384 
PAL7E0 A TOLOGY OF NEW YORK. 
abundance, but the majority are fragmentary and very imperfect. It is only 
from the examination of numerous individuals that the characters of the spe¬ 
cies can be satisfactorily determined. 
Formation and localities. In the Schoharie grit, at Schoharie, and in the Hel- 
derberg mountains; and from the same horizon in Ulster county, N. Y. 
Gyroceras transversum. 
PLATE LVI, FIGS. 1-t. 
Oyrtocei'as transversum, Hall. Thirteenth Rep. N. Y. State Cab. Nat. Hist., p. 104. 1800. 
Gyroceras “ “ Illustrations of Devonian Fossils: Cephalopoda, pi. 57, tig-s. 1-4. 1876. 
Comp Gyroc-eras constrictum, Meek and Worthen. Geological Survey of Illinois, p. 446, pi. 12. 1868. 
Shell large, curved, curvature regular. The depth of .the curvature amounts 
to twenty-two mm. in a fragment having a length of 110 mm. Transverse 
section elliptical; lateral diameter the longer. The ventro-dorsal and trans¬ 
verse diameters are in the ratio of three to four. Tube very gradually 
enlarging. Apical angle about 6°. 
Chamber of habitation small, having a length equal to the lateral diameter 
of the tube at the last septum, slightly contracting toward the aperture, and 
again expanding. Crenulated zone narrow, marked by broad, shallow fur¬ 
rows. Aperture entire, with a very deep sinus in the ventral margin. 
Air-chambers regular, gradually increasing in depth toward the grand 
chamber, varying from four, seven, to ten mm. in three specimens, having 
transverse diameters of twenty-three, sixty, and sixty-seven mm respectively. 
Septa smooth, slightly concave. Sutures straight, and at right angles to the 
spiral axis of the tube. 
Siphuncle small, cylindrical, having a diameter of two mm. where the tube 
has a transverse diameter of fifty-three mm. 
Test strong, reaching a thickness of three mm. on the chambers of habita¬ 
tion. Surface marked by fine, irregular lamellose, imbricating lines of 
growth, crossed by numerous rounded, revolving strife. The ventro-lateral 
sides of the tube are ornamented, at about every third air-chamber, with 
large, rounded nodes, which may extend into spines on perfect specimens. 
