MIOCENE MOLLUSCA AND CRUSTACEA. ot 
est individual I have seen from New Jersey is a fragment showing the area 
and byssal border, with a small part of the body of the shell, and appears 
to have been about the size of Conrad’s figure. The specimens are all so 
fragile that the different layers shell out one from the other, so that it is 
very difficult to handle them, and the one above mentioned is evidently 
impertect both on the inside and outside. In fact, | have never seen the 
external portions of one, other than that of the area and the byssal margin. 
The shell is sometimes fully an inch in thickness even in this imperfect con- 
dition. In the number of ligamental grooves the shells vary, of course, 
with the age; while the grooves also vary in size, depth, and shape. In 
other respects the species appears to be very constant in its characters. 
Localities: From New Jersey I have received specimens from Shiloh 
and Jericho, in Cumberland County. They represent the gray marls, and 
the marly limestones, and are seen as casts in the brown clays. Specimens 
are present trom both the collections at Rutger’s College and that of the 
U.S. National Museum. Mr. Conrad says, in his remarks on the species, 
that the European species figured by Goldfuss is certainly identical with 
the American specimens, while Deshayes thought those from Italy, which are 
certainly closely allied, represented a distinct species, and gave it the specific 
name Soldani. ‘The species is a very abundant form in the limestone, and 
also in the gray marls, at Jericho, N. J., and Mr. Conrad states that it is 
“vastly abundant in the blue clay” in Maryland. 
Family MYTILIDZE. 
Genus MYTILOCONCHA Conrad. - 
Mytiloconcha Conrad: Proc. Acad. Nat. Sciences, Philadelphia, 1862, }. 290. 
Mytiloconcha (Conrad) Tryon: Structural and Systematic Conch., vol. 3, p. 262. 
“Subfaleate, thick; perlaceous, laminated; hinge thick, elongated; 
pointed at the apex; an oblique tooth or ridge and parallel furrow through- 
out the entire length of the hinge area.” (Conrad.) 
Mr. Conrad proposed this genus for two species of mytiloid shells 
which are peculiar to the Atlantic coast Miocene, one of which has a broad 
