ASTARTIDAE 375 



Crassostrea virginica Gmelin Eastern Oyster 



Plate 28a 



Gulf of St. Lawrence to the Gulf of Mexico and the West Indies. 



2 to 6 inches in length. This is the familiar edible oyster which varies 

 greatly in size and shape. The valve margins are only slightly undulating or 

 are straight. The muscle scar is usually colored a deep purple, the rest of the 

 shell being white inside and dirty-gray exteriorly. Beaks usually long and 

 strongly curved. "Blue Points," a form originally harvested at Blue Point, 

 Long Island, are rounded in shape and with a rather deep, lower valve. 

 "Lynnhavens" arc broad, elongate forms originally harvested at Lynnhaven 

 Bay, Virginia. These variations are due to environmental differences. C. 

 brasiliana Lamarck and C. floridensis Sowerby are this species. 



Crassostrea rhizophorae Guilding (brasiliana of authors) is found in the 

 Caribbean region, and it is a lightweight shell, deep-cupped, with a flat upper 

 valve small and fitting well down into the lower valve. The inner margin of 

 the lower, attached valve is splotched with bluish purple. Common. 



Crassostrea gigas Thunberg Giant Pacific Oyster 



Plate 29g 

 British Columbia to California. Japan. 



3 to 12 inches in length, of various shapes, but generally characterized 

 by its large size, its coarse, widely spaced, concentric lamellae or very coarse 

 longitudinal flutings or ridges on the outside. Interior enamel white, often 

 with a faint purplish stain on the muscle scar or near the edges of the shell. 

 Very rarely with a greenish stain. A common, large and marketable oyster 

 introduced yearly into Canada and the United States from Japan. The form 

 lapermisi Schrenck is round. The typical gigas is the long, strap-like form. 

 O. gigas Aleuschen is an invalid name and does not preoccupy that of Thun- 

 berg's. Also known as the Japanese Oyster. 



Order EULAMELLIBRANCHIA 

 Suborder HETERODONTA 

 S7iperfa77nly ASTARTACEA 



Family ASTARTIDAE 

 Genus Astarte Sowerby 18 16 



Astarte borealis Schumacher Boreal Astarte 



Plate 28q 

 Arctic Seas to Massachusetts Bay. Alaska. 



I to 2 inches in length, ovate, moderately compressed. External liga- 

 ment large. Concentric ridges strong near the beaks but disappearing near 



