GASTEROPODA OP THE LOWER GREEN MARLS. 85 



V. Conradi, and its relations are certainly much nearer to V. Bradliana, 

 which Paetel classes under Cynibiola Swainson. 



Formation and locality : This species, so far as yet known, has not been 

 found within the limits of New Jersey, but as it is found just across the 

 line, in Delaware, it is probable that it will yet be noticed. Its position 

 would be in the Lower Marls. The types are in the collection Acad. Nat. 

 Sci., Phila., and are from the Delaware and Chesapeake Canal. 



Genus ROSTELLITES Conrad 1855, and VOLUTOMORPHA Gabb, 1876. 



The differences between these two genera, Bostellites and Volutomorpha, 

 are siich that among- specimens badly preserved, as are nearly all the Gas- 

 teropods of the New Jersey Cretaceous, it is almost if not quite impossible 

 to distinguish, or to draw the line of division between them, even where 

 the characters can be partially detected. The shells have the same general 

 form, and the same surface structure pertains to both; while as to the mat- 

 ter of columellar folds, the only character mentioned as distinctive by Mr. 

 Gabb under his original generic description, I find perfectl)'' unreliable. It 

 would also appear that Mr. Gabb himself found this to be the case before 

 he had finished writing the generic description, as he remarks that it (^Volu- 

 tomorpha) "differs from them all IVoliUodema and Fulgoraria'] in having 

 essentially a single large oblique fold. When more than one occurs, the 

 secondary folds are smaller than the large primary." So it appears 

 there may be as many as three folds, if only one is larger than the rest, 

 which is nearly always the case when there are two or more, in all Volutes. 

 If the single fold is all the difference there is, and there are frequently two 

 or more, the difference does not seem to be very marked. On the typical 

 specimens of V. bella and V. mucronata, both of which Mr. Gabb includes 

 in his genus, there are two nearly equal folds. The most reliable feature 

 which I observe among the specimens in hand and in which they differ from 

 Bostellites Conrad, as exemplified by B. Texana Conrad, is the more unequal 

 convexity of the volutions in the upper and lower parts, and a very slightly 

 greater spreading of the anterior canal at the base of the aperture in Bos- 

 tellites; but this even is not constant. The surface structure differs only in 

 degree, the vertical folds being usually more distant and more strongly 



