Page:American Seashells (1954).djvu/501

Rh round and slightly gaping at the posterior end. Exterior brownish gray and may be with brown, concentric rings of growth. Interior dull-white. Beaks inflated and high. Ligament large and strong. No lunule or escutcheon. Weak radial ribs seen at both ends only. Concentric growth ridges prominent near the margins. Muscle scars and pallial line deeply impressed. Foot of animal large and suffused with heavy, red mottlings. Very commonly dredged in cold, northern waters.

Genus Clinocardium Keen 1936

Clinocardhim ciliatuvt Fabricius Iceland Cockle Plate 320 Greenland to Massachusetts. Alaska to Puget Sound, Washington.

1/4 to 3 inches in size, a little longer than high, with 32 to 38 ridged radial ribs which are crossed by coarse concentric lines of growth. Externally drab grayish yellow with weak, narrow, concentric bands of darker color. Interior ivory. Periostracum gray and conspicuous. Especially abundant from Maine northward in offshore waters. Clinocardium nuttalli Conrad Nuttall's Cockle Plate 31b

Bering Sea to San Diego, California.

2 to 6 inches in length; smaller ones being almost round, adults tending to be higher than long; moderately compressed; commonly with 33 to 37 coarse radial ribs which are creased by half-moon-shaped riblets. Older specimens worn smoothish. Exterior drab-gray, with a brownish yellow, thin periostracum. Common offshore. Once called C. corbis Martyn. Known locally as the Basket Cockle.

Clinocardiimi fucanum Dall Fucan Cockle

Sitka, Alaska, to oif Monterey, California.

1 to 1/4 inches in length, longer than high, moderately inflated, and with 45 to 50 low, poorly developed, radial ribs which are crossed by mi- croscopic concentric lines. No wavy, radial furrow on the upper posterior edge of the shell. Color whitish with a grayish-brown periostracum. Com- mon in the Puget Sound area.

Young C. nuttalli are distinguished from this species by their 2 first ribs behind the ligament which are large, rounded and make a wavy edge to the shell. In small specimens of C. ciliatmn, the top edges of the ribs are sharp; in jucanuvi they are rounded.