APR. 1903. NEW SPECIES AND SUBSPECIES OF MAMMALS ELLIOT. 159 



mouse of the plains, its longer-tailed relative being a mountain 

 species. The buff spot on the chest, mentioned in the descrip- 

 tion, is absent in some specimens, and others again have the 

 white under parts tinged with buff. The brightly colored rump 

 renders this form rather conspicuous. It bears also some resem- 

 blance to P. thurberi, but its long tail, large ears and brighter 

 coloring would serve to distinguish it. 



Peromyscus *oresterus. Sp. nov. 



T\pe locality. Vallecitos, San Pedro Martir mountains, Lower 

 California, Mexico, 9,000 feet elevation. 



Gen. char. Color pale; tail medium length. Skull with brain 

 case broad, rostrum heavy, nasals broad. 



Color. Upper parts pinkish buff lined with black on top of 

 head and dorsal region, making these darker than the rest; line 

 from nose to below the eye, shoulders and upper part of sides of 

 body pinkish buff; end of nose, lips, cheeks, lower part of sides 

 of body and entire under parts pure white; base of fur plumbeous; 

 tail above dusky; sides and beneath creamy white; hands and feet 

 white; ears brownish black, with tufts of creamy buff hairs cover- 

 ing basal half. 



Measurements. Total length, 201; tail vertebrae, 96; hind foot, 

 21: ear, 20.5. Skull: occipito-nasal length, 26; Hensel, 20; 

 zygomatic width, 12; interorbital constriction, 4; length of nasals, 

 9; breadth of rostrum, 4; palatal length, 10; postpalatal length, 

 7; width of brain case, n. 



This is a pale species belonging to the thurberi group, but 

 apparently very distinct from all of the described forms. Only 

 fifteen specimens were obtained, seven at Vallecitos, the type 

 locality, and two at Agua de las Fresas, a short distance to the 

 north, both localities being in the very midst of the San Pedro 

 Martir mountains, and six at Hanson Lagoon, in the Hanson 

 Laguna range. There is a slight variation in the measurements 

 between the examples, the tail of the type being longer than the 

 others. The extreme dimensions of the fifteen examples are: 

 total length, 160-201; tail vertebrae, 71-96; hind foot, 20.5-21; 

 ear, 19-21.5. The difference in total length is mainly in the 

 length of tail, which member often varies considerably in species 

 of this genus. One of these specimens has a narrow line from 

 the chest to the anal region in which the hairs are white to the 

 roots, but this is not perceptible in the one selected for the type, 



*6p<SrtpoS, dwelling in the mountains. 



