4 20 CHARLES S. PROSSER 



All of the limestone of the Devonian age in Ohio has been referred by New- 

 berry, to the Corniferous limestone, and this term is in general use at the present 

 time. It may be questioned whether it is wise to break in upon this here, but 

 inasmuch as several geologists hold that the Devonian limestone of Ohio covers 

 more than the single epoch known as Corniferous in New York, a more compre- 

 hensive term, viz., the Upper Helderberg limestone, is counted preferable. A 

 twofold division of the series is possible and proper in Ohio, the division being 

 based on both lithology and fossils. The divisions are known as Lower and 

 Upper Corniferous, or as Columbus and Delaware limestones. For the upper 

 division the term Sandusky limestone is sometimes used. 1 



On the "Geological Map of Ohio," accompanying this report, the 

 "key to formations" mentions the Upper Helderberg limestone, 

 Marcellus shale, Hamilton limestone, and Hamilton shale, which 

 are all represented by one color on the map. 



The substitution of the name "Upper Helderberg limestone" 

 for "Corniferous limestone" did not meet any of the objections 

 raised by Winchell, Hall, and Whitfield to the Newberry classification 

 of the Devonian limestones of Ohio, because, so far as the later 

 formations are concerned, it is not a more comprehensive term than 

 the "Corniferous limestone," and in its classic locality, the Helder- 

 bergs of eastern New York, has never been applied to rocks above 

 the base of the Marcellus shale. The name "Helderberg division" 

 was proposed by Vanuxem in 1842, and included all the formations 

 occurring between the top of the Niagara limestone and the base of 

 the Marcellus shale. 2 In the following year Mather's report appeared, 

 in which the rocks of the Helderberg mountains are described, and 

 it is stated that, on account of their excellent development at this 

 locality, "forming a natural group, strongly marked in their litho- 

 logical and paleontological characters from the strata lying above 

 and below them, the term of Helderberg division is used to designate 

 them." 3 In the northern Helderbergs nearly all of the subjacent 

 Ontario division is absent, and Mather's Helderberg division included 

 all the formations found at this locality between the top of the Hudson 



1 Ibid., Vol. VI (1888), pp. 20, 21. "Upper Helderberg limestone" is also 

 used by Dr. Orton for the formation in his article on "The Trenton Limestone as a 

 Source of Petroleum and Inflammable Gas in Ohio and Indiana" (Eighth Annual 

 Report 0} the United States Geological Survey, Part II (1889), p. 568.) 



2 Geology of New York, Part III (1842), pp. 13, 15, 16. 



3 Ibid., Part I (1843), p. 325. 



