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, 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. 



