Mammals from Salta, N. Argentina. 217 
palatine foramina 5°8x 2:1; length of upper molar series 
4-3 
Type. B.M. no. 97.5.5.14, from Lower Cachi. 
I can find no described species to which this mouse could 
be referred. In general colour it is more like one of the 
fulvous Oryzomys than an Akodon, but its teeth and pro- 
portions clearly show it to be a member of the latter group. 
5. Akodon albiventer, sp. n. 
a. Lower Cachi. 
A medium-sized Akodon of a pale greyish colour, with a 
white belly. 
Size rather less than in A. Spegazzint?. Fur little woolly, 
about 7 or 8 millim. long on the back. General colour pale 
grizzled greyish, the tips of the darker hairs brown, and of 
the paler ones whitish buff, all slaty grey basally. Under 
surface snowy white from chin to anus, fairly sharply 
separated from the dark of the upper surface, but the basal 
halves of the hairs are still slaty grey, although this colour 
is hidden by the white ends. Hyes with whitish rims. Ears 
rather shorter than in the last species, the anterior half of 
their outer side grizzled grey, the posterior half whitish ; 
there are also a few whitish hairs forming an indistinct spot 
just behind them. Forearms, hands, and feet pure white; 
claws rather long, as in A. Spegazzinii; hind feet broad and 
heavy, the soles naked, with 6 elevated pads. Mamma 
2—2=8. Tail about as long as the body without the head, 
well-haired, brown above, white on the sides and below. 
Skull not very unlike that of A. Spegazzinii. Nasals 
rather broader ; interparietals still narrower, but markedly 
broader in the centre than at the sides; palatal foramina not 
extending to the middle of m!, posterior nares broader, the 
palatal edge opposite the back of m°. 
Dimensions of the type, measured in spirit before skinning 
(female) :— 
Head and body 87 millim.; tail 67; hind foot 19°25; ear 
12°5. 
Skull: basal length 21°6; basilar length 20; greatest 
breadth 12°5; nasals 8°6x3°5; interorbital breadth 4:6; 
interparietal 61:2; palate length from hensilion 10°6; 
diastema 6°8; palatal foramina 5°4xX1°8; length of upper 
molar series 43. 
Type. B.M. no. 97.5.5.17. 
This pretty little mouse may be readily distinguished 
from any of its allies, and especially from its neighbour 
A, Spegazzinit, by its pale grey back and snowy belly. In 
fact the colour-contrasts between these two species afford 
