138 MR. OLDFIELD THOMAS ON 



25. MiCROTUS MILLIC'EXS. 



Thos. Abstr. P.Z. S. 1911, p. 49 (Oct. 31). 

 J. 2613, 2614, 2615, 2621, 2639. $. 2632, 2640. Wei- 

 choe, on Si-ho K, W. Sze-chwan. 12,000-12,500'. 



A gi^eyish species with a delicate ilattened skull, long tail, and 

 extra angle on m^ 



Size medium, about as in 3f. Irene. Fur long, soft, and loose ; 

 hairs of back (in winter pelage) about 12 mm. in length. General 

 colour above rather darker than '' hair-brown," passing into 

 " smoke-grey " below. Ears scarcely projecting above the fur, 

 well-haired, greyish brown. Head and feet glossy greyish white, 

 varying to greyish brown ; soles with 6 pads. Tail comparatively 

 long, well-haired, grey -brown above, whitish below. Mammte 

 2—2=8. 



Skull rather lightly built, with a long flattened oval brain-case 

 without marked ridges or angles. Upper profile-line flat or 

 even slightly concave at a point above m". Rostrum of medium 

 length, narrow. Interorbital region smooth, not ridged, flat- 

 tened above. Angles of brain-case scarcely perceptible. Posterior 

 palate normal, the lateral pits of medium depth. 



Incisors rather thrown forward. Molars narrow. M^ with the 

 usual five spaces, all separated, a scarcely perceptible ti'ace of a 

 .supplementary postero-internal projection. M^ with a large 

 supplementary postero-internal salient angle, making three angles 

 on the inner side. M^ nai-row, with the usual transverse first 

 space, the second and thii'd small, united to each other, and a 

 posterior U ; three inner and three outer salient angles (the whole 

 somewhat as in Blasius's figure 221 *, except that the anterior 

 transverse lobe is narrower, and the second and third spaces are 

 united). M, with a large posterior transverse lobe, four lateral 

 closed triangles in front of it, and a fifth united to the antei-ior 

 trefoil, there being in all five inner and four outer salient angles 

 (near fig. 193 of Blasius, if the first lateral closed triangle were 

 open to the anterior trefoil). M^ with the anterior two of the 

 usual five spaces united to each other ; three inner and three 

 outer angles. 



In short, the most salient features of the dentition are the 

 development of the extra postero-internal angle on m" and the 

 junction of the second and third spaces of m^ and first and 

 second of m.,. 



Dimensions of the type, measured in the flesh : — 



Head and body 90 mm, ; tail 53 ; hind foot 18-5 ; ear 14. 



Skull : condylo-basal length 24-3 ; condylo-incisive length 24-6 ; 

 zygomatic breadth 14-2; nasals 6-7; interorbital breadth 4-2; 

 brain-case, length 12-5, breadth 11-5, height including bullse 9, 

 height of supraorbital edge above root of m- 6-9 ; palatilar length 

 12'5 ; palatal foramina 4*8 ; upper molar series (crowns) 5"6. 



Hab. as above. 



* J. 11. Blasius. Naturcc. dcr t^au;;etliieit Dcut:^cllla^ds. 1857. 



