Geol— Vol. I.] SMITH— COMPARATIVE STRATIGRAPHY. 333 



were with each other, and all three regions seem to have 

 been cut off from the Mediterranean during the greater 

 part of the Lower Trias. 



Marine faunas of the Muschelkalk, or Middle Trias, are 

 known at present in the Great Basin, the Humboldt Moun- 

 tains of Nevada, and the Inyo Range of eastern California, 

 where the occurrence of Plychttes, Hungariies, and Acro- 

 chordiceras in both provinces, and in addition of Beyrichites, 

 Balatonites, and Ceratites in Nevada, place the determin- 

 ation of their age beyond doubt. The top of the Pitt shales 

 in Shasta County, California, also belongs here. 



Upper Triassic faunas are certainly known in this region 

 only in northern California, Nevada, and British Columbia. 



Detailed descriptions and figures of marine Triassic 

 faunas of the American region have been published by W. 

 M. Gabb (9), in the Reports of the Geological Survey of 

 California; by F. B. Meek (18), from the Humboldt Range 

 of Nevada; by C. A. White (40), from the Aspen Moun- 

 tains of Idaho; and by J. F. Whiteaves (42), from British 

 Columbia and Queen Charlotte Islands. 



The most striking characteristics of the American region 

 are the commingling in the Lower Trias of Arctic-Pacific 

 and Oriental types, such as Prosphingites, Ussuria, Heden- 

 stroemia, Psetidosageceras, Flemingites, O^hiceras, and 

 Meekoceras; the commingling in the Middle Trias of 

 Arctic-Pacific and Mediterranean types; and the occur- 

 rence in the Upper Trias of a distinctly Alpine fauna, such 

 as Trofites stibbullatus and its allies, intermingled with 

 Trachycerata . 



The Subdivisions of the Trias. 



The accompanying correlation table is based on the 

 stratigraphic work of E. von Mojsisovics, W. Waagen, 

 C. Diener, G. von Arthaber, A. von Krafft, A. Hyatt, and 

 the writer. It is an attempt to represent in graphic form 

 the occurrence and relations of the marine Triassic strata 

 in all regions, and to give a means of comparison with 

 standard and typical sections. 



