OF THE UNITED STATES. 43 



Say, which I have figured in Journ. Acad. Nat. Science, 

 vol. vi. pi. v. fig. 6. 



The greatest diameter of one of my specimens is an 

 inch and three-fourths ; and they have been found five 

 inches long. It is not uncommon in New Jersey, and 

 occurs also in the Ferruginous sand of Delaware and Ala- 

 bama. 



2. B. compressus, (Say,) pi. ix. fi^, 1. 



American Journal of Science, vol. ii, p. 41. 

 Specific character. " Elongated, much compressed ; trans- 

 verse section oblong-oval, narrowed to each end; lobes dilated, 

 dentated on their edges, with from three to five sutures on 

 each side, and a profound. one at tip." 



Mr. Nuttall informed Mr. Say that this fossil is of fre- 

 quent occurrence in the Missouri country, washed out 

 from the banks of the Missouri river, between White 

 river and the Mandan settlements. Mr. N. has seen 

 them more than a foot long, and three or four inches 

 broad at base. 



I regret that I have seen so few specimens of this fossil 

 as not to have satisfied myself that it is distinct from B. 

 ovatus. The name compressus given it by Mr. Say is 

 sufficiently descriptive, as will be seen by reference to the 

 accompanying figure, which was drawn from a specimen 

 lent me by J. P. Wetherill, Esq. 



3. B. asper, (S. G. M.) pi. i, fig. 12, 13, and pi. xiii, 

 fig. 2. 



Specific character. Transversely suboval, with prominent 

 circumscribed, lateral nodes, and numerous septa. 



