182 3I.'ssip. O. Thomas aiul M. A. 0. Iliiiton on the 



for aiiotlier place, it may be mentioned that the features 

 common to tlie three o;enera just named suggest, for each of 

 them, descent — in directions more or less divergent — from 

 the remuikahlc late Pliocene Eiiro|iean genus M/momys ; 

 and no character in any one of the other three living genera 

 seems to he iiicompatihle with such a view of their origin. 



Voles of the genus P/hi'iodii/s are confined to the liighlands 

 of Central Asia, where they are widely distributed, occurring 

 always at high altitudes and most frequently in close associa- 

 tion with the banks of streams. The species show two well- 

 marked types of coloration — some, like P. leucurus, being 

 pallid and sandy, others, like P. looltoni, darker and greyer. 



With regard to the material collected by the Expedition, 

 we are, at present, unable to find any reliable character which 

 will serve to distinguish the specimens from Tinki Dzong 

 and Tingri from P. leiicurufi, which was originally described 

 from the mountains above Tso-Moriri, Ladak. It is, how- 

 ever, quite possible that the Tibetan animal will prove to be 

 distinct from true leucurus. The series from Tingri, long as 

 it is, is insufficient for the purpose, owing to the fact that so 

 many of the skulls collected have been smashed by the traps. 



It may be recorded that the mammary formula in the two 

 females is 2 — 2 = 8, and that the pelage of the young 

 approaches that of tlie adults of the next species in colour, 

 being far darker and less sandy than in adult leucurus. 



" Found in colonies in sand." — A. F. R. W. 



6. Pha'wmijs everestt^ sp. n. 



J. 61; ? . 49. East Everest, 17,000', Otii and 18th 

 September. 



A " grey " species, closely related to P. icalfoni, but con- 

 siderably smaller. 



(Size small (hind foot to 18, condylo-basal length not much 

 exceeding 27 mm.). 



External characters and colour as in P. waltoni, but tail 

 light above and below, instead of being more or less 

 bieolored ; upper parts of a rather dark earthy grey, very 

 different from the sandy tints of P. leucurus. Mammas 

 2—2 = 8. 



i^kuU and teeth essentially as in other species of the 

 genus. Skull rather lightly and delicately built with small 

 flattened Ijullae ; the latter rather smaller than in toultoni^ 

 and diffi ring conspicuously from the huge and inflated bullte 

 o£ leucurus. 



