Mammahjrom Salta, X. Argentina. 217 



palatine foramina 5'8x2"l; length of upper molar series 

 4-3. 



Type. B3r. no. 97.5.5.14, from Lower Cachi. 



I can find no described species to wliicli this mouse could 

 be referred, h\ 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. Spegazzinii. 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. Eyes 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. Mammee 

 2 — 2 = 8. Tail about as long as the body without the head, 

 well- haired, brown above, wdiite on the sides and below. 



Skull not very unlike tliat 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 w^, 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 19'2; ear 

 12-5. 



Skull: basal length 21*6; basilar length 20; greatest 

 breadth 12*5; nasals 8*6 x 3*5; interorbital breadth 4'6 ; 

 interparietal 6xr2; palate length from hensilion 10'6 ; 

 diastema 6"8 ; palatal foramina 5'4xl'8; length of upper 

 molar series 4*3. 



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. Spegazzinii^ by its pale grey back and snowy belly. In 

 fact the colour-contrasts between these two species afford 



