge-teeth 2.2 ; laterals 1.1 ; elongated posterior; anterior ad- ductor impression deep, with a small pedal scar close to it, and bounded pos- teriorly by a strong rib from the hinge ; pallial line simple. Fossil, L. Silurian — Trias. U. States ; Europe, N. S. Wales, Tasmania. ? CARDILTA, Deshayes. Type, C. semisulcata, PI. XVIII. fig. 18. Syn. Hemicyclonosta, Desh. Shell oblong, ventricose, cordate ; beaks prominent, sub-spiral ; hinge with a small tooth and dental pit in each valve ; ligament partly internal con- tained in a spoon-shaped inflection ; anterior muscular scar long, with a pedal scar above ; posterior adductor impression on a prominent sub-spiral plate ; pallial line simple. Distr. 2 sp. Chinese Sea ; Moluccas. Fossil, 2 sp= Eocene — . France, Piedmont. MEGALODON, J. Sowerby. Type, M. cucullatus, PL XIX. fig. 19. (Meg as, large, odous, tooth.) Shell oblong, smooth or keeled ; ligament external ; hinge-teeth 1:2, thick ; 302 MANUAL OF THE MOLLUSCA. laterals 1.1, posterior; anterior adductor impression deep, with a raised margin ; and a small pedal scar behind it. In the typical species the beaks are sub-spiral, the lateral teeth obscure, and the posterior adductors bounded by prominent ridges. Fossil, 14 sp. U. Silurian — Devonian ; U. States, Europe. Sub-genera. ? Goldfussia (nautiloides) Castlenau. Umbones spiral; anterior side concentrically furrowed ; posterior side with two oblique ridges. Fossil, Silurian, U. States. Megaloma (Canadensis) Hall, 1852. U. Silurian, Canada. Umbones very thick, hinge-teeth rugged, almost obliterated with age ; posterior lateral teeth 1.1 ; no muscular ridges. PACHYDOMUS (Morris) J. Sowerby. Etym. Pachus, thick, domos, house. Syn. Astartila, Dana. ? Cleobis (grandis) Dana. ? Pyramus (ellipticus) D. = Notomya, M'Coy. Type, P. globosus (Megadesmus) J. Sby. in Mitchell's Australia. Shell oval, ventricose, very thick; ligament large, external; lunette more or less distinct; hinge-line sunk; teeth 1 or 2 (?) in each valve ; adductor impressions deep ; anterior pedal scar distinct ; pallia! line broad and simple, or with a very shallow sinus. Fossil, 5 sp. Devonian ? N. S. Wales, Tasmania. PACHYRISMA, Morris and Lycett. Etym. Pachus, thick, ereisma, support. Type, P. grande, M. and L. Great Oolite (Bathonian) Minchinhampton. Shell cordate, with large sub-spiral beaks ; valves very thick near the umbones, obliquely keeled ; hinge with one thick conical tooth (behind the dental pit, in the right valve), a small lateral tooth close to the deep and oval anterior adductor, and a posterior lateral-tooth (or muscular lamina ?) ; liga- mental plates short and deep. OPIS, Defrance. Ex. 0. lunulata, PI. XIX. fig. 24. (Opis, a name of Artemis.) Shell strong, ventricose, cordifonn, obliquely keeled ; beaks prominent incurved or sub-spiral ; cardinal teeth 1.1 ; lunule distinct. Fossil, 42 sp. Trias — Chalk. Europe. CAEDINIA, Agassiz. Etym. Cardo-inis, a hinge. Type, C. Listeri, PI. XIX. fig. 23. Syn. Thalassides, Berger 1833 (no descr.) Sinemuria, Christol. Pachy odon, Stutch. (not Meyer nor Schum.) Pronoe, Ag. Shell oval or oblong, attenuated posteriorly, compressed, strong, no pearly, marked by lines of growth ; ligament external ; cardinal teeth ob CONCHIFERA. 303 scure, laterals 1 — 0, 0 — 1, remote, prominent ; adductor impressions deep pallial line simple. Fossil, 20 sp. Lias — . Inf. Oolite, Europe ; along with marine shells. Sub-genus? Anthracosia, King, 1844; Unio sub-constrictus. Sby. U. Sil. — Carb. 40 sp. They occur in the valuable layers of clay-ironstone called " mussel-bands," associated with Nautili, Discina, &c. In Derbyshire the mussel-band is wrought, like marble, into vases. ? MTOCONCHA, J. Sowerby. Type, M. crassa, PI. XIX. tig. 25. (Mya, mussel, concha, shell.) Shell oblong, thick, with nearly terminal depressed umbones ; ligament external, supported by long narrow appressed plates ; hinge thick, with an oblique tooth in the right valve ; anterior muscular impression round and deep, with a small pedal scar behind it ; posterior impression large, single ; pallial line simple. This shell, which is not nacreous inside, is distinguished from any of the 'Mytilida by the form of its ligamental plates and muscular impressions ; the hinge-tooth is usually overgrown and nearly obliterated by the hinge-margin as in aged examples of Cardita orbicularis and Cypricardia vellicata. Fossil, 26 sp. Permian — Miocene. (D'Orb.) Europe. Sub -genus. ? Hippopodium (ponderosum, Sby.) Coneybeare. Lias, Europe. Shell oblong, thick, ventricose ; umbones large ; ligament external ; ventral margin sinuated; hinge with one thick, oblique tooth in each valve, some- times nearly obsolete; pallial line simple; anterior muscular scar deep. This shell appears to be a ponderous form of Cypricardia or Cardita ; it is a characteristic fossil of the English Lias, but only very aged examples have been found. CARDITA, Bruguiere. St/n. Mytilicardia and Cardiocardita, (ajar) Bl. Arcinella, Oken. Type, C. calyculata, PI. XX. fig. 5. Etym. Cardia, the heart. Shell objong, radiately ribbed ; ligament external ; margins toothed ; hinge-teeth 1:2, and an elongated posterior tooth; pallial line simple; anterior pedal scar close to adductor. Animal with the mantle lobes free, except between the siphonal orifices ; branchial margin with conspicuous cirri ; foot rounded and grooved, spinning a byssus ; labial palpi short, triangular, plaited ; gills rounded in front, taper- ing behind and united together, the outer pair narrowest. C. pectunculus, Brug. (Mytilicardia, Bl.) has an anterior tooth. C. con- eamerata, Brug. found at the Cape, has a remarkable cup-like inflection of the ventral margin of each valve. Sub-genus. Venericardia, Lam. V, ajar, PL XX. fig. 6. Shell cordate, ventricose ; hinge without lateral teeth. Animal locomotive, with a sickle- shaped foot like the cockles. P 304 MANUAL OF THE MOLLUSCA. Distr. 50 sp. Chiefly in tropical seas, on rocky bottoms and in shallow water; the Venericardia on coarse sand and sandy mud. W. Indies, U. S. W. Africa, Medit. Red Sea, India, China, Australia, New Zealand, Pacific, W. America. C. dorealis, Conrad, inhabits the sea of Ochotsk ; C. abyssicola, Hinds, ranges to 100 fms. ; C. squamosa, to 150 fms. Fossil, 1 00 sp. Trias — . U. S. Patagonia, Europe, S. India. ? VEKTICORDIA, Searles Wood, 1844. Syn. Hippagus, Philippi, not Lea. (Verticordia, a name of Venus.) Type, V. cardiiformis (Wood, in Sby. Min. Con.) PL XVII. fig. 26. Shell sub-orbicular, with radiating ribs ; beaks sub-spiral ; margins den- ticulated; interior brilliantly pearly ; right valve with 1 prominent cardinal tooth ; adductor scars 2, faint ; pallial line simple ; ligament internal, ob- lique ; epidermis dark brown. Distr. 2 sp. China Sea (Adams). Medit. ? (Forbes.) Fossil, 2 sp. Miocene — . Brit. Sicily. Hippagus isocardioides, Lea, 1833, Eocene, Alabama: is edentulous. SECTION 6. SINU-PALLIALIA. Respiratory siphons lony ; pallial line sinuated. FAMILY XIV. Shell regular, closed, sub-orbicular or oblong; ligament external; hinge with usually 3 diverging teeth in each valve ; muscular impressions oval, polished; pallial line sinuated. Animal free, locomotive, rarely byssiferous or burrowing ; mantle with a rather large anterior opening ; siphons unequal, united more or less ; foot linguiform, compressed, sometimes grooved; palpi moderate, triangular, pointed ; branchiae large, sub-quadrate, united posteriorly. The shells of this tribe are remarkable for the elegance of their forms and colours; they are frequently ornamented with chevron-shaped lines. Their texture is very hard, all traces of structure being usually obliterated. The Venerida appeared first in the Oolitic period, and have attained their greatest development at the present time ; they are found in all seas, bu most abundantly in the tropics. VENUS, L. Syn. Merceneria, Antigone and Anomalocardia (flexuosa) Schum. Chione Megerle (not Scop,) Erycina (cardioides) Lam. 1818. Type, V. paphia, L. PL XX. fig. 7. Shell thick, ovate, smooth, sulcated or cancellated ; margins minutely crenulated; cardinal teeth 3—3; pallial sinus small, angular; ligamen prominent ; lunule distinct. CONCHIFERA. 305 Animal with mantle-margins fringed; siphons unequal, more or less separate ; branchial orifice sometimes doubly fringed, the outer pinnate ; anal orifice with a simple fringe and tubular valve ; foot tongue-shaped ; palpi small, lanceolate. V. textilis, and other elongated species, have a deep pallial sinus ; V. gemma (Totten) has a very deep angular sinus, like Arlemis ; V. reticulata has bifid teeth, like Tapes ; V. tridacnoides, a fossil of the U. States, has massive valves, ribbed like the clam-shell. The N. American Indians used to make coinage (wampum) of the sea-worn fragments of Venus mercenaria, by perforating and stringing them on leather thongs. Distr. 176 sp. World-wide. Low-water — 140 fathoms. V. astar- toides, Behrings' Sea. V. verrucosa, Brit. Medit. Senegal, Cape, Red Sea; Australia ? Fossil, 160 sp. Oolites — . Patagonia, U. S. Europe, India. ? Volupia rugosa, (Defrance, 1829.) Shell minute, Isocardia-shaped, concentrically ribbed, with a large luimle. Eocene, Hauteville. Saxidomus (Nuttalli) Conrad. Oval, solid, with tumid umbones ; lunule, 0 ; teeth 3 — 4, unequal, the central bifid ; pallial sinus large. Distr. 8 sp. India, Australia, W. America. CYTHEREA, Lam. Etym. Cytherea, from Cythera, an Aegean Island. Syn. Meretrix, Gray. Dione, Megerle. Examples, C. dione, PL XX. fig. 8. C. chione, fig. 14, p. 26. Shell like Venus ; margins simple ; hinge with 3 cardinal teeth and an anterior tooth beneath the lunule ; pallial sinus moderate, angular. Animal with plain mantle-margins ; siphons united half-way. Distr, Same as Venus. Recent 113 sp. Fossil, 80 sp. MERGE, Schum. Etym,. Meroe, an island of the Nile. Syn. Cuneus (part) Megerle (not Da Costa). Sunetta, Link. Type, M. picta (= Venus Meroe, L. Donax, Desh.) PI. XX. fig. 9. Shell oval, compressed ; anterior side rather longest ; hinge with 3 car- dinal teeth, and a long narrow anterior tooth ; lunule lanceolate ; ligament in a deep escutcheon. Distr. 1 0 sp. Senegal, India, Japan, Australia. TRIGONA, Miihlfeldt. Etym. Trigonos, theee- cornered. Type, T. tripla, PI. XX. fig. 10. Shell trigonal, wedge-shaped, sub-equilateral ; ligament short, prominent ; cardinal teeth 3 — 4, anterior f remote ; pallial sinus rounded, horizontal. Distr. 28 sp. W. Indies, Medit, Senegal, Cape, India, W. America. Fossil, Miocene — . Bordeaux. T. crassatelloides attains a diameter of 5 inches and is very ponderous. P 2 306 MANUAL OF THE MOLLUSCA. Sub -genus, Grateloupia, Desra, G. irregularis, PL XX. fig. 11. Shell sub-equilateral, rounded in front, attenuated behind ; hinge with 1 anterior tooth, 3 cardinal teeth and several small posterior teeth ; pallial sinus deep, oblique. Fossil, 4 sp. Eocene — Miocene. U. States, France. ARTEMIS, Poli. Etym. Artemis, in Greek myth. Diana. Type, A. exoleta, PL XX. fig. 12. (Sijn. Dosinia, Scopoli.) Shell orbicular, compressed, concentrically striated, pale ; ligament sunk ; lunule deep ; hinge like Cytherea ; margins even ; pallial sinus deep, angular, ascending. Animal with a large hatchet-shaped foot, projecting from the ventral margin of the shell ; mantle-margins slightly plaited ; ^iphons united to their ends ; orifices simple ; palpi narrow. Distr. 