I02 Bulletin 12 230 



the number of Brachipods common to the Indiana faunas and 

 Osage group being twenty-three. Nearly the same number of 

 species is common to the Waverly of Ohio and the Indiana 

 faunas, and we maj^ regard the Waverly fauna the equivalent in 

 Ohio of the Riverside and New Providence shale faunas in Indi- 

 ana. The small number of species common to these faunas and 

 the Marshall of Michigan is probably due to the fa<ft that very 

 few of the Marshall species have been figured, which makes their 

 identification in the Indiana faunas difficult and uncertain. 



DEVONIAN FAUNAS. 



Review of Previous Correlations. 



The earliest attempts to classify the Devonian rocks of Indiana 

 and Kentucky date back to the period when Wernerian ideas 

 were dominant in Geology. 



In 18 19 W. B. Stilson,* following the example of McClure in 

 applying the Wernerian system to American rocks, referred all 

 of the horizontal strata of Indiana to the "Secondary formation." 



In the following year Thomas Nuttallf attempted to classify 

 the horizontal strata of Indiana and other states of the Mississippi 

 valley, and referred them to the "Secondary formation." 



As pointed out by Williams,^ Lardner Vanuxem was one of 

 the earliest, if not the first, in America to show the fallacy of the 

 Wernerian system and to use fossils for purposes of correlation. 

 In an article published in 1829 Vanuxem states his belief in the 

 primary importance of the use of fossils in correlating rocks, in 

 the following words: "The analogy "or identity of rocks I deter- 

 mine by their fossils in the first instance and their position and 

 mineralogical characters in the second or last instance." || Other 

 geologists were not slow to see the importance of this idea, and in 



*Sketch of the Geology and Mineralog}' of a Part of the State of Indi- 

 ana. — Am. Jour. Sci., vol. i, 1819, pp. 131-133. 



tjour. Acad. Nat. Sci. Phila., vol. 2, 1821, p. 44. 

 JBull. U. S. G. S., vol. 80, p. 32. 

 ||Am. Jour. Sci., vol. 16, 1829, p. 255. 



