Clam

Clam, name given to many edible marine bivalve mollusks that live in sand or mud, including the jacknife clam, the quahog or cherrystone clam, and the pismo clam; also refers to some freshwater bivalves. The giant clams of Indian Ocean and Pacific Ocean coral reefs may reach a diameter of 4 ft (2.4 m) and weigh one-quarter ton (0.27 metric tons).