MammaJs from San Juan, Western Argentina. 217 



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

 breadth 25-2 ; upper tooth-series 11-2. 



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

 Alt. 2700 m. 



Type. Adult female. B.M. no. 21. 6. 21. 11. Original 

 number 1296. Collected 29t!i January, 1921. 



Readily distinguishable from other species by its large 

 bullfe. 



[The tbllovving Ahrocoma, obtained by Sr. Budin jnst 

 across the border in the neighbouring province of Mendoza, 

 may be conveniently described here : — 



Abrocoma vaccarum, sp. n. 



Colour as in A. schtstacea and faniatina. Size about as in 

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



Skull slightly longer than that oH famatina, shorter than 

 in the other species. Muzzle sleiuler, 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 aud 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; ujiper tooth-series 9*7. 



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

 Altitude 3000 m. 



Tt/pe. 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 bullae. All 

 these Argentine species of Abrocoma 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 

 isolated.] 



9. Octomi/s joannius, sp. n. 



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



Like 0. mimax in all respects, cranial and external, except 

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

 and flat or even slightly convex above instead of being concave^ 

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



