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410 Aviericmi Seashells
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 graybrown.
Interior chalky-white. A fairly common species, commonly washed
ashore on Californian beaches.
Frotothaca staininea Conrad Common Pacific Littleneck
Aleutian Islands to Lower California.
Plate 31m, n
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 nillilaria 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
Subgenus Rudhapes Chiamenti 1900
Tapes philippinarwn Adams and Reeve Japanese Littleneck
Puijct Sound southward.
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