318 MICROTIN^ 



conceal the claws ; claws not lengthened ; thumb with a minute 

 nail. Soles with 6 pads, densely hairy behind. 



Skull with well-arched dorsal contour, the braincase deeper 

 and less angular, and the temporal ridges (in adults) rather more 

 closely approximated posteriorly (near the interparietal) than in 

 other species. Anterior palatal foramina long and narrow, 

 extending backwards to terminate between the front edges of 

 the anterior cheek-teeth, instead of in advance of the tooth-rows 

 as usual. Auditory bullae very large and globular. 



Cheek-teeth remarkable for the complexity of m^. Measured 

 at the grinding surface this tooth is in antero-posterior length 

 about equal to m^ and considerably longer than m^. In its most 

 complex condition the crown of m^ in this species has an anterior 

 loop, followed by six alternating triangles and terminated by a 

 small posterior loop (Fig. 91, la) ; and it has four salient angles on 

 each side. Of the triangles the posterior three vary in develop- 

 ment in different individuals and also in the degree to which they 

 are confluent with each other and with the posterior loop behind. 

 When most reduced the tooth resembles that of A. blanfordi lahulius 

 and possesses 4 outer and 3 inner salient angles (Fig. 91, is). 



The enamel of the incisors is pale yellow. 



For external and cranial measurements, see tables at end of 

 volume. 



9. Alticola worthingtoni Miller. 

 (Synonymy under subspecies.) 



Range. — Central Asia between latitudes 42° and 44° N. and 

 longitudes 80° and 88° E. Typical subspecies known from the 

 Thian-Shan Mountains (Koksu 9000 feet; Kapkak 8000 feet; 

 and S. Muzart 7000 feet) and from the Bogdo-ola Mountains, 

 South-East Dzungaria, at an altitude of 6000 feet. A second 

 subspecies, A. w. subluieus, occurs in Djarkent, Semiretschensk. 



Characters. — Externally this species resembles A. phasma, but 

 is distinguished by its less pallid dorsal coloration and shorter 

 tail pencil, the latter measuring about 5 mm. instead of 13 mm. 

 in length. The skull is distinguished by its shorter and broader 

 incisive foramina, slightly smaller bullae, and less complex m^. 



Fur soft and full, about 10 mm. long on back. General 

 colour of upper parts a light yellowish-grey, much greyer and less 

 yellow than in A. phasma ; under parts pure white or " pale pink 

 buff," irregularly clouded by the slaty bases, and not so sharply 

 contrasted with the flanks as in ^. phasma ; white not extending so 

 far upon the cheeks. Tail from a third to about two-fifths of the 

 head and body measurement, densely clothed, the hairs completely 

 concealing the annulations and forming a short terminal pencil 

 of about 5 mm. in length. Claws more or less concealed by the 

 long hairs clothing the dorsal surfaces of the digits; soles hairy 

 behind the pads. 



