GEOLOGICAL SURVEY OF THE TERRITOEIES. ' 409 



fore, has a single division for the European Miocene, and another for the 

 Eocene, both for indication of geological age ; and it has, too, one for the 

 Arctic and another for the Alaska Tertiary, for indication of original 

 derivation of species rather than for comparison of geological divisions. 

 The American divisions are defined by stratigraphy as by paleontology. 

 The Upper Tertiary or the IMiocene (?) is represented in the Rocky 

 Mountains by the Green Eiver Group, and some identical strata of Elk 

 Station and of South Park. The second group in descending order, named 

 as yet Upper Eocene, has for its essential members Carbou, Evauston, 

 and Washakie deposits, which may be hereafter subdivided into two 

 stages. The lower Eocene is considered in separate geographical divis- 

 ions, of identical age, as far, at least, as it is known as yet, the Eaton 

 Mountains, Golden, Black Butte, and Six miles above Spring Caiion. 

 Detached areas of the same group, which have as yet furnished to ex- 

 amination a too small number of fossil plants, are united with the 

 essential divisions. The Placer Mountains and the Caiion City go with 

 the Eaton ; the Gehrung's, Marshall's, and Erie coal deposits with 

 Golden ; the Point of Eock and Hallville, with the upper and lower 

 divisions of Black Butte, ; and the dift'ereut localities at and around 

 Port Ellis, with Six miles above Spring Caiion. More precise details of 

 the distribution of each species are given, with their descriptions. The 

 Elk Creek division is as yet scarcely fixed by its remains of fossil plants. 

 It could have been omitted or united, perhaps, with Spring C^non but for 

 a few peculiar species which seem to indicate a distinct iiora, and which 

 may afford matter for consideration. The distribution of the table is, 

 besides, clear and explains itself. 



