MOLLUSCA. 375 



■height, 7.5 mm.; convexity, 2 mm. Beaks rather prominent, 

 directed backward, situated about two^fifths the length of the 

 shell from the anterior end. Anterior portion of the shell in 

 front of the beaks, subsemielliptical in outline, somewhat in- 

 flated ; posterior portion compressed, rostrate, the postero-dorsal 

 margin concave, the posterior extremity sharply and narrowly 

 rounded, the postero-ventral margin gently convex. Hinge-line 

 elongate, the anterior row of teeth straight, about 12 in number; 

 posterior row slightly concave, with 16 or 18 teeth. vSurface of 

 the shell as shown in impressions of the exterior, marked by fine, 

 regular, concentric costas. 



Remarks. — This species was first identified as L. pinnaformis, 

 but a careful examination of the type of that species has led to 

 the conclusion that the two forms are distinct. Both are 

 similarly marked by fine, regular, concentric cost«, but L. marl- 

 boroensis is proportionally a much longer shell, with a more 

 elongate posterior extremity, which is alsO' more conspicuously 

 compressed. Certain examples of L. marlboro€ns-is^ especially 

 those which are incomplete at the posterior extremity, resemble 

 L. pinnaformis very closely, but every individual of the species 

 which is certainly complete posteriorly has the decidedly more 

 elongate form. From all other species besides L. pinnaformis 

 in the New Jersey faunas, L. marlboroensis may be distinguished 

 by its conspicuously inflated anterior portion and compressed 

 posterior region. 



Formation and locality. — ^Wenonah sand, Crawfords Corner 

 (126^), near Marlboro (130). 



Geographic distribution. — New Jersey. 



Leda protexta Gabb. 



Plate XXIX., Fig. 26. 



i860. Leda protexta Gabb, Jour. Acad. Nat. Sci. Phil., 2d ser., 

 vol. 4, p. 303, pi. 48, fig. 23. (Not Leda protexta Gabb, 

 Jour. Acad. Nat. Sci. Phil., 2d ser., vol. 4, p. 397, pi. 

 68, fig. 35-) 



1861. Leda protexta Gabb, S'ynop. Moll. Cret. Form., p. 189 



(133)- 



