BULLETIN OF THE GEOLOGIICAL SOCIETY OF AMERICA 



Vol. 22, pp. 281-680, PLS. 25-29 AUGUST 31, 1911 



EEVISION OF THE PALEOZOIC SYSTEMS^ 



BY E. 0. ULRICH 



{Presented in abstract before the Society December SO, 1908, and 

 December 28, 1910) 



CONTENTS 



Page 

 Part I. Introductory chapters » 



Present instability in stratigrapliic classification 289 



Causes 289 



Dual nomenclatures 290 



Mutual concession 290 



Possibilities of correlation by fossils 291 



Investigations tending toward revision of stratigraphic classification 292 



The natural basis of geologic time divisions 292 



Chamberlin and Salisbury's classification 294 



Shifting of faunas 295 



General discussion 295 



The case of Triarthrus hecki 296 



Rate of progress in migration of faunas 297 



Recurrence of species and faunas 298 



General discussion of recurrence 298 



Recurrence of the Catheys fauna 299 



Utican aspect of the Maquoketa fauna 300 



Recurrences of the Spergeu fauna 301 



Value of fossil evidence in correlation not seriously impaired by 



recurrence of faunas 302 



Uniform composition of widely transgressing faunas 303 



Extent of Paleozoic continental seas 304 



General discussion of the subject 304 



Early Richmond transgression 305 



Late Richmond submergence 306 



Slight erosion of interior Silurian and Devonian lands 307 



Instance of slight erosion in the Big Horn Mountains 308 



Late Ordovician erosion in the Mississippi Valley 308 



Late Cincinnatian erosion in northern Appalachian areas 311 



Erosive agencies relatively ineffective in negative areas 311 



Periodic revivals of erosion processes 313 



Cycles of erosion and deposition 314 



1 Published by permission of the Director of the U. S. Geological Survey, who, in view 

 of the fact that this paper presents a new classification, at variance with adopted usage, 

 disclaims responsibility for the classification, correlations, names, and redefinitions. 

 Manuscript received by the Secretary of the Geological Society February 25, 1911. 

 XX — Bull. Grol. See. Am., Vol. 22, 1010 (281) 



