12 Fretp Museum or NATURAL History—Zoo.LocGy, Vou. 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 10 percm. Distinguished 
from Mus hindet, 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- 
tebre 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 Pere 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 verreauxt and Mus brockmani; tail 
decidedly longer than head and body; mamme 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 vertebre 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. 
