CEPHALOPODA. 339 



GOMPHOCERAS ABRUPTUM, n. Sp. 

 PLATE XCIV, TIG. 1. 



A compressed fragment, consisting of a portion of the grand chamber and the 

 air-chambers, shows the following characters, some of which may be greatly 

 obscured by its imperfect preservation : 



Point of greatest transverse section at the base of the chamber of habita- 

 tion, from which the tube rapidly contracts to the apex, giving to its septate 

 portion a short, conical appearance. 



Chamber of habitation large, with the sides sloping gradually to the aper- 

 ture, and a gentle constriction around the middle. 



The surface of the internal mould shows lamellose lines of growth. 



The fragment has a length of 100 mm., and a greatest transverse diameter 

 of seventy mm. 



This species is distinguished from G. solidum by its short, conical, apical por- 

 tion, and its more gradually contracting chamber of habitation, with the con- 

 striction of the tube near the middle of the chamber. The specimen is covered 

 with a tubular, branching, parasitic Bryozoan, as shown in the figure given on 

 plate 94. 



Formation and locality. In the shales of the Hamilton group, near Caze- 

 novia, N. Y. 



GOMPHOCERAS MANES, n. Sp. 

 PLATE - SUPPLEMENT. 



Shell large, straight, fusiform. Point of greatest gibbosity at the base of the 

 chamber of habitation, or on the last septum. Tube regularly and gradually 

 enlarging to the point of greatest transverse diameter, and gradually contract- 

 ing to the aperture. 



Chamber of habitation large, with the sides sloping very gradually to the 

 aperture. 



Aperture large ; margins entire. A slight bend in the margin probably 

 indicates the small aperture or the ventral side. 



