pismo clam Tivela stultorum, one of the best-known and most highly prized edible bivalves of the Pacific coast of N. America, occurs only in California. Its shells are triangular in shape; large, measuring up to 18 cm (7") across. and so thick that a big specimen can weigh almost 2 kg (4.25 lb); varying in colour ‘from pale buckskin to deep chocolate’; and with a varnished appearance.
The clam takes its name from Pismo Beach. There, and at Moro Bay and in part of Monterey Bay, it is most abundant. Its preferred habitat is the intertidal zone of a flat sandy beach exposed to the Pacific surf. Its range does not extend beyond California.