n.
or heart clam
Any of approximately 250 species (family Cardiidae) of marine bivalve s distributed worldwide.
They range in diameter from about 0.5 in. (1 cm) to about 6 in. (15 cm). The two valves of the shell are equal in size and shape and range in colour from brown to red or yellow. Most species live just below the low-tide line, though some have been obtained from depths of more than 1,500 ft (500 m) or in the intertidal zone. Many species are marketed commercially for their meat.
Great heart cockle ( Dinocardium robustum )
Harry Rogers