62 CRETACEOUS GROUP 



Placuna, Lam. 



P. scabra (S. G. M.) 



Specific character. With numerous beaded cc-stse, radiating 

 from the hinge to the margin ; shell thin, suborbicular, com- 

 pressed. 



From one inch to three inches in diameter. 



Found hitherto only in fragments in the blue marls. 



Plicatula, Lam. 



P. urticosa, (S. G. M.) PI. x, fig. 2. 



American Journal of Science, vol. xxiv, pi. x, fig. 2. 



Specific character. Irregularly oval, flattened, thin, grega- 

 reous ; with fifteen or twenty squamous costae, some of which 

 bifurcate near the margin. 



Length, an inch and a half; breadth, an inch. 



Found in the arenaceous marls of New Jersey and Ala- 

 bama, by Mr. Conrad. 



Referred in the former edition to Ostrea. 



Inoceramus. 



1. I. Barabiniy (S. G. M.) PI. xvii, fig. 3, and pi. 

 xiii, fig. 11. 



Specific character. Obliquely elliptical, not ventricose, 

 with concentric, prominent, subacute ribs : beaks prominent, 

 approximate. 



This species is extremely variable both in outline and 

 size. PI. xvii, fig. 3, represents an imperfect specimen 

 of a large size ; and pi. xiii, fig. 11, shows another much 

 smaller, but with a nearly entire margin. From the older 

 cretaceous strata of Greene county, Alabama. 



