MOLLUSCA. 777 



the species. The two species differ in the number of columellar 

 folds, V. gabbi having only one, while V. ovata has two. 



Formation and locality. Navesink marl, Atlantic Highlands 

 (108), Crosswicks Creek (195), Mullica Hill (Whitfield). 



Geographic distribution. New Jersey. 



Volutoderma jamesburgensis n. sp. 

 Plate XCL, Figs. 22-23. 



Description. Shell of medium size, the dimensions of the 

 type specimen being: height, 30 mm.; maximum diameter, 17 

 mm. Volutions about four in number, the spire of moderate 

 height, apical angle about 58. Suture well defined; just below 

 the suture is a rounded ridge marked by conspicuous oblique 

 costse about one millimeter apart on the outer volution; just 

 below this ridge is a narrow, concave band, outside of which, 

 upon the shoulder of the volution, is a series of strong rounded 

 nodes about three mm. apart from center to center on the outer 

 volution, which continue longitudinally as strong, rounded 

 ribs to the anterior extremity of the shell. Surface also marked 

 by fine, vertical lines of growth ; revolving lines entirely absent. 

 The internal cast is similar in general form, the suture is well 

 defined, the volutions are flattened above, or even slightly concave, 

 towards the aperture, sloping downward to the line of maximum 

 diameter beneath the row of strong nodes on the exterior, below 

 which the sides are nearly vertical to the suture below, or in the 

 body volution becoming concave towards the anterior extremity. 

 The vertical ribs are shown on the internal casts, but are much 

 weaker than upon the exterior of the shell. 



Remarks. This species is based upon a natural mould of 

 the exterior of the shell with the internal cast of the same indi- 

 vidual. It is one of the few individuals of this genus from 

 the Cretaceous formations of New Jersey whose external char- 

 acters are known to any considerable degree. 



Formation and locality. Merchantville clay-marl, near 

 Jamesburg (140). 



Geographic distribution. New Jersey. 



