210 CRITIQUES AND ADDRESSES. [ix. 



distributional province from the Eocene and Miocene 

 marsupials, which are Austro-Columbian. So far as the 

 imperfect materials which exist enable a judgment to be 

 formed, the same law appears to have held good for all 

 the earlier Mesozoic Mammalia. Of the Stonesfield 

 slate mammals, one, Amphitherium, has a definitely 

 Australian character ; one, Phascolotherium, may be 

 either Dasyurid or Didelphine ; of a third, Stereognathus, 

 nothing can at present be said. The two mammals of 

 the Trias, also, appear to belong to Australian groups. 



Every one is aware of the many curious points of 

 resemblance between the marine fauna of the European 

 Mesozoic rocks and that which now exists in Australia. 

 But if there was this Australian facies about both the 

 terrestrial and the marine faunas 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 suggestion 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 durino 1 

 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, the difficulty 

 in which we were left, some time ago, by the arguments 