85 sp. Boreal — Tropical seas; low-water — 80 fms. Fossil, 8 sp. Miocene — . U. States, Europe, S. India. Sub-genera. Cyclina, Desh. V. Sinensis, Chemn. Orbicular, vcntricose, margins crenulated, no lunule, sinus deep and angular. Distr. 10 sp. Senegal, India, China, Japan. W. America. Fossil, 1 sp. Miocene, Bor- deaux. dementia (papyracea) Gray. Thin, oval, white; ligament semi-internal; posterior teeth bifid, sinus deep and angular. Animal with long, united siphons, and a large crescentic foot, similar to Artemis. Distr. 3 sp. Australia, Philippines. LUCINOPSIS, Forbes. Syn. Dosinia, Gray, 1847 (not Scop.) Mysia, Gray, 1851 (not Leach). Cyclina, Gray, 1853 (not Desh.) Type, Venus undata, Pennant, PL XX. fig. 13. (Lucina, and opsis, like.) Shell lenticular, rather thin ; right valve with 2 laminar, diverging teeth, left with 3 teeth, the central bifid: muscular impressions oval, polished; pallial sinus very deep, ascending. Animal with mantle-margins plain; pedal opening contracted; foot pointed, basal ; siphons longer than the shell, separate, divergent, with fringcc orifices. (Clark.) Distr. 1 sp. Norway, Brit. Fossil, 3 sp. Miocene. Brit. Belgium. TAPES, Miihlfeldt. Syn. Paphia, Bolten, 1798. Pullastra, G. Shy. Example, T. pullastra, PL XX. fig. 14. (Tapes, tapestry.) Shell oblong, umbones anterior, margins smooth ; teeth 3 in each valve more or less bifid ; pallial sinus deep, rounded. Animal spinning a byssus; foot thick, lanceolate, grooved; mantle plai CONCHIFEKA. 307 or Finely fringed ; freely open in front ; siphons moderate, separate half-way or throughout, orifices fringed, anal cirri simple, branchial ramose ; palpi long, triangular. Distr. 78 sp. Norway, Brit. Black Sea, Senegal, Brazil, India, China, New Zealand. Low- water — 100 fms. (Beechey). Fossil, Miocene — . Brit. France, Belgium, Italy. The animal is eaten on the continental coasts ; it buries in the sand at low-water or hides in the crevices of rocks, and roots of sea-weed. VENERUPIS, Lamarck. Etym. Venus^ and rupes, a rock. Syn. Gastrana, Schum. Example, V. exotica, PL XX. fig, 15. Shell oblong, a little gaping posteriorly, radiately striated and ornamented with concentric lamellae ; three small teeth in each valve, one of them bifid ; pallia! sinus moderately deep, angular. Animal with the mantle closed in front, pedal opening moderate ; siphons united half-way, anal with a simple fringe and tubular valve, branchial siphon doubly fringed, inner cirri branching ; palpi small and pointed. Distr. 19 sp. Brit. — Crimea ; Canaries ; India, Tasmania ; Kamts- chatka, Behring's Sea — Peru. In crevices of rocks. Fossil, Miocene — . U. States, Europe. PETRICOLA, Lamarck. Etym. Petra, stone, colo, to inhabit. Syn. Rupellaria, Bellevue ; Choristodon, Jonas ; Naranio, Gray. Type, P. lithophaga, PI, XX. fig. 16. f>. pholadiformis, PI. XX. fig. 17. Shell oval or elongated, thin, tumid, anterior side short ; hinge with 3 teeth in each valve, the external often obsolete ; pallial sinus deep. Animal with the mantle closed in front, much thickened and recurved over the edges of the shell ; pedal opening small ; foot small, pointed, lanceo- late ; siphons partially separate, orifices fringed, anal with a valve and simple cirri, branchial cirri pinnate ; palpi small, triangular. Distr. 30 sp. U. S. France, Red Sea, India, New Zealand, Pacific, W. America (Sitka — Peru). Burrows in limestone and mud. Fossil, 12 sp. Eocene — . U. S. Europe. GLAUCOMYA, (Bronn) Gray. Syn. Glauconome, Gray 1829 (not Goldfuss 1826). Type, G. Sinensis, PI. XX. fig. 18. (Glaucos sea -green, my a mussel.) Shell oblong, thin ; epidermis dark, greenish ; ligament external ; hinge with 3 teeth in each valve, one of them bifid j pallial sinus very deep and angular. Anwud with a rather small, linguiform foot ; pedal opening moderate ; 308 MANUAL OF THE MOLLUSCA. siphons very long, united, projecting far into the branchial cavity when retracted, their ends separate and diverging ; palpi large, sickle-shaped ; gills long, rounded in front, the outer shortest. Distr. 11 sp. Embouchures of rivers; China, Philippines, Borneo, India. FAMILY XV. MACTRIDJE. Shell equivalve, trigonal, close, or slightly gaping ; ligament (cartilage) internal, contained in a deep triangular pit ; epidermis thick ; hinge with 2 diverging cardinal teeth, and usually with anterior and posterior laterals ; pallial sinus short, rounded. Animal with the mantle more or less open in front; siphonal tubes united, orifices fringed; foot compressed; gills not prolonged into the branchial siphon. Sections of the shell exhibit an indistinct cellular layer on the external surface and a distinct inner layer of elongated cells. (Carpenter.} MACTRA, L. Etym. Mactra, a kneading trough. Syn. Trigonella, Da Costa (not L.) Schizodesma (Spengleri), Spisula (solida), Mulinia (lateralis) Gray. Type, M. stultorum, PI. XXI. fig. 1. Shell nearly equilateral ; anterior hinge tootli A-shaped, with sometimes a small laminar tooth close to it ; lateral teeth doubled in the right valve. Animal with the mantle open as far as the siphons, its margins fringed ; siphons united, fringed with simple cirri, anal orifice with a tubular valve ; foot large, linguiform, heeled; p,alpi triangular, long and pointed; outer gills shortest. The Mactras inhabit sandy coasts, where they bury just beneath the sur- face; the foot can be stretched out considerably, and moved about like a finger, it is also used for leaping. They are eaten by the star-fishes and whelks, and in the I. of Arrau M. subtruncata is collected at low-water to feed pigs. (Alder.} Distr. 60 sp. All seas, especially within the tropics • — 35 fms. Fossil, 30 sp. Lias — . U. States, Europe, India. ? Sub-genus. Sowerbya, D'Orb. S. crassa, Oxfordian, France. Carti- lage-pit simply grooved; lateral teeth very large. GNATHODON, Gray. Etym, Gnathos a jaw-bone, odous a tooth. Syn. Kangia, Desm. Type, G. cuneatus, PL XXI. fig. 2. Shell oval, ventricose ; valves thick, smooth, eroded ; epidermis olive ; cartilage-pit central ; hinge teeth f ; laterals doubled in the right valve, elongated, striated transversely ; pallial sinus moderate. Animal with the mantle freely open in front ; margins plain ; siphons CONCHIFERA. 309 short, partly united ; foot very thick, tongue-shaped, pointed; gills unequal, the outer short and narrow ; palpi large, triangular, pointed. Distr. 1 sp. N. Orleans (3 other sp. ? Mazatlan, California; Moretori B. Australia. Petit.) Fossil, 1 sp. Miocene — . Petersburg, Virginia. G. cuneatus was formerly eaten by the Indians. At Mobile, on the Gulf of Mexico, it is found in colonies along with Cyrena Carolinensis, burying 2 inches deep in banks of mud ; the water is only brackish, though there is a tide of 3 feet. Banks of dead shells, 3 or 4 feet thick, are found 20 miles inland : Mobile is built on one of these shell-banks. The road from New ' Orleans to Lake Pont-chartrain (6 miles) is made of Gnathodon shells pro- cured from the east end of the lake, where there is a mound of them a mile long, 15 feet high, and 20 — 60 yards wide ; in some places it is 20 feet above the level of the lake. (Lyell.) LUTRARIA, Lamarck. Otter' s-shell. Type, L. oblonga, Gmel. PL XXI. fig. 3. (= L, solenoides, Lam.) Shell oblong, gaping at both ends ; cartilage-plate prominent, with 1 or 2 small teeth in front of it, in each valve ; pallial sinus deep, horizontal. Animal with closed mantle-lobes ; pedal opening moderate ; foot rather large, compressed ; siphons united, elongated, invested with epidermis ; palpi rather narrow, their margins plain ; gills tapering to the mouth. Distr. 18 sp. U. States, Brazil, Brit. Medit. Senegal, Cape, India, N. Zealand, Sitka. Fossil, 10 sp. Miocene — U. States, Europe. Resembles My a ; burying vertically in sand or mnd, especially of estu- aries ; low- water, 12 fms. L. rugosa is found living on the coasts of Por- tugal and Mogador, fossil on the coast of Sussex. (Dixon.) ANATINELLA, G. Sowerby. Type, A. Candida, (Mya) Chemn. PL XXIII. fig. 6. Shell ovate, rounded in front, attenuated and truncated behind ; cartilage in a prominent spoon-shaped process, with 2 small teeth in front ; muscular impressions irregular, the anterior elongated ; pallial line slightly truncated behind. Distr. 3 sp. Ceylon, Philippines ; sands at low- water. FAMILY XVI. TELLINIDJE. Shell free, compressed, usually closed and equivalve ; cardinal teeth 2 at most, laterals 1 — 1, sometimes obsolete; muscular impressions rounded, polished; pallial sinus very large; ligament on shortest side of the shell, sometimes internal. Structure obscurely prismatic- cellular ; prisms fusi- form, nearly parallel with surface, radiating from the hinge in the outer layer, transverse in the inner. 310 MANUAL OF THE MOLLUSCA. Animal with the mantle widely open in front, its margins fringed ; foot tongue-shaped, compressed ; siphons separate, very long and slender ; palpi large, triangular ; gills united posteriorly, unequal, the outer pair sometimes directed dorsally. The Tellens are found in all seas, chiefly in the littoral and laminarian zones ; they frequent sandy bottoms, or sandy mud, burying beneath the sur- face ; a few species inhabit estuaries and rivers. Their valves are often richly coloured and ornamented with finely sculptured lines. TELLINA, L. Tellen. Etym. Tel line, the Greek name for a kind of mussel. Syn. Peroneea (part) Poli. Phylloda (foliacea), Omala (planata) Schum. Psammotea (solid ula) Turt. Arcopagia (crassa) Leach. Examples, T. lingua-felis, PI. XXT. fig. 5. T. carnaria, fig. 6. Shell slightly inequivalve, compressed, rounded in front, angular and slightly folded posteriorly, umbones sub-central ; teeth 2.2, laterals 1 — 1, most distinct in the right valve ; pallia! sinus very wide and deep ; ligament external, prominent. Animal with slender, diverging siphons, twice as long as the shell, their orifices plain ; foot broad, pointed, compressed ; palpi very large, triangular ; gills small, soft and very minutely striated, the outer rudimental and directed dorsally. Tehimdes, Lam. T. planissima, PI. XXI. fig. 7. Valves with no pos- terior fold ; lateral teeth wanting. T. carnaria (Striyilla, Turt.) has the valves obliquely sculptured ; T.fa- bula, Gron. has the right valve striated, the other plain. T, Burnett, Cali- fornia, has the right valve flat ; T. hinulata, Pliocene, S. Carolina, much resembling it in shape, has the left valve flat. Distr. above 200 sp. In all seas, especially the Indian Ocean ; most abundant and highly coloured in the tropics. Low-water — Coral zone, 50 fins. AY ellington Channel; Kara Sea; Behrings' Sea ; Baltic: Black Sea. Fossil, 130 sp. Oolites — . U. States, S. America (Chiloe) Europe. DIODONTA, Schumacher. Etym. Di- two, odonta teeth. Syn. Fragilia, Desh, Type, Tellina fragilis, L. PI. XXI. fig. 8. Shell equivalve, convex, with squamose lines of growth ; cardinal teeth 2 in right valve, 1 bifid tooth in left ; pallial sinus deep and rounded ; um- bonal area punctate ; ligament external. Animal with the mantle open in front, its margins fringed; siphons elongated, slender, separate, unequal, orifices with cirri ; foot small, com- pressed, linguiform ; palpi large, triangular ; gills unequal, soft, finely striated. Diodonta inhabits shallow water, boring in mud and clay, and not travel- ling about like the Tellens. CONCHIFEEA. 