American and Englhh Fossil Floras. 505 



Cretaceous period because they were absent in our Eocenes, but 

 these, it must not be foigotten, are throughout only the mud of an 

 estuary or small inclosed sea, and were deposited under peculiar 

 conditions. We should have precisely equal grounds for asserting 

 the non-existence of everything not now found within the area of 

 the English Channel. An examination of the fauna of its bed would 

 not convey the slightest indication that numerous survivals of Cre- 

 taceous genera are still flourishing in distant seas. Yet such is the 

 case. So with the Reptilia. We have many examples of long 

 isolated lands being tenanted by unwieldy survivals from past ages, 

 and maintaining themselves until brought into contact with newer 

 types of development from elsewhere. There is reason to believe 

 that America was so isolated until some period in the Tertiary, and 

 that such primitive types as Mosasaurus should have continued to 

 exist until exterminated by the arrival of mammalia is paralleled in 

 so many instances to-day that no difficulty in admitting the possi- 

 bility need be felt. 



The issue before us is whether we will believe that in America 

 a Cretaceous fauna extended into the Eocene, or that an Eocene 

 flora extended back to the Cretaceous. In other words, is it more 

 difficult to conceive that ancient organisms lived to a later date 

 than we have been accustomed to believe ? our own ideas on the 

 subject having been formed from the study of a very limited area ; 

 or that a flora, so developed that it naight be an existing one, 

 flourished in America for incalculable ages before anything ap- 

 proximating to it in development made its appearauce in Europe ? 



In support of the first proposition, we have the innumerable sur- 

 vivals of old types at the present day, wherever the struggle for 

 existence has been less severe, and the fact that the Cretaceous-look- 

 ing types are largely mingled with others of a Tertiary facies. The 

 Tertiary facies of the Flora, on the other hand, is not diminished 

 by the presence of any distinctly Cretaceous plants. I think all the 

 evidence I have been able to bring forward is in favour of a newer 

 rather than an older date, and this is decidedly more in harmony 

 with the march of evolution. 



The presence at the base of the British Eocenes, and nowhere else 

 in Europe, of a flora so nearly resembling that of the Dakota series 

 of America, seems to prove that England formed part of a continent 

 that stretched across the Atlantic at that date. The Eocenes of 

 England are the muds of an estuary which opened to the east, and 

 all our Eocene seas were on that side, while an enormous river flowed 

 from the west. Later in the Eocene we have a large influx of 

 tropical American plants and land moUusca, and I believe a critical 

 statement of the evidence in support of this land connection would 

 place it beyond all reasonable doubt. An increase of temperature 

 drove the old flora north, and we find it succeeded in both areas by 

 a more tropical-looking flora which, considering the enormous dis- 

 tance separating them, is of strikingly uniform character. The land 

 connection afterwards became disrupted in the west and extended 

 towards the east, so that this tropical flora, arriving from America, 



