One of the two varieties of clam, the other being soft-shell clam. On the East Coast, hard-shell clams, also called by their Indian name, quahog, come in three sizes. The smallest are littleneck clams, which have a shell diameter less than 2 inches. Next comes the medium-sized cherrystone clam, about 2 1/2 inches across. The largest of this trio is the chowder clam, (also simply called large clam,) with a shell diameter of at least 3 inches. Among the West Coast hard-shell varieties are the Pacific littleneck clam, the pismo and the small, sweet butter clams from the Puget Sound. See also clam.