Leukoma staminea, commonly known as the Pacific littleneck clam, the littleneck clam, the rock cockle, the hardshell clam, the Tomales Bay cockle, the rock clam or the ribbed carpet shell,^[2] is a species of bivalve molluscin the family Veneridae.^[3] This species of mollusc was exploited by early humans in North America; for example, the Chumash peoples of Central California harvested these clams in Morro Bay approximately 1,000 years ago,^[4] and the distinctive shells form middens near their settlements.^[5]

Like other members of Veneridae, this species has a chalky shell, the umbo being anterior to the midline of the shell, but closer to the midline than to the anterior end of the shell. The two equal-sized valves are oval or heart-shaped. The width of the shell is greater than a quarter of its length, and the shell seldom exceeds 6 cm (2.4 in) in length. The umbones point towards the anterior end of the shell. The hinge has three cardinal teeth in each valve, and a row of small teeth along the ventral margins of the valves. There are numerous concentric ridges, more clearly demarcked at the anterior end, but the radial ridges are often more clearly sculpted. The foot is large and there is a clearcut pallial sinus.^[2]

Leukoma staminea is native to the eastern Pacific Ocean. Its range extends along the coasts of North America from the Aleutian Islands and Alaska in the north to Baja California in the south. It usually occurs in protected areas on sand, hard mud and clayey-gravel substrates from the mid and lower shore down to depths of about 10 m (33 ft), usually buried less than 8 cm (3 in) beneath the surface of the sediment. Occasionally it is in more exposed locations, in gravel-filled cracks in rocks or in empty burrows of other clams.^[2]

(From Wikipedia, June 9)