Descriptions of some Shells, &§c. 349 
ly crenulated in some adult specimens—in the younger, perfectly 
smooth. Of large specimens, length, 0.90 of an inch. 
Height, 1.00 do. 
Thickness, 0.50 do. 
The proportions vary ; but of more than twenty individuals, that 
which had least proportionate altitude, (Fig. 2, ¢.) had less length 
than height. 
Found on the beach of Provincetown harbor, (Mass.) in compa- 
ny with A. Castanea of Say. 
As the propriety of separating this shell from Mr. Say’s, A. Casta- 
nea may be doubted, I now give it asa variety. In the form and 
arrangement of the teeth, it certainly differs but little, if at all: still, 
from a comparison of many specimens, it is believed that it will al- 
ways be distinguished, by the lighter color of its epidermis, by its 
outline, and other less marked differences. The principal figures in 
the plates (a, 6, c, d,) represent a shell with rather more than the 
average elevation, but not so much as other individuals in my pos- 
session, see f. Should this prove to be a different species, it may 
have the name of A. procera. 
A. Danmoniensis, Sow. and others. Fig. 3, a, b, c, d. 
~ Venus Danmoniensis, Montague, Dill, &c. 
V. Crassatella, Blain. 
Crassina Danmoniensis, Lam. 
I give figures, that a comparison may be made between the Euro- 
pean and American shells of this species. 
As the crenulation of the inner margin is often made a specific 
characteristic, it may be interesting to notice that, in this species, as 
in the preceding, our young, and half grown, shells, have their mar- 
gins perfectly smooth. The epidermis is very adherent, beautifully 
glossy, and varying in color, from light greenish-yellow, through 
yellowish-brown, to dark chesnut-brown. 
Inbabits gravelly bottom, Newport harbor, (R. I.) obtained by 
the dredge from deep water. 
Comparing this shell with the figures and descriptions of the books 
and with a European specimen in the cabinet of Lt. Harwood, I 
Was at once convinced that it was A. Danmoniensis, but supposed it 
was now first found on the coast of the United States; Mr. Conrad, 
however, informs me that a valve from the Eastern coast, always 
considered the same as the British species, has been many years in 
Mr. Hyde’s cabinet. 
