166 Mr. G. DoUman on the 



from tlie following localities : — Mt. Suswa, Man, Lemek 

 Valley (Amala District), south side of Aberdare Mountains, 

 Nakuru, and the LaiTOgie Mountains (N. of Laikipia). 



In examining the skins of British East African Otomys, 

 it is very easy to mistake cmiescens for small specimens of 

 angoniensis eJassodon, the general colour of the two forms 

 being very alike. . The short thick skull of canescens, how- 

 ever, is very distinct from the larger and longer skull of 

 elassodo7i. 



Division C. 



Lower incisors with, two well-marlced deep grooves. 

 Ventral surface of tail light. 



Section I. 



Skull showing the same arched or humped appearance as is found in the 

 thomasi group, the interorbital region raised up, and the nasals and 

 general line of the brain-case depressed so as to accentuate this 

 arched character. 



Group ]. 



m^ with 6 laminae. 



(18) Otomys dartmouthi, Thos. 



Otomys dartmonthi, Thos, Ann. & Mag. Nat. Hist, (7) vol. xviii. p. 141 

 (1906). 



This species stands by itself among the Otomys with two 

 deep grooves in the lower incisors, being the only one with 

 6 laminse in m^. 



Externally dartmoutJii is very distinct, the fur being a 

 great deal more woolly than in any otlier East African 

 Otomys. General colour of dorsal surface pale brown finely 

 speckled with yellowish buff. Backs of hands and feet dirty 

 buff. Yentral surface of body slate-grey washed with buff. 

 Tail rather dark above, almost black; sides and ventral 

 surface buff. 



Skull, as in all the members of this division, excepting 

 fortior, of the same arched or humped type as is found in the 

 thomasi group, but the deep double grooving of the lower 

 incisors immediately distinguishes the skulls of dartmouthi 

 and its allies from those of thomasi and the other members of 

 that group. Molars fairly large, m^ with 6 laminae. 



Dimensions of the type: — 



Head and body 150 mm. ; tail 93 ; hind foot 26-5 ; 

 ear 25. 



Skull : greatest length 37*6 mm. j basilar length 30*5 ; 

 zygomatic breadth 19*5 ; width of brain-case 15*5 ; length 



