

BULLETIN OF THE GEOLOGICAL SOCIETY OF AMERICA 

 VOL. 24, PP. 377-398 AUGUST 23, 1913 



COBRELATION" PEOBLEMS SUGGESTED BY A STUDY OF 

 THE FAUNAS OF THE EASTPOKT QUADRANGLE, MAINE x 



BY HENRY SHALER WILLIAMS 



(Read before the Society December 28, 1912) 



CONTENTS 



Page 



Part I. The facts , 377 



Introductory 377 



General correlation of the Edmunds fauna 380 



Niagara group of Hall as represented in the Rochester shale of Hart- 



nagel, 1907 381 



Comparison of the Edmunds and Rochester faunas 381 



Place of the significant Brachiopods of the Edmunds fauna in the 



typical Silurian section of England 382 



Edmunds species in the Gotland section 384 



The Bohemian fauna, E 2 384 



The Podolian faunas 385 



Summary of the facts of correlation 386 



Part II. Problems involved in correlating fossil faunas 387 



General considerations 387 



Problem 1 389 



Definition of the problem 389 



A. Identical species . . 390 



B. Plasticity and fixity of form 390 



C. Personal equation of the describer of species 391 



Problem II 393 



General discussion of the problem 393 



Hypothesis of migration 395 



Evolution hypothesis 396 



Conclusions :>!M'> 



Discussion '.VM 



Part I. The Facts 



INTRODUCTORY 



At the last meeting of the Society I read a brief paper setting forth 

 the general correlations of the several faunas of the Eastpori quadrangle. 1 



x Published by permission of the Director of the United States Geological Survey. 



Manuscript received by the Secretary of the Society January 15, 1918. 

 •Correlations of the Paleozoic faunas of the Eastpori quadrangle, Maine. Pull. Geol. 

 8oc. America, vol. 23, 1911, pp. 349-356. July 15, 1912. 



XXVI— Bull. Geol. Soc. Am., Vol. 24, 1912 (377) 