311 Distr. 3 sp. Greenland, Brit. Medit. Black Sea, Senegal, Cape. Fossil, Miocene — . Brit, France, Belgium. CAPSULA, Schumacher. Etym. Dimin. of capsa, a box. Syn. Capsa (part) Brug. 1791. Sauguinolaria Lam. 1818, not 1801. Type. C. rugosa, PL XX. fig. 19. (= Venus deflorata, Gmel.) Shell oblong, ventrieose, slightly gaping at each end ; radiately striated ; cardinal teeth 2 in each valve, one of them bifid ; ligament external, large, prominent ; siphonal inflection short. Animal like Psammobia ; foot moderate ; gills deeply plaited, attenuated in front, outer small, dorsal border wide, fixed ; siphons moderate. Distr. W. Indies, Red Sea, India, China, Australia. Fossil 4 sp. U. Green-sand — . U. States, Europe. (D'Orb.) Fig. 218. Psammobia vespertina, Chemn, £, Brit. PSAMMOBIA, Lamarck. Sunset-shell. Etym. Psammos sand, bio to live. Syn. Psammotea (zonalis) Lam. Psammocola, Bl. Gari, Schum. Ex. P. Ferroensis, PL XXI. fig. 9. P. squamosa, PL XXI. fig. 10. Shell oblong, compressed, slightly gaping at both ends; hinge-teeth f > ligament external, prominent ; siphonal inflection deep, ia contact with the pallial line ; epidermis often dark. Animal : mantle open, fringed ; siphons very long, slender, nearly equal, longitudinally ciliated, orifices with 6 — 8 cirri; foot large, tongue -shaped; palpi long, tapering ; gills unequal, recumbent, few plaited, Distr. 40 sp. Norway, Brit. India, New Zealand, Pacific. Littoral — coralline zone, 100 fms. P. gari is eaten in India. Fossil, 24 sp. Oolite? Eocene—. U. States, Europe. SANGUINOLARIA, Lamarck. Name, from the type, Solen sanguinolentus, Chemu. Syn. Soletellina {diphos} BL Lobaria, Schum. Aldus, Oken. Ex. S. livida, PL XXII. fig. 1. S. diphos, fig. 2, S. orbiculata, fig. 3. Shell oval, compressed, rounded in front, attenuated and slightly gaping behind ; hinge-teeth §, small ; siphonal inflection very deep, connected with the pallial line ; ligament external, on very prominent fulcra. Animal: mantle open, fringed; siphons very long, branchial largest P3 312 MANUAL OF THE MOLLUSCA. orifices fringed ; foot large, broadly tongue -shaped, compressed; palpi long pointed ; gills recumbent, inner laminge free, dorsal border wide. Distr. 20 sp. W. Indies, Red Sea, India, Madagascar, Japan; Aus- tralia, Tasmania, Peru. Fossil, 30 sp. Eocene — . U. States, Europe. SEMELE, Schumacher, 1817. Et>/m. Semele, in Greek myth, the mother of Bacchus. Syn. Amphidesma, Lam. 1818.* Type, S. reticulate, PL XXI. fig. 11. Shell rounded, sub-equilateral, beaks turned forwards; posterior side slightly folded; hinge-teeth 2.2, laterals elongated, distinct in the right valve; external ligament short, cartilage internal, long, oblique; pallia! -sinus deep, rounded. Distr. 40 sp. W. Indies, Brazil, India, China, Australia, Peru. Fossil, 10 sp. Eocene — . U. States, Europe. Sub-genera. Cumingia, G. Sowerby. C. lamellosa, PL XXI. fig. 12. Shell slightly attenuated and gaping behind, lamellated concentrically ; car- tilage-process prominent; pallial sinus very wide. Distr. 10 sp. In sponges, sand, and the fissures of rocks, — 7 fathoms. W. Indies, India, Australia, W. America. Fossil, Miocene — . Wilmington, N. Carolina. Syndosmya, Recluz. Syn. Abra, Leach MS. Erycina (part) Lam. 1805.f Type, S. alba, PL XXI. fig. 13. Shell small, oval, white and shining ; posterior side shortest ; umbones directed backwards ; cartilage- process oblique ; hinge-teeth minute or obsolete, laterals distinct ; pallial sinus wide and shallow. Animal with the mantle open, fringed; siphons long, slender, diverging, anal shortest, orifices plain; foot large, tongue- shaped, pointed ; palpi triangular, nearly as large as the gills ; branchiae un- equal, triangular. Distr. Norway, Brit. Medit. Black Sea, India. The sp. are few, and mostly boreal, ranging from the laminarian zone to 180 fms. (Forbes j They live buried in sand and mud, but when confined are able to creep up the sides of the vessel with their foot. (Bouchard.} Fossil, 6 sp. Eocene — . Brit. France. Scrolicularia, Schumacher. Syn. Trigonella (part) Da Costa (not L.) Ligula (part)). Mont. "Le Lavignon" (Reaumur) Cuv. Listera, Turt. (not R. Brown.) Lutricola, Bl. Mactromya, D'Orb. (not Ag.) Type, S. piperata (Belon) Gmelin, PL XXI. fig. 14. (See p. 60.) Shell oval, com- pressed, thin ; sub-equi-lateral ; ligament external, slight ; cartilage-pit shal- * The name Amphi-desma, as employed by Lamarck, included species of Semele, Loripes, Syndosmya, Mesodesma, Thracia, Lyonsia, and Kellia; in addition to which it has since been applied to some Oolitic Myacites. t The name Erycina was originally appplied by Lamarck to a number of minute fossil shells, including sp. of Syndosmya, Venus, Lucina, Tellina, Astarte,and. Kellia. In 1808 Fabricius employed it for a well-known group of insects. CONCHIFERA. 313 low, triangular ; hinge-teeth small, 1 or 2 in each valve, laterals obsolete ; pallial sinus wide and deep. Animal with the mantle open, margins denticulated ; siphons very long, slender, separate, orifices plain ; foot large, tongue-shaped, compressed ; palpi very large, triangular, gills minutely striated, the outer pair directed dorsally. Lives buried, vertically, in the mud of tidal estuaries, 5 or 6 inches deep. (Montagu.} The siphons can be extended to 5 or 6 times the length of the shell. (Deshayes}. The animal has a peppery taste, but is sometimes eaten on the coasts of the Mediterranean. Distr. Norway, Brit. Medit. Senegal. Fossil, Pliocene, Brit. MESODESMA, Deshayes. Et-ym. Meso- middle, desma ligament. Syn. Eryx, Sw. (not Baud.) Paphia (part) Lam. 1799 (see p. 299, note). Erycina (part) Lam. 1818 (not Lam. 1805, nor Fabr. 1808). "Donacille," Lam. 1812 (not characterized). Examples, M. glabratum, PI. XXI. fig. 15. M. donachnn. fig. 16. SJiell trigonal, thick, compressed, closed; ligament internal, in a deep central pit; a minute anterior hinge-tooth, and 1—1 lateral teeth in each valve ; muscular scars deep , pallial sinus small. Animal with mantle-margins plain ; siphons short, thick, and separate, orifices cirrated, branchial cirri dendritic ; foot compressed, broadly lanceo- late : gills large, unequal ; palpi small. Sul-genus. Anapa, Gray. A. Smithii, PL XXI. fig. 17. Umbones anterior, siphonal inflection obsolete. Distr. 20 sp. W. Indies, Medit. Crimea, India, New Zealand, Chili ; sands at low-water. Fossil, 7 sp. Neocomian — . U. S. Europe (Donacilla, D'Orb.) ERVILIA, Turton. Lentil-shell. Et.ym. Ervilia, diminutive of ervttm, the bitter- vetch. Type, E. nitens, P. XXI. fig. 18. Shell minute, oval, close ; cartilage in a central pit ; right valve with a single prominent tooth in front and an obscure tooth behind ; left valve with 2 obscure teeth ; no lateral teeth ; pallial sinus deep. Distr. "VV. Indies, Brit. Canaries, Medit. Red Sea. — 50 fms. DONAX, L. Wedge- shell. Ex. D. denticulatus, PL XXI. fig. 19. Etym. Donax, a sea-fish, Pliny. Syn. Chione. Scop. Cuneus, Da Costa. Capisterium, Meusch.* Latona and Hecuba, Schuin. Egeria, Lea (not Roissy). Shell trigonal, wedge-like, closed; front produced, rounded; posterior side short, straight ; margins usually creuulated ; hinge-teeth 2.2 ; laterals * Meuschen was a Dutch auctioneer; the names occur in his " sale catalogues." Idivtte imposuere nomina absurda. Linnaeus. 314 MANUAL OF THE MOLLUSCA. 1 — 1 in each valve ; ligament external, prominent ; pallial sinus deep, hori- zontal. Animal with the mantle fringed; siphons short and thick, diverging, anal orifice denticulated, branchial with pinnate cirri; foot very large, pointed, sharp-edged, projected quite in front ; gills ample, recumbent, outer shortest ; palpi small, pointed. Distr. 45 sp. % Norway, Baltic, — Black Sea, all tropical seas. In sands near low- water mark ( — 8 fms.) buried an inch or two beneath the surface. Fossil, 30 sp. Eocene — . U. States, Europe. Sub-genera. ? Ampkick&na, Phil. A. Kindermanni, California. Shell oblong, nearly equilateral, gaping at each end ; teeth f ; ligament external, pallial line sinuated. fyhigenia, Schum. (Capsa, Lam. 1818, not 1801. Donacina, Fer.) 1. Brasiliensis, PL XXI. fig. 20. Shell nearly equilateral, smooth; hinge- teeth 2.2, one bifid, the other minute ; laterals remote, obsolete in the left valve : margins smooth. Distr. 4 sp. W. Indies, Brazil, W. Africa, Pacific, Central America. Inhabits estuaries; I. ventricosa, Desh. is rayed like Galatea, and has its beaks eroded. ? Isodonta (Deshayesii) Buv. Bull. Soc. Geol. Oxf, Trance. GALATEA, Brliguiere. Si/n. Egeria, Roissy. Potamophila, Sby. Megadesma, Bowdich. Type, G. reclusa, PL XXI. fig. 21. Shell very thick, trigonal, wedge-shaped ; epidermis smooth, olive ; um- bones eroded ; hinge thick, teeth 1.2, laterals indistinct ; ligament external, prominent ; pallial sinus distinct. Animal with the mantle open in front ; siphons moderate, with 6—8 lines of cilia, orifices fringed ; foot large, compressed ; palpi long, triangular; gills unequal, united to the base of the siphons, the external pair divided into 2 nearly equal areas by a longitudinal furrow, indicating their line of attachment. Distr. 2 or 7 sp. ? Nile, and rivers of W. Africa. FAMILY XVII. SOLENID^. Shell elongated, gaping at the ends; ligament external; hinge-teeth usually 2.3, compressed, the posterior bifid. External shell layer with defi- nite cell- structure, consisting of long prisms, very oblique to the surface, and exhibiting nuclei ; inner layer nearly homogeneous. Animal with a very large and powerful foot, more or less cylindrical : siphons short and united (in the typical Solens, with long shells) or longer and partly separate (in the shorter and more compressed genera) ; gills narrow, prolonged into the branchial siphon. CONCHIFERA. 315 Fig. 2] 9. Solen siliqua, L. •§•; the valves forcibly opened, and mantle divided as far as the ventral foramen, to show the foot. SOLEN (Aristotle) L. Razor-fish. Type, S. siliqua, PL. XXII. fig. 4. Syn. Hypogsea, Poli. Vagina, Megerle. Ensis, Schum. Ensatella, Sw. Shell very long, sub-cylindrical, straight, or slightly recurved, margins parallel, ends gaping : beaks terminal, or sub-central ; hinge-teeth f ; liga- ment long, external; anterior muscular impression elongated; posterior oblong ; pallial line extending beyond the adductors ; sinus short and square. * Animal with the mantle closed except at the front end, and a minute ventral opening ; siphons short, united, fringed ; palpi broadly triangular ; foot cylindrical, obtuse. Distr. 25 sp. World- wide, except Arctic seas : — 100 fms. Fossil, 10 sp. Eocene — . U. States, Europe. The Razor-fishes live buried vertically in the sand, at extreme low- water, their position being only indicated by an orifice like a key-hole ; when the tide goes out they sink deeper, often penetrating to a depth of 1 or 2 feet. They never voluntarily leave their burrows, but if taken out soon bury them- selves again. They mayjbe caught with a bent wire, and are excellent articles of food, when cooked. (Forbes.