262 THE DEVONIAN AND CARBONIFEROUS. [bull. 80. 



■ 



In this determination two distinct methods of correlation were exhib- 

 ited. The geologists familiar with the standard sections of the New 

 York system, and of the Appalachian province in general, applied the 

 principle of "persistent parallelism of strata," and, having gone care- 

 fully over the ground, believed they had established beyond dispute the 

 correlation of rocks at the base of the Mississippian series with the upper 

 member of the New York Devonian, i. e., the Chemung group. 



The " Chemung group" of Iowa and Missouri was originally thus de- 

 termined, and was defended on this basis for a number of years against 

 the counter evidence of fossils. When the fossils were studied and com- 

 pared with the fossils of the Chemung of New York they were found to 

 closely agree generically, but specifically there were very few cases of 

 identity. To correct this discrepancy a gradual modification of the 

 species or combination of species constituting the local faunas was as- 

 sumed to have taken place coordinate with difference in longitude on 

 passing westward. The fallacy in this assumption deceived some of the 

 ablest geologists of the country, and for nearly twenty years general 

 reliance upon their authority stood in the way of the acceptance of the 

 truth. 



On the principle of establishing correlation of horizon by identity of 

 the fossils all the evidence went to prove that the so-called " Chemung" 

 rocks of the Mississippi Valley were of Carboniferous age. M. de Ver- 

 neuil so identified the specimens he saw when on a visit to this country 

 in 1847. D. D. Owen, one of the earliest geologists to study the rocks 

 of this province, and others who followed him, recognized the " Car- 

 boniferous aspect" of the fossils. But these identifications of the fos- 

 sils were not generally accepted as outweighing the other evidence of 

 supposed correlation with Chemung rocks until the year 1861, when 

 Messrs. Meek and Worthen established the Kinderhook group. 



The Kinderhook group was the result of pure paleontologic correla- 

 tion, in which the fauna at the base of the "Carboniferous limestones," 

 often in saudy or shaly strata, was distinctly recognized, by comparison 

 with authentic Carboniferous species of Europe, as of Carboniferous age. 

 The identifications upon which the name was applied were of Illinois 

 fossils; the correlation included led to the correct correlation of the 

 "Goniatite beds" of Indiana, and later of the Waverly group of Ohio, 

 and the recognition of the "Black shales" of the Mississippi province 

 as the termination of the Devonian series. Although the correlation 

 included the faunas of the Chemung of Iowa and Missouri, the appli- 

 cation of the name "Chemung" there had become locally fixed to the 

 particular rocts, irrespective of their supposed equivalency, and the 

 name was not immediately dropped. The fundamental error in the 

 Chemung correlation was made near the eastern end, on passing from 

 Chautauqua County, New York, across to Cleveland, Ohio. Passing 

 westward from Ohio the error was not noticeable, so that the identity 

 of many Ohio Wajrerly species with those found in the Western Che- 



