Mammals of the 1021 Mount Everest E.vpedition. 183 



Diineii.sioii3 of tlie type (inoasured 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 heij^ht (median) 6'6 ; least distance across temporal 

 ridges, (a) at inter[)arietal 7'.^, (h) in interorbital region 0'3 ; 

 nasals 6-6 X 3-2 ; dental lengtii IG'9 ; molars (at giinding- 

 snrface) 6'3. 



Hah. East Everest, at high altitudes (17,000'). 



Ti/pe. Adult male. Original number 61. Collected 

 Sept. 18, 1921, by Mr. A. F. R. WoUaston. 



In fully adult or old skulls of this genus the temporal 

 ri Iges 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 temj)oral muscles suffer a trans- 

 formation in the passage from youtli 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 Sutlej 

 Valley) are the only specimens of those forms sufiiciently 

 perfect to be used for comparison ; in that of waltoni the 

 condylo-basal length is 27*5, while in lo. petulans it is 

 2C"4 mm. 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. waltoni attains a considerably greater size than that 

 attained by everesti, and that in this respect to. petulans is 

 intermediate. 



"In colonies on turf-slopes.'^ — A. F. R. W. 



7. Microtus [Alticola) sp. 



S . 55 juv. East Everest, 17,300', 13th September. 

 Too young for precise determination. 



[Hare (probably Lepus otostolus, Hodgs.). 



" Common at l-4,000'-15,000' in dry country. One seen 

 at 18,500' N.E. of Everest."— >l. F. R. W.] 



• Ann. & Mag. Nat. Hist. (8) xii. p. 452. 



