128 Mr. G. Dollman on 



Size small ; hind foot markedly smaller than that of 

 A. lailsoni. General colour of back dull buff washed with 

 brownish black, the dark tint more dominant down the 

 middle o£ the back. Flanks rather purer and more buffy in 

 colour, speckled over with brownish-slate colour, the general 

 effect much greyer and duller than in luilsoni, where the 

 flanks are pure rufous buff with hardly any dark speckling. 

 Face and back of head slaty brown, faintly speckled with 

 pale buff. Sides of face pale dirty buff. Lips white. 

 Backs of hands and feet and entire under parts white ; hairs 

 of belly white to roots. Tail, as in A. ivilsoni, greyish 

 brown above and silvery grey below. 



Skull much smaller and slighter than that of A. rvilsoni, 

 with markedly shorter nasals and narrower brain-case. 

 Auditory bullae less inflated aud smaller. Cheek-teeth con- 

 spicuously smaller. 



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



Head and body 7 7 mm. ; tail 55 ; hind foot 12*5 ; ear 13. 

 Skull: greatest length 22*7; basilar length ]7'5; condylo- 

 incisive length 20*7 ; zygomatic breadth 10"6; interorbital 

 breadth 4 ; breadth of brain-case (across squamosal region) 

 10"2 ; length of nasals 9 ; length of palatal foramina 5'4; 

 length of upper molar series 4. 



Hab. Nyama Nyaugo, Eusso Nyiro. Altitude 3200 feet. 



Type. Adult male. Original number 1820. Collected 

 on January 30th, 1911. 



The smaller size and much less rufous colouring readily 

 distinguish this Eusso Nyiro Acomys from the Morabassa 

 species, A. wilsoni. 



Arvicanthis massaicus, Pagenst. 



S . 1441, 1442, 1449, 1453, 1455, 1465, 1494, 1509, 1513 ; 

 ? . 1456, 1460, 1468, 1479, 1493, 1495, 1510, 1512. 

 Euraruti, Laikipia Plateau. 



Arvicanthis jmmilio, Sparr. 



c? . 1580, 1581, 1585, 1587, 1600, 1606, 1609, 1623, 1628, 

 1634, 1640, 1683 ; ? . 1584, 1588, 1599, 1602, 1607, 1616, 

 1638, 1643, 1645, 1652, 1669. Solai, Mt. Kenya. 



Arvicanthis rumruti, sp. n. 



S . 1413, 1432, 1440, 1457 ; ? . 1415, 1416, 1426, 1414, 

 1456. Rumruti, Laikipia Plateau. 



A small light-coloured species allied to A. abyssinicus 

 2n(Ecei>s, Wrought. 



