THE JURASSIC PERIOD 



705 



of many species from the Upper Jurassic beds of the Queen Charlotte 

 Islands and British Columbia with those of the western interior, 

 imply shallow-water connection of these areas. Whether this con- 

 nection was through British Columbia direct, or by way of Alaska 

 and down the east side of the Rocky Mountains, is not known. 

 The presence of fresh-water beds (the Morrision [or Como] beds of 

 Colorado, Montana, and Wyoming) , sometimes regarded as of late 

 Jurassic age in some parts of the western interior, would, were 



Fig. 477. Lower part of the LaPlata (Jurassic) sandstone, southwest of 

 La Sal Mountains, Utah. (Cross, U. S. Geol. Surv.) 



their age established, show that the sea-water withdrew before the 

 end of the period. 



Marine Jurassic limestone has been reported recently from 

 western Texas, 1 and though the exposures are limited, their con- 

 nections are probably southward with the Jurassic of Mexico, where 

 the system is somewhat wide-spread. 



The Pacific coast. Marine deposition was in progress on the 

 Pacific coast 2 (California and Oregon), though much of the system 



1 Cragin, Jour. Geol., Vol. V; and Hill, Am. Jour. Sci., Vol. IE, 1897, p. 

 449, and Physical Geography of Texas, Topographic Atlas, U. S. Geol. Surv. 



2 For tne Jurassic of the Pacific coast, see Hyatt, Bull. Geol. Soc. of Am., 

 Vols. Ill and V, both articles chiefly paleontological; Meek, Paleontology of 

 California, Vol. I, and the California folios of the U. S. Geol. Surv. 



