322 THE HOLARCTIC REGION. [CHAP. 



The list of more or less peculiar generic types among the 

 rodents is relatively large. Foremost among these stands a very 

 large flying-squirrel {Eupetaurus}, inhabiting the regions north of 

 Kashmir and Tibet, and distinguished from all other members 

 of the family to which it belongs by its tall-crowned (Jiypsodonf] 

 cheek-teeth. In the dormouse family (Myoxida) the squirrel- 

 tailed species, which is the sole representative of the genus 

 ~Myoxus in its restricted sense, and the common dormouse, alone 

 constituting Muscardinus, are exclusively European ; fossil forms 

 occurring through the upper and middle Tertiaries. 



In the Muridce. the hamsters (Crtcetus), if regarded as generi- 

 cally distinct from their allies the white-footed mice (Sitomys] of the 

 New World, are absolutely characteristic of the eastern division of 

 the Holarctic region, where they range over a large portion of 

 Europe and northern Asia. Extinct species are abundant in the 

 European Tertiaries. Two genera of the mole-like rodents, 

 having the dentition of voles, but approximating in the form of 

 their body and limbs to the moles, constitute a sub-family which is 

 also restricted to this area. Of these mole-voles, the first genus 

 (Ellobius] is represented by one species from Russia and another 

 from Afghanistan, while the second (Siphneus) includes several 

 forms from North and Central Asia; fossil species of the latter 

 having been described from the Plistocene of the Altai and the 

 Pliocene of northern China. The great mole-rat (Spalax typhlus) 

 of southern Europe, Persia, Mesopotamia, Syria and Egypt, repre- 

 sents the only genus among the Spalacidce. which is confined to 

 the present area. The Dipodidce, on the other hand, contain 

 several characteristic eastern Holarctic generic types. The most 

 aberrant of these are the rat-like animals constituting the genus 

 Sminthus, of which one species inhabits eastern and northern 

 Europe and Central Asia, while a second is found in Kashmir, 

 and a third in the Kansu district of China. Of the more typical 

 forms, the true jerboas (Dipus), characterised by having only three 

 toes, are exclusively Holarctic, ranging from Egypt into Central 

 Asia, where they always frequent desert districts. Of the genera 

 with five toes, Euchoretes is represented by a single long-snouted 

 and long-eared species from the neighbourhood of Yarkund ; and 

 Platycer corny s, which differs by its flattened and lancet-shaped 