} CULTELLUS, Schumacher. Type, C. lacteus, PI. XXII. fig. 5. Etym. Cultellus a knife. Shell elongated, compressed, rounded and gaping at the ends ; hinge- teeth 2.3 ; beaks in front of the centre, supported internally by an oblique rib ; pedal impression behind the umbonal lib ; posterior adductor trigonal ; pallial line not prolonged behind the posterior adductor ; sinus short and square. Animal (of C. Javanicus) with short, fringed siphons ; gills1 narrow, half as long as the shell, transversely plaited; palpi large, angular, broadly at- tached ; foot large, abruptly truncated. Distr. 4 sp. Africa, India, Nicobar. Sub-genera. Ceratisolen, Forbes. (Polia, D'Orb. Pharus, Leach, MS. Solecurtoides, Desm.) C. legumen, PlTXXII. fig. 6. Shell narrow, sub- equilateral, anterior adductor impressions elongated, a second pedal scar near 316 MANUAL OF THE MOLLL'SCA. the pallial sinus. Animal with a long, truncated foot ; siphons separate, diverging, fringed. Distr. 1 sp. Brit. Medit. Senegal, Red Sea. Fossil, 1 sp. Pliocene — . Italy. Machcera, Gould. (Siliqua, Megerle. Leguminaria, Schum.) M. polita, PI. XXII. fig. 7- Shell smooth, oblong; epidermis polished; umbonal rib extending across the interior of the valve ; pallial sinus short. The animal, figured hy Middeudorff, is similar to Solecurtus. Distr. India, China, Ochotsk, Oregon, Sitka, Behring's Sea, Newfoundland. M. costata, Say, is often obtained from the maw of the cod-fish. Fossil, 4> sp. U. Green- sand — . Brit. France. SOLECURTUS, Blainville. Etym. Solen and curtits, short. Syn. Psammosolen Risso. Macha, Oken. Siliquaria, Schum. Ex. S. strigilatus, PI. XXII. fig. 8. S..Caribams, PL XXII. fig. 9. Shell elongated, rather ventricose, with sub-central beaks ; margins sub- parallel ; ends truncated, gaping ; ligament prominent ; hinge-teeth f ; pal- lial sinus very deep, rounded ; posterior adductor rounded. Animal very large and thick, not entirely retractile within the shell ; mantle closed below ; pedal orifice and foot large ; palpi triangular, narrow, lamellated inside; gills long and narrow, outer much shortest; siphons separate at the ends, united and forming a thick mass at their bases ; anal orifices plain, branchial fringed. The Solecurti bury deeply in sand or mud, usually beyond low-water, and are difficult to obtain alive. P. Caribceus occurs in countless myriads in the bars of American rivers, and on the coast of New Jersey in sand exposed at low-water ; by removing 3 or 4 inches of sand its burrows may be dis- covered; they are vertical cylindrical cavities, 1£ inches in diameter and 12 or more deep, the animal holds fast by the expanded end of its foot. Distr. 25 sp. U. States, Brit. Medit. W. Africa, Madeira. Fossil, 30 sp. Neocomian — . U. S. Europe. Sub-genus, Novaculina, Benson. N. gangetica, PI. XXII. fig. 10. Shell, oblong, plain ; epidermis thick and dull; pallial sinus rather small ; anterior pedal scar linear. Distr. India, China. In the mud of river- estuaries. FAMILY XVIII. MYACID.E. Shell thick, strong and opaque ; gaping posteriorly; pallial line sinuated ; epidermis wrinkled. Structure more or less distinctly cellular, with dark nuclei near outer surface ; cartilage process composed of radiated cells. Animal with the mantle almost entirely closed ; pedal aperture and foot small ; siphons united, partly or wholly retractile ; branclmc 2 on each side, elongated. CONCHIFEBA. 317 Fig. 220. Mya truncata, L. £. Brit, (after Forbes.) m MYA, L. Gaper. Etym. Myax (-acis) a mussel, Pliny. Syn. Platyodon, Conrad. Types, M. truncata, PI. XXIII. fig. 1. M. Arenaria, fig. 170, p. 244. Shell oblong, inequivalve, gaping at the ends ; left valve smallest, with a large flattened cartilage process ; pallial sinus large. Animal with a small straight linguiforrn foot ; siphons combined, covered with epidermis, partially retractile ; orifices fringed, the branchial opening with an inner series of large tentacular filaments ; gills not prolonged into the siphon ; palpi elongated, free. M, anatina, Chemn. (Tugonia, Gray) W. coast of Africa ; posterior side extremely truncated ; similar cartilage-processes in each valve. Fossil, Miocene, Dax, and the Morea. Distr. 10 sp. Northern Seas, W. Africa, Philippines, Australia, Cali- fornia. The Myas frequent soft bottoms, especially the sandy and gravelly mud of river -mouths ; they range from low-water to 25 fathoms, rarely to 100 or 145 fms. M. arenaria burrows a foot deep ; this species and M* truncata are found throughout the northern and Arctic seas, from Ochotsk and Sitka to the Russian Ice-meer, the Baltic, and British coast ; in the Mediterranean they are only found fossil. They are eaten in Zetland and N. America, and are excellent articles of food. In Greenland they are sought after by the walrus, the Arctic fox, and birds. (0. Fabricius.) Fossil, Miocene — . U. States, Brit. Sicily. Most of the fossil "Myas" have an external ligament, and are related either to Panopaa or Pholadvmya. CORBULA, Bruguiere. .Etym. Corbula, a little basket. Type, C. sulcata, PL XXIII. fig. 2. Syn. Erodona, Baud. (= Pacyodon, Beck.) Agina, Turt. Shell thick, inequivalve, gibbose, closed, produced posteriorly; right valve with a prominent tooth in front of the cartilage pit ; left valve smaller, with a projecting cartilage process ; pallial sinus slight : pedal scars distinct from the adductor impressions. Animal with very short, united siphons ; orifices fringed ; anal valve tubular ; foot thick and pointed ; palpi moderate ; gills 2 on each side, ob- scurely striated. 318 MANUAL OF THE MOLLUSCA. Distr. 50 sp. U. S. Norway, Brit. Medit. W. Africa, China. Inhabits sandy bottoms ; Lower laminarian zone — 80 fms. Fossil. 90 sp. Inf. Oolite — . U. States, Europe, India. The external shell- layer consists of fusiform cells ; the inner is homogeneous and adheres so slightly to the outer layer, that it is very frequently detached in fossil specimens. Corbulomya, Nyst (C. complanata, Sby.) Crag. Brit. Sub-genera. Potamomya, J. Sby. P. gregaria, Eocene, I. Wight. Car- tilage process broad and spatulate, received between two obscure teeth in the right valve. The estuary Corbula differ very little from the marine species. P. labiata (Azara, D'Orb.) PI. XXIII. fig. 3, lives burie* in the mud of the R. Plata, but not above Buenos Ayres, and consequently in water which is little influenced by the superficial ebb of the river. The same species is found in banks widely dispersed over the Pampas near S. Pedro, and many places in the Argentine Republic, 5 yards above the R. Parana. (Darwin.) Sphenia, Turt. S. Binghami, PI. XXIII. fig. 4. Shell oblong; right valve with a curved, conic tooth in front of the oblique, sub -trigonal car- tilage-pit. Animal with thick united siphons, fringed at the end, anal valve conspicuous ; foot finger-like, with a byssal groove. Distr. Brit. France. Burrowing in oyster-shells and limestone, in 10 — 25 fms. Fossil, Miocene — . Brit. NEJGRA, Gray. Etym. Neara, a Roman lady's name. Type, N. cuspidata, PL XXIII. fig. 5. Syn. Cuspidaria, Nardo. Shell globular, attenuated and gaping behind; right valve a little the smallest ; umbones strengthened internally by a rib on the posterior side ; cartilage process spatulate, in each valve, (furnished with a moveable ossicle, Deshayes) with an obsolete tooth in front, and a posterior lateral tooth ; pallial sinus very shallow. Animal with the mantle closed; foot lanceolate; siphons short, united, bran- chial largest, anal with a membranous valve, both with a few lonsc, lateral cirri. Distr. 20 sp. Norway, Brit. Medit, Canaries, Madeira, China, Moluccas, New Guinea, Chile. Prom 12—200 fms. Fossil, 6 sp. Oolite — . Brit. Belgium, Italy. Fig. 221. Thetis, minor, Sby. Neocomian, I. Wight. CONCHIFERA. 319 THETIS, Sowerby. Etym. Thetis, in Greek myth, a sea-nymph. Syn. Poromya (anatinoides) Forbes. Embla (Korenii) Loven ?. Inoce- ramus (impressus) D'Orb. ? Corbula (gigantea) Sby. Type, T. minor, fig. 221. T. hyalina, PI. XXII. fig. 11. Shell sub-orbicular, ventricose, thin, translucent, surface regularly granu- lated, interior slightly nacreous ; ligament (1) external ; hinge-teeth 1 or 2 ; umbones strengthened inside by a posterior lamina; adductor (a, a') and pedal impressions (p) separate, slightly impressed, posterior adductor bordered by a ridge; pallial line nearly simple, sub-marginal. Animal with short siphons, the branchial largest, surrounded at their base by 18 — 20 tentacles, generally reflected on the shell; mantle open in front; foot long, narrow and slender. (Mc Andrew.) Distr. 5 sp. Norway, Brit. Medit. Madeira, Borneo, China. 40 — 150 fms. Fossil, 7 sp. Neocomian — . Brit. Belgium, France, S. India. Sub-genus ? Eucharis, Recluz ; Corbula quadrata, Hinds, Guadaloupe. Shell equivalve, obliquely keeled, gaping ; beaks anterior ; hinge-teeth 1 — 1 ; ligament external ; pallial line simple ; surface granulated. PANOP.EA, Menard de la Groye. Etyin. Panope, a Nereid. Ex. P. Americana, PI. XXII. fig. 12. Syn. ? Pachymya (gigas) Sby. U. Greensaud. Brit. France. Shell equivalve, thick, oblong, gaping at each end ; ligament external, on prominent ridges ; 1 prominent tooth in each valve ; pallial sinus deep. Animal with very long, united siphons, invested with thick, wrinkled epidermis ; pedal orifice small, foot short, thick and grooved below ; gills long and narrow, extending far into the branchial siphon, the outer pair much narrower, faintly pectinated ; palpi long, pointed and striated. In P. Norvegica the pallial line is broken up into a few scattered spots, as in Saxicava ; the animal itself is like a gigantic Saxicava. (Hancock.) This species ranges from Ochotsk to the White Sea, Norway and N. Britain ; it was formerly an inhabitant of the Medit. where it now occurs fossil. ( = P. Bivonte, Phil.) The British specimens have been caught, accidentally, by the deep-water fishing-hooks. P. australis is found at Port Natal, buried in the sand at low-water ; the projecting siphons first attracted attention (doubtless by the strong jets of water they sent up when molested) but the shells were only obtained by digging to the depth of several feet. The Medit. sp. P. (jlycimeris attains a length of 6 or 8 inches. Distr. 6 sp. Northern Seas, Medit. Cape, Australia, New Zealand, Pata- gonia. Low-water — 90 fms. Fossil, 140 sp. Inf. Oolite — . IT. States, Europe, India. 