384 PALAEONTOLOGY AND EVOLUTION xi 



must, therefore, have existed, as such, before the 

 Carboniferous epoch in other words, in Devonian 

 times and its terrestrial population may never 

 have been other than such as existed during the 

 Devonian, or some previous epoch, although much 

 higher forms may have been developed else- 

 where. 



Again, let me say that I am making no 

 gratuitous ass-umption of inconceivable changes. 

 It is clear that the enormous area of Polynesia is, 

 on the whole, an area over which depression has 

 taken place to an immense extent ; consequently 

 a great continent, or assemblage of subcontinental 

 masses of land must have existed at some former 

 time, and that at a recent period, geologically 

 speaking, in the area of the Pacific. But if that 

 continent had contained Mammals, some of them 

 must have remained to tell the tale ; and as it is 

 well known that these islands have no indigenous 

 Mammalia, it is safe to assume that none existed. 

 Thus, midway between Australia and South 

 America, each of which possesses an abundant 

 and diversified mammalian fauna, a mass of land, 

 which may have been as large as both put together, 

 must have existed without a mammalian in- 

 habitant. Suppose that the shores of this great 

 land were fringed, as those of tropical Australia are 

 now, with belts of mangroves, which would extend 

 landwards on the one side, and be buried beneath 

 littoral deposits on the other side, as depression 

 went on; and great beds of mangrove lignite 



