PALMOSTOLOQY 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. l-l. 



Cyrtocrrax tranxrersiim. Hall. Thirteenth Rep. N. Y. State Cab. Nut. Hist., p. 104. I860. 



ftyrocerax " " Illustrations of Devonian Fossils : Cephalopoda, pi. 67, tigs. 1-4. IM'ti. 



Comp Oyroeeras cotutrktitm, Mkkk and Worthes. Geological Survey of Illinois, p. 44ij, pi. 12. i 



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 striae. The ventrolateral 

 sides of the tube are ornamented, at about every third air-chamber, with 

 large, rounded nodes, which may extend into spines on perfect specimens. 



