CHAPTER V. 



EASTERN ARCTOG^EA. 



Mammalian groups peculiar to Eastern Arctogsea Tertiary Mammalian 

 Faunas of Eastern Arctogaea Oligocene Fauna Miocene Fauna Older 

 Pliocene Fauna Pikermi and allied Faunas Siwalik Fauna Higher 

 Pliocene Faunas. 



ALTHOUGH northern Europe and Asia forms but one zoological 

 region with the corresponding part of North America, 

 yet there are numerous groups of mammals con- 



fined respectively to its eastern and western portions, ^u> Eastern 

 which clearly show that the communication between 

 the two areas was always more or less limited. In this chapter 

 attention will be first directed to some of the most striking 

 peculiarities of the mammalian fauna of Eastern Arctogaea, after 

 which the whole fossil fauna may be taken into consideration. 



In addition to the total absence of existing opossums (Didel- 

 phyid(E\ and the presence in its warmer portions of fruit-bats 

 (Pteropodidce), which, however, are common to Notogaea, Eastern 

 Arctogaea is especially characterised as being the home of all the 

 higher Primates; namely the family Stmiidce, which includes the 

 man-like apes and gibbons, and the Cercopithecidcz, embracing all 

 the other Old World monkeys. From the South American monkeys 

 (Cebidcz) both these families are broadly distinguished by having 

 two pairs of premolar and three of molar teeth, whereas in the 

 former group there are three pairs of both premolar and molar 

 teeth. Not only are the two families in question confined at the 

 present day to the Eastern hemisphere, but the same appears to 

 have been the case at all epochs, since no trace of a fossil monkey 

 has ever been recorded from North America. This remarkable 

 isolation of the distributional areas of the Simiidcz and Cercopi- 

 thecidce on the one hand, and of the Cebidce. (and Hapalidcz) on 



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