LAMELLIBEANCHIATA OF THE LOWEE MAELS. 149 



diflfers materially in its surface character from those of that species, as 

 identified by various authors, from other and more southern localities, but 

 not from Dr. Morton's figured specimen, which was from Arneytown, N. J., 

 but which shows the concentric sulci much less strongly developed than 

 those to which I refer. I am much inclined to think they are all of one 

 species, however, and that this one and V. inflata are merely dwarfed indi- 

 viduals. In some of the New Jersey examples, which are internal casts, the 

 sulci of the surface are preseved to their fullest extent, while on other casts 

 they are entirely obliterated. This seems to have arisen from different 

 conditions of preservation, and fi-om a difi'erence in the material of the 

 filling and matrix. 



Formation and locality. — In the micaceous clays below the Lower Marls 

 at Haddonfield, New Jersey. From the collection of the Academy of Natu- 

 ral Sciences at Philadelphia. 



Veniella trigona. 



Plate XIX, Figs. 11-14. 



Venilia trigona Gabb. P. A. N. Sci., Phil., 1861, p. 324. Synopsis, Meek, Check-list, 

 p. 13. Geol. Surv. N. J., 1868, p. 726. 



The type specimen of this species, an internal cast, represents an 

 extremely ventricose shell of a trapezoidal or subtriangular outline pro- 

 foundly angular on the umbonal ridge, and with large, prominent, incurved 

 and rather distant beaks. Posterior end narrow and nearljr at right angles 

 with the posterior third of the basal line. The latter border of the shell is 

 strongly rounded upwards on the interior half and merges gradualh^ into 

 the anterior margin. Hinge-line sharply bent beneath the beaks, and the 

 hinge appears to have been characterized by strong teeth on the anterior of 

 the plate. Cardinal slope very abrupt and nearly vertical, giving a nearly 

 flattened postero-cardinal surface to the cast extending to the umbonal angles 

 above the position of the muscular scars. Muscular scars very strong and 

 prominent on the cast, the posterior ones large, and on the type are followed 

 by a ridge for some distance toward the beaks. A second cast shows a some- 