320 MANUAL OF THE MOLLUSCA. SAXICAVA, Bellevue. Etym. Sazum* stone, cavo, to excavate, S. rugosa, PI. XXII. fig. 13. Syn. Byssomya, Cuv. Rhomboides, Bl. Hiatella (minuta) Daud. Biapholius, Leach. Arcinella (carinata) Phil. Shell when young symmetrical, with 2 minute teeth in each valve ; adult rugose, toothless ; oblong, equivalve, gaping, ligament external ; pallial line sinuated, not continuous. Animal with mantle-lobes united and thickened in fro at ; siphons large, united nearly to their ends, orifices fringed ; pedal opening small, foot finger- like, with a byssal groove ; palpi small, free ; gills narrow, unequal, united behind and prolonged into the branchial siphon. Five genera and 15 species have been manufactured out of varieties and conditions of this Protean shell. It is found in crevices of rocks and corals, and amongst the roots of sea-weed, or burrowing in limestone and shells ; at Harwich it bores in the cement stone (clay iron-stone), at Folkestone in the Kentish-rag, and the Portland stone employed in the Plymouth Breakwater has been much wasted by it. Its crypts are sometimes 6 inches deep (Couch] ; they are not quite symmetrical, and like those of the Lithodomus are in- clined at various angles, so as to invade one another, the last comers cutting quite through their neighbours ; they are usually fixed by the byssus to a small projection from the side of the cell. The Saxicava ranges from low- water to 140 fathoms ; it is found in the Arctic Seas, where it attains its largest size ; in the Medit, at the Canaries, and the Cape. It occurs fossil in the Miocene tertiary of Europe and in the U. States, and in all the Glacial deposits. GLYCIMERIS, Lamarck. Etym. Glukus, sweet, meris, bit. Type, G. siliqua, PL XXII. fig. 14. Syn. Cyrtodaria, Daud. Shell oblong, gaping at each end ; posterior side shortest ; ligament large and prominent; epidermis black, extending beyond the margins; anterior muscular scar long, pallial impression irregular, slightly sinuated. Animal larger than its shell, sub-cylindrical; mantle closed, siphon united, protected by a thick envelope ; orifices small ; pedal opening small anterior ; foot conical ; palpi large, striated inside, the posterior border plain ; gills large, extending into branchial siphon. Distr. Arctic Seas, Cape Parry, N. W. America. Newfoundland. Fossil, Miocene — . Brit. Belgium. FAMILY XIX. ANATINIDJD. Shell often inequi valve, thin ; interior nacreous ; surface granular ; liga- ment external, thin; cartilage internal, placed in corresponding pits and' CONCHIFERA. 321 furnished with a free ossicle ; muscular impressions faint, the anterior elon- gated ; pallial line usually sinuated. Animal with mantle margins united ; siphons long, more or less united, fringed ; gills single on each side, the outer lamina prolonged dorsally beyond the line of attachment. Pholadomya and its fossil allies have an external ligament only ; Cock* lodesma and Pandora have no ossicle. The external surface of these shells is often rough with large calcarious cells, sometimes ranged in lines, and covered by the epidermis ; the outer layer consists of polygonal cells, more or less sharply denned ; the inner layer is nacreous. ANATINA, Lamarck. Lantern- shell. Type, A. rostrata, PI. XXIII. fig. 7. (Anatinus, pertaining to a duck.) Syn. Laternula, Bolten M. S. Auriscalpium, Muhlf. Osteodesma, Bl, Cyathodonta (undulata) Conrad ? W. America. Shell oblong, ventricose, sub -equi valve, thin and translucent, posterior side attenuated and gaping ; umbones fissured, directed backwards, supported internally by an oblique plate ; hinge with a spoon-shaped cartilage-process in each valve, furnished in front with a transverse ossicle ; pallial sinus wide and shallow. Animal with a closed mantle and long united siphons, clothed with wrinkled epidermis ; gills one on each side, thick, deeply plaited j palpi very long and narrow ; pedal opening minute, foot very small, compressed. Distr. 20 sp. India, Philippines, New Zealand, W. America. Fossil, 50 sp. Devonian ? — Oolite — . U. States, Europe. Sub-genera. Periploma (inequivalvis) Schum. " Spoon-hinge" of Petiver ; oval, inequivalre, left valve deepest ; posterior side very short and contracted. Distr. W. Indies, S. America. Cochlodesma, Couthouy, C. praetenue, PI. XXIII. fig. 8. (Bontia, Leach MS. Ligula, Mont, part.) Oblong, compressed, thin, slightly inequi- valve ; umbones fissured ; cartilage processes prominent, without an ossicle ; pallial sinus deep. Animal with a broad, compressed foot ; siphons long, slender, divided throughout ; gills one on each side, deeply plaited, divided by an oblique furrow into two parts, the dorsal portion being narrower, com- posed of a single lamina only, and attached by its whole inner surface. (Han- cock.} Distr. 2 sp. U. States, Brit. Medit. Fossil, Pliocene, Sicily. Cercomya, Agassiz. C. undulata, Sby. (= Rhynchomya, Ag.) Shell very thin, elongated, compressed, attenuated posteriorly ; sides concentrically furrowed, umbones fissured, posterior (cardinal) area more or less defined. Fossil, 12 sp. Oolite — Neocomian; Europe. THEACIA (Leach) Bl. Syn. Odoncinetus, Costa. Corimya, Ag. Rupicola (concentrica) Bellevue. 322 MANUAL OF THE MOLLXJSCA. Type, T. pubescens, PI. XXIII. fig. 9. Shell oblong, nearly equivalve, slightly compressed, attenuated and gaping posteriorly, smooth or minutely scabrous ; cartilage processes thick, not pro- minent, with a crescentic ossicle ; pallial sinus shallow. Quter shell layer composed of distinct, nucleated cells. Animal vnfta the mantle closed; foot linguiform; siphons rather long, separate, with fringed orifices; gills single, thick, plaited; palpi narrow, pointed. T. concentrica and T. distorta, Mont, are found in the crevices of rocks, and burrows of Saxicava ; they have been mistaken for boring-shells. Distr. 10 sp. Greenland, U. States, Norway, Brit. Medit. Canaries, China, Sooloo : 4—110 fms. Fossil, 30 sp. (Trias ?) L. Oolite — . U. States, Europe. PHOLADOMYA, G. Sowerby. Recent Type, P. Candida. PL XXII. fig. 15. I. Tortola, Shell oblong, equivalve, ventricose, gaping behind ; thin and translucent, ornamented with radiating ribs on the sides ; ligament external ; hinge with one obscure tooth in each valve ; pallial sinus large. Animal with a single gill on each side, thick, finely plaited, grooved along its free border, the outer lamina prolonged dorsally ; mantle with a fourth (ventral) orifice. (Owen.) Fossil, 150 sp. Lias — . U. S. Europe, Algeria, Thibet. Homomya (hortulana) Ag. Shell thick, concentrically furrowed, without radiating ribs ; 6 sp. Oolites, Europe. MYACITES (Schlotheim) Bronn. Syn. Myopsis (Jurassi) Ag. Pleuromya, Ag. Arcomya (Helvetica) Ag. Mactroinya (mactroides) Ag. Anoplomya (lutraria) Krauss. JSx. M. sulcatus, Flem. (Allorisma, King, Pal. Tr. 1850, PI. XX. fig. 5.) Shell oblong, ventricose, gaping, thin, often concentrically furrowed; umbones anterior ; surface granulated ; ligament external ; hinge with an obscure tooth or edentulous ; muscular impressions faint ; pallial line deeply sinuated. ' Fossil, 50 sp. L. Silurian — L. Chalk. TJ. S. Europe, S. Africa. Sub -genera ? Goniomya,&%. My a literata, PI. XXII. fig. 16. (Lysia- nassa, Miinster, not M. Edw.) Shell equivalve, thin, granulated ; ligament external, short, prominent. Fossil, 30 sp. U. Lias — Chalk. Europe. Tellinomya (nasuta) Hall; Silurian, U. S. Europe. Not characterised. ? Grammysia, Yerneuil. Nucula cingulata, His, U. Silurian, Europe- Valves with a strong transverse fold extending from the umbones to the middle of the ventral margin. ? Sedgwickia (corrugata) M'Coy. = ? Leptodomus (senilis) M'Coy. CONCHIFERA. 323 Shell thin, ventricose, concentrically furrowed in front ; escutcheon long and flat. Silurian — Carb. Europe. CEROMYA, Agassiz. Etym. Keraos horned, mya, mussel. Type, C. concentrica (Isocardia) Sowerby, Min. Con. 491, fig. 1. Shell Isocardia-shaped, slightly inequivalve ? very thin, granulated, often eccentrically furrowed; ligament external; hinge edentulous; right valve with an internal lamina behind the umbo ; pallial line scarcely sinuated ? Fossil, 14 sp. Inf. Oolite — . Green-sand ? Europe. Sub-genus ? Gresslya (sulcosa) Ag. (Amphidesma and Unio. sp. Phil.) Shell oval, rather compressed ; urnbones anterior, incurved, not prominent ; valves thin, close, smooth or concentrically furrowed ; pallial sinus deep. Fossil, 17 sp. Lias — Portlandian. Europe. The lamina within the pos- terior hinge-margin of the right valve produces a furrow in the casts, which are more common than specimens retaining the shell. ? CARDIOMORPHA, Koninck. Type, C. oblonga (Isocardia) Sby. (not Kon.) Carb. lime. Shell Isocardia-shaped, smooth or concentrically furrowed, umbones pro- minent, hinge edentulous ; hinge -margin with a narrow ligamental furrow, and an obscure internal cartilage-groove. Fossil, 38 sp. L. Silurian — Carb. N. America, Europe. EDMONDTA, Koniuck. Ex. E. sulcata, Ph. (T. Pal. Soc. 1850, PL XX. fig. 5.) Carb. Brit. Syn. Allorisma, King (part). Sanguinolites, M'Coy (part). Shell oblong, equivalve, thin, concentrically striated, close ; umbones an- terior; ligamental grooves narrow, external; hinge-line thin, edentulous, furnished with large oblique cartilage-plates, placed beneath the umbones, and leaving space for an ossicle ? pallial line simple ? Fossil, 4 sp. Carb. — Permian. Europe. LYONSIA, Turton, 1822 (not R. Brown). Syn. Magdala, Leach, 1827. Myatella, Brown. Pandorina, Seaochi. Type, L. Norvegica, PI. XXIII. fig. 10. Shell nearly equivalve, left valve largest, thin, sub-nacreous, close, trun- cated posteriorly; cartilage plates oblique, covered by an oblong ossicle; pallial sinus obscure, angular. Structure intermediate between Pandora and Anatlna ; outer layer composed of definite polygonal cells. Animal with the mantle closed ; foot tongue-shaped, grooved, byssiferous ; siphons very short, united nearly throughout, fringed; lips large, palpi narrow, triangular. Distr. 9 sp. Greenland, N. Sea, Norway, W. Indies, Madeira, India, Borneo, Philippines, Peru. . 243 MANUAL OF THE MOLLUSCA. L. Norvegica ranges from Norway to the sea of Ochotsk ; in 15 — 80 fms. Fossil ? Miocene — . Europe. (100 sp. L. Sil. — . D'Orb.) ? Entodesma (Chilensis) Phil. Shell thin, saxicava-shaped, slightly in- equivalve and gaping, covered with thick epidermis ; hinge edentulous ; each valve with a semi-circular process containing the cartilage. PANDORA. (Solander) Brug. Type, P. rostrata, PL XXIII. fig. ] 1. (Pandora, the Grecian Eve.) Shell inequivalve, thin, pearly inside ; valves close, attenuated behind ; right valve flat, with a diverging ridge and cartilage furrows; left valve convex, with two diverging grooves at the hinge ; pallial line slightly sinuated. Outer layer of regular, vertical, prismatic cells, 250 times smaller than those of Pinna (fig. 260). (Carpenter.} Animal with mantle closed, except a small opening for the narrow, tongue-shaped foot ; siphons very short, united nearly throughout, ends diverging, fringed ; palpi triangular, narrow ; gills plaited, one on each side, with a narrow dorsal border. Distr. 13 sp. U. States, Spitzbergen, Jersey, Canaries, India, N. Zealand, Panama: 4 — 110 fms. burrowing in sand and mud. Fossil, 4 sp. Eocene — . U. States, Brit. MYADOKA, Gray. Type, M. brevis, PI. XXIII, fig. 12. Shell trigonal, rounded in front, attenuated and truncated behind ; right valve convex, left flat ; interior pearly ; cartilage narrow, triangular, between 2 tooth-like ridges in the left valve, with a free sickle-shaped ossicle; pallial line sinuated : structure like Anatina ; outer cells large, rather prismatic. Distr. 