MOLLUSC A. 511 



in the Red Bank sand. Near Swedesboro, in the first of these 

 formations, the specimens are rather common and occur with 

 the shell perfectly preserved. In this condition the shell is cov- 

 ered externally with a brownish epidermal layer which is easily 

 exfoliated. Upon the exfoliated shells the radiating markings 

 are much more conspicuous than upon the epidermal surface. 

 The Red Bank specimens have only been recognized from the 

 impressions of the external surface of the shells. 



Formation and locality. Marshalltown clay-marl, near 

 Swedesboro (177) ; Red Bank sand, Red Bank (116), near Mid- 

 dletown (112). 



Geographic distribution. New Jersey, Alabama, Mississippi, 

 Texas. 



Crenella elegantula Meek & Hayden. 

 Plate LVL, Pig. 6. 



1861. Crenella elegantula M. & H., Proc. Acad. Nat. Sci. Phil., 



1861., p. 441. 

 1864. Crenella elegantula Meek, Check List Inv. Foss. N. A., 



Cret and Jur., p. n. 

 1876. Crenella elegantula Meek, Rep. Inv. Cret. and Ter. Foss. 



Up. Mo., p. 75, pi. 28, figs. 6 a-c. 



Description. Shell obliquely subovate in outline; the dimen- 

 sions of a perfect cast of a left valve are: height, 10.5 mm.; 

 width, 8.5 mm.; convexity, 5 mm. Valves ventricose, umbo 

 prominent, beak nearly terminal, small and strongly incurved. 

 Surface marked by exceedingly fine radiating costse which can 

 be seen upon the internal cast, indicating that the shell substance 

 was very thin. 



Remarks. This species differs from C. serica in its much 

 larger size, its proportionally broader form, and in the absence 

 of the conspicuous concentric markings of the shell. The New 

 Jersey examples are apparently identical with the western speci- 

 mens from which the species was described, and the same form 

 occurs in the southern Ripley beds. 



