LAMELLIBEANCHIATA OF THE LOWER MARLS. 187 



general line of the hinge. Hinge slightly concave posterior to the beaks, 

 and the margin considerably thickened, as indicated by the form of the cast. 

 Anterior to the beaks the cardinal line declines at a low angle from the 

 direction of the posterior side. Basal line very strongly cm-ved ; exti-emi- 

 ties rounded, the anterior the most sharply so. Anterior muscular scar 

 moderately large, triangularly ovate, bordered by a rounded furrow on the 

 posterior side, indicating a slightly thickened rib on the interior of the shell. 

 Posterior scar larger, triangular, and faintly marked. Pallial sinus deep 

 and extending to near the middle of the shell's length. Hinge features un- 

 known. Indications exist on the cast of a divided tooth-like projection on 

 the left valve, with a socket-like plate on the right. 



The species appears to be a very rare one in the Cretaceous beds of 

 New Jersey, only one individual cast having been seen so far as I can learn. 

 Mr. Gabb originally descril^ed it as ' a species of CuUellus, but soon after 

 referred it to the genus Siliqua, under which most authors agi*ee in classing 

 it. Mr. Meek, in his list of New Jersey fossils, first referred it to the genus 

 Ospriasolen, a reference to or a description of which I have not been able 

 to find in any other work, and do not know what characters it includes, or 

 if he intended it for this individual shell. 



Formation and locality. — In the Lower Green Marls ("?) in Burlington 

 County, New Jersey. Collection of the Academy of Natural Sciences, 

 Philadelphia. 



PHOLADID^. 



Genus PHOLAS Linn. 



Pholas cithara. 



Plate XXV, Figs. 14-16. 



PhoJas cithara Morton. Synopsis, p. 68, PI. IX, Fig. 10. Gabb, Synopsis, p. 166. Meek, 



Check-list, p. 16. Geol. Surv. K J., 1868, p. 728. 

 P. pectorosa Conrad. J. A. N. Sci., new ser., Vol. II, p. 299, PI. XXVII, Fig. 9. 

 ClavijyJiolas cithara (Morton) Meek. Geol. Surv. X. J., 1868, p. 728. 

 Martesia cithara (Mort.) Gabb. P. A. X. Sci., Phil., 1876, p. 304. 



Shell triangularly ovate, acutely pointed behind and subtruncate in 

 front. Valves very ventricose, the depth and thickness when united about 



