580 E. O. ULRICH REVISION OF THE PALEOZOIC SYSTEMS 



than in northern Ohio, Pennsylvania, and New York, because of misap- 

 prehension respecting the stratigraphic relations of the Chattanooga shale 

 to the upper Devonian in New York. 



Prevailing inconsistencies in metliod — Examples. — Eeal inconsist- 

 ency in method is shown in the practice of referring the Helderbergian 

 series to the base of the Devonian, whereas the Eichmondian is placed at 

 the top of the Ordovician. These two series hold precisely analogous 

 positions in the diastrophic histories of their respective periods. Accord- 

 ing to the method here adopted, both represent introductory stages, the 

 Helderbergian to the Devonian, the Eichmondian to the Silurian. The 

 Saint Peter sandstone, with the Everton and Joachim limestones, simi- 

 larly constitute an introductory series to the Ordovician, while the Chatta- 

 noogan represents the opening epoch of the Waverlyan. To be consistent, 

 therefore, if the Helderbergian is early Devonian, then the Saint Peter is 

 early Ordovician, the Eichmondian is Silurian, and the Chattanoogan 

 should be Waverlyan. 



Coming to formations that for either faunal or lithologic reasons have 

 been referred to groups or series to which they do not strictly belong, the 

 following instances are probably as good as any. In each case the more 

 important stratigraphic break has been subordinated to one of less signifi- 

 cance. The first of these concerns the mistaken reference of the Lowville 

 by myself and others to the Stones Eiver group, which, as may be seen 

 in the correlation tables, comprises the lower half of the Chazyan and is 

 separated from the Lowville by the upper Chazyan Blount group. Study 

 of diastrophic movements, stratigraphic relations and faunas finally 

 proved the intimate relationship of the Lowville to the Black Eiver group 

 of the Mohawkian series, of which it should henceforth constitute the 

 basal part. 



The oldest Eichmondian formation, the Arnheim, offers the second 

 illustration. This formation has been referred by authors to the top of 

 the Maysville group, but the Arnheim represents a return of Gulf of 

 Mexico waters after a long stage of emergence. That warping occurred 

 during this intermediate stage is indicated by the difference in distribu- 

 tion of the Arnheim when compared with that of the preceding McMillan 

 formation. The relatively long duration of the intervening emergence 

 is shown by the appearance of new organic types and the important 

 changes that occurred in derivatives of the preceding facies of the Ordo- 

 vician gulf fauna. 



The Warsaw is of Tennessean, not Waverlyan, age. — Tlie tliird and 

 fourth instances are seen in formations adjacent to the Waverlyan- Ten- 



