198 PALEONTOLOGY OF NEW JEESEY. 



strong concentric markings so prominent on that one, and is also more 

 attenuated behind. There are some features about the shell in its general 

 expression which are almost indescribable, but which give it more the ap- 

 pearance of a species of Lithophagus than that of a true Modiola, and leave 

 an uncertainty about its true generic relations, the specimens being only 

 casts. 



Formation and locality, — From Mr. Ware's pits, near MuUica Hill, New 

 Jersey. In the Middle Marls. 



PTERIID^ Meek. 



Genus PINNA Linn. 



Pinna rostriformis. 

 Plate XVI, Figs. 3 and 4. 



Pinna rostriformis Morton. Jour. Acad. Nat. Sol. Phil., 1st ser., Vol. YIII, p. 214, PI, 

 X, Fig. 5. Gabb, Syn., p. 166. Meek, Check-list, p. 9. Geol. Surv. New Jer- 

 sey, 1868, p. 725. 



P. Morton. Synopsis, p. 63. 



Shell below a medium size, elongate-triangular in form, with a some- 

 what attenuated, nearly pointed beak; hinge-line straight and extending 

 nearly the length of the shell; basal margin broadly sinuate along the ros- 

 tral third of its length, and gently convex beyond that line ; posterior mar- 

 gin rounded below and gradually receding above to the extremity of the 

 hinge. Valves very ventricose, subangular along the middle, marked by 

 moderately prominent radii on the upper two-thirds of the surface, and by 

 strong concentric undulations parallel to the lines of growth, becoming 

 quite strong on the basal unradiated area. 



All the specimens which I have seen of this species have been imper- 

 fect, and all with the external prismatic layers of the shell exfoliated, so 

 that the absolute surface markings have not been observed. The species 

 bears a very strong resemblance to P. laqueatd Conrad, but is more slender 

 toward the apex, giving a decided sinuosity to the basal line along the ros- 

 tral portion of the valves. 



Formation and locality. — In the Middle Marl Beds, at Timber Creek, 

 New Jersey. 



