ON POSSIL PLANTS. 73 



Ilî 

 General Eemarks. 



The general couclusiou indicated by the above facts is the stroiig resemblance of the 

 tlora of the Mackenzie River beds with that of the Laramie of other parts of Canada and 

 of the United States, and also with Ihe Tertiary of Greenland, Spitzbergen, Alaska and 

 the Hebrides. They thus confirm the inferences as to this similarity, and as to the Lower 

 Eocene age of the Upper Laramie, stated by the author in " The Report on the 49th 

 parallel" in 1875, in subsequent 'Reports of the Geological Survey,' and in previous 

 volumes of these Transactions. 



It is to be observed, in connection with this, that recent observations in the western 

 parts of the United States by Mr. Whitman Cross and others, lead to the conclusion that, 

 locally, plants of Middle Tertiary age have been inadvertently mixed with those of the 

 true Laramie, and that this has tended to mislead palseobotanists. Farther, it seems pro- 

 bable that due attention has not been paid to the distinction of the Lower Laramie and 

 the Upper, or to the separation of the former from the Belly River series of the Upper 

 Cretaceous, which has a very similar flora. It is also quite possible that the line between 

 the Eocene and the Upper Cretaceous may ultimately be drawn, as I have suggested in 

 a previous paper, between the Upper and Lower Laramie. The intervention, in the 

 Northwest Territories of Canada, of a thick series of barren beds of red clay, and the 

 afhnities of the Lower Laramie flora with that of the Upper Cretaceous, certainly tend to 

 this conclusion. In the mean time there can scarcely be any doubt that the flora of the 

 Upper Laramie, of the Atanekerdluk series in Greenland, and of the Spitzbergen and 

 Alaskan Tertiaries, corresponds with that of the Eocene in Europe, and is also identical 

 with the Fort Union flora of the Missouri region, formerly regarded as Miocene. On these 

 points and as to the evidence of the stratigraphical position of the Laramie between the 

 Cretaceous and the Lower Miocene, I would refer to previous papers in these Transactions. 



Lastly, it is worthy of note 'that while the Greenland flora of this age is temperate, 

 that of the temperate regions of America is of the same character and closely allied to that 

 now extant, showing that the conditions of temperature were those of great uniformity 

 over a wide range of latitude rather than of excessive heat in the north. This leads to 

 the inference that the causes of the mild Arctic temperature were geographical rather 

 than astronomical, a conclusion which I have elsewhere stated and maintained. 



While the above paper was in the press, I received the memoirs of Nathor.st ou the Tertiary 

 Flora of Japan, and of Ettingshauseu on that of New South Wales. These suggest some very 

 interesting comparisons. The early Tertiary Flora of Japan coinciJes in many specie^ with the 

 Upper Laramie Flora of the Hebrides, Greenland, Northern Canada, Alaska and Saghalien, indicating 

 the prevalence in later Cretaceous and early Eocene times of a similar tliira throughout the Northern 



Sec. IV, 1889. 10. 



