PAUEUSTOLOaV OF .V//IV YORK. 



Test thin, having a thickness of .35 mm. Surface marked hy fine, con- 



ntric lines of growth, crossed by indistinct, longitudinal ridges. 



A specimen, preserving a portion of the chamber of habitation, with twelve 



air-chambers, has a length of fifty-five mm., of which twenty mm. pertain to 



the outer chamber. 



This species somewhat resembles G. tumidum, but may be distinguished by the 

 position of the plane of greatest transverse section, and the less tapering apical 

 portion of the tube. In general form and size it is related to G. Conradi, but 

 in the latter species the endogastric curvature, the point of greatest gibbosity, 

 and the crenulations at the base of the chamber of habitation are very distinc- 

 tive. The specimens, as occurring in the soft carbonaceous shales and in the 

 coarser beds, present slight differences, which appear to be due principally to 

 the mode and condition of preservation. 



Formation and localities. In the shales of the Hamilton group, at Pratt's Falls, 

 Onondaga county, and Cazenovia, Madison county, N. Y. 



GOMPHOCERAS CoNRADI. 



PLATE XLVI, K1GS. 1-3. 



(iomphoeeras (Apiocerax) Conradi, Hall. Thirteenth Rep. N. Y. Slate Cab. Nat Hist., p. 100. ix«0. 



Fifteenth Rep N. Y. State Cab. Nat. Hist, pi. 8, fig. 8. 1843. 

 Cyrttieerat Comadi, IIai.l. Illustrations of Devonian Fossils: Cephalopoda, pi. 47. figa, 1. 2, 11. 1S70. 



Shell small, clavate, nearly straight, curvature of the dorsal side rather more 

 than the ventral, making the curvature endogastric. From the slope of the 

 sides of the chamber of habitation, the indication is that of an exog;istric 

 curvature. Transverse section broadly oval, slightly flattened on the dorsal 

 side. Tube enlarging gradually from the apex to a point nearly on the 

 centre of the chamber of habitation, thence contracting gradually to the 

 aperture. Apical angle about 20°. Apex acute. 



The length of the chamber of habitation is nearly equal to the lateral 

 diameter of the tube at the last septum. Ventral side more convex than the 

 dorsal ; both sides slope gradually to the aperture, and show a flattened area 

 extending from the base midway to the aperture. Tube marked by a slight 



