128 DISTRIBUTION OF EXTINCT ANIMALS. [part ii 



Lemurs and Marsupials — proves, that we have here hardly made 

 an approach towards the epoch when the mammalian type itself 

 began to diverge into its various modifications. Some of the 

 Carnivora and Ungulates do, indeed, exhibit a less specialised 

 structure than later forms ; yet so far back as the Upper 

 Miocene the most specialised of all carnivora, the great sabre- 

 toothed Machairodus, makes its appearance. 



The Miocene is, for our special study, the most valuable and 

 instructive of the Tertiary periods, both on account of its 

 superior richness, and because we here meet with many types 

 now confined to separate regions. Such facts as the occurrence 

 in Europe during this period of hippopotami, tapirs, giraffes, 

 Tragulidse, Edentata, and Marsupials — will assist us in solving 

 many of the problems we shall meet with in reviewing the 

 actual distribution of living forms of those groups. Still more 

 light will, however, be thrown on the subject by the fossil forms 

 of the American continent, which we will now proceed to 

 examine. 



