528 
MoUusca. 
ing classes, and are caught chiefly in the winter months. 
Their size varies from five or six inches to half an inch 
in diameter. The shell is generally white ; it has 
twenty-six longitudinal ridges, is transversely wrinkled, 
and has somewhat imbricated striae. The foot of these 
animals is largely developed, and is to them a most im- 
portant organ, as they use it not merely for progression, 
but in the excavation of hollows in the sand or mud in 
which they dwell. 
The Chama, which is akin to the cockle, was used by 
the ancients to engrave various figures upon, from which 
circumstance those small bas-reliefs, so valued now, 
have obtained among the Italians and collectors the 
name of Cameos. The shells of some of these arc 
decorated with red or yellow stripes, diverging from 
the hinge, and spreading to the edges. The Giant 
Chama has been found to weigh more than five hundred 
pounds, and the oyster-like animal within was large 
enough to furnish a meal for twenty men. The animals 
which inhabit these shells are sometimes called Clams. 
The shells are often used in Catholic countries for 
containing holy water. 
THE PHOLAS. (Pholas dactylus.) 
This is a shell of a rather elongated form, gaping at both 
