MOLLUSCA. 377 



to have considered Perrisonota protexta Con. as a synonym of 

 Leda protexta Gabb, but they are certainly distinct species, al- 

 though there is some doubt as to the wisdom of making any 

 generic distinction between them. 



Formation and locality. Navesink marl, Crosswicks Creek 

 and Mullica Hill (Coll. Phil. Acad. Nat. Sci.). 



Geographic distribution. New Jersey. 



Leda cliffwoodensis n. sp. 

 Plate XXIX., Figs. 24-25. 



Description. Shell elongate, the dimensions of a nearly per- 

 fect internal cast being: length, 21.5 mm. ; height, 9 mm. ; thick- 

 ness, 3.5 mm. The beaks moderately pointed and directed back- 

 ward, situated about four-tenths of the length of the shell from 

 the anterior extremity. Anterior portion of the shell in front 

 of the beaks, subsemielliptical in outline, postero-dorsal margin 

 concave, posterior extremity subtruncate, 'rounding rather ab- 

 ruptly below into the gently convex postero-ventral margin. 

 Hinge very long, the anterior portion nearly straight, with about 

 20 teeth, the posterior portion concave, with 30 or more teeth, 

 the teeth of each series diminishing in size regularly as they 

 approach the beaks, the two series meeting beneath the beaks in 

 a very broadly obtuse angle. Surface of the shell, as indicated 

 by external impressions, smooth. 



Remarks. This species is a common one in the Cliffwood 

 clays. It is an elongate form of rather large size, somewhat 

 similar in general outline to L. protexta, but it may always be 

 distinguished from that species by reason of its much more com- 

 pressed form. The species, perhaps, most closely resembles 

 Perrisonota protexta, but it differs from that form in the much 

 more posterior position of the beaks. 



Formation and locality. Cliffwood clay, Cliffwood Point 

 (105, 185), near Matawan (186, 107, 189). 



Geographic distribution. New Jersey. 



