CEPHALOPODA. 
347 
This species resembles G. oviforme, but is distinguished by its curved tube, 
apparently larger aperture, the position of the plane of greatest transverse 
section, and the rapid slope of the sides of the chamber of habitation to 
the comparatively small aperture. The same differences distinguish the G. 
raphanus. 
Formation and locality. In the shales of the Hamilton group near Cazenovia, 
Madison county, N. Y. 
Gomphoceras raphanus, n. sp. 
PLATE XCIV, FIGS. 2-5, 10. 
Shell small, straight, slender, exogastric. Transverse section subcircular or 
very broadly oval. Longitudinal section fusiform. Plane of greatest trans¬ 
verse section at the base of the chamber of habitation. Apical angle about 
28°. Apex acute. 
Chamber of habitation small; length less than the diameter of the tube at 
the base. Sides convex, and sloping rapidly to the aperture. Crenulated 
zone narrow, and marked by obscure furrows, which are carried over the 
walls of the air-chambers. 
Aperture, as observed in a specimen much flattened from compression, 
large, having a width equal to that of the grand chamber, or to twice the 
length of the entire aperture. The minor aperture is marked by a small, 
semicircular sinus from the ventral margin of the large aperture. 
Air-chambers regular, showing but slight variation from near the outer 
chamber to the apex, and having a depth of from four to five mm.; the last 
one or more, at the base of the chamber of habitation, usually shallower than 
the preceding. 
Septa smooth, thin, slightly concave, the concavity not amounting to the 
depth of one air-chamber. A small areola around the siphuncle indicates its 
abrupt expansion in the cavities of the air-chambers. Sutures straight and 
horizontal. 
Siphuncle near the ventral side, small, nummuloid, with a diaTneter at the 
septa of less than one-half the diameter at the expanded portions. 
