THE DELAWARE LIMESTONE 415 



of the Second Geological Survey of Ohio, and in his first report 

 their distribution was shown on the "Preliminary Geological Map 

 of Ohio," 1 together with some account of their occurrence, lithology, 

 and fossils; 2 while the chapter on the Devonian system in the first 

 volume of the Geological Survey of Ohio contained a more elaborate 

 description. 3 He made two divisions of this limestone: the upper 

 one, termed the Sandusky limestone, described as blue and thin- 

 bedded, from fifteen to twenty feet thick, quarried at Sandusky 

 and Delaware ; and the lower division, called the Columbus limestone, 

 well shown in the quarries near that city, and described as a very 

 light-colored limestone often containing chert. 4 Dr. Newberry 

 stated that the upper portion of the Sandusky limestone contained 

 several characteristic Hamilton fossils in considerable abundance, 

 as Spirijer mucronatus, Cyrtia [Cyrtina] hamiltonensis, etc.; and on 

 account of the presence of these fossils he was for a long time in doubt 



whether the Sandusky limestone should not be considered as a representative of 

 the Hamilton rather than of the Corniferous group; but, on gathering all the fossils 

 of this formation, the list was found to include a much larger number of Cornif- 

 erous than of Hamilton species. 5 



Dr. Newberry concluded that the limestones were to be correlated 

 with the Corniferous of New York, while the Hamilton was restricted 

 to a bed of marl and marly limestone which at Prout's Station, south 

 of Sandusky, was stated to be from ten to twenty feet in thickness, 

 containing "great numbers of Hamilton fossils, with none which are 

 peculiar to the Corniferous." At Delaware, in central Ohio, a light- 

 gray marl between the Black shale and Corniferous limestone was 

 thought to probably represent the Hamilton, but it was stated that 

 south of this locality no trace of it had yet been found. 6 



On the contrary, Professor N. H. Winchell, who described several 

 of the counties in central and northwestern Ohio, came to the con- 

 clusion that the upper Corniferous was probably to be correlated 

 with the Hamilton formation. Under his description of Delaware 

 County we find the following: 



1 Geological Survey of Ohio, Report of Progress in i86g (1870), frontispiece. 



2 Ibid., pp. 17, 18. 



3 Report 0} the Geological Survey 0} Ohio, Vol. I, Part I (1873), pp. 142-49. 



4 Ibid., p. 143. 5 Ibid., p 144. 6 Ibid., p. 150. 



