LAMELLIBKANCDIATA OF ilJE LOWEU MAULS. 81 



hinge-line, instead of backward as is usual with nearly all shells. Hinge- 

 line shorter than the width of" the body of the shell and forming an angle 

 of about 1 10° to the axis of the valve. Left valve, the only one known, ex 

 tremely ventricose, with a rather small beak, ^\dlich is but little elevated 

 above the line of the hinge, and situated in advance of the anterior mar- 

 gin of the valve. Height of the valve a little greater than its extreme width 

 or length. Surface of the cast marked by numerous, regularly increasing 

 concentric irndulations, whicli are moderately sharp on the crests and the 

 interspaces broadly concave. There are also indications of radiating lines 

 along the middle of the valve, as in many species of the genus. 



The species difters from any hitherto described American species of 

 the genus, in having the axis of the shell directed forward of a right 

 angle to the hinge instead of Ijackward. In the general oiitline it some- 

 what resembles I. pcrplexus (Whitf., Pal. Black Hills of Dakota, p. 3j2, PI. 

 X, Figs. 4 and 5), but differs in the great convexity of the valve, greater 

 forward obliquity of the axis, and stronger as well as more regularly un- 

 dulated surface. It resembles in convexity and in the direction and posi- 

 tion of the beak /. cdtus Meek and Hayden (Invert. Pal. Territories, pi. xiv, 

 fig. 1), but differs entirely in the direction of the obliquity or of the axis of 

 the valves. 



Formation and locality. — In very dark friable, but coarse marl of the 

 Lower Beds, at Holmdel, New Jersey, from a collection by the Rev. Dr. 

 Riley. 



PINNIDtE. 



Genus PINNA Liun. 



Pinna laqueata. 



Plate XVI, Figs. 1 and 2. 



P. laqueata Conrad. J. A. N. Sci., 2d ser., Vol. Ill, p. 328. Gabb, Syu.,p. 166. Meek, 

 Check-li.st, p. 9. Geol. Siirv. N. .1., 1868, ]). 725. 



Shell of moderate size, very rapidly expanding from the apex and 



ventricose, giving a subquadrangular section. Surface marked by from 



nine to eleven strong, simple, radiating ribs on the dorsal portion, which 



are broad and rounded on the top and separated by very l)road concave 

 4418 MON fi 



