322 PALAEONTOLOGY OF NEW YORK. 



the apical angle, ami depth of the air-chambers. The air-chambers in G. rude 

 have a much greater depth, and the crenulated band has a marked character, 

 not shown in this species. The specimens are in the same condition of preser- 

 vation as the associated Orthoceratites, with the minute specific characters 

 much obscured by compression and the process of weathering. 

 Formation and locality. In the Schoharie grit, at Schoharie, N. Y. 



GOMPHOCERAS ILLiENUS, n. sp. 

 PLATE-SUPPLEMENT. 



Shell curved, arcuate (?); curvature exogastric. Transverse section broadly 

 elliptical, lateral diameter the longer. Greatest transverse diameter near 

 the middle of the chamber of habitation. 



Chamber of habitation with a length equal to its greatest lateral diameter. 

 Dorsal and lateral sides nearly straight. Ventral side sloping rapidly to the 

 aperture from the point of greatest gibbosity. Crenulations forming a narrow 

 fossa at the base of the chamber of habitation of two mm. in width, and 

 crossed by small, irregular furrows. 



Aperture large, trilobate, elongate ; width equal to the greatest diameter 

 of the tube. The small aperture formed by a deep and rounded curve in 

 the margin of the shell. The large aperture, narrow, becoming nearly 

 tubular at the ends, and projecting beyond the lateral margins of the shell. 



The depth of the air-chambers has not been observed. Septa smooth, 

 moderately concave. Sutures straight and horizontal. 



Siphuncle not observed. 



Test not preserved. The surface-markings, as shown on a portion of the 

 internal mould, were sharp, lamellose, transverse striae. 



The specimen described consists of the chamber of habitation nearly entire, 

 but slightly compressed, and has a length of forty-five mm., with an equal 

 transverse diameter. 



