APLYSIID. 363 
narrowed 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 lateral foot-lobes the 
animal swims with considerable facility. 
CYLINDROBULLA, Fischer. Shell cylindrical, bulliform, thin, 
fragile, spire very short, suture slit; outer lip incurved, closing 
the aperture in the middle. A. Beauii, Fischer (1xxxix, 63). 
Lopieer, Krohn. 
Distr.—4 sp. Atlantic, South Europe. LZ. 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. 
Famity APLYSIID A. 
Shell wanting, or rudimentary and covered by 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. 
Htym.—Aplysia (from a and pluo\), unwashable; the Aplysia 
of the Greek 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. 
