ORDER TESTACEA. 107 
At other times the anterior tooth is lamelliform, as in the 
Mya pictorum, L., an oblong and thin species known to 
every one. 
Lamarck distinguishes the 
HYREA, Lam. 
In which the angles are so decided that the shell is nearly 
triangular. (H. rugosa, Encyc. Meth.) 
CASTALIA, Lam., 
When the slightly heart-formed shell is striated in radii; the 
teeth and plates of the hinge are transversely sulcated, which 
gives them some affinity with the trigoniz. (Castalia ambigua, 
Lam.) 
There are certain marine mollusca which have a similar 
animal, and about the same kind of hinge, that should be 
placed near the unios; the summits of the shell, however, are 
more convex, and it is marked by projecting ribs, extending 
from the summits to the edge. ‘They form the 
CarpITA, brug., 
Which are more or less oblong, or heart-shaped; the inferior 
margin in some gaping. (Chama antiquata, Chemn., &c.) 
CYPRICARDIA, Lam. 
Carditz, in which the tooth under the summit is divided 
into two or three. ‘Their form is oblong, and their sides un- 
equal. (Chama oblonga, Gm., &c.) 
M. de Blainville also separates the 
CORALLIOPHAGA, Blainv., 
Where the shell is thin, and the lateral plate considerably 
effaced, which may cause their approximation to venus. 
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