74 Merriam Voles of the Snbf/ 



The three species here recognized agree almost exactly in size, 

 the only difference being that the tail of oregoni is about 10 milli 

 meters longer than that of either of the others. In color oregoni 

 holds an intermediate position, bairdi being the palest and serpens 

 the darkest of the three. 



Following are descriptions of the known species : 



Microtus oregoni (Bachman.) 



Armcola oregoni Bachman, Journ. Acad. Nat. Sci., Phila., VIII, pt. 1, 60- 

 61, 1839. 



Type locality. Astoria, Oregon. 



General characters. Size rather small ; pelage short and coarse with a 

 decided ' pepper and salt' appearance : tail longer and ears more promi 

 nent than in the other members of the subgenus. 



Color. Upper parts brownish bister; under parts dark, more or less 

 washed with buffy ; tail blackish above, paler below. 



Cranial characters. Compared with the other known members of the 

 subgenus (bairdi and serpens) the braincase is narrower, less flattened, and 

 less subquadrate, the interparietal larger and more squarely rectangular, 

 the zygomata more strongly bowed outward, the frontal more distinctly 

 grooved interorbitally, and the ascending arms of the premaxillse longer. 



Measurements. An adult $ from type locality: total length, 140; tail 

 vertebrae, 42; hind foot, 17. 



Microtus bairdi sp. nov. 



Type from Glacier Peak, Crater Lake, Oregon (altitude about 7800 feet, 

 or 2350 meters). No. 79906, $ ad., U. S. Nat. Mus., Biological Survey 

 collection. Collected August 24, 1896, by C. Hart Merriam and Vernon 

 Bailey. Original No. 5813. 



General characters. Size small, a little smaller than M. oregoni; ears 

 and tail rather short ; coloration pale. 



Color. Upper parts uniform rather pale grayish bister, with a faint 

 reddish brown cast, and glossy ; under parts whitish, the plumbeous basal 

 fur showing through; tail bicolor; dark above, whitish beneath; feet 

 soiled whitish ; nose dusky. 



Cranial characters. Skull rather small and flat; braincase subquadrate 

 (broad in type specimen) ; zygomata bowed well outward ; rostrum short ; 

 audital bullse large and well rounded ; incisive foramina short, not reach 

 ing nearly to incisors. Compared with M. oregoni the rostrum as seen 

 from above is much shorter. 



The dental characters are those of the submenus Chilotus. 



Remarks. -This interesting new Vole may be distinguished at a glance 

 from M. oregoni by its shorter ears and tail and very much paler color. 1 

 have named it in honor of Professor Baird, who first recognized and 

 named the subgenus. 



