.. 
Mammals of the 1921 Mount Everest Eepedition, 183 
Dimensions of the type (measured in the flesh) :— 
Head and body 101 mm.; tail 30; hind foot (without 
claws) 18; ear 11. 
Skull: condylo-basal length 26°8; interorbital constriction 
3°9; breadth of brain-case 12°1; occipital breadth 12:4; 
occipital height (median) 6°6 ; least distance across temporal 
ridges, (a) at interparietal 7°3, (0) in interorbital region 0°3 ; 
nasals 6°6 x 3°2 ; dental length 16°9 ; molars (at grinding- 
surface) 6°3. 
Hab, East Everest, at high altitudes (17,000’). 
Type. Adult male. Original number 61. Collected 
Sept. 18, 1921, by Mr. A. F. R. Wollaston. 
In fully adult or old skulls of this genus the temporal 
ridges fuse anteriorly to form a sharp but low median inter- 
orbital crest ; and those portions of the brain-case which are 
under the influence of the temporal muscles suffer a trans- 
formation in the passage from youth to age exactly similar 
to what occurs in the Orkney voles*. In the skull of the 
type of everesti the temporal ridges are nearly fused, and 
the specimen has attained a stage of development which 
in P. leucurus is only reached when the condylo-basal length 
has risen to about 29 mm. The skulls of the types of 
P. waltoni (Lhasa, Tibet) and w. petulans (Upper Sutle] 
Valley) are the only specimens of those forms sufficiently 
perfect to be used for comparison; in that of walton?t the 
condylo-basal length is 27°5, while in w. petulans it is 
264mm. In both skulls the temporal ridges are still very 
feeble and widely separated (by 1°5 and 1 mm. respectively), 
so that these specimens, in a craniological sense, are still far 
from being adult. One may conclude from these facts that 
P. waltont attains a considerably greater size than that 
attained by everest’, and that in this respect ww. petulans is 
intermediate. 
‘Tn colonies on turf-slopes.”—A. F. R. W. 
7. Microtus (Alticola) sp. 
3. 55 juv. East Everest, 17,300’, 13th September. 
Too young for precise determination. 
[Hare (probably Lepus otostolus, Hodgs.). 
“Common at 14,000’-15,000' in dry country. One seen 
at 18,500! N.E. of Everest.”—A. Ff. R. W.] 
* Ann. & Mag. Nat. Hist, (8) xii. p. 452. 
