23 
CRASSATELLA UNDULATA. Tab. 9, fig. 1. 
Oblong subovate, much compressed, with coarse concentric 
Hines; umbo flattened, and with regular concentric grooves; 
apex subacute; inner margin entire. 
Syn. Crassatella undulata, Say. Journ . A. N. S. v . 4 ,pL xi$ 
fig • 2 - 
Localities. James River, near Smithfield, Va.; abundant; 
York-town, Ya. Upper Tertiary. 
Variety, A. Thick and ponderous; not much compressed. 
A specimen in the collection of the Academy is marked St. 
Mary’s county, Md. 
Young shells of this species closely resemble C. compressa 
©f Lamarck, as figured in Deshayes’ Coq. Fos. des env. de Par . 
CRASSATELLA MELINA. Tab. 9, fig. 2. 
Ovate, thick, not compressed ; anterior margin obtusely 
rounded; posterior margin oblique and angular; dorsal margin 
nearly straight; concentric lines coarse; umbonial slope suban- 
gular and scarcely curved; beaks with concentric grooves; in- 
ner margin entire. 
Locality . Cumberland Co. N. J. Upper Tertiary. 
This shell is intermediate to C. undulata and Marylandica , 
but is perfectly distinct from both. It occurs abundantly in 
the tertiary marl, accompanied by Perna maxillaia and several 
new and interesting species. The existence of this formation 
in New Jersey was first ascertained by means of some fossils 
brought very lately from Stow creek, by Mr. Samuel Griscom, 
who has since accompanied me to the spot. We traced it several 
miles north of Stow creek, and in one instance found its surface 
composed of a bed of the Ostrea virginiana or common oyster, 
erroneously supposed to have been deposited by the Indians, 
These beds occur in the same manner at Easton, Md. and 
except in the Crag on the Potomac, always present fragments 
of Pecten madisonius , and other extinct species. There can 
be little doubt that all those beds of oyster shells beneath ths 
