American Indians used parts of the shell from these bivalve mollusks to make wampum beads used for barter, ornamental, ceremonial and spiritual purposes. The two main varieties of clams are hard-shell and soft-shell. The hard-shell clams found on the East Coast (where they're also called by the Indian name quahog) come in three sizes. The smallest are littleneck clams, which have a shell diameter less than two inches. Next comes the medium-size cherrystone clam, about 2½ inches across. The largest of this trio is the chowder clam (also called simply "large" clam), with a shell diameter of at least three inches. Among the West Coast hard-shell varieties are the pacific littleneck clam, the pismo and the small, sweet butter clams from Puget Sound. Soft-shell clams, also called soft clams, actually have thin, brittle shells. They can't completely close their shells because of a long, rubbery neck (or siphon) that extends beyond its edge. The most common East Coast soft-shell is the steamer clam. The most famous West Cost soft-shells are the razor clam (so named because its shell resembles a folded, old-fashioned straight razor) and the geoduck clam (pronounced GOO-ee-duck). The geoduck is a comical-looking, 6-inch-long clam with a neck that can reach up to about 1½ feet long. On the East Coast and in the Pacific Northwest, clams are available year-round. In California, the season is November through April. Clams are sold live in the shell, fresh or frozen shucked, and canned. When buying hard-shell clams in the shell, make sure the shells are tightly closed. If a shell is slightly open, tap it lightly. If it doesn't snap shut, the clam is dead and should be discarded. To test a soft-shell clam, lightly touch its neck; if it moves, it's alive. The guideline for buying shucked clams is plumpness and clear liquid. Store live clams up to two days in a 40°F refrigerator; refrigerate shucked clams up to four days. Clams can be cooked in a variety of ways, including steaming and baking. All clams should be cooked gently to prevent toughening. Clams are high in protein and contain fair amounts of calcium and iron.
From The Food Lover's Companion, Fourth edition by Sharon Tyler Herbst and Ron Herbst. Copyright © 2007, 2001, 1995, 1990 by Barron's Educational Series, Inc.