OF THE UNITED STATES. 61 



back covered with elevated, concentric squamous plates ; 

 within, marked with numerous obsolete, longitudinal strias. 



Length, from one to four inches. 



This species is almost invariably attached to other 

 shells, particularly to Gryphsea : the dorsum is often en- 

 tirely concealed by this circumstance, but the internal 

 strise are so characteristic as to identify the species. 



Found by Mr. Conrad in the marls of Burlington 

 county, New Jersey. 



3. P. pelagicum, (S. G. M.) PI. v, fig. 2. 



Specific character. Suboval, convex, with twenty-five or 

 thirty narrow, elevated ribs. 



Length, about an inch. 



This species, unlike the preceding, has never been 

 found attached. Its general aspect is much like that of 

 P. duplicata, Sowerby, pi. clix, fig. 3, an Oolitic fossil. 



Anomia, Lam. 



1. A. argentaria, (S. G. M.) PI. v, fig. 10. 



Specific character. Discoidal, thin, with numerous delicate, 

 concentric strise. 



From St. Georges, Delaware &c. 



2. A. tellinoides, (S. G. M.) PI. v, fi^. 11. 

 Specific character. Irregular or suboval, with concentric 



undulations. . • < 



Common in the marls of New Jersey &c. 



This species has the external aspect of Tellina ; it is 



much thicker than the preceding one. In the former 



edition I referred it to A. ephippium, from which it is 



obviously distinct. 