10 sp. N. Zealand, N. S. Wales, Philippines. MYOCHAMA, Stutchbury. Type, M. anomioides, PI. XXIII. fig. 13. Shell inequivalve, attached by the dextral valve and modified by form of surface of attachment ; posterior side attenuated ; left valve gibbose ; carti- lage internal, between 2 tooth-like projections in each valve, and furnished with a moveable ossicle; anterior muscular impression curved, posterior rounded, pallial sinus small. Animal with mantle-lobes united ; pedal opening and siphons surrounded by separate areas ; siphons distinct, unequal, small, slightly fringed ; a minute fourth orifice close to the base of the branchial siphon ; visceral mass large, foot small and conical; mouth rather large, upper lip hood-like; palpi tapering, few-plaited ; gills one on each side, triangular, plaited, divided by an oblique line into two portions ; excurrent channels 4, 2 at the base of the gills and two below the dorsal laminae (Hancock. An. Nat. Hist. 1853.) CONCHIFERA. 325 Distr. 3 sp. New South Wales ; attached to Crassatella and Trigonia, in 8 fm. water; the fry (as indicated by the umbones) is free, regular, and Myadora-shaped. CHAMOSTREA, Rolssy. Type, C. albida, PL XXIII. fig. 14. Syn. Cleidothaerus, Stutch. Shell inequivalve, chama-shaped, solid, attached by the anterior side of the deep and strongly-keeled dextral valve ; umbones anterior, sub-spiral ; left valve flat, with a conical tooth in front of the cartilage ; cartilage internal, with an oblong, curved ossicle ; muscular impressions large and rugose, the anterior very long and narrow ; pallia! line simple. Animal with mantle-lobes united by their extreme edge between the pedal orifice and siphons ; pedal opening small, with a minute ventral orifice behind it ; siphons a little apart, very short, denticulated ; body oval, terminating in a small, compressed foot ; lips bilobed, palpi disunited, rather long and ob- tusely pointed ; gills one on each side, large, oval, deeply plaited, prolonged in front between the palpi, united posteriorly ; each gill traversed by an oblique furrow, the dorsal portion consisting of a single lamina with a free margin. (Hancock, An. Nat. Hist. Feb.. 1853.) Distr. 1 sp. New South Wales. FAMILY XX. GASTROCHJENID.E. Shell equivalve, gaping; valves thin, edentulous, united by a ligament, sometimes cemented to a shelly tube when adult ; adductor impressions 2, pallial line sinuated. Animal elongated, truncated in front, produced behind into two very long, united, contractile siphons, with cirrated orifices ; mantle-margins very thick in front, united, leaving a small opening for the finger-like foot ; gills narrow, prolonged into the branchial siphon. The shell-fish of this family, the tubicolida of Lamarck, are burrowers in mud or stone. They are often gregarious, living in myriads near low-water line, but are extracted from their abodes with difficulty. GASTROCH^ENA, Spengler, 1783. Type, G-. modiolina, PL XXIII. fig. 15. (G aster, ventral, chama, gape.) Shell regular, wedge-shaped, umbones anterior ; gaping widely in front, close behind ; ligament narrow, external ; pallial sinus deep. Animal with mantle closed, and thickened in front; foot finger-like, grooved, sometimes byssiferous , siphons long, separate only at their extre- mities ; lips simple, palpi sickle- shaped, gills unequal, prolonged freely into the branchial siphon. G. modiolina perforates shells and limestone ; its holes are regular, about 326 MANUAL OF THE MOLLUSCA. 2 inches deep and ^ inch diameter ; the external orifice is hour-glass shaped, and lined with a shelly layer which projects slightly. When burrowing in oyster-shells it often passes quite through into the ground below, and then completes its abode by cementing such loose material as it finds into a flask-shaped case, having its ne'ck fixed in the oyster-shell ; in some fossil species the siphons were more separated, and the flasks have two diverging necks. The siphonal orifices are rarely 4-lobed ; PL XXIII. fig. 15 a. Distr. 10 sp. TV. Indies, Brit. Canaries, Medit. Red Sea, India, Mauri- tius, Pacific Ids. Gallapagos, Panama : — 30 fms. Fossil, 20 sp. Inf. Oolite — . U. States, Europe. Sub-genus. Chama, Retz. 1788. C. mumia. PI. XXIII. fig. 16. ( = Fistulana clava, Lam.) Shell elongated, contained within a shelly tube ; posterior adductor nearly central, with a pedal scar in front; siphonal inflec- tion angular, with its apex joining the pallial line. Tube round, straight: tapering upwards, transversely striated, closed at the lower end when com- plete, and furnished with a perforated diaphragm behind the valves. D-istr- Madagascar, India, Philippines, Australia ; burrowing in sand or mud. Fossil, Inf. Oolite — . U. S. Europe, S. India. CLAVAGELLA, Lamarck. Ex. C. bacillaris, PI. XXIII. fig. 17. Shell oblong, valves flat, often irregular or rudimentary, the left cemented to the side of the burrow, when adult, the right always free ; anterior mus- cular impression small, posterior large, pallial line deeply sinuated. Tube cylindrical, more or less elongated, sometimes divided by a longitudinal par- tition; often furnished with a succession of siphonal fringes above, and terminating below in a disk, with a minute central fissure, and bordered with branching tubuli, Animal with the mantle closed in front, except a minute slit for the foot, and furnished with tentacular processes ; palpi long and slender ; gills 2 on each side, elongated, narrow (floating freely in the branchial siphon ?) Some specimens of the recent C. aperta have 3 frills to their tubes, and C. bacillaris has twice that number occasionally. They are formed by the siphonal orifices when the animal continues elongating, after having fixed its valve and ceased to burrow ; or perhaps, in some instances, when it is com- pelled to lengthen its tubes upwards by the accumulation of sediment. Brocchi mentions that on breaking the tube of the fossil C. echinata, he sometimes found the shell of a Saxicava or Petncola beside the loose valve of the Clavagella, into whose tube they must have entered after its death. C. elongata is found in coral ; C. australis lives at low tide, and spirts out water when alarmed. Distr. 6 sp. Medit. Australia, Pacific: — 11 fms. Fossil, 13 sp. U. Green-sand — . Brit. Sicily, S. India, CONCHIFERxV. 32? AspERGiLLUM, Lam. Watering-pot shell. Type, A. vaginiferum, PI. XXIII. fig. 18. St/n. Clepsydra, Schum. Shell small, equilateral, cemented to the lower end of a shelly tube, the mnbones alone visible externally ; tube elongated, closed below by a perfo- rated disk with, a minute central fissure ; siphoiial end plain or ornamented with (1—8) ruffles. Animal elongated ; mantle closed, thickened and fringed with filaments in front ; foot conical, anterior, opposed to a minute slit in the mantle ; palpi lanceolate ; gills long, narrow, united posteriorly, continued into and attached to the branchial siphon. Distr. 4 sp. Red Sea, Java, Australia, N. Zealand ; in sand. Fossil, 1 sp. (A ? Leognanum, Horning. Miocene, Bordeaux.) FAMILY XXL PHOLADID^E. Shell gaping at both ends ; thin, white, brittle and exceedingly hard ; armed in front with rasp-like imbrications ; without hinge or ligament, but often strengthened externally by accessory valves ; hinge-plate reflected over the umbones, and a long curved muscular process beneath each ; anterior muscular impression on the hinge-plate; pallial sinus very deep. Animal club-shaped, or worm-like; foot short and truncated; mantle closed in front, except the pedal orifice; siphons large, elongated, united nearly to their ends ; orifices fringed ; gills narrow, prolonged into the ex- halent siphon, attached throughout, closing the branchial chamber: palpi long ; anterior shell-muscle acting as substitute for a ligament. The Pholadidce perforate all substances that are softer than their own valves (p. 242);* the burrows of Pholas are vertical, quite symmetrical, and seldom in contact. The ship-worms {Teredines} also make symmetrical per- forations, and however tortuous and crowded never invade each other, guided either by the sense of hearing or by the yielding of the wood. The burrow * M. Cailliaud has proved that these valves are quite equal to the work of boring in limestone, by imitating the natural conditions as nearly as possible, and making . such a hole with them. Mr. Robertson also, has kept the living Pholades in blocks of chalk, by the sea-side at Brighton, and has watched the progress of the work. They turn from side to side never going more than half-round in their burrow, and cease to work as soon as the hole is deep enough to shelter them; the chalk powder is ejected at intervals by spasmodic contractions from the branchial siphon, the space between the shell and burrow being filled with this mud. (Journ. Conch. 1853, p. 31 J.j It is to be remarked that the condition of the Pholades is always related to the nature of the material in which they are found burrowing; in soft sea beds they attain the largest size and greatest perfection, whilst in hard, and especially gritty rock, they are dwarfed in size and all prominent points and ridges appear worn by friction. No notice has been taken of the hypothesis which ascribes the perforation of rocks, &c., to ciliary action, because, in fact, there is no current between the shell or siphons and the wall of the tube. O MANUAL OF THE MOLLUSCA. has frequently a calcarious lining, within which the shell remains free; Teredina cements its valves to this tube when full-grown. The opening of the burrow, at first very minute, may become enlarged progressively by the friction of the siphons, whieh are furnished with a rough epithelium ; but it usually widens with much more rapidity by the ivastiny of the surface. As the timber decomposes the shelly tubes of the Teredo project, and as the beach wears away the pholas burrows deeper. PHOLAS, L. Piddock. Etym. Pholas, a burrowing shell-fish, from pholeo, to bore. Type, P. dactylus, fig. 222. Ex. P. Bakeri, PI. XXIII. fig. 19. Shell elongated, cylindrical ; dorsal margin protected by accessory valves ; pallial sinus reaching the centre of the shell. Animal with a large truncated foot, filling the pedal opening ; body with a fin-like termination; combined siphons large, cylindrical, with fringed orifices. The common piddock is used for bait on the Devon coast ; its foot is white and translucent when fresh, like a piece of ice ; the hyaline stylet (p. 29) lodged in it, is large and curious. P. costata is sold in the market of Havannah, where it is an article of food. Fig . 22. Pkolas dactyhis. Chalk, Sussex Coast. u, umbonal valves ; p, post-umbonal valve ; d, dorsal valve. P. dactylus has two accessory valves to protect the umbonal muscle, with a small transverse plate behind ; a long unsymmetrical plate fills up the space between the valves in the dorsal region. P. Candida mA parva have a single umbonal shield, and no dorsal plate; these differences are only of •specific value. In P. crispata, L. (Zirfaa, Leach) the umbonal shield is not distinctly calcified, but there is a small posterior plate ; the surface of the valves is divided into two areas by a transverse furrow. Distr. 25 sp. U. S. Norway, Brit. W. Africa, Medit. Crimea, India, Australia, N. Zealand, W. America : — 25 fms, Fossil, 25 sp. (U. Lias — ) Eocene — , U. States, Europe, The secondary species belong to the next group. CONCHIFERA. 