78G 



COMPENDIUM OF GENERIC DISTINCTIONS. 



Family. PATELLID.3D. Shell conical ; apex turned for- 

 wards. 



Genus. PATELLA. Shell oval, interior smooth ; apex 

 nearly central. World-wide. 



Family. DENTALID^!. Shell tubular, curved, regular, 

 open at each end, tapering from mouth ; aperture circular. 



Genus. DENTALIUM. As family. Most seas. 



Family. CHITONID5!. Shell composed of eight over- 

 lapping plates, lodged in a leathery mantle, each plate with 

 a process from its front edge. 



Genus. CHITON. As family. World- wide. 



Genus. CHITONELLUS. Border velvety, exposed portions 

 of the plate small. Hot seas. 



Order. PULMONIFERA Foot broad. Breathing 



organ a simple chamber lined with network of respiratory 

 vessels. 



Section. INOPERCULATA. Without operculum. 



Family. HELICID5!. Shell external. Anima ; with 

 four retractile tentacles, upper pair largest and having _ye- 

 specks at tips. Foot distinct ; body spiral. Respiratory 

 aperture on right side, under edge of shell. Mouth with 

 horny-toothed upper mandible. 



Genus. HELIX. Aperture of shell transverse, oblique, 

 rounded, or semilunar ; margins distinct. Animal with 

 long foot pointed behind. World-wide. 



Genus. BULIMUS. Shell oblong or turreted ; longitudinal 

 edges of aperture unequal ; columella entire. Animal like 

 Helix. Warm seas. 



Genus. PUPA. Shell oblong or cylindrical ; aperture 

 rounded. Animal with short foot, pointed behind. World- 

 wide. 



Family. LIMACID.ffi. Shell small or rudimentary, 

 internal, or concealed by mantle, placed over respiratory 

 cavity. Animal long ; foot not distinct. 



Genus. LlMAX. Shell internal, oblong, edge mem- 

 branous. Foot very long ; mantle shield-shaped ; head and 

 tentacles retractile. World-wide. 



Genus. TESTACELLA. Shell small, ear-shaped at end of 

 body. Back of animal with two long furrows, from which 

 others ramify. Many parts of world. 



Genus. ARION. Shell oval, or made of chalky granules. 

 Tail rounded, with gland at tip. Most parts of world. 



Family. LIMNJEID/E. Shell large and thin, lip sharp. 

 Muzzle short and wide ; eyes at base of tentacles ; mouth 

 with upper mandible. 



Genus. LIMN^EA. Shell spiral, rather long, last whorl 

 very wide ; aperture rounded in front. Tentacles triangular. 

 Most parts of world. 



Genus. PHYSA. Spiral to left, and polished. Tentacles 

 long and slender ; bvl^e of mantle with a deep fringe. 



Genus. PLANORBIS. Shell flattened, many whorls ; 

 aperture semihmar. Foot round and short ; eyes at inner 

 base of tentacles. 



Section. OPERCULATA. With an operculum. 



Order. OPISTHOBRANCHIATA. Shell small or 

 absent. Branchiae towards end of body. 



Sub-order. TECTI-BRANCHIATA. Gills covered by 

 shell or mantle. 



Family. BULLION. Shell rounded, thin ; spire small ; 

 aperture long, rounded, and waved in front. Animal in- 

 vesting shell ; disc-like nead ; eyes none, or in disc. One 

 gill on right of back. Edge of mantle overlapping shell. 



Genus. BULLA. Shell oval, swollen, partly invested by 

 animal ; aperture larger than shell. Head-disc two-lobed 

 behind. Warn) and hot seas. 



Genus. CYLICHNA. Shell cylindrical ; aperture narrow 

 and rounded in front. Animal not investing shell. Many 

 parts of world. 



Genus. APLUSTRUM. Shell oval, swollen ; aperture 

 blunt in front ; outer lip sharp. Foot capable of investing 

 the whole shell. Warm seas. 



Genus. PHILINE. Shell oblong; aperture very wide in 

 front. Head large and oblong ; eyes none ; foot short and 

 broad. Warm and temperate seas. 



Family. APLYSIARffl. Shell none, or small and covered 

 by mantle. Animal like slug ; head distinct ; foot long, 

 forming a tail behind. Very large lobes at sides. 



Genus. APLYSIA. Shell oblong, flexible, translucent. 

 Animal oval ; neck long ; four tentacles. Sides with large 

 lobes used as fins ; gill in centre of back. Most seas. 



Genus. DOLABELLA. Shell hatchet-shaped. Gill near 

 end of body. Hot seas. 



Genus. LOBIGEU. Shell oval, transparent ; on middle ot 

 back covered with epidermis. Animai slender ; eyes small, 

 on sides of head. Two pairs of rounded lobes on sid<:s. 

 Warm seas. 



Family. PLEUROBRANCHIDjE.- Shell mostly limpet- 

 like ; mantle covering back ; gill on sides. 



Genus. UMBRELLA. Shell limpet-like, flat, round, and 

 concentric. Foot large, deeply notched in trout.. Mantle 

 small. Gill on right side, forming a series of plumes. Warm 

 and hot seas. 



Siil-order. NUDIBRANCHIATA. No shell in adult. 

 Gills always external on back or sides of body. 



Family. DORIDjE. Oblong ; gills in circle on middle of 

 back. Tentacles two. Skin with spiculte. 



Genus. DORIS. Oval, flattened ; mantle large. Tentacles 

 retractile. All seas. 



Family. TRITONIAD.ffi. Gills along sides of hue!: ; 

 tentacles retractile. 



Genus. DENDUONOTUS. Long ; tentacles laminated ; 

 branched appendages in front of head. Single series ot <.','iU s 

 on each side of buck. Northern seas. 



Genus. DOTO. Slender ; sheaths of tentacles trumpet- 

 shaped ; tentacles slender, not laminated. Northern seas. 



Family. BOLIDE. Gills papillose, along sides of b;i<-k ; 

 tentacles not retractile. No distinct mantle. 



Genus. EOLIS. Rather oval. Gills numerous and over- 

 lapping; mouth with horny upper jaw. World-wide. 



Genus. GLAUCUS. Long and slender. Gills on three 

 pairs of lateral lobes. Atlantic and Pacific. 



Order. NUCLEOBRANCHIATA. Respiratory ami 

 digestive organs forming a kind of nucleus on posterior part 

 of back. 



Family. FIROLID&. Long, cylindrical, translucent ; 

 Ventral and tail fins. Mantle with circular lip. 



Genus. FIHOLA. Head long and slender ; fin with small 

 sucker. Tail keeled ; branchial processes numerous, 

 conical, and slender. Tentacles four; eyes black and dis- 

 tinct. Warm and hot seas. 



Genus. CARINARIA. Shell glassy, limpet-shaped, keeled. 

 Animal large, translucent ; head thick and cylindrical. 

 Warm and hot seas. 



Order. PTEROPODA Sides towards the front fur- 

 nished with swimming flaps. 



Sub-order. THECASOMATA. Animal with external 

 shell ; head indistinct ; foot and tentacles scarcely visible. 



Family. HYALEID/E. Shell straight, curved, globular, 

 or needle-shaped. Animal with two large fins. Body 

 inclosed in mantle. 



Genus. HYALEA. Shell globular, translucent. Animnl 

 with long appendages to mantle, passing through slits hi 

 shell. Warm and hot seas. 



