and allied East- Afriran Spezies. 339 



Face and lieaJ similar in colour to back. Nose and ocular 

 rinjjs yellowish buff, the nasal region speckled with black. 

 Backs of hands and foot bully white. Under surface of body 

 wliite ; hairs of belly greyish at base, with long white tips. 

 AVhite ventral surface sharply marked off frouj the buff- 

 coloured flanks, the cantrast more marked than in any member 

 of this group. Tail much as in iesticularis, but shorter and 

 rather less hairy; above rather darker, more as in the 

 ahifssinicus group. 



Skull a trifle shorter than in testicularis. Zygomatic 

 region narrow anteriorly, expanded in the squamosal part, 

 thus ditlering from the typical species, where the zygomatic 

 arches are almost pirallel. 



Dimensions of the type (measured in the flesh) ; — 



Head and body 14:5 mm. ; tail 143 ; hind foot 30 ; ear 19. 



Skull: greatest length 36*5 mm.; basilar length 30; 

 condylo-incisive length 34'5 ; zygomatic breadth 18'4 ; 

 interorbital constriction 5; squamosal breadth of cranium 

 14*2; length of nasals 14; ])alatilar length 16'5 ; length of 

 palatal foramina 6'9 ; alveolar length of upper molar series 7. 



Hah. Between Chak Chak and Dem Zubeir, West Bahr- 

 el-Ghazal. 



Type. Ailult male. B.M. no. 8. 4. 2. 45. Original num- 

 ber 38. Collected on September 3rd, 1907, by A. L. Butler, 

 Esq. 



The most characteristic feature about this western race of 

 testicularis is the sharp contrast between the white ventral 

 surface and ochraceous-buff colouring of the flanks ; in the 

 Sennaar species and t. jeheUe, recently described by Heller 

 from Lado, the light ventral surface is not sliarply marked 

 off from the dark colour of the flanks, but gradually merges 

 into it. In addition, this new race differs from the other two 

 forms in having no trace of the dark dorsal stripe ; the darker 

 and more ochraceous colouring of the entire dorsal surface is 

 a further point wherein tiiis western form differs from the 

 typical species. The Museum collection contains four 

 specimens referable to this subspecies — three from the type 

 locality and one from Tamburas, Bahr-el-Ghazal. 



(4) Arvicanthis luctuosus, sp. n. 



A large dark-coloured species, probably allied to testicularis. 



Size of body large ; tail shorter than length of body, hind 

 foot large. General colour of back dark blackish brown, 

 coarsely speckled with light buffy grey, the effect almost as 

 in niloticus, but light speckliug not quite so prominent. 



