PELECYPODS 435 
gnons, 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 parc délevage at 
Marennes. It is a collection of artificial ponds, the fioors of 
which are covered with alge, 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. 
O. 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 O. 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.” 
FAMILY PECTINIDE 
Genus Pecten 
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 
