BULLETIN OF THE GEOLOGICAL SOCIETY OF AMERICA 

 Vol. 11, pp. 241-332 May 10, 1900 



LOWER DEVONIC ASPECT OF THE LOWER HELDERBERG 

 AND ORISKANY FORMATIONS* 



BY CHARLES SCHUCHERT 



{Read before the Society December 28. 1899) 

 CONTENTS 



Page 



Introduction 242 



Silurian of Murchison 245 



Application of the term by geologists 245 



Downtonian 247 



American equivalents 248 



Table of English and American Siluric equivalents 251 



Conclusions 252 



Lower Devonic 252 



Devonian of Sedgwick and Murchison 252 



Lower Devonic of Germany and the American equivalents 257 



Views of writers as to its extent, character, and divisions 257 



1. Gedinnian, fauna of the lowest Lower Devonic, or zone of Spirifer 



mercuri 258 



2. Siegen, fauna of theSiegen grauwacke, or zone of Spirifer primsevus. 258 



3. Lower Coblenzian, zone of Spirifer hercynix 267 



4. Upper Coblenzian, zone of Spirifer paradoxus 267 



Conclusions • 268 



American Lower Devonic. 269 



Helderbergian subdivisions 269 



Helderbergian fauna 274 



Relation to the Siluric 274 



Relation to the Devonic 275 



Table of the Helderbergian fauna 278 



Oriskanian subdivisions 289 



Stratigraphic names applied to the Oriskanian 289 



General character and distribution of the Oriskanian 289 



Oriskanian fauna 291 



■ Table of the Oriskanian fauna 292 



Table of European and American Lower and Middle Devonic forma- 

 tions 297 



Summary , 298 



* Published by permission of the Secretary of the Smithsonian Institution. 

 This paper was first read by title at the meeting of the Society held in Columbus, Ohio, in 

 August, 1899. 



XXXVI— Bull. Geol. Soc. Am., Vol. 11, 1899 (241) 



