8fi PALEONTOLOGY OF NEW JERSEY. 



posterior end parallel to the margin, and three slightly curved ones on the 

 anterior end also nearlj- parallel to the margin. Area, longitudinall}' striate. 



This shell differs from Area (Nemodoii) Eufaulcnsis Gabb in being more 

 inequilateral, more pointed and prolonged behind, more ventricose, less 

 sinuate in the middle, and in the character of the radiating lines of the 

 surface. 



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

 at Haddonfield, New Jerse}'. There may be some question as to the 

 locality of this shell, as the locality is not marked on the label It was 

 found among Haddonfield specimens in the collection of the Academy of 

 Natural Sciences of Philadelphia, and is supposed to have come from 

 that place. Still it is somewhat questionable. 



Genus NEMOAKGA CoDrad, 1870. 

 (Am. Jour. Conch., vol. v, p. 97 (name only). 



Nemoarca cretacea. 



Plate XII, Figs. 8-in. 

 Nemoarca cretacea Conrad. Am. Jour. Conch., Vol. V, p. 97, PI. IX, Fig. 21, 1870. 



Shell small, seldom attaining more than half an inch in extreme length, 

 trapezoidal in form, the transverse diameter being nearly once and a half 

 the height. Valves very ventricose, with large, strongl}^ inflated, prominent 

 beaks, situated nearly opposite the middle of the length. Hinge-line straight 

 and low; area naiTOw, the length a little less than the greatest length of the 

 body of the shell. Hing-e-plate narrow, marked by about twelve short, 

 oblique teeth which diverge from the center on each side, and two or 

 three transverse teeth nearly parallel to the hinge line at the posterior end. 

 Muscular imprints too faint to be observed on well-preserved casts of the 

 interior. No internal rib boi'dering the posterior scar. Surface marked l)y 

 from four to six fine radiating ribs on the posterior slope, and twenty-four to 

 twenty-six on the body of the shell and anterior end. Strongest on the 

 posterior part of the body of the shell and gradually decrea.sing in size 

 anteriorly. On some individuals one or more of the ribs on the posterior 

 slope appear to be divided, while all are strongly elevated and rather sharp 

 with narrow interspaces. On the matrix there are remains of distinct elevated 

 concentric lines at regular distances crossing the radiatinsr ril)s. 



