114 



This table shows the following proportional distribution :- 



Eliminated genera 



Species of general distribution 



Exclusively Quilchena - - - - . 



Lignite Tertiary 



Miocene Tertiary 



Oligooene (Green river) 



Eocene 



10 



3 



4 



21 



22 



12 



1 



An analysis of this table makes it clear that the species are about equally distributed 

 between the Eocene and the Miocene, while somewhat more than half as many occur in the 

 Oligocene or Upper Eocene. To deal with specific cases, Carpinus grandis, although found 

 in the Eocene, is essentially a Miocene type. Prunus merriami and Salix perplexa are 

 known only to the Miocene. Ulmus speciosa is an Oligocene type characteristic of the Green 

 River group. Alnus serrulata fossilis is a recognized constituent of the Upper Eocene at 

 Bridge creek, Oregon. Pinus lardyana and P. steenstrupiana, found for the first time on this 

 continent, are distinctively Miocene types, which is also true of Populus mutabilis oblonga, 

 all three being European species. Ficus decandolleana is likewise from the European 

 Miocene. 



On the other hand, Oornus suborbifera, Corylus americana, Dryophyllum stanleyanum, 

 Juglans m'gella, Popalus genetrix, Quercus castaneopsis, Bhamnus elegans and Salix varians 

 are essentially Eocene types, and chiefiy of Laramie age. "With respect to Dryophyllum, 

 it may be observed that the four species known to the United States are all of Eocene age, 

 whence it may be inferred that the genus is characteristic of that formation. 



