THE TEETIAEY LAKES. 3 



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 Wasatch 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 commenced. Extensive lakes were 

 formed in the depressions of the Laramie and older beds which formed the 

 surface, which were probably connected over a tract extending from near 

 the Missouri River to Eastern Wyoming and Colorado. At the same time 

 a similar body of fresh water occupied a large part of what is now Centi-al 

 Oregon and certain areas in Northwestern Nevada, according to King. 

 The sediments now deposited constitute the White River formation, and the 

 faunal distinctions which I have discovered to characterize the eastern and 

 western basins have led me to employ for them the subdivisional names of 

 White River beds for the former and Truckee (King) for the latter. It 

 may have been during the early part of this period, or during the Uinta, 

 that there existed two contemporary bodies of water, separated by a wide 

 interval of territory. One of these extended over a considerable tract in 

 Northern Nevada, and deposited a coal bed near Osino. A formation prob- 

 ably the same has been found by Professor Condon in Central Oregon 

 underlying the Truckee Miocene beds. The other lake left its sediments 

 near Florissant, in the South Park of Colorado. This formation I have 

 named the Amyzon beds,* from a characteristic genus of fishes which 

 is found in it. It has been referred to the Green River formation by 

 King, but without the necessary paleontological evidence, as it appears 

 to me. 



The oscillations of the surface which brought the White River period 

 to a close are not well understood. Suffice it to say here, that after an 

 interval of time another series of lakes was formed, Avhich have left their 

 deposits at intervals over a wider extent of the continent than have those 

 of any other epoch. These constitute the beds of the Loup Fork period, 

 which are found at many points between the SieiTa Nevada and the Rocky 

 Mountains from Oregon to New Mexico, and over parts of the Great Plains 



* American Naturalist, May, 1879. 



