190 EASTERN ARCTOG^A. [CHAP. 



Eastern and Western Arctogaea, which will be still more apparent 

 after the consideration of the mammals of North America, seem at 

 first sight to indicate that these two areas should form distinct 

 divisions of the realm, yet the community of the fauna of the 

 northern portion of the two hemispheres forbids this view. This 

 question may, however, be more fully discussed in the chapter 

 devoted to the Holarctic region. 



Before entering upon the consideration of the different zoolo- 

 gical regions into which the realm is divided, it is 

 Mlmma r Han essential to take a brief survey of the Tertiary mam- 

 Faunas of malian faunas of Eastern Arctogaea. By this alone 



Eastern . 



Arctogeea. it is possible to understand the true relations of the 



existing faunas to one another ; while such a survey 

 also serves to demonstrate that the regions in question are but 

 features of the present epoch of the earth's history ; and that even 

 as late as the Pliocene portion of the Tertiary epoch the dis- 

 tinctions now obtaining between the Holarctic, Oriental, and 

 Ethiopian regions had no existence. In our survey we may omit 

 the Eocene period, and commence with the lower Oligocene ; and 

 it will simplify matters to give lists of some of the more important 

 and better known generic types characterising the faunas of the 

 different horizons. The leading affinities of many of the genera 

 mentioned have been already alluded to in the present or preced- 

 ing chapters ; but it would vastly exceed the limits of our space 

 to attempt to point out the distinctive features of the others. 

 Accordingly, the reader must either take them on trust, and treat 

 them practically as abstract terms, or he must refer to some 

 palaeontological treatise in order to find the real nature of the 

 animals indicated by such generic names. 



Although it is essential to our purpose to notice the Oligocene 



faunas of Eastern Arctogaea, it is important to 



FauIS* 06116 observe that our knowledge of these is practically 



limited to Western Europe. We are consequently 



quite unable to say how far the geographical range of such 



faunas extended, although it is probable that this embraced a 



large portion of the Eastern Holarctic region. Whether, however, 



at this epoch Ethiopian Africa had received a large mammalian 



fauna must be left for future discoveries to determine. 



