610 E. O. ULEICH REVISION OF THE PALEOZOIC SYSTEMS 



relations which disprove the hitherto supposed contemporaneity of the 

 concerned formations. The methods employed in determining these 

 relations are explained and illustrated by examples in discussing the 

 principles of correlation by diastrophic movements. A few, finally, are 

 based mainly on hypothetical grounds. Of the last only the group con- 

 taining the Saint Peter sandstone and the Niagaran series, some of which 

 are thought to be older, others younger, than was assumed heretofore, 

 are of sufficient consequence to be likely to excite adverse comment. 



The most important changes in the grouping of formations occur in 

 the Eopaleozoic part of the column. Here the great expansion of the 

 stratigraphic sequence supplies the main grounds for the proposed divis- 

 ion of the era into four sharply defined periods or systems, instead of the 

 two, Cambrian and Ordovician, hitherto recognized. The two iiew sys- 

 tems, for which the names Ozarkian and Canadian have been selected, 

 are not, as may be supposed, instituted by mere subdivision of the stra- 

 tigraphic units previously comprised in standardized Cambrian and 

 Ordovician sections, but they are composed mainly of formations whose 

 stratigraphic positions had been misinterpreted and whose aggregate 

 thicknesses had been greatly underestimated. The facts are presented 

 in sufficient fullness in other chapters. Also those furnishing the basis 

 for the proposed division of the Mississippian into two systems, for the 

 denial of systemic rank to the Permian and for the union of the Triassie 

 and Jurassic in a single system. I follow Chamberlin and Salisbury and 

 Schuchert in recognizing the Comanchean system. They and other au- 

 thors are followed in dividing the Cenozoic or Tertiary into two systems. 



In the classification recently proposed by Schuchert the Eopaleozoic 

 is divided into six systems, the Cambrian as here recognized being divided 

 into the "Georgic'^ and "^Acadic" systems, and the post-Moliawkian part of 

 the Ordovician of the present work being united with the Eichmondian 

 to make a "Cincinnatic" system. I regret exceedingly that T can not ac^ 

 cept these innovations. To do so would mean the sacrifice of consistency, 

 which I deem the chief merit of my scheme. Though avowedly based on 

 diastrophic principles, I shall endeavor to show presently that the evi- 

 dence relied on in these cases by Schuchert is not so important as he 

 conceives. 



Beginning with the Cambrian, the fourteen systems or periods are 

 grouped into four eras, in the midst of the last of which — the Ceno- 

 zoic — we are now living. The completed three preceding eras comprise 

 each four systems, as follows : The Eopaleozoic, including the Cambrian, 

 Ozarkian, Canadian, and Ordovician; the Neopaleozoic, including the 