329 PHOLADIDEA, Turton, 1819. Type, P. papyracea, PI. XXIII. fig. 20. Shell globose-oblong, with a transverse furrow; ; anterior gape large, closed in the adult by a callous plate ; 2 minute accessory valves in front of the beaks. Animal with a fringed disk at the end of the combined siphons, and a horny cup at their base. Distr. 6 sp. Brit. N. Zealand, Ecuador. Low-tides — 10 fms. Sub-genera. Martesia (Leach) Bl. 1825. M. striata, PI. XXIII. fig. 21 Valves lengthened behind, when full grown, by a plain border ; umbonal valves 1 or 2 ; dorsal and ventral margins often with narrow accessory valves. 10 sp. W. Indies, Africa, India. M. striata burrows in hard timber. M. terediniformis was found in cakes of floating wax on the coast of Cuba. (G-. B. Sby.) M. australis in (fossil ?) resin, on the coast of Australia. M. rivicola in timber 12 miles from the sea, in Borneo. M. scutata, Eocene, Paris, lines its burrow with shell. Jouannetia (semicaudata) Desm. (Pholadopsis, Conrad; Triomphalia, Sby.) Shell very short, sub-globose ; right valve longest behind : anterior opening closed by a callous plate developed from the left valve overlapping the margin of the right valve, and fixed to the single unsymmetrical umbonal plate. Distr. 3 sp. Philippines, W. America. Fossil, Miocene — . Prance. Parapholas, Conrad, P. bisulcata, PL XXIII. fig. 22. Valves with 2 radiating furrows. Distr. 4, sp. California, Panama, Torres Strts. XYLOPHAGA, Turton. Etym. Xulon, wood, phago, to eat. Types, X. dorsalis, PL XXIII. fig. 23 ; X. globosa, Sby. Valparaiso. Shell globular, with a transverse furrow ; gaping in front, closed behind ; pedal processes short and curved ; anterior margins reflected, covered by 2 small accessory valves ; burrow oval, lined with shell. Animal included within the valves, except the slender contractile siphons, which are furnished with pectinated ridges, and divided at the end ; foot thick, very extensile. Distr. 2 sp. Norway, Brit. S. America. Bores an inch deep, and across the grain, in floating wood, and timbers which are always covered by the sea. TEREDO (Pliny) Adanson. Type, T. Norvegica, PL XXIII. figs. 26, 27. Syn. Septaria, Lam. Shell globular, open in front and behind, lodged at the inner extremity of a burrow partly or entirely lined with shell ; valves 3 lobed, concentrically striated, and with one transverse furrow ; hinge-margins reflected in front marked by the anterior muscular impressions ; umbonal cavity with a long curved muscular process. 330 MANUAL OF THE MOLLUSCA. Fig. 223. Ship-worm, Teredo Norvegica, removed from its burrow. Animal worm-like; mantle-lobes united, thickened in front, with a minute pedal opening ; foot sucker-like, with a foliaceous border ; viscera in- cluded in the valves, heart not pierced by the intestine ; mouth with palpi ; gills long, cord-like, extending into the siphonal tube ; siphons very long, united nearly to the end, attached at the bifurcation and furnished with 2 shelly pallets or styles ; orifices fringed. T. navalis is ordinarily a foot long, sometimes 2| feet ; it destrovs soft wood rapidly, and teak and oak do not escape ; it always bores in the direc- tion of the grain unless it meets the tube of another Teredo, or a knot in the timber.* In 1731-2 it did great damage to the piles in Holland, and caused still more alarm ; metal sheathing, and broad-headed iron nails have been found most effectual in protecting piers and ship-timbers. The Teredo was first recognised as a bivalve mollusc by Sellius, who wrote an elaborate treatise on the subject, in 1733. (Forbes.} T. corniformis, Lam. is found burrowing in the husks of cocoa-nuts and other woody fruits floating in the tropical seas ; its tubes are extremely crooked and contorted, for want of space. The fossil wood and palm-fruits (Nipadites) of Sheppy and Brabant are mined in the same way. The tube of the giant Teredo (T. arenaria, Rumph. Furcella, Lam.) is often a yard long and 2 inches in its greatest diameter ; when broken across it presents a radi- ating prismatic structure. The siphonal end is divided lengthwise, and some- times prolonged into two diverging tubes. T. Norveyica and T. denticidata are divided longitudinally and also concamerated by numerous, incomplete transverse partitions, at the posterior extremity. T. bipalmulata (Xylotrya, Leach) has the siphonal pallets elongated and penniform (PL XXIII. fig. 28) ; a species with similar styles occurs in the fossil wood of the Green- sand of Blackdown. Distr. 14 sp. Norway, Brit. Black Sea; Tropics:— 119 fras. Fossil, 24 sp. Lias — . U. States, Europe. Sub-genus, Teredina, Lam. T. personata, PI. XXIII. figs. 24, 25. Eocene, Brit. France. Valves with an accessory plate in front of the inn- bones ; free when young, united by their margins to the shelly tube when adult. The tube is sometimes concamerated ; its siphonal end is often trun- cated ; and the opening contracted by a lining which makes it hour-glass shaped, or six-lobed (fig. 2 5 a.). * The operations of the Teredo suggested to Mr. Brunei his method of tunnelling the Thames. MANUAL OF THE MOLLUSCA. 13 PLATE XIII. The real size of each species is indicated by the accompanying line. Doridida, PAGE 1. Doris Johnstoui, A. and H. Brit, (low-water) ..................... 190 2. Goniodoris nodosa, Mont. sp. Brit ..................................... 191 3. Triopa clavigera, Mull. sp. Brit ........................................ 191 4. jJEgirus punctilucens, D'Orb. Brit ............................. , ....... 191 5. Polycera quadrilineata, Miill. sp. Europe. (Lamiuariau zone) ...... 191 6. Idalia aspersa, A. and H. Northumberland ........................... 192 TritoniacJce. 7. Trilonia plebeia, Jolinst. Brit. (Coralline zone) .................. 192 8. Scyllsca pelagica, L. Devon (pelagic) ................................. 193 9. Tethys fimbriata, L. Medit. (pelagic) ................................. 393 0. Dendronotus arborescens, Miill. sp. Brit ............................ ] 93 1. Doto coronata, Gm. sp, Brit ........................ ................... 193 2. Lomanotus marmoratus, A. and H. Devonshire coast ............... 194 .3. JEolis coronata, Forbes. Brit. (Laminarian zone) .................. 194 4. Glaucus Atlanticus, Bl. Gulf-weed banks .............................. 195 5. Embletonia pulchra, A. and H. N.Brit ............................... 195 6. Proctonotus mucroniferus, A. and H. Dublin Bay ................... 195 .7. Hermrea bifida, Mont. Brit. Lit. — Lamiuarian zone ....... . ....... 196 8. Alderia modesta, Loven. Brit. Salt-marshes ........................ 196 Ehjsiadce. 9. Elysia viridis, Mont. sp. Brit ........................................... 197 ). Acteonia corrugata (head) A. and H.. Falmouth ..................... 197 1. Cenia Cocksii, A. and H. Falmouth ................................. 197 2. Limapontia nigra, Johnst. Brit ......................... , .............. 197 14 MANUAL OF THE MOLLUSGA. PLATE XIV. Ojjistho-bratichiata. PAGE 1. Tornatella tornatilis, L. Brit 180 2. Cylindrites acutus, Shy. Bath Oolite, Brit 180 3. Acteonella Renauxiaua, D'Orb. %. L. Chalk, Prance... , 180 4. Cinulia avellana, Brongn. U. Green-sand, Brit 180 5. Tornatina voluta, Quoy sp. •§-. I. Guam, Australia 181 6. Bulk ampulla, L. \. India" 182 7. (Atys) naucum, L. i. Philippines 182 8. Linteria viridis, Rang. Pitcairn's Id 182 9. Acera Imllata, Miill. Brit 183 10. Cylichna cylindracea, Mont. Brit 183 11. Aplustrum aplustre, L. sp. \. Mauritius 183 12. Scaphander lignarius, L. sp. f. Brit 184 13. Bullsea aperta, L. sp. Brit 184 14. Aplysia depilans, (hybrida, Sby.) Brit 185 15. Dolabella verrucosa, Gmel. sp. •£. Mauritius 186 16. Lobiger Philippii, Krohn. Sicily 186 17. Pleurobranchus membrauaceus, Mont. §. Brit 187 18. Umbrella umbellata, Dill w. \. Mauritius 187 Nucleobranckiata. 19. Carinaria cymbium, L. £. Medit 200 20. Cardiapoda placenta, E. and S. ±. Atlantic 200 21. Atlanta Peronii, Les. 22, operc. 23 fry. S.Atlantic 200 24. Oxygyrus Keraudrenii, Rang. 25, operc. S. Atlantic 201 26. Beilerophiiia minuta, Sby. Gault, Brit 201 27. Bellerophon bi-carinatus, Lev. i. Garb. Limestone, Touruay ... 201 28. expausus, Sby. i. U. Silurian, Brit 201 29. Porcellia Puzosi, Lev. •£. Carb. Limestone, Belgium 201 30. Cyrtolites ornatus, Conrad, (cast) f . L. Silurian, U. States 201 31. Ecculiomphalus Bucklandi, Portl. £. Silurian, Tyrone 201 Pteropoda. 32. Hyalea tridentata, Gmel. Atlantic — Medit 204 33. Cleodora pyramidata, L. Atlantic 205 34. Creseis aciculata, Rang. Atlantic 205 35. Cuvieria columnella, Rang. S.Atlantic 205 36. Yagmella depressa, Basterot. §. Miocene, Bordeaux 205 37. Eurybia Gaudichaudi, Souleyet." S. Pacific (Huxley} 206 38. Psyche globulosa, Rang. Newfoundland 206 39. Cymbulia proboscidea, Peron. Medit , 206 40. Tiedemannia Neopolitana, Chiaje. Medit 206 41. Limacina antarctica (J. Hooker.) S. Polar Seas, 63°— 46° 207 42. Spirialis bulimoides, D'Orb. sp. Atlantic 207 43. Cheletropis Huxleyi, Forbes. £. S.E.Australia 207 44. Macgillivraia pelagica, Forbes, f. C. Byron, E. Australia 207 45. Clio borealis, Brug. Arctic Seas 208 46. Pueumodermon violaceum, D'Orb. f. S.Atlantic 208 47. Spongio-branchsea australis, D'Orb. -f-. S. Atlantic, Falkland Ids. 209 48. Trichocyclus Dumerilii, Esch. V0- South Seas 209 49. Pelagia'alba, Q. and G. Amboiua 209 50. Cymodocea diaphana, D'Orb. Atlantic 209 PI. 14. 3 MANUAL OF THE MOLLUSCA. 15 PLATE XV. All, except those marked *, are dorsal views. Terebratulida. PAGE 1 . Terebratula maxillata, Sby. i. Bath Oolite, England 215 2, diphya. F. Col. £. Alpenkalk, Tyrol 215 &. Terebratulina cuput-serpeutis, L. Norway — Medit 21G 4. Waldheimia australis, Q,uoy. f. Port Jackson 216 5 . impressa, Buch. Oxford clay, England 2 '. o 6. Lyra Meadi, Cumb. 1 316. £. U. Green-sand, England 217 7. Terebratella Magellanica, Chemn. f . Cape Horn 2 1 7 8. Trigonosemus Palissii, Woodw. Chalk, Belgium 217 9. Megerlia truncata, Lam. f. Medit 219 10. Argiope decollate. Chemn. f. Medit 220 11. Thecidium radians, Brougn. Chalk, Belgium 221 12.* hieroglyphicum, Defr. (interior.) Chalk, Belgium 221 13. Stringocephalus Burtiai, Defr. var. •£•/ Devonian, Europe 222 SpirlferidcB. 14. Spirifera Walcotti, Sby. i Lias, Bath 223 15. Cyrtia exporrecta, Wahl. U. Silurian, Europe 223 16. Athyris lamellosa, Lev. ^. Carb. limestone, N, Amer. — Europe 224 17. Uncites gryphus, Schl. ^. Devonian, Belgium 225 RJi y n chon ellidce. 18.*E,hynchonella acuta, Sby. §. Lias, Europe 226 19, furcillata, Buck. Lias, Europe 226 20. spinosa, Schl. §. Inf. Oolite, Europe 220 21. Atrypa reticularis, L. sp. \. Sil. -Devon. N. Amer. — Europe ... 227 22. Pentamerus Knightii, Sby. i. "U. Silurian 227 OrtHda. 23. Orthis rustica, J. Sby. f . U. Silurian, Europe 229 24.*Strophomena rhomboidalis, Wahl. §. U. Siltaian, N-. Amer. — Europe , 230 25. Leptscna liassina, Bouch. f. Lias, Europe 2B1 26- Calceola sandalina, Lam. |. Devonian, Europe 232 Productia&. 27- Producta horrida, J. Sby. i. Magn. limestone, Europe 2:>3 28.* proboscidea, Vcrn. i. Carb. limestone, Belgium 283 29. Chonetes striatella, Dalrn. U. Silurian, Europe 235 Craniada. 30. Crania Ignabergensis, Retz. Chalk. Sweden 236 Di&cinida. 