14 Miller A New Vole from Bering Sea. 



clearer on rump, paling on the sides to the soiled buff of the under parts, 

 which are slightly darker on chest. Tail bicolor, brownish above, yel 

 lowish white beneath. Feet dirty whitish. 



Skull and teeth. The skull is imperfect, lacking the occipitals and one 

 of the audital bullre. It resembles that of M. kamtschaticus very closely, 

 but the rostrum is slightly narrower anteriorly, the mandible is less 

 heavily built, and the bony palate is noticeably different in form. In the 

 palate of M. kamtschaticus the lateral bridges are broad and well developed 

 and the lateral pits are deep and very noticeable. In M. abbreviatus the 

 bridges are small and barely complete, while the pits behind them are 

 shallow and inconspicuous. In no one of the seven specimens of M. 

 kamtschaticus with which I have compared it is the peculiar palate of 

 M. abbreviatus closely approached. 



Teeth slightly smaller than in M. kamtschaticus, but enamel pattern 

 essentially the same in the two species. M. abbreviatus, however, has the 

 anterior loop of the front lower molar distinctly longer than in M. kamt 

 schaticus. In M. kamtschaticus there is usually a well developed fourth 

 outer salient angle on the posterior upper molar. This is quite absent in 

 M. abbreviatus, but the character is not likely to prove constant. 



Measurements.*' Total length, 120; tail vertebrae, 19 (pencil, 9); hind 

 foot, 22.5; ear from meatus, 9.5; ear from crown, 6. Skull: greatest 

 length, 27; zygomatic breadth, 15; interorbital constriction, 4; nasals, 

 7.8; mandible, 17.4; maxillary tooth row (alveoli), 6.4 ; mandibular tooth 

 row (alveoli), G.(>. 



General remarks. Microtus abbreviatus is closely related to both M. 

 kamtschaticus and M. kadiacensis, though in external appearance its short, 

 densely haired tail gives it a much closer resemblance to the members of 

 the subgenus Phaiomys. In cranial and dental characters it differs from 

 M. kadiacensis much as it does from M. kamtschaticus, since these two species 

 agree closely in palate structure and in the form of the front lower molar. 



*A11 from skin in alcohol. 



