420 GEOLOGICAL SUEVEY OF THE TERRITORIES. 



13i per cent, of its species in common with Alaska, 20a per cent, with 

 the Arctic iiora, 40 per cent, witli the Miocene ; and our Lower Eocene 

 has only S^ per cent, of its species in common with the Alaska, lOg per 

 cent, with the Arctic, and 25 per cent, with the European Miocene. 

 Or counting the species of Alaska, Arctic, and Miocene of Europe as 

 Miocene, the relation of the American Tertiary flora with this forma- 

 tion of Europe is, for the Miocene, 47f ; the Ui^per Eocene, 57^-, and 

 for the Lower Eocene, 37 per cent. 



This comparison, somewhat unreliable on account of the greater or 

 less degree of affinity of a few species, may be, however, admitted in 

 full contidence for our purpose^ and proves that the flora which we con- 

 sider as representing our Miocene, that of Green Kiver, Elko, and South 

 Park, does not bear to that of Europe a marked annlogy by its forms. 

 These, indeed, appear of younger type, more intimately related even by 

 identity to species of our time. The flora of the group marked as Upper 

 Eocene has, j;e)- contra, the greatest analogy to that of the European 

 Miocene by the identity of its most common species of Poindus, Querciis, 

 JJlmiis, Bettda, Flatanus, Fagus, &c. It may be that farther researches 

 may force a separation of this group from the Eocene, though as yet 

 there is no apparent line of division, either in ilie measures or in the 

 distribution of the flora. I believe that the discrepancy is merely ^ 

 apparent, resulting from and indicating a precedence in time of our 

 botanical types over those of Europe. This fact has already been re- 

 marked upon in considering the flora of the Carboniferous formations, 

 and jt becomes the more evident as the history of the old vegetable 

 world is better known. The relation of the Lower American Eocene to 

 the Miocene of Europe, 37 ])er cent., does not indicate a difierence more 

 marked than could be expected between the flora of two members of 

 the same formation ; and the difierence, too, is becoming more and 

 more definite, and will continue in the same way as far as the acquaint- 

 ance with our fossil flora is more intimate. The most common species 

 of fossil-iflants are not only found over wide areas, and therefore col- 

 lected from all the explorers, and in numerous specimens ; but they pass 

 through the 'difierent stages of the formations. The first researches 

 bring them to view from everywhere; the selection, however, becomes 

 more discerning and exclusive in proportion to the amount of materials 

 supplied for cojuparison. 



On the question of the distribution of Tertiary fossil species in regard 

 to climatic circumstances, the table does not show anything more than 

 what has been observed from that of the former report. The relation 

 of our Upper Eocene flora with that of Alaska and Greenland is well 

 defined, while the vegetable types of the Lower Eocene are rather trop- 

 ical than Arctic. It is then possible that the characters which I have 

 considered as resulting from climatic influences have a relation to difier- 

 ence of age of the formations. If it is the case, Ave may expect to find 

 the flora of the Lower Eocene with the same southern types from Yan- 

 couver Island to the Mississippi, while the Arctic facies may predomi- 

 nate in the LTpper Eocene from Greenland to the Same southern latitude. 



This important question of the regulation of Tertiary groups of vege- 

 tables according to their geological stations, or to climatic influences, 

 cannot be settled without long researches. Some species of the Lower 

 Eocene appear to have, with types of the present flora of Cuba, a 

 relation which has not been recognized betbre. Such are forms of 

 FlabcUaria and Calamopsis ; Myrica Torreyi, compared to a. Lomatia ; a 

 gronp of Ficus, ^'presented by Ficm planicostata, F. Clinioni, F. spec- 

 tabilis, F. coryli/olia; — Cissus hcvigatuSjAkuritcs Foccnicu,-din\ the group 



