186 MICROTUS. 



Geogr. Distr. Type locality and Pahranagat Valley, Southern 

 Nevada. 



Genl. CImr. Size large; tail short; colors dark; hip glands con- 

 spicuous in adult males; first upper molar with five closed triangles; 

 second with four; sometimes there is a small inner lobe at base of 

 posterior triangle; third with anterior crescent, three closed triangles 

 and a posterior loop with two inner lobes. 



Measurements. Total length, 210; tail vertebrae, 55; hind foot, 

 25.5. Skull: basal length, 32; nasals, 10.2; zygomatic breadth, 19. 3; 

 mastoid, 14.3; length of upper molar series, 8. 



268. californicus. {Arvicola), Peale, Mamm. U. S. Expl. Exped., 

 1S48, p. 46. 



trowbridgi, Baird, N. Am. Mamm., 1857, p. 529. 



Type locality. Shores of San Francisco Bay, California. 



Geogr. Distr. "California, west of the Colorado Desert and the 

 Sierra Nevada, and from Santa Isabel, San Diego county, California, 

 to the Rogue River and Umpqua Valleys, Oregon." 



Genl. Char. Ear five-eighths length of hind foot; tail twice as 

 long as hind foot; posterior upper molar has two exterior and one 

 interior triangle; the posterior crescent sends out a lobe near the 

 bend; first upper molar has four external salient angles, and five 

 internal, besides the anterior loop. 



Color. Above pale yellowish brown mixed with black; sides 

 lighter; beneath grayish white tinged with yellow; feet brownish 

 gray; tail dark brown above, paler beneath. 



Measurements. Total length, 170; tail vertebrae, 48; hind foot, 

 2o; ear, 12. 



a—vallicola. {Microtus'), Bailey, Proc. Biol. Soc. Wash., 1898, p. 89. 



Type locality. Lone Pine, Inyo county, California. 



Geogr. Distr. Valley of Eastern California. 



Genl. Char. Larger and darker than M. californicus ; middle 

 upper molar with lobe at base of fourth triangle often developed into 

 a loop. 



Color. Above dull sepia, lined with black, slightly suffused with 

 yellowish; beneath smoky plumbeous; feet dusky; tail above black- 

 ish, below grayish. 



Measurements. Total length, 200; tail vertebrae, 57; hind foot, 23. 



b.—constrictus. Bailey, N. Am. Faun., igoo. No. 17, p. 36. 

 T\pe locality. Cape Mendocino, California. 

 Geogr. Distr. Coast region near Cape Mendocino. 

 Genl. Char. Smaller than M. californicus and grayer. 



