No. 517] 



MIOCENE TREE i 



43 



broken that its positive identification is not pos- 

 sible" (Knowlton). 



Persea pscudocarolineiisis Lx. Tlie Lamar speci- 

 men figured, "the best one found," consists of 

 the upper half of a leaf; what there is of it ap- 

 pears to agree with the Californian species, al- 

 though it has more lateral viens. 



Rhus mixta Lx.! 



Aralia whitneyi Lx. Also in the Intermediate. 

 None of the Yellowstone specimens are perfect, 

 but they appear to belong to this handsome 

 species. 



Thus the species common to the Lamar and Auriferous 

 gravels, hut not knoicu from Basal Eocene, are few, and 

 in several cases of doubtful identity. As the reference 

 of the Lamar to the Miocene rests wholly on the resem- 

 blance of the flora to that of the Auriferous gravels, with 

 the exception of the indication afforded by Farjus lon<ii- 

 folia, it must be considered at least somewhat dubious. 

 It is also to be remarked that eleven species of plants are 

 supposed to be common to the Yellowstone Fort Union 

 and the Auriferous gravels, although two of these, at 

 least, are doubtfully from the gravels, while in four or 

 live cases the Yellowstone material is fragmentary or 

 doubtful.' 



It is one thing, however, to recognize distinct elements 

 in common between the Auriferous gravels and the 

 Lamar, and another to prove the latter Miocene thereby. 

 The former may be conceded, the latter I think not. 



Lesquereux enumerates thirteen species from the Au- 

 riferous gravels which are almost identical with living 

 species; he also cites seventeen which are evidently, but 

 not very closely, related to living ones. Of the thirteen, 

 four are enumerated from the Lamar; of the seventeen, 

 not one. Of the four common to the Lamar, three are 

 dubious, and only Juglans leonis (a species represented 

 to-day by the Asiatic J. regia) appears to be of satis- 

 factory standing. 



