350 
PALEONTOLOGY OF NEW YORK. 
Gomphoceras Ajax, n. sp. 
PLATE XCIV, FIG. 8. 
This species is recognized from a large fragment, consisting of a portion of 
the chamber of habitation, with several attached air-chambers, possessing 
the following characters: 
Transverse section broadly oval. Point of greatest gibbosity near the 
base of the chamber of habitation. The curvature of the tube, as indicated, 
is exogastric. 
Chamber of habitation large, with the sides sloping gradually to the aper¬ 
ture. Crenulated zone narrow, and marked by indistinct furrows and fine, 
rounded striae, which are continued over the cast of the walls of the air- 
chambers. 
Air-chambers regular, having a depth of about eight mm. Septa thin, 
smooth, with a concavity equal to the depth of the chambers. Sutures 
straight, slightly oblique. 
Siphuncle near the ventral side, apparently submarginal, marked by a 
distinct longitudinal ridge along the internal mould of the chamber walls. 
The fragment has a length of about eighty mm., of which fifty mm. per¬ 
tain to the chamber of habitation. The greatest lateral diameter is eighty- 
five mm., and the greatest ventro-dorsal diameter is sixty-eight mm. 
This species is distinguished from G. Fischeri by the position of the plane of 
greatest transverse section, and more gradual contraction of the tube toward 
the aperture. It more nearly resembles G. lunatum , but differs in the position 
of the siphuncle and the oblique, septal sutures. So far as known, this species 
is the only one from the Portage group. It differs conspicuously from G.potens, 
of the Chemung, by its much shallower air-chambers. 
Formation and locality. In the shales of the Portage group, at Penn Yan, 
Yates county, N. Y. 
