XI PALEONTOLOGY AND EVOLUTION 379 



exists in Australia. But if there was this 

 Australian facies about both the terrestrial and 

 the marine faunae of Mesozoic Europe, and if 

 there is this unaccountable and immense break 

 between the fauna of Mesozoic and that of 

 Tertiary Europe, is it not a very obvious sugges- 

 tion that, in the Mesozoic epoch, the Australian 

 province included Europe, and that the Arctogaeal 

 province was contained within other limits ? The 

 Arctogaeal province is at present enormous, while 

 the Australian is relatively small. Why should 

 not these proportions have been different during 

 the Mesozoic epoch ? 



Thus I am led to think that by far the simplest 

 and most rational mode of accounting for the 

 great change which took place in the living 

 inhabitants of the European area at the end of 

 the Mesozoic epoch, is the supposition that it 

 arose from a vast alteration of the physical 

 geography of the globe; whereby an area long 

 tenanted by Cainozoic forms was brought into 

 such relations with the European area that 

 migration from the one to the other became 

 possible, and took place on a great scale. 



This supposition relieves us, at once, from tho 

 difficulty in which we were left, some time ago* 

 by the arguments which I used to demonstrate 

 the necessity of the existence of all the great 

 types of the Eocene epoch in some antecedent 

 period. 



