141 Mr. O. Thomas on a 



Skull conspicuously ridged and angular, even more so than 

 in ^f.Jav(lnensis, and quite the opposite to the smooth rounded 

 skull of M. luclfer. ^Muzzle narrow and ])inched in above. 

 Zy<;oinata not widely expanded, the breadth across them not 

 or scarcely greater than the mastoid breadth. Supraorbital 

 projections well marked, as are the swollen prominences at 

 the anterior corners of the brain-case behind the temporal 

 fossa.\ Opening of posterior nares narrow, without distinct 

 median sj)ine. 



Dimensions of the type (measured in skiu) : — 



Head and body 375 millim. ; tail 47, with terminal hairs 

 77 ; hind foot (s. u.) 52. The hind foot in two males 

 measures S-i and 58 millim. 



Skull : greatest length 82 ; basal length 70 ; zygomatic 

 breadth 37; mastoid breadth 37"3 ; interorbital breadth 19"2; 

 breadth across supraorbital projections ^2'2''6 ; intertemporal 

 breadth 20 ; breadth of brain-case 31; palate length -ISS; 

 greatest diameter of upper molar 7"2. 



Two male skulls measure 90*3 and 88"5 in greatest length, 

 with zygomatic breadth of 42 and 41'3 respectively. 



IJah. Great Natuna Island. Type from Sinubiug ; another 

 specimen from JMount Kauai, 1000 feet. 



Type. Old female. B.M. no. 9). 11. 8. 10. Collected 

 July 1894 by Ernest Hose. 



This species is no doubt closely allied to M. javanensiSy 

 but differs by its more markedly ridged skull, less expanded 

 zygomata, greater tendency to whiteness on the face and 

 under surface, and longer tail. 



LXIX. — On a new Marmot from North Siberia. 



By Oldfield Thomas, F.K.S. 



The British Museum owes to the generosity of ]\Ir. Talbot 

 Clifton the skin and skull of a marmot obtained by him in 

 the mountains east of Lena, in North-eastern Siberia. Tins 

 specimen I cannot identify with any known species, and would 

 therefore propose to call it 



Arctomys CUftoni^ sj). n. 



Size small, smallest of the Siberian species. Fur thick 

 and woolly. General colour very much as in A. camtsckaticusj 



