at the Falls of the Ohio. 



173 



Falls of the Ohio have been considered the equivalent of 

 the Corniferous limestone (= Ouondago and Corniferous 

 limestones), and generally of the limestones of the Upper 

 Helderberg group of Xew York.] 



These authors recognize the black slate, above the 

 limestone of the Falls, as having a thickness of 104 feet. 



At a later period Major Sidney S. Lyon published a 

 table of the Strati graphical Arrangement of the Bocks of 

 Keiitucky^^' in which he gives the following table of the 

 beds at the Falls of the Ohio and vicinity : 



q Black slate [=Genesee u Nucleocrinus bed. 

 slate]. V Turbo bed. 



r Encriuital limestone.^ Coral beds. 



5 Hydraulic limestone. z Catenipora beds [= W\- 



t Spirifer bed. agara formation]. 



The beds from r to w inclusive have been regarded, I 

 believe, by all geologists, as the equivalent of the Upper 

 Helderberg limestones of Xew York ; and without criti- 

 cal examination of rocks in place, or a careful comparison 

 of the fossils contained in the several beds, I have hereto- 

 fore accepted this determination, and aided in the dissemi- 

 nation of this opinion. 



This view seems in fact to have been unavoidable, since 

 the fossils from the limestones at the Falls of the Ohio 

 have been collected and widely distributed througrhout 

 the country without reference to the successive beds of the 

 formation from which they have been obtained. More 

 recently my attention has been called to the vertical dis- 

 tribution of the species in these rocks, and during the 

 printing of the early pages of volume v of the Palaeontology 



» In tLis table, tlie thin bedded or slaty siliceous limestone, with Cho- 

 netes, and manv other fossils, is not distinctly recog-nized, although it is 

 really an important member. 



