310 
PALAEONTOLOGY 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 strise 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 
has 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 Styliola fissurdla 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 XCIII, 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- 
