CEPHALOPODA. 
321 
Gomphoceras FAX, II. sp. 
PLATE—SUPPLEMENT. 
Shell slender, slightly arcuate; curvature exogastric. Transverse section 
broadly elliptical; lateral diameter the longer. Point of greatest gibbosity 
near the middle of the chamber of habitation. Tube regularly and gradually 
enlarging from the apex to the point of greatest transverse section, and 
rapidly contracting to the aperture. Apical angle, in compressed specimens, 
about 18°. Apex acute. 
Chamber of habitation large, with a length equal to the greatest lateral 
diameter. Crenulated zone narrow, marked by fine, transverse furrows, of 
which traces are remaining over each of the chamber walls of the internal 
mould. 
Aperture small, suboval, slightly extended on the ventral side forming the 
small aperture. Large aperture, having its longer diameter equal to two- 
thirds the lateral diameter of the chamber of habitation. 
Air-chambers regular, numerous, with a depth of from two to five mm. 
Septa smooth, so far as observed. Sutures straight and horizontal. 
Siphuncle small, close to the ventral side, not observed in the cavities of 
the air-chambers. 
Test not preserved. The internal mould preserves traces of. strong lamel- 
lose striae near the aperture. 
A compressed fragment, consisting of the chamber of habitation and about 
eighteen attached air-chambers, has a length of eighty mm. A smaller 
individual, preserving the chamber of habitation entire, and twelve air- 
chambers, has a length of sixty-seven mm., of which twenty-three mm. 
pertain to the chamber of habitation. 
This species resembles, and is associated with, G. Illcmus, but is distinguished 
by its much smaller aperture, which also differs conspicuously in general outline. 
The fragment referred to G. Illcenus indicates a considerably greater curvature 
of the tube than is shown in this species. It is further removed from G. clava- 
tum and G. beta by the relative position of the greatest transverse diameter 
41 
