MICROTUS. 



Genl. Char. Size rather large; tail shorter than hind foot; plan- 

 tar tubercles six; enamel pattern as in M. nivalis, Europe. 



Color. Above pale yellowish brown, rufous on top of head and 

 on rump, the plumbeous bases of the under fur giving a darkish tone 

 to the upper parts; side pale buff, grading into the yellowish white 

 of the under parts. Face yellowish rufous, darkest on upper lips; 

 feet whitish. Tail, above like back, beneath buff. 



Measurements. Total length, i6o; tail vertebras, 26; hind foot, 

 20. Taken in the flesh from a specimen in the Field Museum, ob- 

 tained by the author on Hall Island, Bering Sea, July 14, 1899. 



a .—fisheri . {Microius), Merr., Proc. Wash. Acad. Scien., 1900, p. 23. 



Type locality. St. Matthew Island, Bering Sea. 



Genl. Char. " Similar to M. ahhreviatus, but yellow suffusion 

 even more intense, particularly on belly; nasals and rostrum (above) 

 decidedly longer, zygomata more strongly bowed outward; bullae 

 broader, less pointed anteriorly, and less flattened on outer side." 

 (Merr., 1. c.) 



Measurements. Total length, 178; tail vertebras, 32; hind foot, 24. 



279. townsendi. [Arvicola), Bach., Journ. Acad. Nat. Scien. Phil., 



1839, p. 60. 



occidentalis. Peale, U. S. Expl. Exped., Mamm., 184S, p. 45. 



Type locality. Lower Columbia River, Oregon, near mouth of 

 the Willamette. 



Geogr. Distr. Port Moody, British Columbia, to the Willamette 

 Valley and Taquina Bay, Oregon. 



Genl. Char. Size very large; ears two-thirds the length of hind 

 foot; tail less than half the length of head and bod\'. Middle upper 

 molar has four triangles; last upper molar has one interior and two 

 exterior closed triangles, and one anterior spherical triangle; anterior 

 lower molar has four salient angles on either side and three exterior 

 and three interior triangles. 



Color. Above yellowish rusty brown lined with black; sides 

 paler with less black. Under parts soiled ashy white tinged with 

 brownish; feet pale brown. Tail, dark brown above, paler beneath. 



Measurements. Total length, 190-226; tail vertebrffi, 66; hind 

 foot, 25-26; ear, 15. 



280. tetramerus. (Arviccld), Rhoads, Proc. Acad. Nat. Scien. Phil., 



1894, p. 283. 

 Type locality. Beacon Hill Park, Victoria, British Columbia. 

 Geogr. Distr. Vancouver Island. 



Genl. Char. Size medium, tail long; middle upper molar want- 

 ing fifth section. 



