1918] Kellogg: Microtus calif ornicus Group of Meadow Mice 29 



animals, Agelaius phoeniceus aciculatus, Eutamias merriami kernensis 

 and Neotoma fuscipes simplex, occupy almost the same area as 

 Microtus californicus kernensis. Furthermore, this seems to be the 

 area of intergradation between Cnemidophorus tigris iigris and 

 Cnemidophorus tigris mundus as well as of Uta stanshuriana elegans 

 and Uta stanshuriana hespcris. Other examples could be cited, but 

 the evidence points to the fact that in this region there has been a 

 differentiation of species to form new races in several unrelated 

 groups of animals, some of which have become fully differentiated 

 and others of w^iich have not. 



Microtus californicus mohavensis, new subspecies 

 Mohave River Meadow Mouse 



Microtus californicus, Elliot (1904, p. 299), part. Oro Grande. 

 Microtus californicus vallicola, of authors, part. 



Type specimen. — Male adult ; no. 5987, Mus. Vert. Zool. ; Victor- 

 ville, 2700 feet altitude, San Bernardino County, California ; April 6, 

 1907 ; collected by J. Grinnell and Walter P. Taylor ; original no. 2036. 



Range. — Known only from a limited area along the Mohave River, 

 in San Bernardino County, from Victorville north to Oro Grande. 

 Vertical range from 2500 feet up at least to 2700 feet; zonal range 

 Lower Sonoran. (See map.) 



Total number of specimens examined, 31, from the following 

 locality in California. San Bernardino County: Victorville, 31. 



Diagnosis.— ^ize large (hind foot, 22 to 25 mm., condylobasal 

 length of skull in largest individuals, 33 mm.) ; second upper molar 

 without posterior internal loop or lobe ; skull large, angular and 

 ridged in adults (ratio of zygomatic breadth to condylobasal length 

 about 56%) ; interorbital region not developing single median ridge 

 with age. 



Color. — Mass effect of dorsal area ranging from Dresden brown to 

 mummy brown, with varying admixture of long dark overhairs. In 

 fresh pelage: Upperparls with light ends of hairs grading from 

 ochraceous-tawny to cinnamon-buff, faintly varied by the sepia or 

 aniline black overhairs. Sides lighter than upperparts, with light 

 tipped hairs more nearly cinnamon-buff than those of upperparts. 

 Rump not conspicuously brighter than rest of upperparts. Under- 

 parts French gray, irregularly darkened by the appearance, at the 

 surface, of the plumbeous hair bases. Anal area whitish. Terminal 

 portions of whiskers grayish, bases darker. Nose usually not any 

 darker than area in front of eyes. Ears moderate in size, with anterior 

 border covered with hairs of the same color as light tipped hairs of 

 upperparts. Tail distinctly bicolor, covered to a varying degree above 

 with light seal brown or fuscous black hairs; below pale gull gray. 

 Hands and feet covered with pallid neutral gray hairs. In worn 

 pelage: Mass effect much duller and lighter. Light tipped portions 



