GASTEROPODS 363 
The shells are nacreous within, and the animal, with its rows of 
waving cirri upon each side, is very suggestive of Trochus. 
They are, for the most part, shallow-water or littoral forms. 
Genus Turbo 
T. castaneus. This species has a range as far north as Cape Hatteras, 
and is especially abundant at Tampa, on the west coast of Florida. The 
peculiar operculum is sufficient to identify the genus at once. One 
variety of this species has a crenulated shoulder upon the body-whorl 
and is referred to as Turbo crenulatus. <A series of intermediate 
forms establishes the specific identity of the two varieties. (Plate LX VII.) 
FAMILY NERITDE 
The Neritide are strictly littoral forms, almost entirely confined 
to the warmer waters of tropical seas. The animal preserves the 
usual diatocardian features—has a short snout and long tenta- 
cles. Unlike the trochids and Turbo, it has no cirri along the 
epipodial margin. The shells are peculiarly shaped, the spire 
being greatly flattened and scarcely noticeable on account of the 
unduly large development of the body-whorl; thus the shell takes 
on a decidedly patelliform appearance. It is without an umbilicus. 
In the principal genus Nerita the outer lip is sharp on the edge, 
but greatly thickened just within. 
Genus Nerita 
N. peleronta. This shell has two teeth on the wide, flat columellar 
lip, and about them is a blotch of red, suggesting blood. The common 
name of this shell, ‘‘bleeding-tooth,” is very appropriate. Found in 
southern Florida. (Plate LXVIL.) 
N. tessellata is a smaller species, with heavy revolving ribs, and is 
further decorated with transverse oblique black lines. The operculum 
is caleareous. Both of these species have the habit of absorbing the 
entire inner portion of their shells. They belong to the West Indian 
fauna, and occur in great numbers on rocky or coral shore stations. 
They also may be found on the east Florida coast, well to the south. 
A third species, N. versicolor, often occurs, associated with the other 
two. It is somewhat smaller than the others and can easily be distin- 
guished by the four teeth on the columellar lip, the edge of the 
columella being convex. (Plate LXVII.) 
GENUS Neritina 
The genus Neritina is very closely allied to the last, having 
quite the same form of shell; but it is usually more globular and 
