LAMELLIBEANCHIATA OF THE LOWER MARLS. 179 



being al:)Out the same. Very ventricose on the right valve and of a sub- 

 triangular form. Beak large, inflated and enrolled, nearest the anterior end. 

 Anterior umbonal ridge subangular, and marked by a narrow groove, which 

 divides the concentric ridges at this point. Posterior end short, with a very 

 marked fold separating the postero-cardinal slope from the body of the valve. 

 Body of the valve marked by coarse, strong, and rounded concentric folds, 

 varving in number according to the size of the shell. Left valve less ven- 

 tricose than the right, and destitute of the strong folds, or marked only by 

 irregular concentric lines. 



The species bears considerable resemblance to C. Murcliisoni Lea, from 

 the Eocene sands of Claiborne, Alabama. In fact it is quite difficult to point 

 out characters by which they can be distinguished as seen on the imperfect 

 specimens which I have examined from New Jersey. These are scarcely half 

 the length of the one figured by Mr. Gabb in the Journal of the Academy of 

 Natural Sciences, unless that figure be an enlargement. I have not seen a 

 left valve in a condition for illustration, and none of the examples shoAv the 

 interior in a condition to be described, as they are extremely fragile and 

 will not bear handling. The small specimen figured by Mr. Conrad as C. 

 perhrevis from North Carolina loc. cit. is so exactly like the New Jersey forms 

 both in size and general ajjpearance, that the figure would answer perfectly 

 for an illustration of one of these. In Mr. Conrad's remark on the generic 

 relations of this group of Cretaceous Corhulcc he appears to consider them 

 as pertaining to the genus Fachi/don Gabb on account of their spiral beaks; 

 and in the same connection one obtains an explanation of Mr. Conrad's 

 reasons for the formation of so many genera by that author, in his intima- 

 tion of a belief "that all life was destroyed at tlie close of the Cretaceous 

 era;" a belief not warranted by facts, and one intended to lead a paleon- 

 tologist into any amount of excess in the formation of genera and species. 



Formation and locality. — In the dark micaceous clays below the Lower 

 Marls at Haddonfield, New Jersey. From the collection of the Academy 

 of Natural Sciences of Philadelphia. 



