1920] Howell: A Study of the California Jumping Mice 227 



These groups comprise: (1) Z a/pus trinotatus eureka and Z. orarius, 

 in the humid coast belt; (2) Z. pacificiis alleni, in the Boreal Zone of 

 the main Sierran mountain mass; and (3) Z. major, in the isolated 

 Warner Mountains of extreme northeastern California. Carrying our 

 enquiries to the northward, it is found that group 1 is replaced at 

 some indeterminate point by Z. trinotatus trinotatus, and that the 

 latter continues up the coast of Washington and also towards the 

 interior, into the Cascade Mountains of that state. But the Cascade 

 Mountains of Washington and of Oregon are separated by the Colum- 

 bia River gap, and in the latter state there is an evident barrier 

 between the coast and the mountains, constituted by differences in 

 relative humidity and in temperature. Hence, on the main mountain 

 mass of Oregon occurs Zapus pacificus pacificus, which is apparentlj^ 

 distinct from any form which has been found to the north of that 

 state. The relationships of the two races of pacificus (Z. p. pacificus 

 and its southern neighbor Z. p. alleni) are discussed elsewhere. 



Zapus major, of the third group, undoubtedly has its closest 

 affinities with the jumping mice which occur in the isolated mountain 

 ranges of the Great Basin region. With this group is placed Z. mon- 

 tanus, for, although that species is found on the southeastern border 

 of the Cascades, and hence adjacent to the range of Z. p. pacificus, 

 its relationship clearlj^ is not close to the latter form. It is nearer 

 to group 3, although specifically distinct from any form now known 

 to the writer. The type localities of pacificus and monianus are only 

 about thirty miles apart, and are separated by a remarkably even 

 slope, containing not the slightest obvious geographical barrier. It 

 must be inferred, therefore, that the two forms arose separately, in 

 different faunal areas. 



Of montmius, nine, and of pacificus, five, topotypic specimens are 

 available. This is a larger number than has heretofore been assembled, 

 and it seems desirable, therefore, although not strictly within the scope 

 of this paper, to compare these two species on the improved basis. 

 When Preble (1899) monographed the genus, but two typical examples 

 of pacificus were known, and these were in faded, washed-out pelage. 

 My specimens were taken during the latter part of July and the middle 

 of August, and appear to be normal in every way. The underparts 

 of both species are pure white ; the pattern of coloration is as usual 

 for Zapus, but the sides of pacificus are ochraceous buff, while those of 

 montanus are much duller, and close to tawny olive. In the dorsal 

 area of the former, the black hairs are very slightly in the majority ; 



