284 Organic Remains of the Ferruginous 



EXOGYRA. Say* 



E. costata. (Say.) This fossil is equally abundant with those last 

 described, and is found in the ferruginous sand from New Jersey to 

 South Carolina. Mr. Say is certainly correct in making a distinct 

 genus of this fossil, in proof of which it will be found that Mr. Sow- 

 erby has placed a congeneric shell with Chama, (C. conica) while 

 Mr. Brongniart classes another with Gryphaea. (G. auricularis.f ) 

 The true Exogyra has but a single muscular impression in each valve, 

 which sufficiently distinguishes it from Chama, while it differs still 

 more strongly from Gryphaea. It is an interesting fact that all those 

 European fossils which belong to the genus Exogyra have been found 

 exclusively in acknowledged secondary deposits. Thus the Chama 

 conica and C. haliotoidea of Sowerby are peculiar to the green sand 

 of England, while the Gryphaga auricularis of Brongniart has been 

 found, in France, only in chalk marl. 



OSTREA. Ijam. 



1. O.falcata. (S. G. M.) This handsome species is about an 

 inch and a half long, thin, curved, and plicated longitudinally from 

 the hinge margin to the point. It is abundant at St. George's, in 

 Delaware, and is also found in many parts of New Jersey. 



2. O. cristagalli ? I found a few valves at St. George's, which 

 have so much resemblance to this species, that I shall for the present 

 adopt the name. The O. cristagalli is a well known fossil of the 

 English chalk. 



3. O I obtained at Mullica Hill, in N. J. a solitary 



inferior valve of an ostrea which differs from any I have seen. It is 

 five inches long, deeply costated, and replaced with true flint. J 



4. O My friend Mr. T. A. Conrad has lately pre- 

 sented me with a single valve, very convex, with ten or twelve deep 

 plications. It is entirely different from any of the preceding species. 



Anomia. 



A. ephippium'^ (Lam.) It is extremely difficult to distinguish be- 

 tween the recent and fossil anomiae, for which reason, for the present 



* Amer. Jour. Science, Vol. II. p. 43. 



t Cuv. and Brong. Des. Geolog. des Env. de Paris, pi. VI. fig. 9. 



X In the Jour. Acad. Nat. Sc. I mentioned the O. flabelhda, (Lam.) as a marl 

 fossil. The specimens, however, were subsequently found to be from the tertiary 

 deposit of Maryland. 



