DEVONIAN. 317 



The Olentangy shale extends from the top of the Delaware limestone to the base of the 

 Ohio shale, a vertical distance of about 31 feet in Franklin County. It has been found to be 

 almost invariably present in the central strip from Sandusky southward. In Pickaway Coimty, 

 where the Devonian limestones last appear, this shale occurs, and from thence southward 

 overlaps on the older rocks until at Bainbridge it rests on Niagaran limestones. The Devonian 

 shales cross the Ohio River at Vanceburg, and even near Fox Springs, Fleming County, Ky., 

 the basal shale has the appearance of the Olentangy. As seen in the river bank at Delaware, 

 the Olentangy is a soft bluish shale, with numerous disklike argillaceous limestone concretions 

 near the basal portion and layers of impure limestone in the middle and upper portions. The 

 formation contains few fossils in central Ohio but becomes quite fossiliferous in the Sandusky 

 region, where it includes a limestone member at the top, which has been known as the Prout 

 limestone. The thickness of the formation is there also greatly increased. 



Stauffer ^^^ states that the Columbus limestone is the equivalent of the Dimdee 

 limestone of Michigan and the Jeffersonville limestone of Indiana, which are repre- 

 sented in New York by the Onondaga. He places the Delaware limestone of Ohio 

 as equivalent to the Marcellus and correlates the formations of Michigan, Ohio, 

 and New York thus : 



Michigan. Ohio. New York. 



Traverse group. /Olentangy shale. fHamilton beds. 



IDelaware limestone. IMarcellus shale. 



Dundee limestone. Columbus limestone. Onondaga limestone. 



Devonian strata outcrop in three widely separated areas in Indiana — on the 

 Wabash, near Pendleton, and in southern Indiana. The intervening stretches are 

 completely covered by drift. In all sections showing the lower and upper limits 

 of the Devonian in the State the base rests upon Silurian limestones and the top is 

 overlain by Mississippian strata. Kindle*'*" gives the formations present in the 

 northern, central, and southern sections and states the correlation with the New 

 York Devonian as follows : 



Devonian formations in Indiana. 



When the first attempts were made to determine the age of the New Albany shale, its 

 known fauna was limited to one or two species of Lingula. Since the discovery of the Lex- 

 mgton fossils by Borden in 1874 " the formation has been correlated with the Genesee of the 

 New York scale. The discovery by the writer of a new fauna in the New Albany shale at 

 Delphi throws some additional light on the difficult problem of the true position of this forma- 

 tion in the time scale. Associated with several species which are new or undetermined, we 

 find in this fauna Spaihiocaris emersoni, a weU-known representative of the Naples fauna of 

 New York. This fossil is not known in the Genesee in the New York sections but occurs in the 

 Portage and even as high as the Lower Chemimg.* 



" Geol. Survey Indiana, 1874, pp. 112-134. 



6 Clarke, J. M., Bull. U. S. Geol. Survey No. 16, 1885, p. 47. 



