MIOCEKE MOLLUSCA AND CKUSTACEA. 37 



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 

 imperfect both on the inside and outside. In fact, I 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 from 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 MYTILID^. 

 Genus MYTILOCONCHA Conrad. 



Mytiloconcha Conrad : Proc. Acad. Nat. Sciences, Philadelphia, 1862, p. 290. 

 Mytiloconcha (Conrad) Tryon: Structural and Systematic Conch., vol. 3, p. 262. 



"Subfalcate, 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 



