l6o THE ARCTOG^EIC REALM. [CHAP. 



whole of the tropical and temperate parts of the realm with the 

 exception of Madagascar. Remains of Sperm ophilus and Sciurus 

 are met with in the later Tertiaries of Europe'; and the extinct 

 Plesiarctomys, which is common to the Oligocene and Miocene of 

 Europe and North America, seems to be a connecting form 

 between the squirrels and marmots, having upper molar teeth of 

 the tritubercular type. 



As regards the cosmopolitan family Muridcz, including the 

 rats, voles, lemmings, etc., it will suffice to say that originally it 

 was undoubtedly Arctogaeic ; the forms respectively inhabiting the 

 Neogaeic and Notogaeic realms being comparatively recent immi- 

 grants. Both the subfamilies of the voles (Microtince) and the 

 CricetincB are common to the entire Holarctic region ; the latter 

 being represented in the eastern half by the hamsters (Cricetus) 

 and in the western by the white-footed mice (Sitomys], while they 

 are the sole rodents inhabiting Madagascar, and have one species 

 in Ethiopian Africa, where there is also the closely allied Deomys, 

 forming a subfamily by itself. The cricetines are indeed evidently a 

 primitive type, which in the Old World have been largely supplanted 

 or driven south by the more specialised. Murince (true rats and mice) ; 

 but as these are represented in the Middle Tertiaries of both 

 eastern and western Arctogaea, it is difficult to decide which was 

 their original habitat. Little need be said in regard to the hares 

 (Leporidce), except that they range over the whole of Arctogasa, 

 and have two outlying representatives in Neogaea, which are 

 doubtless comparatively recent immigrants, although one is known 

 to have inhabited Brazil since the Plistocene. 



A not less marked feature of Arctogaea is the absence of most 

 of the Neogaeic rodent families noticed in the preceding chapter. 

 The existence of members of one of these (Octodontida) in Africa 

 is mentioned in the same place 1 , where a reference to the occur- 

 rence of allied forms (Theridomyidce] in the European Tertiaries 

 will also be found 2 . 



One of the most important features in connection with the 

 Arctogaeic ungulates is the total absence of the 



Ungulates. 5 6 



peculiar subordmal groups characteristic of the 

 1 See also the chapter on the Ethiopian region. 2 Supra, p. 86. 



