Notes on Fossil Woods. 501 



closely correspond in age with our Laramie. The Filiates 

 hebridica of Forbes is our Onoelea sensibilis. The species 

 of Ginkgo, Taxus, Sequoia and Gtyptostrobus correspond, and 

 we have now probably found a Podocarpus as noted above. 

 The Platanites Hebridicus is very near to our great Platanus 

 nobilis. Corylus Macquarrii is common to both formations ; 

 as well as Populus arctica and P. Bichardsoni, while many 

 of the other exogens are generically the same and very 

 closely allied. These Ardtun beds are regarded by Mr. 

 Gardner as Lower Eocene or a little older than the Gelinden 

 series of Saporta. and nearly of the same age with the so- 

 called Miocene of Atane-kerdluk in Greenland. I have 

 ever since 1875, maintained the Lower Eocene age of our 

 Laramie and of the Fort Union Group of the Northwestern 

 United States, and the identity of their flora with that of 

 McKenzie River and Greenland ; and it is very satisfactory 

 to find that Mr. Gardner has arrived at similar conclusions 

 with respect to the Eocene of Great Britain. 



An important consequence arising from this is, that the 

 period of warm climate which enabled a temperate flora to 

 exist in Greenland was that of the later Cretaceous and 

 early Eocene, rather than, as usually stated, the Miocene. 

 It is also a question admitting of discussion, whether the 

 Eocene flora of latitudes so different as those of Greenland, 

 Mackenzie River, N. W. Canada and the Western States, 

 were strictly contemporaneous, or successive within a long 

 geological period in which climatal changes were gradually 

 proceeding. The latter statement must apply at least to 

 the beginning and close of the period ; but the plants them- 

 selves have something to say in favour of contemporaneity. 

 The flora of the Laramie is not a tropical but a temperate 

 flora, showing no doubt that a much more equable climate 

 prevailed in the more northern parts of America than at 

 present. But this equability of climate implies the possi- 

 bility of a great geographical range on the part of plants. 

 Thus it is quite possible, and indeed highly probable, that 

 in the Laramie age, a somewhat uniform flora extended from 

 the Arctic seas through the great central plateau of America 

 far to the south, and in like manner along the western coast 



