LAMELLIBEANCHIATA FROM THE EOCENE" MARLS. 241 



He also describes his shell as inequivalve, while this one is not perceptilil}' 

 inequivalve, except foi' the overlapping of the beaks, which is so slight, and 

 only at the extreme point, that there is really no difference in size. The 

 posterior prolongation, moreover, is equally large on each valve, which it 

 would not be in Corhula. Most of the species of Necera are radiatingly 

 ribbed, but there are species known which are smooth, such as N. hya/liia 

 Hinds ; figured in Chenu's Manuel Conch, et de Pal. Conch., Vol. H, p. 50, 

 Fig. 210. Mr. Conrad's species is fi'om the Cretaceous, while this is from 

 the beds referred to the Eocene. Mr. Meek figures a somewhat similar 

 species, N. ventricosa, from the Fox Hills group of Dakota, in the Report of 

 the U. S. Geological Survey of the Territories (Hayden), Vol. IX ; Report 

 on Invertebrate Fossils (Meek), PI. XXX, Fig. 3, but in that one the beaks 

 are erect, while these have a strong backward direction when taken in a lat- 

 eral view of the shell. 



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

 River, New Jersey. In the collection of the American Museum of Natural 

 History, New York City. (Eocene.) 



PHOLADID^. 



Genus PARAPHOLAS Courad. 1848. 



(Proc. A. N. Sci., Phil., 1848, p. 121.) 



Parapholas Kneiskerui, u. sp. 



Plate XXX, Figs. 22-24. 



An internal cast of both valves in conjunction represents a shell of an 

 elongate-ovate or elongate-pyriform shape, measuring seven-eighths of an 

 inch in length by half an inch in diameter at the larger end ; is all that 

 represents this species among the collections from the State. The anterior 

 end is globose to the oblique mesial division, behind which it is rapidly 

 narrowed to less than one-fourth of an inch at the posterior extremity, 

 which appears to have been widely gaping. The mesial constriction is 

 deep and very oblique, reaching the basa^' margin somewhat behind the 

 middle of the entire length. Posterior area of the valves concentrically 

 marked; anterior section of the valve triangular and rather small, with 

 faint indications of a few radii ; antero-basal pads large and broad, extend- 

 4418 MON 9 16 



