PELECYPODS 455 
and C. quadrigenarium on the southern shores of California. The former 
is a full, round, heart-shaped shell with about thirty somewhat scaly 
ribs. The edge of the shell is deeply toothed; the color light brown- 
ish ; the diameter from two to three inches. It preserves all the features 
of the genus as regards both shell and anatomical characters. The other 
species, C. quadrigenarium, very strongly resembles C. magnum in size 
and shape. It lacks 
the flattened area on 
the posterior portion 
of the shell which is 
characteristic of the 
east-coast species, and 
its uniform brownish- 
white coloration is less 
striking. It has about 
forty regularly spaced, 
radiating ribs, which 
are smooth upon the 
umbonal region, but 
elsewhere are armed 
with spiny processes. 
Diameter about six in- 
ches.(Plate LXXXTV.) 
C. islandicum, C. 
pinnulatum. Both 
of these are cold-water 
species and occur along 
the New England coast. 
The former has a shell 
which varies from one half of an inch to two inches in length, and has from 
thirty-six to thirty-eight sharp, three-sided, radiating ribs, the furrows 
between them being rounded and wrinkled by growth-lines. A yellow- 
ish-brown epidermis covers the shell and bristles into a sort of fringe upon 
the sharp edges of the ribs. C. islandicwm cannot be said to be a very 
common species in New England, although collectors have so reported it. 
Specimens from Massachusetts are not as large as those of more northern 
habitat. It does not occur south of Cape Cod. C. pinnulatumis one of the 
“small fry” among the cockles. Its largest diameter is less than one 
half of an inch; but what it lacks in size it seems to endeavor to make 
up in abundance, for it is scattered everywhere along the 
coast from New York northward. Specimens can nearly 
always be found in the stomachs of fishes, which, by the way, 
form an excellent hunting-ground for rare species of mol- 
lusks of small size. There are twenty-six slightly rounded 
: ribs, with deep linear grooves between them. Upon the ribs, 
Cardiwm especially in the posterior portion of the shell, are arched 
*  seales, folded so as to appear like blunt spines. The species 
may easily be distinguished from the young of C. islandicum by the 
smaller number of ribs. The animal, C. pinnulatum, is said to be exceed- 
ingly lively and able to make rapid progress over gravelly bottom by exe- 
euting sudden leaps. It has a long, recurved, very strong foot, and its 
movements are effected as described above. Itis abundant at Bar Harbor. 
Cardium islandicum. 
