Mammals from San Juan, ]Yestern Argentina, 217 



6*2 ; greatest horizontal diameter of bulla 17"4 ; bi-meatal 

 brendtli 25*2 ; upper tootli-series 11*2. 



Hah. as above. Type from Los Sombreros, Sierra Tontal. 

 Alt. 2700 m. 



Ti^pe. Adult female. B.M. no. 21. 6. 21. 11. Original 

 number 1296. Collected 29tli January, 1921. 



Readily distioguishable from other species by its large 

 builfe. 



[The t'oUowiug Ahrocoma, obtained by Sr. Budin just 

 across the border in the neiohbouring province of Mendoza, 

 may be conveniently described here : — 



Ahrocoma vaccarum, sp. n. 



Colour as in ^4. schistacea and famatina. Size about as in 

 famatina, but the ears decidedly larger and the tail shorter. 



Skull slightly longer than that o'i famatiiui, shorter than 

 in the other species. Muzzle slender, the nasals not peculiarly 

 attenuated. Mastoid islands rather small. Bullae smaller 

 than in any of the other species. Molars fairly large. 



Dimensions of the type : — 



Head and body 191 mm. ; tail 94 ; hind foot 28; ear 25. 



Skull : greatest length 47 ; condylo-basal length 44*3 ; 

 zygomatic breadth 24*2 ; nasals 18*5 X 5*4 ; interorbital 

 breadth 6*8 ; greatest horizontal diameter of bulla 15 ; 

 bi-meatal breadth 23*7; upper tooth-series 9*7. 



Hab. North-western Mendoza; type from Punta de Vacas. 

 Aliitude 3000 m. 



Type. Adult female. B.M. no. 21. 6. 24. 20. Original 

 number 1364. Collected 12th March, 1921. Two specimens. 



Distinguishable by the short tail and small bullse. All 

 these Argentine species of Abrocuma are nearly allied and 

 very similar to each other, but the characters used, slight as 

 they are, seem to be locally constant, while the respective 

 mountain habitats are well separated and often completely 

 isulated.] 



9. Octomys joannius, sp. n. 



c?. 1270; ? . 1273, 1332. Pedernal, 1200 m. 



Like O. mimax in all respects, cranial and external, except 

 that the frontal region of the skull is quite materially broader, 

 and flat or even slightly convex above instead of being concave 

 in the interorbital space. In correlation with this the pre- 



