THE DELAWARE LIMESTONE 419 



Professor Whitfield published later a list of the fossils found in 

 these shales, together with a description of two new species, under 

 the title of "Species from the Marcellus Shales." 1 A more complete 

 account of their stratigraphy was also published under the title of 

 "Note on the Marcellus Shale and Other Members of the Hamilton 

 Group in Ohio, as Determined from Pakeontological Evidence." 3 

 In this article Professor Whitfield positively identified the shales 

 as of Marcellus age, stating that 



only a few feet above the "bone-bed" occurs the dark -brown shale in question, 

 with the peculiar fossils, which I have no hesitation in pronouncing the equivalent 

 of the Marcellus shales of New York. Admitting this — and there certainly appears 

 to be no alternative — the rocks found above this limit should represent the Hamil- 

 ton group of the New York system. 3 



In the Ohio report Professor Whitfield stated that in August, 1879, ne 



read a notice of the occurrence in Ohio of rocks representing the Marcellus shales 

 of New York .... in which it was shown that a considerable thickness of the 

 limestones previously recognized as " Corniferous " in Ohio, were above the 

 horizon of the beds which I had recognized, from palseontological and lithological 

 evidence, as of the age of the Marcellus shale, and would be of necessity equiva- 

 lents of the Hamilton group. 4 



Finally, Professor Whitfield published descriptions of several "species 

 from the limestones above the ' bone-bed,' in the vicinity of Columbus, 

 Ohio, and not known to occur below that horizon," which included 

 such well-known Hamilton species as Spirijer ziczac Hall, Pterinea 

 flabella (Con.) Hall, Nyassa arguta H. & W., and Grammy sia bisulcata 

 (Con.) H. & W.s 



Dr. Orton, in describing the geological scale of Ohio in the volume 

 on petroleum and natural gas, changed the name of the formation 

 from the "Corniferous" to the "Upper Helderberg limestone," 

 and assigned the following reason : 



1 Annals of the New York Academy of Sciences, Vol. II (1S83), pp. 212-15. 

 Descriptions of all the species were published in the Report of the Geological Survey 

 of Ohio, Vol. VII (1893 [1895]), pp. 441-47. 



2 Annals of the New York Academy of Sciences, Vol. II (1883), pp. 233-41. 

 This article, with additions, was republished in Report of the Geological Survey of 

 Ohio, Vol. VII, pp. 432-41. 



3 Ibid., p. 235, and Report of the Geological Survey of Ohio, Vol. VII, p. 433. 



4 Report of the Geological Survey of Ohio, Vol. VII, p. 434, footnote. 



5 Ibid., pp. 447-52. 



