OF THE UNITED STATES. 61 
back covered with elevated, concentric squamous plates; 
within, marked with numerous obsolete, longitudinal striz. 
Length, from one to four inches. , 
This species is almost invariably attached to other 
shells, particularly to Gryphea: the dorsum is often en- 
tirely concealed by this circumstance, but the internal 
striz 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, pl. 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 strie. 
From St. Georges, Delaware &c. 
2. A. tellinoides, (S.G.M.) PI. v, fig. 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. 
