362 
PALEONTOLOGY OF NEW YORE. 
Cyrtoceras (Gomphoceras ?) formosum, n. sp. 
PLATE XCV, FIGS. 8, 9. 
Shell arcuate, exogastric. Point of greatest transverse section apparently near 
the middle of the chamber of habitation. 
Chamber of habitation large, with the sides sloping very gradually to the 
aperture. 
Aperture comparatively large ; its characters have not been fully observed 
Air-chambers, septa and siphuncle unknown. 
Tube ornamented with regular, shallow, transverse furrows, four in the 
space of twelve mm., with minutely undulating lines of growth between the 
ridges, crossed by regular, continuous, sharp, crenulating strife, of which 
there are six in the space of seven mm. Near the aperture the transverse 
furrows disappear, and the surface shows coarse, lamellose lines of growth. 
The peculiar surface ornamentation here described gives the tube a very char¬ 
acteristic, cancellated appearance. The furrows and lines of growth make a 
decided sinus on the ventral side. 
The fragment figured, belonging to the chamber of habitation, is much 
compressed, and has a length of nearly eighty mm. 
This species is characterized by the remarkable surface ornamentation, which 
bears no similarity to any of the other forms described in this volume. It is 
doubtfully referred to the genus Gomphoceras on account of its gibbous chamber 
of habitation and the evident curvature of the tube, while the ornamentation 
is similar to several species of Cyrtoceras from the Silurian system. 
Formation and locality. In the shales of the Hamilton group, at Dresden, near 
Penn Yan, Yates county, N. Y. 
