MO'LLUSCA. 523 



Description. — "Shell small, inequivalve, and very inequilateral, 

 subovate in outline, largest across the anterior side of the beaks, 

 and strongly constricted just behind them, the posterior end 

 being narrowed on the hinge-line and excavated at this point. 

 Valves somewhat ventricose, the right one less convex than the 

 left, and very decidedly depressed in the central region and 

 toward the basal line, showing a decided twist or arcuation of 

 the valves as seen in a basal view. Anterior end broadly 

 rounded, and the posterior pointedly rounded. Beaks small, 

 appressed, incurved, and apparently directed backward, as is 

 usual in this group oif shells, from the expansion or inflation 

 of the anterior side of the hinge line. Cardinal margin, as seen 

 on the cast, inflected both in front and behind the beaks, form- 

 ing an apparent lunule and escutcheon on the cast, probably pro- 

 duced mainly from a thickening of the hinge-plate within. Mus- 

 cular imprints and pallial line and hinge not observed." (Whit- 

 field.) 



The dimensions O'f the specimen illustrated by Whitfield are : 

 length, 31 mm.; height, 27.5 mm.; thickness, 10 mm. 



Remarks. — Whitfield records the specimen he has identified as 

 P. elliptica, from the "Lower Green Marls at Mullica Hill and 

 Holmdel" and the specimen which he has figured seems to have 

 the lithologic features of the Navesink marl, although this can- 

 not be asserted certainly because no locality is recorded with the 

 species, and it might possibly be from the Manasquan marl. The 

 type of the species, preserved in the collection of the Philadel- 

 phia Academy of Science is apparently from the Manasquan 

 marl, judging from its lithologic characters. The types of the 

 two species described by Whitfield as P. trimcata and Veleda 

 nasuta are both from the Manasquan, and both are clearly iden- 

 tical with the type of P. elliptica. 



The species has not been met with in the recent collections of 

 the Survey, and until authentic specimens are found elsewhere, 

 the species, may be considered as restricted in its range to the 

 Manasquan. 



Formation and locality. — Manasquan marl, near Mullica Hill ? 

 and near New Egypt (Whitfield). 



Geographic distribution. — New Jersey. 



