220 0)1 Mammals from Western Argentina. 



inflated anteriorly, not visible from below outside the 

 premaxillse ; behind the posterior border of the nasals is but 

 little indented in the centre, and the premaxillse surpass them 

 by but a short distance. Interorbital space narrow, its 

 anterior portion more definitely concave than usual. Mastoid 

 islands on top of skull variable, generally ratiier small. 

 Bullae of medium size, smaller than \\\ famatince , larger than 

 in vxdcani. 



Dimensions of the type : — 



Head and body 395 mm. ; tail 340 ; hind foot 100 ; 

 ear 83. 



Skull : greatest length 91 ; condylo-incisive length 82 ; 

 zygomatic breadth 46 ; nasals 33 x 10*5; interorbital breadth 

 (not at notches) 19; diastema 26 ; length of bulla 17 ; upper 

 tooth-series (crowns) 19*4 ; breadtli of jt>* 4*7. 



Hah. as above. 



Type. Adult female. B.M. no. 21. 6. 21. 39. Original 

 number 1303. Collected 2nd February, 1921. 



The series obtained is remarkably uniform in colour and 

 skull-characters. 



Readily distinguishable ixom famatince by its smaller size 

 and more slender muzzle. 



[The following Lagidium was obtained by Sr. Budin at 

 Punta de Vacas, on the Transandean route in Mendoza, and 

 may be here described : — 



Lagidium viatorum, sp. n. 



Size about as in tontalis ; interorbital region broader. 



General colour rather mor6 uniform neutral grey, not 

 lightened on shoulders and rump. Ends of hairs of lower 

 surface distinctly ochraceous or cinnamon-buff, instead of the 

 yellow of L. tontalis. White axillary patches present. 



Skull of about the same length as in tontalis, but more 

 bulky throughout. Nas ils more inflated in their anterior 

 halvea, reaching backwards nearly as far as the premaxillaj. 

 Interorbital region decidedly broader than in tontalis, its 

 anterior part less decidedly concave. Bullse about as in 

 tontalis. Incisors of both adult specimens pale yellow in 

 front. Molars comparatively large. 



Dimensions of the type: — 



Head and body 400 mm.; tail 335; hind foot 105; 

 ear 80. 



Skull: greatest length 91; condylo-incisive length 82; 

 zygomatic breadth 48 ;i nasals 34"5 x 11 ; interorbital breadth 



