LAMELLIBEANCHIATA FROM THE EOCENE MARLS. 239 



cardinal line sloping from the beak nearly equally on each side, the margins 

 forming an angle of about one hundred and thirty degrees. Beak small, 

 but broad and compressed ; disk of the valve depressed, convex, or almost 

 flattened, as seen in casts. Hinge characters known only by the imprint 

 of a linear tooth on each side of the beak, situated about half way between 

 the beak aud the posterior end of the shell, on the posterior side, and still 

 further out proportionally on the anterior end. Muscular markings not 

 seen. Surface of the shell, as indicated on the cast, marked by faint eon- 

 centric lines of growth parallel to the margin. 



This species differs from either of those described from the Lower 

 Marls in its transverse and equilateral form. Its transverse or elliptical 

 character at once distinguishes it from V. lintea Con., and its equilateral form 

 from V. teUinoides, and the want of regular, even, concentric ridges on the 

 disk of the shell, and small beak, from V. transversa. So far as it is yet 

 known, it is a much smaller species than either of the last, but the examples 

 known may be small individuals. 



Formation and locality. — In the upper layers of the Upper Marls at 

 Shark River, New Jersey. 



CORBULIDiE. 



Geuus CORBULA Biug. 



Corbula (Neaera) nasutoides, u. sp. 



Plate XXX, Figs. 18 and 19. 



Shell of moderate size or larger, transversely ovate, inequivalve, an- 

 terior end longest and most inflated, and the left valve somewhat larger 

 than the right. Valves both rather ventricose, the left inflated on the ura- 

 bones. Beaks large, full, and strongly incurved, directed posteriorly in 

 appearance; that of the left valve more incurved than the right one. Pos- 

 terior end of the valves narrowed and rounded at the extremity, without 

 posterior umbonal angle or truncation of the extremity. Surface of the 

 valves marked only by concentric lines of growth. 



The species, as known from casts retaining part of the external features, 

 bears considerable resemblance to C. na.s'.(ta Conrad (— C. Alabamiensis Lea) 



