PELECYPODS 435 



{/nons, which sway in the wind, are said to frighten away the pre- 

 daceous ray which is apt to hover about the preserves. The 

 pares are finally thinned out by sending the oysters to other 

 pares to be fattened. There is a celebrated pare d'elevage at 

 Marennes. It is a collection of artificial ponds, the floors of 

 which are covered with algae, which harbor vast numbers of 

 diatoms and other microscopic organisms on which the oysters 

 feed. The green diatom (Navicula ostrearia) gives to the oysters 

 of Marennes the green color and peculiar flavor which is so much 

 esteemed by the epicures of France. To the American, however, 

 the green oyster is not acceptable. 



GENUS Ostrea 



O. virginica. A description of this species, our common oyster, is 

 hardly necessary. Every one has seen the rough, shaggy, unlovely 

 shell. The hinge is toothless, but has a wide depression for the liga- 

 ment. The animal, having stationary habits, has practically no foot at 

 all. There is but one large adductor muscle, around which curve the 

 gills, the latter being united to each other posteriorly. The mantle 

 margin is finely and doubly fringed. Although Ostrea is a stationary 

 mollusk, it has no byssus. 



0. virginica has been introduced at San Francisco, where it lives 

 well, but does not seem to multiply very rapidly. The native species, 

 O. lurida, is about two inches long, dark in color, and stained a pur- 

 plish hue. It is not very delicately flavored. 



O. frons. This species has a thinner shell than 0. virginica, with 

 coarsely serrated margins. It occurs in beds in the neighborhood of 

 mangroves all along our South Atlantic shores. It cannot compare 

 with its Northern relative in flavor, but, like the European Ostrea 

 edulis, it is sometimes " not bad." 



The scallop-shells (Pecten) are objects too familiar to require 

 any general description. The rounded valve, usually ornamented 

 with radiating ribs, and the wing-like projections (called " ears "), 

 from each side of the umbonal region, are never-failing char- 

 acters. The outline of Pecten has been considerably employed 

 in conventional designs for mural decorations ; indeed, the figure 



