MOLLUSCA. 625 



1861. Siliquaria biplicata Gabb, Synop. Moll. Cret. Form., p. 



226 (170'). 

 1864. Siliquaria biplicata Meek, Check List Inv. Foss. N. A. r 



Cret. and Jur., p. 15. 



1867. Leptosolen biplicata Con., Am. Jour. Conch., vol. 3, pp. 



15 and 1 88. 



1868. Leptosolen biplicata Con., Cook's Geol. N. J., p. 727. 

 1876. Leptosolen biplicata Gabb, Proc. Acad. Nat Sci. PhiL 



(1876), p. 304. 

 1886. Leptosolen biplicata Whitf., Pal. N. J., vol. i (Monog. 



U. S. G. S., vol. 9), p. 183, pi. 25, figs. 1-2. 

 1905. Leptosolen biplicata Johns., Proc. Acad. Nat. Sci. Phil. 



(1905), p. 17. 



Description. The dimensions of an average specimen are: 

 length, 35 mm.; height, n mm.; convexity, 3 mm. The largest 

 example observed is" nearly 60 mm. in length. Shell elongate, 

 with straight, subparallel dorsal and ventral margins, the anterior 

 and posterior margins rounded, the anterior usually a little more 

 sharply rounded than the posterior, the greatest anterior exten- 

 sion at or above the mid-height of the shell. Gaping at both ends, 

 more widely so posteriorly. Beaks small, scarcely elevated above 

 the hinge-line, situated a little more than one-fourth the length 

 of the shell from the anterior extremity. Valves nearly regularly 

 convex from the dorsal to the ventral margin, the slope to the 

 cardinal margin usually a little more abrupt ; the anterior extrem- 

 ity of the shell compressed, with two obscure, sometimes obsolete 

 plications extending obliquely forward and downward from the 

 beak. In the casts a strong furrow passes from the beak down- 

 ward towards the ventral margin, with a slight posterior ob- 

 liquity, growing shallower below and becoming obsolete at a point 

 about three-fourths the height of the shell from the dorsal mar- 

 gin. Surface of the casts marked by more or less inconspicuous 

 concentric lines of growth. 



Remarks. This is a strongly marked species which cannot, be 

 mistaken for any other in the New Jersey Cretaceous faunas. 

 The strong furrow extending downward from the beak in the 

 casts represents a thickened rib upon the inner surface of the 



4O PAIy 



