12G Mr. G. Dollman on 



are considerably different. The same applies in the case of 

 A. hystreUa, recently described from Nimule, Uganda, by 

 Heller, the tail in the Nimule species being markedly shorter 

 and the general colour of the animal a great deal richer. 



Acomys percivali, sp. n. 



cJ. 1742, 1756, 1762; ?. 1743, 1744, 1747, 1749. 

 Ciianler Falls. Eusso Nyiro. 



A dark slate-coloured species rather smaller than A. kempi 

 described above. 



Size rather less than kempi or ignitus. Feet and ears 

 small. Dorsal spines long and stout, more so than in kemjn, 

 resembling in tiiis respect Acomys loitherbyi, de Wint. 

 General colour of dorsal surface dark slaty brown (dark 

 neutral tint no. 1, 'Repertoire de Couleurs'), some of the 

 spines tinted with rufous, in one specimen to such an extent 

 as to give the animal a reddish-grey appearance. Flanks, 

 sides of head and neck similar in colour to back. Line of 

 demarcation between dorsal and ventral surfaces less sharply 

 defined than is usually the case in this genus. Backs of 

 hands and feet dirty white, conspicuously grizzled with slaty 

 brown, a feature that is very evident on the hind feet 

 and markedly different from the white feet of the allied 

 species. Ventral surface pure white tinted with slaty grey, 

 many of the hairs having pale slate-coloured bases and 

 anntilations ; the grey tint most evident on the throat. 

 Tail dark brown above and greyish brown below, the hi- 

 coloured eflfect not very marked. Hairs oii tail quite short ; 

 black above, silver-grey below. 



Skull small and narrow, with comparatively long nasal 

 region and small brain-case. Auditory bullse small and 

 rather flat. 



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



Head and body 94 mm. ; tail 85 ; hind foot 15 ; ear 1 5. 



Skull : greatest length 27'5 ; basilar length 21"5 ; con- 

 dylo-incisive length 25-5 ; zygomatic breadth 12"7 ; inter- 

 orbital breadth 4'5 ; breadth of brain-case (across squamosal 

 region) 11"9; length of palatal foramina 7"4; Avidth ol" 

 palate (inside w^) 2"7; length of upper molar series 4. 



Hab. Chanler Falls, Eusso Nyiro. Altitude 3000 feet. 



Type. Old male. Original number 1762. Collected by 

 Messrs. Percival and Kemp on January 23rd, 1911. 



The unusually dark colour of the pelage of this Acomys 

 distinguishes it at once from the allied forms. It is quite 

 probable that specimens of this species occur in which the 



