450 PALEONTOLOGY OF NEW YORK. 



removal of .the fossil, and is a cast from the inside of the shell, which preserves 

 only slight evidence of surface striae, and the nodes represented are such only 

 as would he preserved on a cast of the interior. 



I'ntil recently only two specimens of this species were known to me, and 

 these, preserving little more than one volution, showed no evidence of septa or 

 other indications of being a Cephalopod, and it was referred with doubt to the 

 genus Porcellia, in the Illustrations of Devonian Fossils published in 1876. 

 Further collections have added great numbers of individuals, but without 

 giving satisfactory evidence of the entire structure. Of several hundred speci- 

 mens only three present external evidence of the septate character, and the 

 greater proportion of the specimens of which sections have been made, preserve 

 only the chamber of habitation, with a simple curved septal termination, or 

 with one or t\vo septa and air-chambers. 



The species has been found only in some shaly and pyritiferous calcareous 

 layers in the Marcellus shale, and so far as known has a very limited vertical 

 and horizontal distribution. It is associated with Styliola and Tentaculites 

 figured on plate 31 A of this volume. 



Formation and locality. In a calcareous band in the Marcellus shale at Cherry 

 Valley, N. Y. 



GoNIATITES BICOSTATU8. 



PL\rE9 LXXII, FIGS. 8-10 i UEXtV, KG. 1. 



Gimintltt* bit-ostatu*. Hall. Geolog. Surv. of N. Y. : Rep. Fourth District, p. 245, fig. 8. , 1843. 



Thirteenth Rep. N. Y. State Cab. Nat. Hist., p. 108, tifrs. lit. 20. 1860. 

 " " " Illustrations of Devonian Fossils : Cephalopoda, pi. 72, figs. 8-10. 1876. 



Shell depressed-spheroidal in the young state, becoming discoidal in its advanc- 

 ing growth, with the sides more or less convex, and often flattened from 

 compression, and the periphery regularly rounded. The proportions of 

 thickness and lateral diameter, in a specimen which is somewhat compressed, 

 are as one to three and a half. This proportion varies according to the 

 stage of growth, accidents of imbedding, and mode of preservation. 



Volutions about three or more, partially exposed; gradually enlarging 



