12 Field Museum of Natural History — Zoology, Vol. X. 



ceous; a slight dusky marking in front of and narrowly bordering 

 the anterior half of the eye; ears thinly clothed with tawny hairs; 

 feet creamy white; underparts creamy white, the hairs slaty at their 

 bases; tail dusky all around, annulations lo per cm. Distinguished 

 from Mus hindei, to which it has slight superficial resemblance, by 

 its much longer tail and its smaller, flatter skull. 



Measurements. Total length 315; head and body 154; tail ver- 

 tebras 161; hind foot (c. u.) 31; ear 19.5. Skull of type: Greatest 

 length 36.3; basilar length 27.5; zygomatic breadth 17.9; nasals 

 14.7; least interorbital breadth 5.2; postpalatal length 12.6; pal- 

 atine slits 8.2; diastema 8.2; upper toothrow 6.1. 



Mus niveiventris sp. nov. 



Type from Voi, British East Africa. No. 17099, Field Museum 

 of Natural History. Adult female. Collected April 22, 1906, by 

 E. Heller. 



Characters. Allied to Mus verreauxi and Mus hrockmdni; tail 

 decidedly longer than head and body; mammae 3-2 = 10. Tail 

 shorter than in brockmani -and color of upperparts very much darker. 

 Slightly smaller than verreauxi; tail shorter; underparts entirely 

 white with hairs white instead of slaty basally; skull smaller with 

 relatively larger molars. Upperparts mixed buff or ochraceous buff 

 and dusky producing a general effect of dull cinnamon to wood brown, 

 in much worn pelage clear Mars brown; ears practically naked except 

 near the edges where they are very thinly clothed with whitish hairs ; 

 underparts entirely creamy white to the roots of the hairs; dusky 

 orbital very slight and scarcely evident. 



Measurements. Type: Total length 262; head and body 109; 

 tail vertebree 153; hind foot (c. u.) 23; ear 17.5. Skull of type: 

 Greatest length 30; basilar length 23.5; zygomatic breadth 14.2; 

 nasals 13; least interorbital breadth 4.4; postpalatal length 10.2; 

 diastema 8.1; palatine slits 7; maxillary toothrow 4.7. 



Mus niveiventris subfuscus subsp. nov. 



Type from Lake Elementeita, British East Africa. No. 16972, 

 ^ Field Museum of Natural History. Adult male. Collected Febru- 

 ary 9, 1906, by E. Heller. 



Characters. Similar to Mus. niveiventris but slightly darker 

 colored above and with hairs of underparts broadly slaty at bases 

 except on middle of chin and throat; skull essentially as in nivei- 

 ventris but braincase averaging broader. Smaller and shorter-tailed 

 than Mus verreauxi; skull smaller; molars larger. 



