184 MICROTUS. 



Color. Above dull yellowish brown mixed with black; sides 

 lighter; beneath whitish ash, base of fur plumbeous; feet brownish 

 white. Tail brown above, soiled white beneath. 



Mc-asurei/ients. Total length, 122-192; tail vertebrae, 33-54; hind 

 foot, 19 23; ear, 9-11. 



n.—ariznnenais. (M/crotus), Baile^', Proc. Biol. Soc. Wash., 1898, 

 p. 88. 



Ty/>e locality. Springerville, Arizona. 



Geogr. Disir. Eastern Arizona. 



Genl. Char. Similar to J/, mon/aniis, but more ferruginous; pal- 

 ate flat, pits shallow; pterygoids thick. 



Color. Above rusty brown; beneath white; feet dark gravish; 

 tail blackish above, grayish below. 



Measurements. Total length, 184; tail vertebra?, 55; hind foot, 

 20. Skull: basal length, 27.3; nasals, 8; zygomatic breadth, 16; 

 mastoid, 12.2; length of upper molar series, 6.5. 



h.—iivwJari'i. (Microtus). Bailey, Proc. Biol. Soc. Wash., iSgS, 

 p. 96. 



Type locality. St. George, Utah. 



Geogr. Distr. Only known from the type locality. 



Genl. Char. Larger and paler than M. montanus. 



Color. Above dull bister lined with black; sides slighth' paler: 

 beneath whitish; feet grayish; tail blackish above, grayish below. 



Measurements. Total length, 179; tail vertebrae, 48; hind foot, 

 23. Skull: basal length, 28.2; nasals, 8.3; zygomatic breadth, 17; 

 mastoid, 13.3; length of upper molar series, 7.3. 



264. nanus. {.Arvicola), Merr., N. Am. Faun., No. 5, 1891, p. 63. pi. 

 II, fig. 5-6. 



Type locality. Pahsimeroi Mountains, Idaho. Altitude. 9.350 

 feet. 



Geogr. Distr. Rocks' Mountains and other ranges from Central 

 Idaho to Nevada and southern Colorado. 



Genl. Char. Size small; ears small; antitragus large, and large 

 fossa innominata; tail more than one-third the length of head and 

 body. Skull: brain case narrow, high; parietal anteriorly subtrun- 

 cate; middle upper molar without postero-internal loop. 



Color. Above pale grizzled bister, mixed with black; sides ash 

 gray; beneath grayish white. Tail above dusk}', beneath whitish. 

 Feet dusky. 



Measurements. Total length, 151: tail vertebrae, 41; hairs, 7.5; 

 hind foot, 18; ear from crown, 4. 



