50 CRETACEOUS GROUP 



Cypmia, Lin. 



A solitary cast of a very small species was found in the 

 strata of the Chesapeake and Delaware canal, and was 

 shown me by Mr. John Finch. 



Patella, Lam. 



P. tentorium, (S. G. M.) PL i, fig. 11. 



Specific character. Depressed, orbicular, with about eighty 

 costiform striae, radiating from the apex to the margin. 



Diameter, rather more than half an inch. 



This fossil has some appearance of a shelly operculum, 

 in which case it would belong to the genus Hipponix. 



I have met with but a solitary individual, which was 

 obtained by Mr. Conrad in blue marl, near Arneytown, 

 New Jersey. 



ACEPHALA. 

 Ostrea, Lam. 



1. O. falcata, (S. G. M.) PI. iii. fig. 5, and pi. ix, 

 fig. 6, 7. 



Journ. Acad. Nat. Sciences, vol. vi. pi. i. fig. 2. 



Specific character. Falciform, auriculated, thin, depressed ; 

 six or seven deep plications commence hear the beaks, and ter- 

 minate at the margin. 



Length, from half an inch to an inch and three-fourths. 



A characteristic fossil of this formation ; abundant at 

 St. Georges, Delaware. Mr. Nuttall found it at Ca- 

 havvba, Alabama. It is also very abundant at Prairie 

 Bluff, on the Alabama river. 



