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



larity between Plat anus dissecta and P. occidentalis now 

 living in the eastern half of the United States, and 

 between TJlmus calif or nica and U. alata of the south- 

 eastern United States. In the case of Plat anus dissecta, 

 its resemblance to the western species, P. racemosa, seems 

 even closer than to P. occidentalis. This resemblance 

 between various forms of the Payette flora and living 

 plants adds further weight to the reference of the Payette 

 to the Miocene rather than to an older period. 



A probable explanation of the conflicting evidence of 

 age as shown by Eocene as well as Miocene representa- 

 tives in the Payette flora is that the disparity in age 

 is more apparent than real. The writer has not yet 

 brought together all the necessary evidence, but recent 

 field studies in the John Day Basin and at other points 

 in eastern and central Oregon point to the placing of 

 the Upper Clarno formation in the Oligocene rather than 

 the Eocene. If this is correct, and the supporting evi- 

 dence will be brought forth in a subsequent paper, there 

 are no typical Eocene plants in the Payette flora, but 

 rather an increased number of Oligocene forms which 

 may be supposed to have been precursors of the Miocene 

 flora to follow. 



The position of the Payette formation, above basalt 

 lavas, is in accord with the relation of the Miocene Mas- 

 call formation to the Columbia lavas in Oregon. Ver- 

 tebrate remains collected from the Payette formation 

 by Buwalda are referred by him to the Middle or 

 Upper Miocene 8 . There appears, therefore, to be an 

 agreement between the evidence of the flora, the fauna, 

 and the stratigraphy in pointing toward the Miocene 

 age of the Payette formation. So far as the plants are 

 concerned, the age would not be younger than Middle 

 Miocene, and in view of the inclusion of Oligocene and 

 possibly Eocene forms, it might better be considered 

 as Lower Miocene. The present knowledge of the west- 

 ern floras does not justify an' attempt to draw the lines 

 of age too sharply, and at this time the writer is satis- 

 fied to make the reference to the Miocene without further 

 specification. 



The Payette flora has a composition so like that 

 of the forests in certain parts of the Pacific Coast region 



8 Buwalda, John P. Letter of Feb. 10, 1922. 



