DESCKirTION OF SPECIES— CUPULIFERiE. 149 



European authors describe a few species fioin the Middle Eocene, and still 

 a larger number from the upper measures, the Oligocene or Armissan. It is, 

 liowever, in the Miocene that the genus reaches its full development; and, judg- 

 ing from data obtained from the study of tin; North American Tertiary floras, 

 the predominance of Oaks increases even into the Upper Miocene and the 

 Pliocene, for, in fifty species which represent the flora of the Chalk Bhiffs of 

 California, nine, or more than seventeen per ceut., belong to Quercus. This 

 proportion, as far as it can be estimated, is far above tliat of the Oaks in the 

 present North American flora; for, counting the arborescent, or woody hard 

 species, which could be preserved by fossilization, in supposing analogous 

 circumstances, the Oaks of the eastern slope of the United States would not 

 constitute more than six per cent, of its flora. 



Prof W. P. Schimper, in his Pak^ontologie Vdgdtale, describes one 

 hundred and sixty fossil species of Oaks, which he distributes in tive different 

 sections : — 



In the first, that of the Salicifolia, he has forty-seven species, four of 

 which are Cretaceous, twelve Eocene, and tliirty-one Miocene. Among the 

 Eocene species, he places three described from Vancouver's Island. 



In the second section, which includes the si^ecies with serrate or dentate 

 leaves, he has thirty-nine species, three of which are Cretaceous and five 

 Eocene ; of these, three are North American. This disproportion in the distri- 

 bution is rather uncertain, however, and explainable in part by the fact that the 

 Eocene floras of Europe, that of Mount Bolca, for example, are still unknown, 

 and also J)y the reason that some species referable to this section are described 

 by Schimper under the generic name of Dryophyllum. Of these, the S(izanne 

 flora (Lower Eocene) has four; that of Gelinden, a still lower formation, has 

 five (these published since the Pal^ontologie Vc^gt'tale was out); and two 

 more have been more recently discovered in the Point of Rocks measures 

 of Wyoming, which, l)y its flora, characterizes the lowest Tertiary of this 

 country. 



Schimper's third section has the species with coriaceous, few-nerved, 

 or indistinctly nerved leaves, which are generally of difficult and uncertain 

 determination. It contains thirty species, three Oligocene, one Quaternary, 

 the other Miocene. Quercus aculiloha, a well-characterized Oligocene species 

 of this section, has been found also at Golden in the Lower Lignitic of 

 Colorado. 



