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456 Sphenia ovoidea Carpenter (Alaska to Panama) is half as large, smoother, and more ovoid in outline without the prominent snout. Uncommon. Genus Cryptomya Conrad 1849 Somewhat like a small, fragile My a, but more fragile, and the right valve is larger and more obese than the left. Large chondrophore in the left valve is thin, flat-topped with an anterior ridge. Posterior gape and pallial sinus almost absent. Siphons very short. Crypt077jya calijormca Conrad Californian Glass Mya Alaska to central Mexico. 1 to I /4 inches in length, oval, fragile, moderately obese. Right valve fatter. Right beak crowds slightly over the left beak. Posterior gape very small. Chondrophore in left valve large, tucks against a small, concave shelf under the right beak. Exterior chalky and with small growth lines. Peri- ostracum dull-gray, faintly and radially striped at the posterior end. Interior slightly nacreous in fresh specimens. Common in sand where it may live as deep as 20 inches. The short siphons enter the burrows of other marine animals. Genus Flatyodon Conrad 1837 Shell somewhat resembling a very fat Mya, with a fairly thick shell, rugose sculpturing and fairly small chondrophore. Platyodon cancel! atiis Conrad Chubby Mya Queen Charlotte Island, B.C., to San Diego, California. 2 to 3 inches in length, rounded rectangular and obese. Gaping widely posteriorly. Shell strong, rather thick and with fine, clapboard-like, concen- tric growth lines. Rarely with very weak radial grooves. Chondrophore in left valve quite thick and arched. Beak of right valve crowds under beak of left valve. Shell chalky and white; periostracum thin, yellowish brown to rusty, and rugose posteriorly. Moderately common near beds of pholads. Lives in sand. Family CORBULIDAE Genus Varicorbida Grant and Ciale 193 1 Varicorlnda operculata Philippi 1848 Oval Corbula North Carolina to the Gulf of Mexico and the West Indies.