48 PALEONTOLOGY OP NEW JEESEY. 



Cardinal slopes straight, more than one-third the length of the shell, and 

 the anterior longest. Left valve very depressed convex, most ventricose 

 above the middle; beak small and pointed. Auriculations large, the anterior 

 double the size of the posterior, very slightly rounded on the margin, and 

 perceptibly narrowing below; posterior shorter on the cardinal line than 

 below; anterior side marked by seven sharply-elevated nodose rays, and 

 the posterior by six, with one or two smaller ones between, near the body 

 of the shell. Body of the shell marked by about thirty to thiily-five slender, 

 rounded but unequal rays with much wider flattened interspaces, with an 

 occasional incipient ray on the outer third of the shell. Ribs marked by 

 distant, elevated or subspinose nodes, most closely arranged on the auricu- 

 lations and obsolete above the middle of the body of the valve. Right 

 valve with the ribs proportionally stronger in the sj^ecimens examined than 

 on the left valve and showing a stronger tendency to alternation of smaller 

 and larger ones than on the opposite, while the imbrications of the ribs are 

 not nearly so strong, not rising into spines, as on the left valve. Auricu- 

 lations of the right valve scarcely percejDtibly radiate, while the concentric 

 markings of the valve are more subdued throughout. 



So far as I have discovered the species was never figured by its author, 

 but its description is more full than usual, so I think the identification is less 

 likely to be questionable than in some other instances. It would seem to 

 be of the type of Pecfen Islandictis, although the ribs are less closely 

 arranged and the interspaces are flattened. Among the few specimens 

 which I have examined I have seen no reason to suppose the valves were 

 so sti'ongly bent as to leave them "about half an inch apart in the middle," 

 as the author states. 



Formation and locality. — In the Lower Green Marls at Holmdel, N. J , 

 collected at Gr. C Schanck's pits, near Marlborough, and pi-esented to the 

 New Jersey collection by the Reverend Dr. Riley. It also occurs at Bur- 

 lington, New Jersey. 



Pecten planicostatus, u. sp. 

 Plate VIII, Fig.s. 10 and 11. 



Shell of medium size, thin and flattened, equilateral, circular in outline, 

 or a little wider than high. Hinge line straight, about half as long as the 



