MOLLUSCA. -567 



Remarks. — This species has previously been recorded only 

 from the Woodbury clay, but in the recent collections of the Sur- 

 vey a sing-le incomplete impression of a specimen has been de- 

 tected in the Merchantville clay-marl. 



Formation and locality. — Merchantville clay-marl, Lenola 

 (163); Woodbury clay, Haddonfield (183). 



Geographic distribution. — New Jersey, Mississippi. 



Super-family CHAMACEA. 



Family DIOBRATIDAE. 



Genus Diceras Lamark. 



Diceras dactyloides Whitfield. 

 Plate I.XII., Figs. 11-12. 



1886. Diceras dactyloides Whitf., Pal. N. J., vol. i (Monog. 

 U. S'. G. S., vol. 9), p. 131, pi. 18, figs. 26-27. 



Description. — "A cast of a single valve of v^^hat appears tO' be 

 without question a Diceras occurs in the collection. It is rather 

 slender in its proportions, and makes nearly two-thirds of a volu- 

 tion in its curvature, and is apparently a cast of a left valve, 

 judging from the curvature of the beak. The muscular scar is 

 very large, and has been deeply impressed in the shell, as the scar 

 is considerably raised on the cast and is nearly half as long as the 

 cast itself. On its front margin there is the filling of a deep 

 groove, which is longitudinally marked with lamellose striae, 

 from' the edges of the shell lamellae; and on tlie opposite side of 

 the cast occurs a flattened surface from the thickening of the shell 

 below the hinge-tooth, probably. 



The striations on the filling of the groove bordering the mus- 

 cular imprint would lead one to suspect the cast might be of a 

 valve of Caprina., but their lamellose character somewhat denies 

 this reference, and the general character of the specimen would 

 rather indicate a Diceras. The specimen is quite obscure, besides 

 being the only one known, and consequently affords almost no 

 means of comparison with previously described species. It, how- 



