MOLLUSCA. 423 



of them have been secured in the recent collections of the Sur- 

 vey. The locality from which it is believed that these specimens 

 were collected, is in the Marshalltown clay-marl and is no longer 

 accessible. 



More or less imperfect specimens of the internal casts of a 

 member of this genus, occur rarely in the Merchant ville and 

 Navesink formations, and more commonly in the Red Bank. 

 These specimens are difficult to determine with entire satis- 

 faction, and it is possible that they should be referred to G. 

 minima Whitf. In size they have not been observed to attain 

 the large dimensions of the complete specimen of G. ensiformis 

 illustrated by Whitfield, the maximum length probably being 70 

 mm. to 80 mm. G. minima was established upon a single indi- 

 vidual about 26 mm. in length, said to differ from G. ensiformis 

 in being much more ventricose, and since none of these casts re- 

 ferred to seem to possess this strong ventricosity, they have all 

 been referred to G. ensiformis. It is altogether possible that the 

 type of G. minima is only a variation of the more common form. 



Formation and locality. Merchantville clay-marl, Lenola 

 (163) ; Woodbury clay, near Haddonfield (183) ; Marshalltown 

 clay-marl, near Woodbury (Whitfield); Wenonah sand, near 

 Marlboro (130); Navesink marl, Atlantic Highlands (io8) r 

 Mullica Hill (1692), near Freehold (133) ; Red Bank sand, Red 

 Bank (116). 



Geographic distribution,. New Jersey, Alabama, Mississippi. 



Gervilliopsis minima Whitfield. 



1886. Gervilliopsis minima Whitf., Pal. N. J., vol. i (Monog. 

 U. S. G. $., vol. 9), p. 74, pi. 15, fig. 7. 



Description. "Shell small, the only specimen observed, a cast, 

 measuring only a trifle over one inch in length, and less than 

 three-eighths of an inch in its greatest width. Shell elongate- 

 elliptical, extremely oblique, slightly curved, and the valves very 

 ventricose. The beaks, as shown on the cast, have been pointed, 

 the area wide, and the anterior hiatus has been proportionally 

 large and distinct. The muscular scars are very distinct and well 

 marked." (Whitfield). 



