336 PROCEEDINGS OF UNITED STATES NATIONAL MUSEUM. 
Fissurella nodosa Born. 
Key West, on rocks between tides, rather rare. A common West 
Indian species. 
Fissurella alternata Say. 
Cedar Keys, on rocks between tides. 
Lucapina ? fasciata Pfr. 
Key West, on rocks at extreme low water: only two living ones 
were obtained. From these it is evident that this animal does not he- 
long to the same genus as the great Lucapina crenulata of California, 
but in the present confused state of the Fissurellide it is impracticable 
to state positively where it should be placed. The shell is about one- 
third covered by the mantle and the anterior (shorter) end is depressed, 
the body of the animal being much thicker behind; the posterior part of 
the shell is raised and its upper surface is therefore directed forward 
and upward. The soft parts (in a!cohol} are of a whitish color; the 
margin of the mantle, which has a smooth surface and simple or non- 
papillose edge, extends widely around the shell, falling and covering 
the head, sides, and back of the foot like a curtain; the branchiz are 
symmetrical, their tips extend forward to the top of the head; the sides 
of the foot and top of the head and muzzle are speckled with reddish 
brown, smooth and with only a single series of lateral papille ; these 
papille begin at the anterior part of the foot on a longitudinal line with 
the tentacles, the anterior ones are about one-third as large as the ten- 
tacles (every alternate one, however, being much smaller); they rapidly 
diminish in size backward and become more distant and uniform (or the 
smal! intercalary ones disappear); there are altogether about twenty on 
each side; the muzzle is long, granulose and rather broad at the end 
and divided in the middle line below; the tentacles are clavate, long, 
with large, black eyes situated on stout tubercles at their outer bases ; 
behind the right eye-tubercle and proceeding from its base is a tentac- 
ular process, slender, cylindrical or longitudinally wrinkled and slightly 
hooked at-the end, which may be an intromittent organ; it was much 
smaller in one specimen than in the other, and in that specimen the lat- 
eral papilla were also smaller and less numerous; the difference seemed 
disproportionate to the difference in total size, but these organs are quite 
variable in this respect, and part of the difference may have been due 
to shrinkage from different strengths of alcohol in which they were 
originally immersed. The dorsal aperture, as in other Fissurellida, 
serves the purpose of an excurrent sewer and is nearly filled by the 
large, oval papilla, through which the rectum opens, and a simple fiill 
of mantle edge. The whole creature is much more like Fissurellid@a 
bimaculata Dall of California, both shell and soft parts, than like the so- 
called Lucapina referred to. The characters of the typical species must 
be more closely inquired into before the proper allotment of the @iffer. 
ent forms included in the different genera can be finally decided. 
