72 CONTRIBUTIONS 
FAMILY CARDIACEA. 
GENUS HIPPAGUS.* — (nobis.) 
Description. Shell cordate, inflated, without teeth; — 
beaks large, recurved; margin slightly overwrapping 
beneath the beak; anterior cicatrix long; posterior cicatrix 
round. y 
Observations. 1 have in vain endeavoured to place this 
shell in one of the established genera. In its general 
characters it approaches most closely to the Isocardia cor, 
but cannot be placed in that genus, being destitute of teeth. 
It bears some resemblance -to the genus Inoceramus of 
Sowerby, but the hinge in that genus “closes by a series 
of oblong fossets,” and besides it is very inequivalve. In 
its natural order, it seems to follow the genus Isocardia, 
and I propose there to place it. 
H. isocardioides. Plate 2. Fig. 50. 
Description. Shell cordate, much inflated, longitudinal, 
minutely and longitudinally ribbed, flattened before and 
behind, ridged along the umbonial slope ; substance of the 
shell rather thick; beaks large, recurved; cicatrices im- 
* A Horse Boat. 
