318 PALEONTOLOGY OF SBW YORK. 



GOMPHOCERAS, Sowerby. 1839. 



The genus Gomphoceras was not recognized in any American publication 

 until 1857, when Mr. Billings described G. obesum, from the Utica group, and 

 G. subgracilis, from the Upper Silurian (Geol. Surv. of Canada: Rep. Progress). 



In 1860 Mr. Hall described G. Conradi, G. Fischeri and G. oviformc, from the 

 Hamilton group (Thirteenth Rep. State Cab. Nat. Hist.). 



In 1861 Mr. Hall described G. eximium, from the Upper Helderberg lime- 

 stone (Fourteenth Rep. State Cab. Nat. Hist.), and G. beta, from the Schoharie grit 

 (Descriptions of New Species of Fossils, p. 44). 



In 1862 Mr. Hall republished the description of G. beta, from the Schoharie 

 grit (Fifteenth Rep. State Cab. Nat. Hist, p. 72). 



In 1866 Mr. Winchell described G. omicron, from the Hamilton group of 

 Michigan (Rep. Lower Peninsula, Mich.). 



Meek and Worthen described G. turbiniforme, from the Hamilton group (Proc. 

 Acad. Nat. Sci. Phila.) 



In 1867 Mr. Hall described G. seploris, from the Niagara group of Wisconsin, 

 and G. scrinium, from the same horizon in Illinois (Twentieth Rep. State Cab. 

 Nat. Hist.). 



In 1875 Hall and Whitfield described G. eos, from the Hudson-river 

 group (Geol. Surv. of Ohio: Pal., vol. 2). 



In 1876 Mr. Hall illustrated Cyrtoceras clavatum [= Gomphoceras], from the 

 Schoharie grit, and Cyrtoceras gibbosum [= Gomphoceras oviforme], from the 

 Hamilton group (Illus. of Devon. Foss.). 



From the geological distribution of the species, as indicated in the above 

 historical sketch, it is shown that the greater number belong to formations 

 above those of recognized Silurian age. The additional species described 

 in the present volume will considerably increase this proportion. The 

 confusion now existing among the heretofore described forms, from an uncer- 

 tain generic reference, renders any attempt at a digest of the whole impos- 

 sible without a revision and examination of all the species recorded under 



