286 



PROCEEDIXGS OF THE ACADEMY OF 



[1899. 



Fig. 2. Enamel pattern of Mlcrotus rnvidnlus (upper figures) and M. 

 pamirensis (lower figures). (X (i.) 



larger than in M. arva/is, but the enamel pattern in the two species 

 is identical. 



Specimens examined. — Fiv^e, all from the type locality. 



Remarks. — Although a member of another subgenus, Microtus 

 raviclidus bears a strong superficial resemblance to 21. hlytlii. The 

 colors of the two species are almost precisely the same, but M. 

 ravidulus, aside from its subgeneric characters, can be distinguished 

 by the dark dorsal surface of the tail, coarser fur, and more con- 

 spicuous dark ' lining ' of back. 



The four skins show no important variations in color. 



Microtus ravidulus is closely related to M. tianschanicus Buchuer 

 from the Juldus Valley. In size, color and cranial characters the 

 two species apparently agree perfectly; but the five specimens of 

 M. ravidulus have the front lower molar of 31. arvalis instead of 

 the very peculiar tooth described and figured by Biichner as occur- 

 ring without exception in the seven specimens of J/, tianschanicus 

 collected by Przewalski. In only one of the latter is there a faint 

 trace of a fourth outer salient angle; and this tooth is specially 

 figured as abnormal. Although both animals occur on the south 

 side of the great Tianschan mountain chain, they are some four 

 hundred miles apart, and probably completely insulated by the 

 Chalyk and Beschan mountains, which would undoubtedly act as 

 barriers to austral species. 



Dr. Abbott tells me that this vole was abundant in the grain 

 fields of the comparatively low, fertile valley about Okchi. It 

 occurred together with a species of Cricetulus, and one or both of 

 the animals laid up abundant underground stores, each containing 

 about a pint of barley heads. Strangely enough, this habit was 

 not known to the owners of the fields. 



^ Wissensch. Resultate der von N. M. Przewalski nacli Central-Asien 

 untern. Reisen, Zoolog. Theil, Bd. i, Siiugethiere, p. 107, 1889. 



