BULLETIN OF THE GEOLOGICAL SOCIETY OF AMERICA 



Vol. 5, 1893, pp. 395-434 MARCH 30, 1894 



TRTA8 AND JURA IN THE WESTERN STATES^ 



BY ALPHEUS HYATT 



(^Read before the Society December 28. 1893) 

 CONTENTS 



Page 



Introductory 396 



American and Sailors Canyons, California 396 



Their Faunas 396 



Moiioth Bed 396 



Daonella Beds 396 



Ammonites Bed 397 



Gryphva Bed 398 



Age and faunal Relationships of the two Areas 398 



Trias of Nevada and Idaho ^ 309 



Lias in California, Nevada and Oregon 400 



Upper Jura in California 402 



Ammonitin?e 402 



Cardioceras duhiuin ^. . . . 402 



PerUphinctes lirgulatiformu 402 



(Ecotraustes denticulata 402 



Associated Forms 402 



Perisphhictes jiUplex 402 



Pelecypoda and Gasteropoda 403 



Auceila? 403 



General Remarks 403 



Aucella erringtom 403 



Comparison of Aucelhe 404 



Aucella elongata 406 



Aucella ohicularia 406 



Conclusions based on Study of Aucelhe 406 



Conclusions derived from Associations and Comparisons of Faunas 407 



Classification of the Jura 410 



Relative Age of the Rocks of different Localities 412 



♦Published by permission of the Director of the Uoited States Geological Survey. 



I also gratefully acknowledge the assistance afforded me both by Alexander Agassiz, Director 

 of the Museum of Comparative Zoology, who permitted the use of the valuable collections of that 

 museum, and by Professor J. D. Whitney, whose donation of some of Gabb's types was of essential 

 Importance in settling the age of the rocks in which they were found. 



LVI-BuLL. Geol. Soc. Am., Vor,. 5, 1893. (395) , 



