MOLLUSCA. 627 



row impressed line seems to have been formed by a fold of the 

 shell from its inner surface. Surface of the cast marked by 

 more or less irregular, concentric lines of growth. 



Remarks. This species is established upon an internal cast 

 which resembles the casts of Leptosolen biplicata in the presence 

 of the strong furrow extending towards the ventral margin from 

 beneath the beak, but it differs in several fundamental respects 

 from that species, and the two can hardly be cogeneric. In L. 

 biplicata the shell is gaping at both ends, while in this one it is 

 apparently closed ; the beak in this shell is situated at the anterior 

 extremity of the hinge-line, the furrow is very near the anterior 

 margin of the shell instead of about one-fourth of the length 

 back, and it has a distinct backward turn near the margin. The 

 shape of the two shells is also different, the dorsal and ventral 

 margins of L. ? terminalis diverging posteriorly. 



There seems to be no genus in which this shell can be properly 

 placed, and eventually it will probably be necessary to construct 

 .a new one for its reception. 



Formation and locality. Mierchantville clay-marl, near James- 

 burg (139)- 



Geographic distribution. New Jersey. 



Leptosolen ? elongata n. sp. 

 Plate LXX., Figs. 27-28. 



Description. The dimensions of the type specimen, a cast of 

 a left valve, are: length, 24 mm.; height, 8 mm.; convexity, 

 2.5 mm. Shell elongate, .dorsal and ventral margins subparallel; 

 anterior margin rounded, its greatest extension above the mid- 

 height ; posterior margin probably rounded or truncate, not com- 

 pletely preserved. Beaks small, terminal, but little elevated above 

 the hinge-line. Valves closed in front, apparently gaping behind ; 

 the surface regularly convex from the dorsal to the ventral mar- 

 gin, curving a little more abruptly above and inflected to the 

 hinge-line in the anterior half of the shell; curving abruptly to 

 the anterior margin in front. In the cast a strong, deep, sharply 

 defined furrow extends downward from the beak towards the 

 ventral margin, and a little obliquely backward, curving a little 



