MAMMALS OF THE MEXICAN BOUNDARY. 



499 



Type-locality. — ^Vicinity of San Francisco Bay, California. 



Geographical range. — Grassy meadow-lands of the Sonoran (mostly 

 Upper Sonoran) Zone of southern California and northern Lower Cah- 

 fornia. "■ 



a. b. c. 



Pig. 125.— Microtus califoknicus. Skvll. a, doesal view, 6, ventral view; c, lateral view. 



Description. — Size, large; mammae, P.|, A§, I.f =4 pairs; skull (fig. 

 125) massive with rostral portion short and depressed; teeth as shown 

 in fig. 126; coloration similar to Microtus edax; pelage full, long, and 

 rather soft; plantar tubercles, 6. 



Color. — Upper parts bistre enLvened by tawny and black hairs, 

 shading to grayish drab on sides and rump; under parts plumbeous, 

 overlaid by hoary tips to the hairs; tail not 

 distinctly bicolor, but dusky above and gray- 

 ish below; feet smoke gray; whiskers mixed 

 brown and white or colorless; head without 

 white or yellowish markings. 



Measurements. — (Adult male,- Cat. No. 60954 

 U.S.N.M., from Tecate Kiver, near Tecate 

 Mountain, northern Lower California, June 26 

 1894; collected by the author). — Total length 

 192 mm. ; tail vertebrae, 59 ; terminal pencil, 6.5 

 hind foot, 24; ear, from crown, 12.5. Skull 

 greatest length, 30; zygomatic breadth, 17.3 

 mastoid breadth, 14; length of nasals, 8.8 

 alveolar length of upper tooth row, 7.7. 



Habits. — When we made our camp on the 

 Tecate River at the foot of Tecate Mountain, in 

 northern Lower California, June 24, 1894, we immediately discovered 

 numerous runways of this, the only species of vole collected on the 



o Elliot has described a subspecies hyperyihrus (in Field Col. Mus., Zool. Ser., Ill, 1903, 

 p. 161 ; also in Land and Sea Mammals of Middle America and the West Indies, Zool. Ser. 

 IV, 1904, pp. 300-303, fig. "51" [skull and teeth], fig. "xlv" [animal]), from San Quen- 

 tin. Lower CaUfomia. 



Fig. 126.— Microtus califoe- 

 Nicus. Crowns of molar 



TEETH, a, UPPER SERIES) 

 ft, lower SERIES. 



