atui aUicd East-African Species. 337 



sliort orange-buff liairs, the general effect more orange- 

 coloured than in any of the allietl species, in this respect 

 reseniblintf the somalicus group. Backs of hands and feet 

 light burt-coloured. Under surface of body whitish; hairs 

 with grey bases and white tips, the tips in many individuals 

 tinged witli buff. Ventral surface not sharply marked off 

 from the flanks, the two areas gradually passing into each 

 other. Hairs on throat, chin, and underside of limbs white. 

 Tail with well-marked dark dorsal area, orange sides, and 

 liglit buff-coloured under surface. 



Skull large, in old individuals nearly equalling tliat of 

 nilotlcus. Zygomatic region rather narrow, not markedly 

 broader in the squamosal portion. Brain-case a good deal 

 narrower than in niloticus, especially in the occipital region. 

 Incisors and molars rather smaller than in the Egyptian 

 species. 



Dimensions in millimetres (measured in the flesh) : — 



Average of 



10 adults. Max. Min. 



Head and body 151 160 146 



Tail 152 170 145 



Hind foot 31 34 29 



Dimensions of adult skull : — 



Greatest length 38*2 mm. ; basilar length 32 ; condylo- 

 incisive length 36 ; zygomatic breadth 18 ; interorbital con- 

 striction 5*6 ; squamosal breadth of cranium 14*5 ; length of 

 nasals 14; palatilar length 17 ; length of palatal foramina 8 ; 

 length of upper molar series 7"3. 



Type locality. Bahr-el-Abiad, Egyptian Soudan. 



This species would appear to be one that enjoys a fairly 

 wide distribution, ranging from Upper Egypt southwards 

 towards the Bahr-el-Ghazal and eastwards as far as Arabia, 

 the specimens from Aden being in every respect identical 

 with those from the Nile Valley. In the Museum collections 

 are specimens from the following localities : — Seunaar, 

 Khartoum, Nakheila, Sherik, Shendi, Gerazi (Soudan), El 

 Kama (Soudan), and Aden. The Sennaar specimens are 

 practically topotypes, Bahr-el-Abiad, the type locality, being 

 situated on tiie south- svest side of Sennaar. 



Isomys variegatus, var. minor ^ described by Sundevall *, is 

 probably more nearly related to testicularis than to niloticus. 

 Tlie description would appear to agree better with the general 

 colour scheme met with in the Southern species ; but until 

 topotypical specimens are available for examination it is 

 * Vet.-Ak. Handl. p. 221 (1843). 



