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. 



Observations. I 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. 



