CEPHALOPUDA OF THE EOCENE MARLS. 285 



tion given of it elsewhere, and the form is certainly distinct from those of 

 the Cretaceous beds below. 



Nautilus Cookana, n. sp. 

 Plate XLViii, Fig. 1, and PI. xlix, Figs. 4-5. 



Shell large, often reaching -^ early a foot in its greatest diameter and 

 proportionally wide and ventricose. Volutions rapidly expanding and prob- 

 ably only three or four in number, rounded on the back and when retain- 

 ing their normal form are but slightly more compressed on the sides. Axis 

 perforate, the umbilicus only of moderate width but very deep, owing to 

 the greater additional breadth of the outer volution at the axis than the pre- 

 ceding one; margins of the umbilicus abruptly rounded. Septa distant, 

 only moderately concave and regularly curved in a dorso-ventral direction, 

 but much more flattened laterally ; the ventral margin, surrounding the pre- 

 ceding volution, somewhat raised. The lines indicating the septa on the 

 casts are only slightly recurved on the sides and are but little directed 

 forward on the dorsum ; not more so than is called for by the difference in 

 the two diameters of the volution. Siphon moderately large, almost cen- 

 trally situated, being slightly nearer the ventral margin in the best pre- 

 served examples examined. Shell unknown, the species known only from 

 internal casts. 



This species is not uncommon in the stony layer at the top of the 

 Upper Marls at Farmiugdale, Deal, Squankum, and Shark River, New 

 Jersey, and so far as can be seen or determined by the casts alone is a true 

 Nautilus. Mr. G. B. Meek, in his list of the fossils of the Shark River 

 Marls given in Geol. N. J. for 1868, includes Nautilus Burtini Got. and N. 

 LamarcJci Desh. as occurring in these beds, and places them both under 

 Conrad's genus Gymomia, which was founded upon the first of these two 

 species. It is possible that a species possessing the features of that genus 

 may occur in New Jersey; but among those which I have seen none 

 show the double sinuate septa of N. Burtini as described by Mr. Conrad, 

 therefore I am inclined to doubt their existence in the State. Most 

 European authors agree in considering N. Burtini and N. Lamarcki as 

 synonyms, but Deshayes points out differences, and Milne Edwards gives 



