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456 American Seashells
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, concentric
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
Varicorlnda operculata Philippi 1848 Oval Corbula
North Carolina to the Gulf of Mexico and the West Indies.
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