236 University of California Puhlioations in Zoology [Vol. 21 



localities in California. Modoc County : East Warren Peak, 1 ; Sugar 

 Hill, 1; Parker Creek, 19; Dry Creek, 3; Goose Lake Meadows, 4; 

 Lassen Creek, 2 (coll. A. B. Howell). 



Diagnosis. — Major is the largest species of Zapus in the state, and 

 skins may be distinguished by the combination of white underparts 

 and dull-colored sides. The skull differs from that of typical alleni 

 in being heavier and slightly longer, with proportionally robust ros- 

 trum, smaller pterygoid fossae, aud larger bullae and incisive fora- 

 mina, the latter averaging less constricted posteriorly. This species 

 differs from montanus in having a heavier skull, rostrum less tapering, 

 incisive foramina larger, molar rows longer, basioccipital slightly 

 wider, and bullae smaller. 



External characters. — In the skins of spring and early summer, 

 the general tone of the sides is warm buff, but this is modified to a 

 slightly greater extent than is usual with California Zapus by the 

 admixture of black hairs. Normally, the latter greatly predominate 

 in the dorsal area, the boundaries of which are poorly defined, but 

 a few of the adults have paler backs. The ears are dull black, faintly 

 marked with lighter hairs, but in none of the specimens before me 

 are these members edged with white, as is said to be the case with the 

 type (Preble, 1899, p. 25). In August the skins are slightly duller 

 in tone but are otherwise similar. 



Skull. — Major has the longest skull, with heaviest rostrum, largest 

 incisive foramina, and longest molar row of any form in the state. 



Measiirements. — Average, in the flesh, of 14 apparently adult 

 specimens from the Warner Mountains, California : length, 231.9 mm, ; 

 tail, 139.4; foot, 30.6. Average of 7 apparently adult topotypes of 

 Z. montanus: length, 226.7; tail, 136.4; foot, 32.7. 



Remarks. — The difference in coloration between major and alleni 

 is so great that the two need never be confused. Specimens taken 

 in August can hardly be distinguished as to color from montanus, but 

 the hind foot of major seems to be a trifle heavier. 



In California, major has been taken only in the Warner Mountains 

 of the extreme northeastern corner of the state, but it may occur in 

 the few other suitable spots that are situated in the Modoc region. 

 So far as I am aware, but the one animal has been secured at the type 

 locality. 



