36 NORTH AMERICAN FAUNA. [no. 19. 



morning. Near f'ort Yukon I found its runways on recently depos- 

 ited silt sparsely j^rown uj) to Equlsetwm. Its burrows in this soft 

 material were very mimerous, and at the entrance to each a little heap 

 of earth in small globular lumps, as if carried in the mouth, was 

 always to be seen. 



Microtus xanthognathus (Leach). Yellow-cheeked Vole. 



This tine species was met with only once. A small colony was found 

 on a little stream near Charlie Village, occupying an old log ]am, 

 part of which had become embedded in a matrix of sand and mud and 

 overgrown with weeds. Burrows perforated this structure in numer- 

 ous places, and well-beaten, open runways connected various openings 

 about the protruding logs. The little animals were quite active during 

 the daytime, and as I walked over the logs I occasionally saw one flash 

 from one opening under a log to another and heard sharp little squeaks 

 sounding all about beneath me. A liberal number of traps placed 

 about yielded nine specimens, chiefly immature. The colony was 

 apparently confined to the log jam, as traps set in suitable places but 

 a few yards away secured only M. d/rummnondi. Four specimens of 

 this vole collected l)y Kobert Kennicott are in the National Museum, 

 one from the mouth of the Porcupine and three from the Yukon, 200 

 miles southwest of that point. 



Microtus operarius (Nelson). Nelson Vole. 



This vole was taken on a small stream about -10 miles above Circle, 

 and a few more were secured between that point and Fort Yukon. It 

 doubtless ranges from there to the coast. Forty-nine specimens were 

 taken at St. Michael. These represent all stages of growth and several 

 phases of color and seem to offer pretty conclusive proof that but one 

 species of Microtm occurs at St. Michael. It was found in all moist 

 parts of the tundra, being particularly numerous along the banks of 

 the small ponds in the tall grass and rank, weedy growths. 



Fiber spatulatus^ sp. nov. Northwest Muskrat. 



Tijpe from Lake Marsh, Northwest Territory, Canada. No. 98567, U. 8. Nat. Mus., 



Biological Survey Collection, 9 yg. ad. Collected July 3, 1899, by AV. H. 



Osgood. Original No., 552. (See Plate VI, fig. 4.) 



Characters. — Similar in general to Fiber zibethicus; size small; color 

 rather dark; skull small; molar teeth very small; nasals short and 

 much expanded anteriorl3^ 



Col(yr. — Similar to Fiber zibethicus^ but apparently less suffused 

 with fulvous. 



Shull. — Similar to that of Fiber zibethicus (Plate VI, tig. 3''), but 

 smaller; jugals more slender, and but slightly produced dorsally ; audital 

 bullae smaller; molar teeth decidedly smaller; nasals much shortened and 



^ Simtulatus, spatulate, in allusion to the shape of the nasals. 

 ^No. 76259, U. S, Nat. Mus., from Wilmington, Mass. 



