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HINNITES. De France. 
Gen. Cuar. An unequal-valved, nearly equal-sided, 
radiated, bivalve ; valves eared, the area of the 
hinge quadrangular, tripartite, its cartilage im- 
mersed in a deep longitudinal pit in the cen- 
tre, the lateral portions striated, supporting the 
ligament ; sinus for the byssus small; muscu- 
lar impression large, connected with impres- 
sions remaining from the attachment of the 
mantle parallel to the margin of the valves. 
A cenvs established by M. de France, who has de- 
scribed two fossil species. Mr. Gray has added one re- 
cent one from the British Museum; and three others 
have been added by my brother and M. des Hayes, the 
last of which is the Pecten Pusio of authors. All the 
species are more or less muricated upon the surface, and 
when advanced in age, employ the squame of the most 
convex valves to attach them to foreign substances. This 
habit and the peculiar form of the hinge pit, distinguish 
them from Pecten and Lima; the form of the hinge, es- 
pecially of the fossil species, approaches near that of Os- 
trea, but the shell does not appear to be attached in the 
young state, nor constantly when old; and when it is at- 
tached, it is by the right valve, which is the most convex, 
not the left as in Ostrea. 
It has been supposed that the attachment is caused by 
the pressure against the sides of holes in which the shells 
have been confined ; but it rather appears to us to be the 
effect of choice on the part of the animal, for it is con- 
stantly the right valve that is attached ; and the surface 
of the other, although they are both distorted, is not 
rendered smooth nor indeed changed, as it would neces- 
sarily be if confined. We possess a specimen of H. Cor- 
tesyi that seems to set the question at rest; it consists of 
two convex valves, one attached by almost its whole 
outer surface (even the ears) to the inside of the other, 
which does not show any marks of having ever been 
fixed. The animal is distinguished from that of the 
Oyster by having its mantle attached to the shell, as is 
