On a new Mountain Vizcacha from Patagonia. 179 
greyer. On the under surface, however, there is no resem- 
blance to the Paraguay animal, the hairs being broadly 
washed with white, though they are, as usual, slaty at base. 
So really white-washed a belly is very unusual in the genus. 
Chin without any marked white patch. Hands and feet 
greyish white. ‘l’ail blackish above and all round at the end, 
the greater part below dull white. 
Skull most like that of A. simulator and its allies. Large, 
evenly bowed; the interorbital region broad, with sharply 
angular edges. Palatal foramina well open, extending back 
to the level of the hinder edge of the first lamina of ml. 
Incisors of normal set.. Molars as usual. 
Dimensions of the type: 
Head and body 105 mm.; tail 78; hind foot 24; 
ear 20. 
Skull: greatest length 29 ; zygomatic breadth 15; nasals 
10; interorbital breadth 5; height of crown from alveolus 
of m? 8:2; palatilar length 12; palatal foramina 7; upper 
molar series 4°7. : 
Hab. Jesematathla, Northern Chaco. Alt. 100 m. 
Type. Adult female. B.M. no. 20.12.18. 20. Original 
number 34, Collected 18th August, 1920. 
- This Akodon of the Paraguayan Chaco is above so like 
A. a. montensis of the country east of the River Paraguay as 
to be almost indistinguishable, but below it is at once separ- 
- able by its broadly white-washed belly—a very unusual 
character in Akodon. Its skull is, on the whole, most like 
that of A. simulator and its allies of North Argentina west of 
the Chaco. 
Considering how small the number of Chaco mammals is, 
the Marquis de Wavrin has done very well in discovering 
two new ones, 
XVIIL.—A new Mountain Vizcacha (Lagidium) from 
N.W. Patagonia. By OLDFIELD ‘THOMAS. 
(Published by permission of the Trustees of the British Museum.) 
THE British Museum has received a number of mammals - 
from Pilcafeu and other places in N.W. Patagonia collected 
by Mr. H. E. Box. As they were collected at very much 
the same places as those obtained by Sr. EK. Budin in 1918, 
and described by me in a previous paper *, the majority of 
them are known to science, but among them are several 
* Ann, & Mag, Nat. Hist. (9) iii. p. 199 (1919). 
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