Mammals of the 1921 Mount Everest Expedition. 181 
26°5; nasals 10°7 x3; interorbital breadth 4°43; breadth of 
brain-case 11°7 ; palatal foramina 5°2x1:6; dental length 
12-6; cheek-teeth (crowns) 4°1. 
Hab. Tibet. Only known from Tingri, 14,000’. 
Type. Adult male. Original number 30. Collected by 
Mr. A. F. R. Wollaston, July 7, 1921. 
Thomas described C. alticola from Shushal on the Pang- 
Kong Lake, Ladak, where it is found at an altitude of 
13,500’; and it also occurs in the valley of the Upper Sutlej 
at Teza. 
5. Phaiomys leucurus, Blyth. 
1863. Phaiomys leucurus, Blyth, J. A. S. B, xxxii. p. 89. 
1879. Arvicola blythi, Blanford, Sci. Res. Second Yarkand Miss., 
Mammals, p. 89 | Mzerotus (Phaiomys) blythi of subsequent writers }. 
6.1. Tinki Dzong, Tibet, 13,500’, 17th June. 
S. 3, 10, 12, 20, 23, 27, 28, 29, & 31 in adult pelage, and 
4,5, 6, 7,8, & 9 juv.; 2. 2,11 both adult. Tingri, Tibet, 
14,000’, 25th June to 10th July. 
Blyth based his genus Phaiomys upon the present species. 
Blanford regarded Phatomys as a synonym of “ Arvicola” 
(=Microtus in current nomenclature), while subsequent 
writers have given it no more than subgeneric rank. In the 
genus Arvicola the specific name “ lewcurus” is preoccupied 
by A. leucurus, Gerbe, 1852 ; and therefore Blanford substi- 
tuted the name “ dblythi” for that originally bestowed upon 
the present species by Blyth. But, in our opinion, Phaiomys 
is entitled to full generie rank ; and, if this be the case, the 
specific name /eucurus, given to the genotype by Blyth, is 
valid and must be restored. 
Phaiomys, though still imperfectly known, is one of the 
most interesting microtine genera. By the peculiar combina- 
tion presented by its external, dental, and eranial characters 
it is sharply distinguished from all its allies—although, taken 
singly, each of its characters can be found in other groups. 
Thus, as regards externals, the curious lemming-like form of 
these voles and their lengthened fore-claws can be matched 
among that little group of Central-Asiatie species of which 
M. brandti is a good example ; the latter, nowever, iJiffers 
widelyin skull and teeth from the present genus. 1n certain, 
though not in all, respects, the cranial and dental characters 
of Phaiomys, as here understood, find their match in the 
North-American Pedomys and in the Eurasian Arvicola, 
genera of wholly dissimilar external appearance. Although 
detailed discussion of this interesting matter must be reserved 
