new Uodenls from Kan-su. 723 



Microtus oniscus, sp. n. 



A small vole allied to M. irene. 



Size decidedly smallei* than in irene. Fur soft and fine, 

 rather less woolly than in irene ; hairs of back almost 10 mm. 

 in length. General colour above lined hair-brown ; below 

 slaty, washed with greyish or drabhy wiiite ; line of demar- 

 cation on sides rather well detined. Ears showing beyond 

 the fur ; coloured like the head. Hands and feet dull 

 whitish ; soles hairy, with six well-developed pads. Tail 

 short ; above drabby, proximally darkening to brown ter- 

 minally, below white. Mammse 2 — 2 = 8. 



Skull lightly built, with slender muzzle and interorbital 

 region; its upper outline not so flat as in M. irene and 

 vu'llicens. Interorbital space narrow, rounded above, without 

 angles or ridges, though it might become ridged in the 

 middle line in old age. Brain-case smooth, rounded, rather 

 narrow, the antero-exterual corners scarcely perceptible. 

 Palatal foramina fairly long. Posterior palate normal, its 

 lateral pits fairly deep. Mcsopterygoid fossa rather narrow. 

 Bullae proportionally small. 



Teetii. — JP and ni^ without additional internal angles. 

 ]\P with the usual four prisms and a posterior lobe, but the 

 latter, instead of being C-shaped, is quite simple, with a 

 single antero-internal angle only; there are therefore three 

 internal and three external angles to the tooth, il/i, as in 

 jU. irene, with only four closed prisms, the normal fifth and 

 sixth (counting from behind and including the posterior 

 transverse lobe) open to each other and to the anterior space ; 

 the latter nearly cylindrical, its outer and inner angles 

 scarcely developed. 



Dimensions of the type (measured in flesh) : — 



Head and body 80 mm. ; tail 25 ; hind foot 15*5; ear 11. 



Skull: condylo-incit-ive length 22*2; condylo-basal 

 length 22 ; zygomatic breadth 13; nasals 6*7; interorbital 

 breadth o'4 ; height of crown above alveolus of m^ 7 ; 

 palatal foramina 4:'5 ; upper molar series (crowns) 5'2. 



Ilab. 40 miles S.E. of Tao-chou, Kan-su. Alt. 11,000^ 



Type. Ai\\x\i male. B.M. no. 11.11.1.3. Original 

 number 181. Collected 10th April, 1911, by Dr. J. A. C. 

 Smith. Presented by the Hon. N. ('liarles Eothscliild. 



This little vole shares with M. irene and il/. millicens 

 alone the combination of a Pitymys-Mkc m^ with a mammary 

 formula of 2 — 2 = 8 and six hind foot-pads. From M. milli- 

 cens it is distinguislied by the absence of supplementary 

 internal prisms on m"^, and from its nearest ally, M. irenCy 

 by its materially smaller size and shorter tail. 



