108 MR. OLDFIELD THOMAS ON MAMMALS [Feb. 18, 



" I did not discover much difterence in the habits of these two 

 Hamsters, but I believe that the long-tailed form (C griseus) 

 burrows for itself, while the short-tailed one (C. camphelU) is 

 more inclined, at least in this region, to take possession of holes 

 of the Red-tailed Rat (Meriones). Both species live on the seeds 

 and leaves of small plants, among Avhicli they can often be seen 

 running about in the late evening. Both species are abundant." — 

 M. P. A. 



7. MiCROTUS ANGUSTUS, Sp. n. 



(S (old). 1517. Mongolian plateau. Alt. 5000'. 4th August, 

 1907. B.M. No. 8.3.5.63. Tj/pe. 



A large pale species of the " Stenocranius " group. 



Size about as in J/. {Stenoa'anius) sloiczowi Kastcli. General 

 colour pale isabella, resulting from a coarsely lined mixture of 

 dull bufFy and brown. Sides clearer bufly ; a marked bufl' patch, 

 probably glandular in nature, just iii front of the hips. Hairs of 

 luider surface cream-bufi' terminally, the grey bases to the hairs 

 showing through. Sides of muzzle and tufts at bases of ears 

 rich bufiy ; the head otherwise like the bod3\ Ears rather short, 

 not pi'ojecting above the (summer) fur, the short hairs clothing 

 its edges pale bufly. Hands and feet uniformly dull bufly above ; 

 pollex with a small nail. Tail well clothed, dull bufly, with a 

 narrow rather darker line along its upper surface. Skull of the 

 extreme " Stenocranius " type, very long and narrow, as shown by 

 the measurements given below. Palatal foramina rather short. 

 Posterior palatal pits deep, the septum between them very 

 nari'ow. Opening of posterior nares narrow, angular. Bulla? of 

 average size. 



Teeth of the usual arvalis type, m^ with four spaces and a 

 posterioi- crescent. M3 with six spaces and an anterior trefoil. 



Dimensions of the type, measured in the flesh : — 



Head and body 112"mm. ; tail 32 ; hind foot 17; ear 10-5. 



Skull — greatest length 26-8 mm. ; basilar length 24 ; zygomatic 

 breadth 12*9; nasals 7 x 3*1 ; interorbital breadth 3; posterior 

 breadth 11; palatilar length 13-8; palatal foramina 5*2 ; length 

 of upper tooth -series (crowns) 5*7. 



Hah. and type as above. 



This Yole is an extreme member of the narrow-headed group 

 called Stenocranius by Kastchenko, but I fail to identify the 

 species with any hitherto described. Radde's Arvicola mongolicus 

 is a dark-coloured species (" dorso fusco "), Mkrotus raddei and 

 M. gregalis are smaller, while 21. slou-zowi and J/, tians/umicus, to 

 which the dimensions most nearly relate it, are from localities so 

 widely distant, with other species intervening, that it cannot 

 possibly be either of them. 



" Probably rare. Caught by hand among grass and weeds in the 

 middle of the afternoon. No other specimens could be found, 

 and there were no burrows about." — 21. P. A. 



