198 
MARINE SHELLS OF WEST COAST OF NORTH AMERICA 
oblique rib merely forms a thickened lobe at the edge, and does project 
into a tooth-like process; on the opposite valve is an excavation in the 
beak for the reception of the tooth and the insertion of the ligament. 
Length, 2inches; height, 1% 0 inches; breadth, 1% inches. (Binney 
and Gould’s Invert. Mass.) 
Type locality, Europe. 
Range. Arctic Ocean and from Bering Island to Puget Sound. 
Mya arenaria Linnaeus, 1758. 
Plate 32, figs, la, lb. 
Syst. Nat. ed. 10, p. 670. Binney and Gould’s Invert. Mass., p. 55, fig. 375. 
M. testa ovata postice rotundata, dente antrorsum porrecto rotundato 
denticuloque laterali. Habitat in O. Europae. Septentrionalis sub arena, 
foraminibus duobus detegenda. Cardinis dens in altera tantum teste 
prominens cum denticulo parallelo versus sulvam. (Linnaeus.) 
Shell ovate, equivalve, nearly equipartite, moderately thick, gaping at 
both ends, especially at the posterior, which cannot be closed on account 
of an outward curvature of the valves; anteriorly shortest and regularly 
rounded; posteriorly narrowed and rounded; surface wrinkled, and in 
some parts raised into ridges at the lines of growth; faint, radiating lines 
and colors depart from the beaks; color dingy white, covered with a very 
thin, dirty-brown epidermis, irregularly wrinkled; beaks small, pointed, 
slightly curved forward, directly under which, in the left valve, rises an 
erect tooth, rounded at its summit, of about equal breadth and height; its 
inner face is smooth and rounded; its outer face is divided into two 
portions, the largest of which is spoon-shaped, the other flat and traversed 
across the middle by a grooved ridge which projects beyond the margin 
of the tooth like a smaller tooth; on the right valve we have a deep 
excavation imbedded in the cavity of the beak; in this and in the concave 
portion of the tooth is fixed the very strong cartilage; anterior muscular 
impression narrow and long, club-shaped; posterior one semi-oval; pallial 
impression scalloped along the base, and very deeply notched behind. 
Common length, Z l / 2 inches; height, 2 inches; breadth, 1 inch. (Binney 
and Gould’s Invert . Mass.) 
Type in British Museum. Type locality, Northeastern Europe. 
Range. Victoria, British Columbia, to Puget Sound and south to 
Monterey; found in old Indian mounds on Vancouver Island—an indica¬ 
tion that the species is native. On the Atlantic it is found far up the St. 
Lawrence River, where it grows smaller and smaller, the whole coast of 
Nova Scotia, and Laborador, Cape Hope, James Bay, Greenland, and in 
England, where it is the most common shell. Abundant as a Pleistocene 
fossil throughout the north. 