31. Discina lamellosa, Brod. ^. Peru 2J7 Lin guild a. 32. Lingula anatina, Lam. £. Philippines 239 16 MANUAL OF THE MOLLUSCA. PLATE XVI. Ostreida. PAGE 1. Ostrea cliluviana, Gmelin. %. Chalk-marl, Brit 254 2. (Exogyrd) conica, Sby. f. U. Green-sand, Wilts 255 3. Anomia Achseus, Gray. §. Kurach.ee, Scinde 255 4 Placunoima macroschisma, Desh. ^-. California 255 5. Placuna sella, Gm. sp. £. China 256 6. placenta, L. (young.) N.Australia 256 7. Carol ia placunoides, Cantr. (hinge.) Tertiary, Egypt 256 8. Pecten plica, L. f. China 258 •y. (Hemi-pecteri) Forbesianus, Ad. f. Sooloo Sea, 14 fms. ... 258 10. (Hinnites) pusio, Pen. f. Brit 258 11. Lima squamosa, Lam. i. China , 258 12. (Plagiostoma) cardiiformis, Sby. Bath Oolite, Brit 25£ 1 3 . (Limatuld) suh-auriculata, Mont. Brit 258 14. (Limeea) strigilata, Brocchi sp. Pliocene, Italy 258 15. Spondylus princeps, Gmel. |-. Sooloo Sea 259 16. (Pedum) spondyloides, Gml. §. Red Sea 259 17- Plicatula cristata, Lam. |. W.Indies 259 Avicullda. 18. Avicula hirundo, L. |. Medit 260 19. (Meleagrina) margaritifera, L. sp. |. Ceylon 260 20. (Malleus) vulgaris, Lam. i. China 261 21.- (Fttfo?//a)Ungdata,Lam. £. Red Sea 261 22. Posidonomya Becheri, Bronn. Garb. Hesse, Brit 262 23. Pinna squamosa, Lam. TV- Medit 263 24. Crenatula viridis, Lam. £. Chinese Seas 263 a,a' adductor impressions. p, pedal muscles. g, suspensors of the gills. bt byssal foramen or notch. • v/'. // J.W.Zowryfc. MANUAL OF THE MOLLUSCA. 17 PLATE XVII. * The figures marked are left valves ; (interiors). Aviculidcz. PAGE 1. Gervillia anceps, Desli. ^-. Neocomian; Brit 262 2. Perna ephippium, L. £. W.Indies 263 3. Inoceramus sulcatus, Park. f. Gault, Brit 263 Mytilida. 4. My tilus smaragdinus, Chemn. ^. India 264* 5. Modiola tulipa, Lam. i. Brit 265 6. pelagica, Forbes. £. S.Atlantic 266 7. lithophaga, L. \. Medit 265 8. Crenella discors, L. Brit 266 9. Dreissena polymorpha, Pallas, f. Brit 266 Arcadce. 10. Area granosa, L. f. Australia , 267 11. pexata, Say. £. S. Carolina 267 12. (Bysso-arca) Note, L. f. Medit 267 13. zebra, Sw. £. Australia 267 14. Cucullsea concamerata, Martini. |. India 268 15. Macrodon Hirsonensis, D'Arch. sp. ^. Bath Oolite, Brit 268 16.*Pectimculus pectiniformis, Lam. f. India 268 17.*Lirnopsis aurita, Broc. sp. Crag, Suffolk 268 18. Nucula Cobboldise, Sby f . Crag, Norwich 269 19.*Nuculina miliaris, Desh. ^-. Eocene, Paris 269 20.*Leda caudata, Donov. Brit 260 21 .* ( Toldia] myalis, Couthouy. f . Crag, Norwich 270 22.*Solenella Norrisii, G. Sby. f. Valparaiso 270 23. ornata, G. Sby. sp. -|. Miocene, Patagonia 270 Trigoniadte. 24.*Trigonia costata, Park. \. Oolite, Brit 271 25. Myophoria decussata, Miinst. sp. Trias, Tyrol 272 26. Verticordia cardiiformis, Wood. f. Crag, Suffolk 304 18 MANUAL OF THE MOLLTJSCA. PLATE XVIII. * The figures marked are left valves. Unionidce, PAGE 1. Unio litoralis, Drap. \. Auvergne 274 2. (Nonocondylad) Paraguayans, D'Orb. \. S.America... 274 3. Castalia ambigua, Lam. \. R. Amazon 275 4. Hyria syrmatophora, Gronov. \. S. Americaf 274 5. *Iridina exotica, Lam. \. Africa, R. Nile 275 6. Mycetopus soleniformis, D'Orb. •£. S. America, ft. Parana 275 7. ^Etheria semilunata, Lam. \. Senegal 275 Chamida. 8. Chama macrophylla, Chemn. \. Antilles 276 9. left valve 10. Diceras arietinnm, Lam. ^. Coral-Oolite, France ., 278 11. • left valve 278* 12. (Requienia) Lonsdalii, J. Sby. \. Neocomian, Spain — Brit. 279 ] 3, Caprotina striata, D'Orb. U. Green-sand, France 289 14. left valve 289 Tiidacnida. 15. Tridacna squamosa, Chemn. £. Bombay 290 16. Hippopus maculatus, Lam. \. N.Australia ., 290 Cardiadce (part). 17. Lithocardium aviculare, Lam. £. Eocene, Paris 291 Cyprinidfe (part). 18. Cardilia semi-sulcata, Lam. Amboina 301 19.*Megalodon cucullatus, J. Sby. \. Devonian, Eifel 301 t The animal of Hyria has two siphon al orifices. PI. 18, 'T.W.lewrv ic. i .13. , MANUAL OF THE MOLLUSOA. 19 PLATE XIX. * The figures marked are left valves. Cardiadcs. PAGE 1. Cardium costatum, L. £. China 290 2. lyratum, G. Sby. £. Madagascar 290 3. hemicardium, L. £. China 291 4,* (Adacnd) edentulum, Pallas, f. Caspian 291 5. Conocardium Hibernicum, Sby. £. Carb* limestone, Kildare ... 292 Lucinidce. 6. *Lucina Pennsylvania, L. §. W.Indies 292 7. (Cryptodon) flexuosa, Mont. Brit 293 8. Corbis elegans, Desh. fc. China 293 9. Diplodonta lupinus, Broc. sp. Miocene, Turin 294 10. Ungulina oblonga, Baud. f. W.Africa 294 "1 1 . Kellia Laperousii, Desh. California 295 12. (Poronia) rubra, Mont, f Brit 294 13. Montacuta substriata, Mont. ^. Brit 295 14. Lepton squamosum, Mont. -J-. Brit 296 15. Galeomraa Turtoni, Sby. Brit 296 J6.*Cyamium antarcticum, Phil. •}. Falkland Ids 294 Cycladida. 17. Cyclas cornea, L. R. Thames 29? 18. — — (Pmdium) amnica, Miill. f . R. Thames 297 19. Cyrenoides Dupontii, Joan, f 298 20. Cyrena cyprinoides, Quoy. i. Ceylon 297 21. (Corbicula) consobrina, Gray. Alexandrian Canal 297 CyprwidcE. 22. Cyprina Islandica, L. £. N.Brit 298 23. Cardinia Listeri, Sby. sp. $-. Lias, Cheltenham 302 24. Opis lunulata, Miller sp. Inf. Oolite, Bridport 302 25. Myoconcha crassa, Sby. ±, Inf. Oolite, Dundry 303 20 MANUAL OF THE MOLLUSCA. PLATE XX. (All the interiors are right valves.) fyprinida. PAGE 1. Astarte sulcata, Da Costa. Brit 299 2. Circe corrugata, Chem. f. Red Sea 299 3. Isocardia cor. L. £. Brit 300 4. Cypricardia obesa, Reeve. i. India 300 5. Cardita calyculata, L. S.Africa 303 6. — ( Venericardia} ajar, Adans. W. Africa 303 Venerida. 7. Venus paphia, L. W. Indies 304 8. Cytherea dione, L. J. W.Indies 305 0. (Meroe] picta, Schum. f. China 305 10. (Trigona) tripla, L. f. W.Africa... 305 11. (Grateloupia) irregularis, Baster. f. Miocene, Bordeaux 326 12. Artemis exoleta, L. i. Brit 326 13. Lucinopsis undata, Pennant sp. Brit 326 U. Tapes pullastra, Wood. f. Brit 326 15. Venerupis exotica, Lam. N.Australia 327 16. Petricola lithophaga, Retz. Medit 327 ' 1 7- pholadiformis, Lam. f . New York 3 27 1 8. Glaucomya Chinensis, Gray. China 327 19. Capsula rugosa, Lam. sp. ^. N.Australia 311 .TWT.nwrv //'•. - - PI. 21. w MANUAL OF THE MOLLUSCA. 21 PLATE XXf. (All the interiors are right valves.) Mactridce-. PAGE 1. Mactra stultomm, L. |. Brit 308 2. Gnathodon cuneatus, Gray. \. New Orleans 308 3. Lutraria oblonga, Gmel. \. Brit... 309 4. Crassatella ponderosa, Gmel. sp. \. Australia 299 TeUmida. 5. Tellina lingua-fells, L. |. Antilles 310 6. carnaria, L. Antilles 310 7. — - planissima, Anton, f, India. (T. rosea, Sby.) 310 8. Diodonta fragilis, L. f. Galway , 310 9. Psammobia Eerroensis, Chemn. Brit 3TT 10. squamosa, Lam, Borneo 311 11. Semele reticulata, Chemn. Antilles 312 12. (Cumingia) lamellosa, G. Sby. Bahamas 312 13. (Syndosmyd) alba, Wood. Brit 312 14. Scrobicularia piperata, Gm. sp. \. Brit 312 15. Mesodesma glabratum, Lam. Ceylon 313 [g, , (Donacilla) donacium, Lam. £. Peru 313 17 (Anapa) Smilhii, Gray. Tasmania 313 18. Ervilia nitens, Mont. Antilles 313 19. Donax denticulatus, L. Antilles 313 20. (Iphigenia) Brasiliensis, Lam. £. Antilles 314 21. Galatea reclusa, Born sp. |. R.Nile 314 22. Tancredia extensa, Lycett. i. Oolite, Brit 293 22 MANUAL OF THE MOLLU8CA. PLATE XXII. * The figures marked are left valves (interiors). Tellixid*. PAGE 1 . Sanguinolaria livida, Lam. i. N. Australia ........................ 311 2. -- diphos, Chemn. £. India ........................... 311 3. - -- orbiculata, Wood. \. S.America .................. 311 Solenidce. 4. Solen siliqua, L. \. Brit .............................................. 315 5. Cultellus lacteus, Spengl. £. Tranquebar ........................... 315 6. -- (Cerati-solen] leguraen, L. f . Brit ...................... 315 7. -- (Machasra) politus Wood. |. India .................... 316 8. Solecurtus strigilatus, L. f. W.Africa , .......................... 316 9. - Caribseus, Lam. |. TJ. States ........................... 316 10. — _— (Novaculina) Gangeticus, Bens. Calcutta ............ 31? 11. Thetis hyalina, Sby. sp. f. China .................................. 319 12. Panopsea Americana, Conrad. ^. Miocene, Maryland ............ 319 13.*Saxicava rugosa, L. f . Brit. — Kamtschatka .............. ...... 320 14. Glycimeris siliqua, Chemn. f . Arctic America ..... . ............ 320 Anatinida. 15. *Pholadomya Candida, Sby. \. W.Indies ............... ...., ....... 322 16. Goniomya literata, Sby. £. Oolite, Brit ............................ 322 17. Solemya togata, Poll sp. \. Medit 271 PI. 22. MANUAL OF THE MOLLUSCA. 23 PLATE XXIII. * The interiors marked are left valves. Myacida. PAGE l.*Mya truncata, L. £. Brit 317 2. Corbula sulcata, Lam. W. Africa 317 3. (Potamomyd) labiata, Maton sp. •§. Bueaos Ayres 318 4. (Spkenia) Binghami, Turt. Brit 318 5. Nesera cuspidata, Olivi. Brit 318 6. Anatinella Candida, Chemn. f. Ceylon 309 Anatinida. 7. Anatina subrostrata, Lam. \. India 321 8. Cochlodesma prsetenue, Mont. Brit 321 9. Thracia pubescens, Pnlt. £. Brit 822 10.*Lyonsia Norvegica. Chemn. sp. f. Brit 323 11. Pandora rostrata, Lam. f. Guernsey 324 1 2. Myodora brevis, Stutch. New South Wales 324 13. Myochama anomioides, Stutch. New South Wales . . , 324 14. Chamostrea albida, Lam. sp. -£. New South Wales 325 GastrocTi&nida. 15. Gastrochsena modiolina, Lam. Galway 325 15a. sp. siphonal orifices, in U. Green-sand, Haldon, Devonshire 326 16. mumia, Spengl. f. India , 326 17. Clavagella bacillaris, Desh. ^. Pliocene, Sicily , 326 18. Aspergillum vaginiferum, Lam. \. Red Sea 327 Pholadidce. 19. Pholas Bakeri, Desh. ^. India ; 328 20. - — (Pholadidea) papyracea, Solr. f . Brit 329 21. - — (Martesia) striata, L. W.Indies 329 22. : — (Parapholas) bisulcata, Conrad. California 329 23. Xylophaga dorsalis, Turt. Brit 329 24. 25. Teredina personata, Lam. London Clay, Bognor 330 25 a. siphonal orifice 26.*Teredo Norvegica, Spengl. Brit 329 27. siponai end of the tube, broken to show septa. 28. bi-pennata, Turt. (styles) Brit 330 24 MANUAL OF THE MOLLUSCA. PLATE XXIV. (Tunicated Mollusca described in the Supplement.) Ascidiada. 1. Molgula tubulosa, Rathke. N. Brit. 2. Cynthia papillosa, Brng. sp. ^. Medit. 3. Pelonrca glabra, Forbes, f. N. Brit, 4. Chelyosoma Macleayanum, Brod. £. Greenland. 5. Boltenia pedunculata, M. Edw. -+$. New Zealand. Clavellinidce. 6. Clavellina lepadiformis, O. F. Miill. North Sea. 7. Perophora Listen, Wiegm. f . Brit. 8. Botryllus violaceus, M. Edw. f. France. 9.*Botrylloides rotifera, M. Edw. France, N. Coast. 10.*Didemnium gelatinosnm, M. Edw. France. ll.*Euco3lium hospitiokto, Sav. Medit. 12.*Distomus fuscus, M. Edw. France. 13. Diazona violacea, Sav. £. Ivica, Medit. 14. Aplidium lobatum, Sav. \. Gulf of Suez. 15. Polyclinum constellatum, Sav. Red Sea. 16. Parascidium flavum, M. Edw. |. France. 17.*Amorcecium argas, M. Edw. France. 18. -- proliferura, M. Edw. (larva). France. 19. Syncecium turgens, Phipps. §. Spitzbergen. 20. Sigillina australis, Sav. ^. Australia. Pyrosomida. 21. Pyrosoma giganteum, Lesueur, ±. Atlantic. Medit. SaJpida, 22. Salpa maxima, Forsk. 5. Medit. Atlantic. 23. Doliolum denticulatum, Q. and G. -f-. New Zealand, 24. Appendicularia flabellum, Chamisso. f . New Guinea. * Magnified figures of zoi'ds separated from the common mass. 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