790 GEOLOGY OF THE YELLOWSTONE NATTOXAL PAEK. 



Of these 29 species, only 4 have been found in the true Laramie. These 

 are Juglans rugosa, Platanus guillelmce, Rhamnus rectinervis, and Diospyros 

 brachysepala, the last open to doubt. All of these species have a wide ver- 

 tical range and are consequently of little value in indicating age. The 

 affinities of this flora with that of the Laramie may therefore be regarded 

 as unimportant. 



The relationship of this flora with the Fort Union, Denver, and Green 

 River groups is also relatively unimportant. There are 7 species found in 

 each of these groups, but none are confined to the Denver, and only 1 to 

 the Green River, and 3 to the Fort Union. The rest are of wide geograph- 

 ical and geological distribution. 



The relationship of the flora of the basic rocks is clearly with that of 

 the Auriferous gravels of California, for no fewer than 17 of the 29 species 

 are common to the two localities, and 12 of the species are exclusively con- 

 fined to them. These are such important species as Aralia whitneyi, Persea 

 pseudo-car olinensis, Laurus californica, Laurus grandis, Magnolia californica, 

 Ficus sordida, Juglans californica, Rhus mixta, etc. Most of these are present 

 in numbers in the Park flora, and there can therefore be no question as to 

 the correctness of their identification. 



Besides the species above enumerated that have actually been found 

 common to the two localities, the numerous new species are in many cases 

 unmistakably related to species known only from the Auriferous gravels. 

 Thus, Magnolia culveri is close to M. californica, and Magnolia spectabilis is 

 so close to M. lanceolata that Lesquereux so identified it. Other examples 

 might be given, but they are unnecessary. The preponderance of evidence 

 points to the similarity of age between the flora of the basic series and that 

 of the Auriferous gravels of California. The fixing of the exact age of the 

 Auriferous gravels is not a difficult matter. They were at, first supposed to 

 be Lower Pliocene in age, but the latest evidence, derived from a more or less 

 complete restiuty of the abundant flora, together with a thorough investiga- 

 tion of the stratigraphy, makes it reasonably certain that it is really Upper 

 Miocene. This is the view taken in the present instance, and this flora in 

 the Yellowstone National Park is referred to the Upper Miocene: 



Aspleniuin iddingsii n. sp. Magnolia? pollardi n. sp. 



Lygodium kaulfusii. Laurus primigenia 1 Uug. 



Equisetum caualieulatum u. sp. Laurus californica Lx. 



