324 
PALAEONTOLOGY OF NEW YORK. 
Siphuncle near the concavo-ventral side, having a diameter at the septa of 
two mm., where the tube has a diameter of twenty-five mm. Its other 
characters not observed. 
Test and surface-markings unknown. 
A small individual, nearly entire, has a length of sixty mm., with a greatest 
lateral diameter of twenty-three mm., and preserves the chamber of habita¬ 
tion and about fifteen air-chambers. Other larger examples have been 
observed, but in a fragmentary condition. 
. This species, in its peculiar curvature and size, resembles G. Conradi, of the 
Hamilton group; but the point of greatest transverse section is different, the 
aperture smaller, and the tube more rapidly contracting toward the aperture. 
It is distinguished from G. fax by the position of the point of greatest trans¬ 
verse section, the endogastric curvature and apical angle. 
Formation and locality. Schoharie grit, Helderberg mountains, Albany 
county, N. Y. 
Gomphoceras absens. 
PLATE XLVI, FIGS. 8, 9, and Supplement. 
Cyrtoceras absens, Hali,. Illustrations of Devonian Fossils: Cephalopoda, pi. 47, fig's. 7, 8. 1876. 
Shell small, arcuate, exogastric. Transverse sectiun elliptical; lateral diam- 
.eter the longer. The ratio of the ventro-dorsal diameter to the lateral 
diameter is about as 3 to 4. Point of greatest gibbosity on the chamber of 
habitation, near the last septum. Apical angle about 20°. 
Chamber of habitation bursiform, having a length equal to the greatest 
lateral diameter of the tube. Dorsal side nearly straight, sometimes slightly 
concave. Ventral side convex, and sloping rapidly to near the aperture, 
where there is a sudden constriction of the tube, which is cylindrical from 
this point to the aperture. Crenulated zone very narrow, but marked by 
broad, shallow, transverse furrows. ' 
Aperture oval, with a width nearly equal to the length of the grand 
chamber. The small aperture is formed by a very small and shallow bend, or 
