84 PALEONTOLOGY OF :N^EW JEESEY. 



liquely and rapidly receding from the extremity of the hinge and most 

 rapidly on the lower half; posterior end obliquely truncate, prolonged 

 backward below to the umbonal angle. Valves moderately ventrieose, 

 with a decidedly angular umbonal ridge behind, and a shallow mesial de- 

 pression extending from the beaks to the basal border, slightlj' affecting 

 the basal line near the middle of its length. Beaks large and rather prom- 

 inent, situated at about the anterior third of the length. Area moderate. 

 Surface marked by numerous fine radiating striae showing upon the cast, 

 which are a little coarser near the posterior angle and on the cardinal 

 slope, possibly somewhat alternating in size on the anterior end, but in- 

 distinctly showing this feature on the internal cast. Hinge-line marked 

 by two distinct linear teeth on the anterior end parallel to the hinge. 

 Those of the rest of the hinge have not been observed. 



This species differs from A. (Cibota) mtiUiradiata Gabb, in being much 

 longer in proportion to its height, as w^ell as in its generic features, which 

 are not always easily recognized in the casts; 



Formation and locality. — In the Lower Green Marls at Holmdel, N. J., 

 Mr. Conrad's specimen, which appears to have been the foundation of the 

 genus Nemodon, was from Haddonfield, New Jersey. 



Nemodon augulattim. 

 Plate XII, Figs. 6 and 7. 



Leda angulata Gabb. Proc. Acad. Nat. Sci. Phil., 1860, p. 94, PI. II, Fig. 12. (Kot 



D'Orb.) 

 L. subangulata Gabb. Synopsis, p. 133. 

 Kuculana subangulata (Gabb). Meek, Check-list, p. 8. 

 N, angulata (Gabb). Meek, Geol. Surv. N. J., 1868, p. 725. 



Nemodon angulatum Gabb. Proc. A. K. Sci. Phil., 1876. p. 316. 

 Compare Trigonarca passa Conrad. Am. Jour. Conch., Vol. V, p. 43, PI. I, Fig. 17. 



The only specimen of this species which I have seen from New Jersey 

 is an internal cast, which I take to be that figured by Mr. Gabb, as above 

 cited, a copy of which figure is given on our plate. It is about twice as 

 long as high, with rather prominent beaks situated at considerable distance 

 from the anterior end, and with a prominent and angular umbonal ridge. 

 The disk of the valve is broadly sinuate, giving a rather emarginate or con- 



