238 THE ETHIOPIAN REGION. [CHAP. 



of the continent; although the mouse-like long-tailed flying- squirrel 

 (Idiurus) is exclusively West African. While true squirrels (Sci- 

 urus] are common to this and the other regions of Arctogaea, the 

 pigmy squirrels constituting the genus Nannosciurus are repre- 

 sented by one species (N. minutus) in West Africa, while all the 

 others are Malayan. The spiny squirrels of the genus Xerus are 

 now, on the other hand, exclusively Ethiopian, although their 

 northern origin is proclaimed by the occurrence of an extinct 

 species in the French Miocene. Dormice (Myoxidce) are exceed- 

 ingly abundant in Ethiopia, and if it is considered desirable to 

 split up the family into more than two genera, the genus Graphi- 

 urus, characterised by the short, cylindrical, and tufted tail, and 

 the simple structure of the molar teeth, will be peculiar to this 

 region, as will also be the single West African form described as 

 Claviglis. Dormice, as mentioned earlier, date in Europe from 

 the lower Oligocene, and therefore they might well have entered 

 Ethiopia with the ancestral lemuroids, although, so far as it goes, 

 their absence from Madagascar is against this view. In the 

 mouse-family (Muridce) five sub-families are met with in Ethiopia, 

 two of which are peculiar to the region. Curiously enough, the 

 cricetine sub-family, which is the oldest of all, and the only one 

 met with in Madagascar, is represented only by a single highly 

 specialised genus (Trilophomys). The inference from this would 

 seem to be that the ancestral cricetines and lemuroids entered 

 Ethiopia together, whence some migrated to Madagascar ; the 

 former group, with the exception of the one peculiar genus, having 

 completely died out on the continent, where the remaining 

 murines are more recent immigrants from the north. In this 

 family the Eastern Arctogaeic group of the gerbils (Gerbillince) 

 includes six genera, out of which no less than five, namely 

 Pachyuromys, Mystromys, Otomys, Dasymys, and Malacomys, are 

 exclusively Ethiopian, the last being West African. The elongated 

 hind limbs and the transverse laminae of the molars readily serve 

 to distinguish the gerbils from the exclusively Ethiopian sub- 

 family Dendromyin&i in which the molars are rooted and tuber- 

 culated and the ears remarkably hairy. The typical genus 

 Dendromys includes two dormouse-like forms, one from South, 

 and the other from East Africa; the other genera being Lima- 



