MIOCENE MOLLUSCA AND CRUSTACEA. 31 
the ribs and on their sides. This feature becomes very conspicuous on the 
larger specimens. Besides this, the lower valve is much more depressed 
or flattened than the upper. The number of ribs on the more convex valve 
o considerable variation. 
is sometimes seventeen or even eighteen, showing 
I have not seen any very large individuals from the New Jersey localities, 
and few of more than 14 inches in diameter. Some of the casts from ‘the 
brown clays, however, indicate shells much larger than this, and some 
fragments of valves from near Shiloh, in the collection at Rutgers College, 
indicate shells of fully 4 inches in width, but no specimens showing more 
than one-sixth part of the entire valve have been collected. 
The species bears some resemblance to Pecten Jeffersonius Say, but is 
very readily distinguished by the more numerous and smaller ribs and by 
their squamose, almost spinose striz. 
Formation and localities: The New Jersey examples, all quite frag- 
mentary except the very young individuals, are from the gray Miocene 
marls near Shiloh and Jericho, and as casts from the brown marly clays 
near the same places in New Jersey. The species is quite common and of 
larger size in the Miocene at Yorktown, Petersburg and vicinity, in Vir- 
ginia; it also occurs in South Carolina. 
PECTEN VICENARIUS? 
Not figured. 
Pecten vicenarius Conrad: Proc. Acad. Nat. Sci. Phil., vol. 1, Ist series, p. 306; op. 
cit. 1862, p. 582; Meek, Check List Mioc. Foss., p. 4. 
Pecten vicenarius Cou: Heilprin, Proc. Acad. Nat. Sci. Phil., 1887, pp. 400 and 402, 
‘Suborbicular, mequivalve, the upper valve ventricose, the inferior 
plano-convex; ribs about twenty, somewhat flattened on the back; ribs of 
the superior valve narrow and more distant than those of the inferior valve; 
surface of both with crowded, regular concentric wrinkles; ears equal, mod- 
erate in size, sinus of inferior valve not profound.” (Conrad.) 
A number of small fragments of a pectenoid shell of small size, which 
were obtained from the well boring at Mr. L. Woolman’s, at Atlantic City, 
form the basis for the citation of the above species as a probable New 
Jersey shell, I should consider the fragments as pertaining to two distinct 
