CEPHALOPODA OF THE CRETACEOUS MARLS. 245 



in tlie shell. Dorsum sharply rounded. Septa distant, rather deeply con- 

 cave; arched forward on the margin of the umbilicus and slightly backward 

 on the sides, but strongly arched forward on the dorsum. Siphon rather 

 large, situated about two-fifths of the entire distance of the length of the 

 septum from the inner border. Aperture as shown by the section of the 

 volution, longer than wide and deeply emarginate on the inner border by 

 the intrusion of the inner volution, giving it a compressed reniform outline. 

 Surface of the shell unknown. 



The type specimens of this species, which are before me, consist of 

 two fragments of casts, one consisting of about half of an inner volution 

 preserving seven chamber fillings; and parts of four chambers of a much 

 larger specimen show it to have been a rather large shell of a form much 

 like the living Nautilus umbilicus, but with the umbilical cavity less angular 

 on the margin and rounded within; the outer volutions embracing the inner 

 ones to nearly the same extent. The sides of the volutions are not quite 

 so much flattened near the umbilical region, giving a little greater propor- 

 tional thickness to this part of the shell. It is so distinct from N. Dekayi of 

 the Lower Green Marls that it is not necessary to compare it with that species. 

 It is less unlike the forms of Nautilus found as casts at Prairie Bluff', Ala- 

 bama, and in many parts of Texas known as N. perlatus Morton, but so far 

 as I know those are not umbilicated, consequently it presents a radical differ- 

 ence in this respect. There are some discrepancies between Mr. Gabb's 

 description and the specimens which it may be well to note. For instance, 

 he states that the sides are flattened and "nearly parallel," which I find to 

 be very far from the case, especially in the larger specimen. He also states 

 that the siphon is "small" and "central." It is considerably nearer the 

 inner margin than the center in both specimens, and in the larger one is fully 

 three-sixteenths of an inch in diameter, being very much larger than in the 

 living form of Nautilus. 



Formation and locality: In the yellow lime sands of the Middle Marl 

 Beds at Vincentown, New Jersey, having been collected by the late Col. 

 Bryan, and is now in the cabinet of the Phila. Acad. Nat. Sci. 



