MOLLUSCA—UOCKLE.. PHOIAS. 769 
THE COCKLE1! 
Or the cardium, or cockle tribe, there are more than fifty spec:es; some 
or other of which are to be procured on the sandy shores of all the known 
seas. They are mostly found immersed a few inches deep in the sand. In 
size, the different species vary considerably, some heing five or six inches in 
diameter, and others not more than half an inch. The cockle has a tolera- 
ble degree of locomotive power, in consequence of its triangular yellow foot, 
which is conspicuous on the shell being opened. With this fect it can also 
draw into threads its glutinous matter, and thus in a manner anchor itself 
on the spot that it has chosen for its residence. The opening of the shell 
is protected by a soft membrane, which wholly closes up the front, except 
in two places, at each of which there is a small, yellow, fringed tube. 
Through these tubes the animal receives and ejects the water which conveys 
nutriment to its body. 
THE.CARDIUM EDULE, OR COMMON COCK LE, 
Wuicu is the species most common in England, has a grayish shell, some- 
what heart-shaped, with about twenty-eight flattish ribs, transversely striated, 
with recurved imbrications. It isa wholesome and pleasant food. Lobsters 
and crabs lie in wait for an opportunity of thrusting in a leg ora claw, 
when the cockle is open, in order to prey on the included animal; but it 
often happens that the younger ones of those crustaceous animals, not being 
sufficiently hard to withstand the violent snapping of the shells of the larger 
species when they close, are deprived of the limb. 
THE PHOLAS# 
Or all animals of the shelly tribe, the Pholades are the most won- 
derful. These animals are found in different places; sometimes cloth- 
ed in their proper shell, at the bottom of the water; sometimes con- 
cealed in lifmps of marly earth; and sometimes lodged, shell and all. 
1The genus Cardium is characterized by a shell equivalve, subcordiform, with protube- 
rant beaks ; valves dentated, or plicated on their internal margin; hinge with four teeth 
in each valve, of which the two primary ones are approximated and oblique, and two late- 
ral distant ones. 
2The genus Pholas has the shell bivalve, equivalve, transverse, gapmg on each side 
with several accessory pieces, either on the hinge, or below it; inferior margin of the 
valves bent outwards; animal destitute of a tubular sheath, projecting anteriorly, two 
united tubes, often surrounded by a common skin, and posteriorly, a short, thick, muscular 
foot, flattened at its extremity. 
97 65 
