TRIASSIC PERIOD. 



407 



Rocks of the Upper Colorado, according to Newberry, lie between the Carboniferous 

 and the Cretaceous; and the whole thickness is 2,000 to 2,500 feet. But it is not yet 

 known whether all these beds are of the Triassic, or whether they cover both the Tri- 

 assic and Jurassic periods. 



The Triassic has been identified by fossils also in British Columbia ( ?), and near the 

 entrance of Pavalouk Bay, etc., in Alaska (Am. J. Sci., III. v. 473) ; also near Sonora, 

 Mexico. Whitney states that the Triassic of California and also that of Alaska is Upper 

 Triassic, or the equivalent of the St. Cassian beds of Central Europe, which is that of 

 the Middle Keuper. 



H. Life. 



The American Triassic formation of the Atlantic Border is remark- 

 able for the paucity of all evidences of distinctively marine life. 



The same is true of the Triassic rocks of the Western Interior. But 

 the beds of the Pacific slope, in the Humboldt Mountains and north- 

 ern California and Mexico, contain many marine fossils. 



Figs. 705-709. 



Fig. 705, Podozamites laneeolatus : 706, Pterophyllum graminioides ; 707, Clathropteris rectiuscu- 

 la ; 708, Pecopteris bullata? ; 709, Cyclopteris linnaeifolia. 



On the Atlantic Border, extensive coast-accumulations may have 

 been formed, containing marine fossils, as on the Pacific side and in 

 Europe ; but none such are now exposed to view. 



1. Plants. 

 The vegetation of the Triassic period included neither SigiUarids 

 nor Lepidodendrids, characteristic groups of the Carboniferous era ; 



