Williams] PALEONTOLOGY AND GEOLOGY. 21 



tion ot the Devonian rocks chronologically, in the geological series, is 

 between the Silurian system of Murchison, and the Carboniferous sys- 

 tem of Couybeare, heretofore regarded as of the Secondary strata of 

 Werner. 



The demarkation of the Paleozoic by its fossils which we owe to 

 Phillips and the determination of the intermediate position of the De- 

 vonian system by Lonsdale were two conspicuous examples of the ines- 

 timable value of fossils for geologic correlation. Heretofore the 

 methods of the Wernerian school were dominant in all geologic classifi- 

 cations and correlations. Afterward in English and American geology 

 paleontology became the indispensible ally ofstratigraphie geology. 



