380 
PALAEONTOLOGY OF NEW YORE. 
two species, in the ornamentation of the tube, form a small group, similar to 
an assemblage of large and robust forms, named in the succeeding descriptions, 
including C. Jason , G. spinosum and G. transversum. 
Formation and localities. In the Upper Helderberg limestone, Oneida and 
Schoharie comities, and in the Helderberg mountains, Albany county, N. Y. 
Gyroceras paucinodum. 
PLATE LIV, FIGS. 1-4. 
Gyroceras (Hercoceras?) paacinodtis, Hall. Illustrations of Devonian Fossils: Cephalopoda, pi. 55, 
tigs. 1-4. 1876. 
Shell discoid, closely coiled, making not less than two nearly contiguous volu¬ 
tions. Transverse section triangular, ventral side the longest. The length 
of the dorso-ventral diameter is about •three-fourths of the lateral diameter. 
Tube regularly and gradually enlarging from the apex to the aperture. 
Apical angle about 7°. 
The extent of the chamber of habitation has not been observed. The 
crenulations are preserved on the internal mould as fine, rounded strife. 
Aperture slightly oblique, opening outward, with a distinct sinus on the 
ventro-lateral margins, and in the middle of the ventral side. 
Air-chambers, septa and siphuncle unknown. 
The test has a thickness of about .5 mm. on the outer volution. Surface 
marked by irregular slightly undulating lines of growth, curving in a retral 
direction. The ventro-lateral angles are ornamented with a row of nodes 
or spines, formed by the outward and backward bending of the lamellfe of 
growth. On the outer volution these nodes are separated by a distance of 
about twenty-four mm., becoming more frequent toward the apex. Sinus 
very broad and deep. 
The internal mould shows the furrows and strife of the crenulations, and 
large rounded nodes on the ventro-lateral angles, corresponding to the 
.‘xternal ornaments of the test. 
Three specimens have a uniform diameter of 100 mm. each, measured’ 
across the disc, with a lateral diameter of forty-three mm. at the aperture. 
