78 MICROT.US. 



Measurements. Total length, 169-184; tail, 44-50; hind foot, 

 22-23. Skvill: Basal length, 28.6; Occipito-nasal length, 29; length 

 of nasals, 8.8; zygmnatie width, 17; interorbital width, 4; width 

 of nasals, 3.4; nlastoid width, n; upper molar series, 7; length of 

 palate to palatal notch, 14.6; to end of ptervgoid, 19.4; length of 

 palatal slits, 5.2; length of single half of mandible, 18.4; lower molar 

 series, 6.8 (Bangs). 



Microtus operarius endoecus Osgood. 



Microtus operarius endoecus Osgood, N. Am. Fauna, 1909, No. 30, 



P- 23- 



Type locality. Mouth of Charlie Creek, Yukon River, about 

 fifty miles above Circle, Alaska. 



Genl. Char. Like .17. operarius, bullae larger. 



Color. Same as .17. operarius (see Syn. N. Am. Mamm., 1901, 

 p. 187). No difference in outward appearance. Type compared with 

 M . operarius in United States National Museum. 



Measurements. Total length, 179; tail, 42; hind foot, 20. Skull: 

 Occipito-nasal length, 27.5; Hensel, 26.1; zygomatic width, 15.8; 

 intertemporal width, 3.7; length of nasals, 7.8; length of upper molar 

 series, 6.7; length of mandible, 15.3; length of lower molar series, 6.q. 

 Ex type in United States National Museum. 



Microtus coronarius Swart h. 



Microtus coronarius Swarth, Univ. Calif. Pub. Zool., VII, 1911, 



p. 131. 

 Type locality. Egg Harbor, Coronation Island, Alaska. 



Microtus (Lagurus) curtatus artemisiae Anthony. 



Microtus curtatus artemisios Anthony, Bull. Am. Mus. Nat. Hist., 

 XXXII, 1913, p. 14. 



Type locality. Ironside, Malhcur County, Oregon. Altitude' 

 4000 feet. 



Gent. Char. Similar to .17. curtains but smaller. Skull shorter, 

 nasals shorter; zygomatic width greater; mastoid breadth greater; 

 bullae smaller, upper tooth-row shorter. 



Color. Upperparts and head gray, washed with pale bistn ; 

 lower rump buffy ; under] >arts while, plumbeous base of hairs conspicu- 

 ous; ears blackish, covered sparsely with buffy hairs; tail above bistre. 

 beneath whitish. Ex type in American Museum of Natural History. 



Measurements. Total length, 120; tail, 24; hind foot, 17. Skull: 

 Occipito-nasal length, 23.2; Hensel, 20. 8; zygomatic width, 14.2; 

 intertemporal width, 3.2; length of nasals, 0.5; length of upper molar 



