i;8 The Tertiary Formations of the [March, 



were reversed ; the east became the continent, and the west be- 

 came the sea. The latter, receiving the drainage of the surround- 

 ing lands, was a body of fresh water, whose connection with the 

 ocean permitted the entrance of a few marine fishes only. This 

 was the great Wasatch lake, whose deposits extend from the 

 upper waters of the Yellowstone far south into New Mexico and 

 Arizona, between the Rocky mountains on the east and the Wa- 

 satch range on the west. Its absence from the east side of the 

 former range indicates the continental condition of that area at 

 the time. The only locality where the Wasatch deposits are 

 extensively deposited on the Laramie, is in the region interme- 

 diate between the two districts in Wyoming Territory. Here the 

 sediments of the former are seen to have succeeded those of the 

 latter, and to have been coincident with an entire cessation of brack- 

 ish conditions. Elevations of the continent northward and south- 

 ward contracted the area of the great Wasatch sea, and perhaps 

 deepened it, for at this time were deposited the fine limestones 

 and silico-calcareous shales of the Green River epoch. There is 

 no evidence that these beds had a greater eastern extension than 

 that of the parent Wasatch lake. King has given distinct names 

 to these ancient lakes. I think it better to pursue the usual 

 course of using for them the names already given to their depos- 

 its, as involving less strain on the memory ; the more as the num- 

 ber of these lakes is being increased by numerous new discoveries. 

 The only known region which it covered west of the Wa- 

 satch range, is represented to-day by the calcareous strata in Cen- 

 tral Utah which I have called the Manti beds. The exact equiv- 

 alency of these is, however, not quite certain. Further contrac- 

 tion reduced this area to perhaps two lake basins, whose deposits 

 now form two isolated tracts in Southern Wyoming, and are known 

 as the Bridger formation. Continued elevation and drainage 

 caused the desiccation of these basins also, leaving only, so far as 

 present knowledge extends, a body of water on the south of the 

 Uinta mountains, in Northeastern Utah. The sediments of this 

 lake form the Uinta formation, which is the latest member of the 

 series now found in the region lying between the Rocky and Wa- 

 satch mountains. 



About the time that the elevation of the present drainage basin 

 of the Colorado river was completed, a general subsidence of 

 level of the great region east of the Rocky mountains com- 



