442 MARINE INVERTEBRATES 
it from all other shells of our coast of similar size, is the coarse, wrinkled 
epidermis of black to chestnut color. The shell is very suggestive of a 
large, overgrown Astarte. Length three and a half inches; height 
three inches. It is found of all sizes, down to one fourth of an inch in 
diameter, upon muddy stations in moderately deep water near the 
mouths of rivers; but the surest way to get it is to search the beach 
after a hard onshore gale. 
FAMILY LUCINIDE 
This family finds its metropolis in warmer waters, and the best 
representatives of it must be sought for upon the Floridian 
beaches or in the shallow bays of that sandy coast. A long ver- 
miform foot is a characteristic of the animal, as is also the fact 
that at times there is only a single gill upon each side of 
the body. In some. of the Lucinidw, more so than in most other 
peleeypods, the chief function of the gills is to furnish a brood- 
ing-place for the thousands of ova which the creatures generate. 
Sometimes a Lucina will be captured with the gills swollen out of 
all proportion, and literally stuffed with tiny, microscopic eggs. 
At such times the gills lose all semblance of branchial organs. 
The shells are orbicular, with depressed small umbones, a distinct 
lunule, a semi-external ligament, two cardinal teeth, and laterals 
(a variable feature). There is no pallial sinus. The color is 
white, and the outlines are rounded. 
Genus Lucina 
L. tigrina. The largest of the group, measuring three inches across 
and nearly the same in height. It is flatly convex and radially ribbed 
by a great number of costz which are crossed and decussated through- 
out with concentric ridges. The color is white. This fine shell lives 
only in southern Florida and is abundant in shallow water on sandy sta- 
tions. (Plate LXXX.) 
L. floridana. One of the most abundant bivalves in Florida, often 
cast in thousands upon the beaches. It lives in shallow protected 
waters and upon sand-flats which are partly exposed at low tide. It 
has the usual round outlines of the genus, with exceedingly small um- 
bones, directed forward, and a smooth surface, save for fine growth- 
lines of a light straw-color. The shell is pure white. Diameter about 
one inch. (Plate LXXX.) 
L. pennsylvanica. A species often associated with the last, but about 
twice as large. Its thin but tough epidermis clings to the shell in raised 
concentric lines, giving it a circularly ribbed appearance. The most 
prominent feature of this species is a depressed line upon either valve 
extending obliquely from the umbones to the posterior ventral: margin, 
