158 THE DEVONIAN AND CARBONIFEROUS. Ibull.80. 



He would correlate the calcareous and associated beds below the Bur. 

 lington and possibly all below the Keokuk with the Pouent or Gatskili 

 aud Vespertine, represented by 6,000 feet of deposits in the Appala- 

 chian region. He adds : 



But all such attempts at synchronizing distant deposits must be limited to a general 

 and vague result, even when corresponding fossils would seem to mark simultaneous 

 origin, and we must not forget the large agency of migration, and the long lapse of 

 years, which in many cases may have been required for the extension of a living race 

 into distant submarine settlements. 



Messrs. C. A. White and R. P. Whitfield, in the introduction to their 

 paper 2 on the Chemung rocks of the Mississippi Valley, which is mainly 

 descriptive of species, state their reasons for recognizing the " Che- 

 mung"^ Iowa. They say the Hamilton group of New York is recognized 

 in Illinois aud Iowa as a reliable Devonian horizon by the fossils ; that 

 the Chemung offers changes even in short distances. In northeastern 

 Ohio they hold that there are few if any species common with those 

 of New York, and the fauna in western Ohio and Michigan is still dif- 

 ferent, but still the Chemung age of each is maintained. It is thus ap- 

 parent that to these authors the correlations in the West were based 

 upon relative stratigraphic position, the generic relations of the fossils, 

 together with a not unremarkable similarity of lithological characters. 



Some species of the " Chemung" of Burlington, Iowa, are said to be 

 the same as those of the u Chemung " of Ohio, " which rocks can be 

 traced continuously to New York." 3 



Notwithstanding an unmistakable resemblance to Carboniferous 

 fauna, they refer them to the Chemung of New York, explaining that 

 u a direct continuity of strata of the Chemung of New York can be 

 traced from that State to those of Ohio." Thus it appears that Messrs. 

 White and Whitfield, relying upon the correctness of the determi- 

 nation of continuity of strata claimed by Hall in 1842 were led to put 

 aside the evidence of fossils, and to explain the differences as due to 

 geographic causes. 



Messrs. Meek and Worthen, in their discussion of this question, made 

 the want of specific identity the chief reason for separating the Bur- 

 lington rocks called " Chemung " from the Chemung of New York, 4 and 

 their reliance upon the Carboniferous aspect of the fossils led them to 

 correctly correlate the formation which had hitherto been called " Che- 

 mung." 



Messrs. W. H. Niles and Charles Wachsmuth, 5 maintained that the 



1 Proc. Boston Soc. Nat. Hist., vol. 7, 1861, pp. 321, 322. 



2 Observations on the Rocks of the Mississippi Valley which have been referred to the Chemung group 

 of New York, together with descriptions of new species from the same horizon at Burlington, Iowa. 

 By R. P. Whitfield and C. A. White, Boston Soc. Nat. Hist., vol. 8, 1862, pp. 289=306. 



3 Ibid., p. 290. 



4 Remarks on the age of the Goniatite limestone at Rockford, Indiana, and its relations to the "Black 

 slate " of the Western States, and to some of the succeeding rocks above the latter. By F. B. Meek 

 and A. H. Worthen. 1861. Am. Jour. Sci., 2d ser., vol. 32, pp. 167-177 and 288. 



5 Evidence of two distinct Geological Formations in the Burlington Limestone. Am. Jour. Sci., vol. 

 42, 1866, pp. 95-99. 



