72 THE DEVONIAN AND CARBONIFEROUS. [bull. 80. 



Devonian, and Carboniferous species occur together. Hall accounted 

 for this fact by the absence in this basin of the rocks which in New 

 York separate these great limestones, thus bringing the representa- 

 tives of the Niagara, Lower Helderberg, and Corniferous together, and 

 causing some confusion of the species at their junction. 



This was in the direction of clear definition for the faunas. Up to 

 this time (and to some extent even to the present), geologists did not 

 appreciate the essential importance of knowing the precise order and 

 association of species making up the successive faunas met with in 

 geological sections. 



James Hall also prepared a paper on u Parallelism of the Paleozoic 

 deposits of the United States and Europe." l This was written after 

 the work on the geological survey of the State of New York had been 

 completed. Interest had also been excited in Europe, and he had the 

 benefit of the studies of several very able European geologists. Lyell 

 had visited America the first time; de Yerneuil had written his paper 

 on the Parallelism of the Paleozoic formations of America with those 

 of Europe ; Daniel Sharpe had written a paper on the Paleozoic rocks 

 of North America; 2 Murchison's Silurian System had been published 

 several years before; also Phillips's Fossils of Devonshire, and McCoy's 

 description of Carboniferous Fossils ; these were all published and at 

 hand for comparison. 



The first part of Mr. Hall's paper was devoted to a comparison be- 

 tween the Paleozoic rocks of New York and those of the West. As 

 bearing upon our present discussion the only point of particular interest 

 in this comparison is the correlation of the " Cliff limestone " with the 

 Niagara, Clinton, and Corniferous limestones of the East. In the West a 

 black shale was found to follow this limestone in some parts of Ohio, 

 Indiana, and Kentucky, which was believed to represent the remaining 

 part of the Devonian ; above it, all over the Mississippi Yalley area, the 

 Carboniferous limestone appeared. Several interesting points appear 

 in the discussion of the comparisons between the American and the 

 European sections made by Messrs. Sharpe, de Yerneuil, and others. In 

 these comparisons the use of fossils was paramount, and all the argu- 

 ments were based upon the presence of fossils, irrespective of the lith- 

 ologic characters of the deposits. The determinations were based 

 chiefly upon a numerical comparison of the recorded lists of fossils ; 

 resemblance of genera and identity of species were recorded as deter- 

 mining the correlation in each case. This principle was carried to the 

 extent of recognizing, in species from what are called now Devonian 

 deposits of America, correlations with Silurian, Devonian, and Car- 

 boniferous species in the different groups of organisms which were com- 

 pared. For instance, in a table 3 the Brachiopods of the Oriskany sand- 



1 It appeared as chapter xvm of Foster and Whitney's Report on Lake Superior, part II, pp. 

 285-318, published in 1851. 

 * Qnar. Jour. Geol. Soc. Lond., August, 1848. 

 8 Ibid, p. 316. 



