74 Merrknv — Volfs of the Subgeiius ('Iilloftis. 



The three species here recoonized agree ahuost exactl_y in size, 

 the only difference being that the tail of oregoiii is about 10 nnlli- 

 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. ) 



Arricola oregoni Bachmafi, Journ. Acad. Nat. Sci., Philu., VIII, pt. 1, 60- 

 61, 1839. 



7)/pe locaUtij. — .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 snbgenus. 



Color. — Upper parts brownish bister; under pai'ts cbirk, more or less 

 washed with butfy ; tail blackisli above, paler below. 



Cranial cJiaracters. — Compared with the otlier known members of the 

 subgenus {bairdi and serpeiis) the braincase is narrower, less flattened, and 

 less subquadrate, the interparietal larger and more squarely I'ectangular, 

 the zygomata more strongly bowed outward, the frontal more distinctly 

 grooved intei'orbitallj', and the ascending arms of the premaxillfe longer. 



Measurements. — An adult (j^ from type locality: total length, 140; tail 

 vertebi'se, 42; hind foot, 17. 



Microtus bairdi sp. nov. 



7)lj>i' from Glacier Peak, Crater Lake, Oregon (altitude al)out 7800 feet, 

 or 2350 meters). No. 79906, V ad., U. S. Nat. Mas., 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 .1/. oregoni; ears 

 and tail rather short; coloration pale. 



Color. — Upper parts uniform rather i)ale grayish bister, witli 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 ; no.se dusky. 



Cra)ii<(l diameters. — Skull lather small and flat; braincase subquadrate 

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

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

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

 from above is nuich shorter. 



The dental characters are those of the subgenus Chilotns. 



lieinarks. — This interesting new Vole may be distinguished at a glance 

 from ^f. oregoni by its shorter ears and tail and very much paler color. I 

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

 named the subgenus. 



