APLYSIIDiE. 363 



uarrowed posteriorly ; the hind edge of the mantle is fimbriated 

 and projects through the fissured suture of the shell ; foot 

 expanded, narrow and rounded anteriorly, broad and truncated 

 posteriorly ; by means of the extended latei-al foot-lobes the 

 animal swims with considerable facility. 



CYLINDROBULLA, Fischer. Shell cylindrical, buUiform, thin, 

 fragile, spire very shoi't, suture slit; outer lip incurved, closing 

 the aperture in the middle. A. Beauii, Fischer (Ixxxix, 63). 



LoBiGER, Krohn. 



Distr. — 4 sp. Atlantic, South Europe. L. Philippii, Krohn 

 (Ixxxix, 65, 66). 



Shell oval, transparent, flexible, slightly convoluted ; covered 

 with epidermis. 



Animal slender, papillose, with two 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. 



The four laterally expanded wing-like lobes easily distinguish 

 this animal from Lophocercus. 



Family AFLYSIID^. 



Shell wanting, or rudimentary and covered b}^ the mantle, 

 oblong, trigonal, 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. 



Etym. — Aplysia (from a and pluo), un washable ; the Aplysia 

 of the Grreek fisherman were sponges unfit for washing. Sea- 

 hare. Syn. — Siphonotus (geographicus), Ad. 



Distr. — 48 sp. West Indies, Norway, Britain, Mediterranean, 

 Mauritius, China. Fossil (?). Tertiary; Sicily. A. depilans, Linn. 

 (Ixxxix, 67, 71). 



Shell oblong, convex, flexible, and translucent, with a posterior 

 slightly incurved apex. 



Animal oval, with a long neck and prominent back ; head with 

 four tentacles, dorsal pair ear-like with eyes at anterior lateral 

 bases; mouth proboscidiform, 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. 



