ALLEN: MAMMALIA. 221 



referred to Radde's " M us sylvaticus var. major" (Reis. Sib., 1862, 1, p. 180). 

 In his review of this group, Barrett-Hamilton (1900, p. 412) states that he has 

 seen no specimens but considers it as probably "the western Siberian representa- 

 tive of M. s. princeps" of southeastern Europe. He also believes that the speci- 

 mens obtained by Przewalski in the mountains of Kansu, and described by 

 Buechner as Mus chevrieri, are the same animal. In the absence of material for 

 direct comparison, our series agrees well enough with the description to make 

 this conclusion seem probable. Sixteen skins with skulls were collected by Mr. 

 Zappey at Lianghokow, 12,000 feet; Tachiao, 12,000 to 13,000 feet; Shuowlow, 

 13,000 to 15,000 feet; and Ramala Pass, 15,000 feet. Possibly these localities 

 indicate approximately the southeastern border of this mouse's range which may 

 thus extend north through Kansu to Siberia. The fact that at Tachiao it 

 occurs together with undoubted examples of the smaller A. sylvaticus draco seems 

 to indicate its specific distinctness from the latter. The coloration is decidedly 

 paler than in the latter, between buff and ochraceous buff above finely lined 

 throughout with black, especially on the mid-dorsal area; the tail is sharply 

 bicolor even in the immature examples; the feet are white, and the under parts 

 whitish, with the slaty bases of the hairs slightly showing through. The ears 

 are conspicuously large, measuring in the dried skins from 18 to 20 mm., as 

 against 15 and 16 for A. s. draco. 



The following measurements were made by the collector in the field : 



Average (6) 221 112 26 



Radde gives total length 215; tail, by calculation, 97; hind foot 24. 



The skull is large, the teeth broad and heavy. The interorbital constriction 

 is so great that the external faces of the molars can be seen when the skull is 

 viewed from above. The supraorbital ridge extends backward to a point about 

 opposite the posterior root of the zygomatic arch. The notch formed by the 

 upper edge of the antorbital foramen is very much deeper in the long axis of the 

 skull than in the skull of A. s. draco. The following cranial measurements are 

 taken from No. 7644: total length, 29.9; basal length, 23; palatal length, 

 14.6; nasals, 12; incisive foramina, 6 ; upper diastema, 7.2; zygomatic breadth. 



