Page:American Seashells (1954).djvu/508

410 Genus Protothaca Dall 1902 Frotothaca tenerrima Carpenter Thin-shelled Littlcneck Vancouver, B.C., to Lower California. About 4 inches in length and 2 % inches high, very compressed, relatively thin, with a chalky texture, with a few raised concentric lines and numer- ous very small radial threads. Lunule fairly defined. Exterior light gray- brown. Interior chalky-white. A fairly common species, commonly washed ashore on Californian beaches. Frotothaca staininea Conrad Common Pacific Littleneck Plate 31m, n Aleutian Islands to Lower California. 1 /4 to 2 inches in length, subovate, beaks nearer the anterior end; sculp- ture of concentric and radial ribs which form beads as they cross each other at the anterior end of the shell. Radial ribs strongrer on the middle of the valves. Beaks almost smooth. Exterior rusty-brown with a purplish cast. A very abundant, wide-spread species with a number of varieties. Sometimes with a mottled color pattern. Variety or form: laciniata Carpenter reaches 3 inches in length, is coarsely cancellatc and beaded, its color rusty-brown to grayish. Variety or form: ruderata Deshayes (typically a northern form) is chalky-white to gray, with concentric ribs large and coarse, commonly lamellate (see pi. 31-0). Compare with Tapes philippinarwn, the Japanese Littleneck. Genus Humilaria Grant and Gale 1931 1 1 nil lil aria kcnnerleyi Reeve Kennerley's Venus Alaska to Carmel Bay, California. 2 M: to 4 inches in length, ovate-oblong, with the beaks near the anterior end. With sharp, concentric ribs whose edges are bent upwards. Spaces between ribs. Color and texture like gray Portland cement. Interior white. Margin of shell finely crenulate, a feature that will distinguish it from worn specimens of Saxidomus. Dredged on mud bottoms from 3 to 20 fathoms. A collector's item, although reasonably common. Genus Tapes Aiiihlfeld 181 1 Subgenus Rudhapes Chiamenti 1900 Tapes philippinarwn Adams and Reeve Japanese Littleneck Puijct Sound southward.