Mammals from East Africa. 121) 



Size ratliei' small, not very much larger than A. souialicu.s, 

 Thos. General colour of upper surface pale greyish brown, 

 faintly tinted with a light straw-coloured wash, but not in 

 any way approaching the huffy coloration of A. abys.nnicus 

 praceps. Face and head greyish ; muzzle not markedly 

 buff-coloured. Ocular rings pale buff, much less evident than 

 in the allied forms. Ears clothed with short grey hairs, faintly 

 tinted with buff; a character that at once distinguishes this 

 species from the Somaliland Arvicanthis, in which the ears are 

 bright orange. Flanks paler and greyer than back, the grey 

 tint passing fairly abruptly into the white of the ventral 

 surface. Backs of hands and feet greyish, faintly washed 

 with pale buff. Under surface of body white, hairs with 

 grey bases and white tips. Tail as in A. a. prceceps, the 

 ventral surface rather less huffy. 



Skull small, in size hardly greater than that of A. somalicus ; 

 molar teeth much smaller than in the allied species. 



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



Head and body 129 ram. ; tail 9.2 ; hind foot 27 ; ear 17. 



Skull : greatest length 31*8 ; basilar length 26"1 ; con- 

 dylo-incisive length 30; zygomatic breadth 16; interorbital 

 constriction 4*3 ; breadth of brain-case (across squamosal 

 region) 13"2; length of nasals 12; palatilar length 14*3; 

 leugth of palatal foramina 7 ; width of palate (inside m}) 2*5 ; 

 postpalatal length 11*7 ; length of upper molar series 5'9. 



Hab. Rumruti, Laikipia Plateau. Altitude 6,500 feet. 



Typ)e. Old male. Original number 1413. Collected on 

 October 25th, 1910. 



This Rumruti Arvicanthis is at once recognized by its 

 small size and the exceedingly pale colour of the pelage. 

 The white under surface is a further character that serves to 

 distinguish this species from the Naivasha race of ab;/s- 

 sinicus, A. a. prceceps. 



It is interesting to note that Mr. Kemp found A. abys- 

 siniciis prceceps living side by side with this small greyish 

 species, and further, that a series of specimens collected at 

 Baringo appear also to represent the Naivasha species. 



Arvicanthis reptans, sp. n. 



A small form allied to A. somalicus^ Thos. 



Size rather less than in somalicus. General colour of 

 dorsal surface pinkish brown speckled with black, the black 

 tint most evident down the middle of the back. Flanks 

 l)urer in colour than back, the general effect more huffy ; 

 buff tint of flanks sharply differentiated from the white belly. 



Ann. & Mag. N. Hist. Ser. 8. Vol. viii. 9 



