Mammals from East Africa, 5G9 



Type-locality. Amala "Rivi-r (also called Mara River), 

 wliicli rises at Kabalolot Hill in the Sotilc, Kenya Colony, 

 and enters Lake Victoria Nyanza in the Tanganyika Colony 

 at 1° 30' S., 34° E. _ 



Descripfion. — This is a dwarf form o£ Rattus, in size a 

 trifle smaller than Mus musculii/}. The type measures : — 

 Head and body 76 mm.; tail 65 ; hind foot 15 ; ear 14. 

 Tlie measurements of the other specimen are about the same. 

 The hair is soft and long, about 10 mm. in length on the 

 back. Colour very similar to that of Rattus concha panya. 

 The sides and flanks are a rich brown, between ''mummy '^ 

 and " Prout's " (Ridgway) ; the back darker, owing to the 

 hairs being tipped with black or dark brown ; hairs of the 

 under surface slate-grey with white tips, resulting in a general 

 pearl-grey colour. There is a fairly well-defined tawny- 

 ochraceous stripe dividing the colours of the upper and under 

 surfaces. Tail shorter than head and body, thickly clothed 

 with short appressed hairs, longer on the terminal third, and 

 forming a perce[)tible pencil at the tip. Colour of tail brown 

 on the proximal two-thirds, and black clothed with whitish 

 hairs on the distal portion ; lighter below. Feet and hands 

 white. Large white spot behind the ear. 



Skull : total length 23-3 mm.; condylo-incisive length 21 3; 

 greatest breadth (at posterior of zygomata) 12'0; breadth of 

 brain-case 10*3 ; length of nasals on median line 8*8 ; inter- 

 orbital constriction 4. 



The palatal foramina extend back to about the middle of 

 the anterior central cusp of m^ ; m^ equal in length (I'S mm.) 

 to ?n^ and ni^ combined. The incisors and molars are typical 

 of Rattus (as distinct from Mus), there being no distortion of 

 the first lamina of m^ nor any subapical notch in the upper 

 incisor. 



The two specimens received of this interesting diminutive 

 rat are both males, so that it is not possible at present to give 

 the mammary formula. The indications are that it will prove 

 to belong to the subgenus Mastomys, since it has little in 

 common with the other African subgenera of Rattus. In 

 general appearance it is like a dwarf R. {Mastomys) couclia, 

 and the propoition of tail to body — about 85 per cent. — is 

 characteristic of the multimammate rats. Practically all the 

 small mouse-like African rats belong to the subgenus Pra- 

 omys, all the known species of which have very long tails. 



• The teeth of the type are not much worn, and show that 

 the specimen, though adult, is young. Thus, the measure- 

 ments given may prove to bo on the small side. 



