.; jo PALEONTOLOGY OF NEW YORK. 



Air-chambers regular, having a depth of about eleven mm. The sutures, 

 in a compressed specimen, make a retral curve or sinus over one side of the 

 tube. 



Surface nearly smooth, showing faint striae of growth. 



The specimen described, which is much compressed, embraces the cham- 

 ber of habitation, with about ten air-chambers, and has a length of 160 mm., 

 and its greatest transverse diameter is eighty-five mm. About sixty-five 

 mm. of the length pertain to the chamber of habitation. The transverse 

 diameter was probably originally much less than it now measures, as the tube 

 lias been greatly disturbed by compression. 



In its general form this species resembles G. Fischeri, but the point of greatest 

 transverse diameter is different, and the tube tapers much more gradually 

 toward the aperture and to the apex. 



This species is the only one yet noticed as occurring in the Genesee slate ; 

 and from its association and other characters its occurrence furnishes several 

 additional facts as to the fauna of this small division of the Hamilton group, 

 which is a bed of passage from the main formation to the shales of the Portage 

 group above. The specimen described, as preserved in the black carbonaceous 

 shale, is extremely compressed, and shows little more than the general outline, 

 the margins of the aperture, and the suture lines marking the depth of the air- 

 chambers. It is associated with the widely distributed Slyliola fissurella and 

 other small forms of Pteropoda and Gasteropoda. 



Formation and locality. In the dark carbonaceous beds of the Genesee slate, 

 south of Alden, Erie county, N. Y. 



GOMPHOCERAS POCULUM, n. Sp. 

 plate rem, FIGS. 7, 8. 



Shell large, straight. Point of greatest transverse diameter at the base of the 

 chamber of habitation. Tube rapidly expanding, with the sides convex. 

 Apical angle, in a compressed specimen, about 40°. 



The base of the chamber of habitation only, has been observed, and pos- 



