rom “Otro Cerro,’ North-eastern Lioja. 497 
) Yy 
have been trusted for purposes of distinction. But fortunately 
a topotype skin has since been received, and this is of the 
same buffy olive colour as the specimens from Potosi referred 
to that species in 1902 *, 
A. alierus is readily distinguishable from the older-known 
species by the absence of the strong yellowish or buffy suffu- 
sion in the fur, 
No. 228, from Chumbicha, erroneously referred to A. areni- 
cola in my previous paper, also proves to belong to this 
species, while an additional specimen, no. 317, las also come 
from that locality. 
11. Akodon orbus, sp. n. 
9. 324. 
A proodont Akodon allied to A. lactens. 
General characters very much as in A. lactens, the colour 
practically the same except that there is no white patch on 
the chin. The tone is slightly duller and more drabby, but 
the difference amounts to little. ars slightly shorter, 
coloured like the bead. Fore-claws similarly elongated, as 
long as those of the hind feet. Tail blackish above, dull 
drabby on sides and below, the difference but little marked, 
Skull of lighter build, with markedly narrower muzzle 
than in lactens. Upper outline more bowed. LBrain-case 
smooth, unridged. 
Incisors similarly thrown forward (proodont), the incisive 
angle of the type 86°; they are light-coloured, as in A. 
lactens, but are distinctly more slender in a specimen as old 
as or older than the type of that animal. Molars rather 
narrower, of similarly high solid structure. 
Dimensions of the type:— 
Head and body 97 mm.; tail 59; hind foot 21; ear 14. 
Skull: greatest length (bone only) 26:4; condylo-incisive 
length 25:2; zygomatic breadth 14°6 ; breadth of muzzle 4°2 ; 
nasals 9°1 ; interorbital breadth 5; breadth of brain-case 12 ; 
palatine foramina 6°4; postforaminal palate 4; upper molar 
series 4°8, 
Type. Old female. B.M. no. 19. 2.7.45. Original 
number 324. Collected 21st August, 1918. 
This species is evidently closely related to <A. lactens, 
discovered by Sr. Budin at Leon, Jujuy, but differs by its 
markedly more slenderly built muzzle, thinner incisors, and 
* Ann. & Mag. Nat. Hist. (7) ix. p. 226 (1902). 
