33G 
PALAEONTOLOGY OF NEW YORK. 
external form of the chambered portion, but the air-chambers are much deeper. 
From G. Fischeri, of the Hamilton group, this species differs in its point of 
greatest gibbosity, more rapidly contracting chamber of habitation, shallower 
air-chambers, and transverse section. 
Formation and locality. In limestones of the Upper Helderberg group, at 
Delhi, Delaware county, 0. 
Gomphoceras Fischeri. 
PLATE XLV, FIGS. 5, 6. 
Gomphoceras ( Apioceras) Fischeri, Hall. Thirteenth Rep. N. Y. State Cab. Nat. Hist., p. 106. 1860. 
“ Fischeri, Hall. Illustrations of Devonian Fossils: Cephalopoda, pi. 45, fig-s. 5, 6. 1876. 
Shell large, fusiform, slightly curved; curvature exogastric. Transverse sec¬ 
tion circular. Tube regularly enlarging from near the apex to the point of 
greatest transverse section, which is posterior to the chamber of habitation, 
at the third or fourth septum; thence more gradually contracting to the 
aperture. Apical angle about 30°. Apex attenuate, and more curved than 
the remaining portion of the tube. 
Chamber of habitation large; length a little less than the greatest trans¬ 
verse diameter ; dorsal side nearly straight; ventral side sloping regularly to 
the aperture. The crenulated band, as shown in the cast, narrow, marked 
by strong ridges and intermediate furrows, which are carried over the walls 
of one or two of the last air-chambers, and may be obscurely traced over the 
internal mould of the entire chambered portion. 
Aperture large, oval. Small aperture marked by a broad, gentle bend in 
the margin on the ventral side. 
Air-chambers regular, gradually increasing in frequency toward the apex, 
varying in depth from four to eight mm. in the length of ninety mm.; the 
last one or two, at the base of the chamber of habitation, shallower than the 
preceding. Septa smooth and thin, so far as observed, and showing a con¬ 
siderable degree of concavity. Sutures straight and horizontal. The internal 
mould of the walls of the air-chambers is marked by a longitudinal carina 
along the line of the siphuncle and under the sinus in the surface-striae. 
