2 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. DO 



slate-color ; cheeks, inner surface of ears, and lower portion of sides 

 clearer and more buffy ; underparts not strongly contrasted, pale 

 cream-buff much clouded by the slate-gray basal color ; feet and tail 

 whitish cream-buff, the tail just perceptibly more yellowish above 

 than below. 



Skull and teeth. — In general form the skull (plate I, fig. i) differs 

 notably from that of Microtus blythi (plate i, fig. 2), M. raddci, M. 

 mandarinus (plate 1, fig. 3) and M. johannis in its narrower, more 

 angular braincase, less spreading zygomata, relatively greater depth 

 at region of anterior zygomatic root, deeper, shorter rostrum, and 

 essentially perpendicular upper incisors. 1 In lateral view the profile 

 does not differ appreciably from that of Microtus agrestis, though 

 the skull is obviously broader than in the European species. As 

 compared with a skull of Microtus mandarinus with same condylo- 

 basal length that of the type of M. warringtoni has the zygomatic 

 breadth 2 mm. less, the interorbital breadth .6 mm. less and the depth 

 at front of m 1 .6 mm. greater. Auditory bullse large and inflated, 

 with wide meatus, their form much more as in M. agrestis than as 

 in M. mandarinus. Interorbital region narrow but not abruptly con- 

 stricted, with two low ridges in the type, these joined to form a low 

 median crest in an older individual. Palate normal, as in M. man- 

 darinus. Teeth with the usual Pliaiomys pattern ; m 1 with 5 closed 

 triangles and a very short, rounded, anterior loop. 



Measurements. — Type and adult female (No. 175859), the latter 

 in parenthesis: head and body, 117 (123) millimeters; tail, 28 (29) ; 

 hind foot, (s. u.) 19 (19) ; ear, 11.5 ( 11.5) ; condylobasal length of 

 skull, 27.2 (27.4) ; zygomatic breadth, 15.2 (16.0) ; interorbital con- 

 striction, 3.2 (3.0) ; occipital breadth, 12.8. (12.8) ; occipital depth, 

 7.0 (7.2) ; nasal, 7.8 (7.8) ; diastema, 8.2 (8.6) ; depth at anterior 

 edge of alveolus of m 1 , 8.2 (8.6) ; mandible, 17.2 (18.2) ; maxillary 

 toothrow (alveoli), 6.2 (6.4); mandibular toothrow (alveoli), 6.4 



(6.4). 



Specimens examined. — Six, all from the type locality. 



Remarks. — The color, skull, and teeth of this vole are exactly as 

 in Microtus brandti as described and figured by Biichner 2 from 

 material collected in the same region of northeastern Mongolia as 

 Radde's original specimens. The large size of M. warringtoni is, 

 however, immediately diagnostic. 



1 This character is approached in M. johannis. 



2 Wissensch. Resultate Przewalski Cent. Vsien Reisen, zool., Vol. I, pp. 117- 



T20, pi. 19, figS. 4-6. 



