CEPHALOPODA. 353 



The specimen figured has a length of forty-seven mm. and embraces eight 

 air-chambers. 



This species is distinguished by its transverse section, apical angle, and the 

 smooth internal mould. It is described from a fragment of the chambered 

 portion, and is referred to this genus on account of the large apical angle, and 

 the elliptical transverse section. 



Formation and locality. In the shales of the Hamilton group, on the shore of 

 Seneca lake, N. Y. 



In the genus Gomphoceras, as in Orthoceras, the actual number of species 

 described from the Chemung group bears a small proportion to the number of 

 forms indicated by numerous fragments, which are too incomplete and imperfect 

 to admit of specific distinction. The upper members of this group are charac- 

 terized by a very distinct fauna, compared with that of the lower beds, and are 



1 



intimately connected with the succeeding formations. In the Waverly group 

 several forms have been observed belonging to this genus, together with Ortho- 

 ceras ; but the present collections from this group are too meager to furnish 

 satisfactory results. The collections from the Upper Chemung are also, com- 

 paratively, very limited. A complete knowledge of the Cephalopodous life of 

 the Upper Devonian system, and of the beds of transition to the higher forma- 

 tions, can only be obtained by the study of larger collections than have yet 

 been made ; and any generalizations at this time would be premature. 



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