218 R. W. Chaney — Flora of Payette Formation. 



If these three species are thus shown to range into the 

 Miocene, the preceding summaries must be changed, as 

 follows : — 



Payette species occurring in the Eocene 8 



Payette species occurring in the Miocene 17 



and 



Payette species found elsewhere only in the Eocene 2 



Payette species found elsewhere only in the Miocene .... 9 



• From a numerical standpoint, the Payette flora is more 

 closely related to the Miocene floras than to those of 

 any other Tertiary system. However, mere numbers of 

 common species are not, in themselves, the sole criteria 

 for placing the age of a flora, The two species which 

 remain to make up those limited to the Eocene are Odos- 

 temon simplex and Quercus simplex. The former is 

 represented in the collections from the Upper Clarno 

 at Bridge Creek by a single specimen; it is closely similar 

 to several of the living barberries. Quercus simplex 

 differs only slightly from several other species of west- 

 ern fossil oaks which range up into the Miocene. 

 Neither of these species carries great weight in indicating 

 Eocene age. Again both Quercus simplex and Salix 

 angusta are species with somewhat indefinite character- 

 istics, so that the record of the range of the former from 

 the Raton to the Upper Clarno and of the latter from the 

 Green River to the Mascall may be in each case in error. 

 On the other hand, the presence in the Payette of species 

 which are characteristic of several localities of the Mio- 

 cene gives more weight to an age reference to that hori- 

 zon than the occurrence in it of several species from 

 another horizon which are of restricted distribution and 

 rare occurrence. In this regard, Platanus dissecta and 

 Ulmus calif omica, both originally described from the 

 auriferous gravels, 4 are typical Miocene species. By 

 reference to the tables of distribution, it will be seen 

 that Platanus dissecta has been found in the Miocene 

 of the John Day Basin (Mascall formation), of Table 

 Mountain, California (Auriferous Gravels), of Corral 

 Hollow, and of central Washington (Ellensburg forma- 



4 Lesquereux, Leo : Fossil Plants of the Auriferous Gravel Deposits of 

 the Sierra Nevada, Mus. Comp. Zool. Mem., vol. 6, No. 2, pp. 1-62, 1878. 



