﻿29(3 CONRAD'S DESCRIPTIONS OF 



interrupted ; concentric lines numerous, regular, minute ; margin within densely 

 crenulate. 



Locality. — Mississippi. Dr. Spillman. 



PTEROPSIS, Gonmd. 



Ovate, thin, equivalve ; hinge plate very broad with an ovate cartilage pit ; ante- 

 rior cardinal tooth very large and elevated, V shaped, anterior to the pit, bifid and 

 extending to the inner margin of cardinal plate ; posterior tooth, long, elevated, 

 compressed, oblique ; posterior cardinal plate widely and profoundly channelled. 

 (Left valve.) 



Ptekopsis papyria, (lutrapja.) Conrad. Amer. Journ. Science, Vol. I. (New 

 Series,) p. 216, pi. 1, fig. 8. 



The generic diagnosis of this shell readily distinguishes it from RaMa, Gray, and 

 its form is very different; the umbo being direct, and the beak much anterior to the 

 middle of the valve, whilst in the allied genus it is posterior ; I found two left valves 

 only of this beautiful and curious shell. The genus, no doubt, is peculiar to the 

 Eocene ; casts are not uncommon in the same formation in South Carolina. 



DIPLODONTA, Brown. 



Diplodonta Astartifoemis. Ovate-triangular, rather thick in substance ; equila- 

 teral, slightly ventricose; lateral slopes very oblique and nearly equal; umbo and 

 summit direct. 



Locality. — Claiborne, Alabama. 



Diplodonta deltoidea. Obtusely ovate-triangular, convex, equilateral ; posterior 

 side subcunieform, the subangulated extremity being about midway between beak and 

 base. 



Length f inch, nearly. 



Locality. — Claiborne, Alabama. 



CRENELLA, Brown. 



Crenella latifrons. Obliquely suboval, inflated, thin, highly perlaceous ; anterior 

 side produced or alated above ; striag very closely arranged, elegant and minute, can- 

 cellate anteriorly. 



Locality. — Alabama. Dr. Showalter. 



