1920] Howell: A Study of the California Jumping Mice 233 



Exterjial characters. — In coloration, typical alleni differs but 

 slightly from pacificus; the sides are a shade brighter, and the dorsal 

 area is usually darker, but not invariably so. The average length 

 of foot in five topotypes of pacificus measured in the flesh by the 

 writer is 32.2 mm., so that this member is not shorter than in alleni, 

 as was indicated by the type and cotype (Preble, 1899, p. 31). The 

 tail of this form is slightly more hairy than is usual in the genus. 



In the spring and summer pelage, the normal coloration is a bright 

 shade of ochraceous buff, and the dorsal area is well defined, with 

 the black hairs predominating on the middle of the lower back, but 

 fewer in proportion anteriorly, so that the top of the head is but little 

 darker than the cheeks. There are two extreme types of coloration, 

 with every degree between. In one, the dorsal area is very dark and 

 the lighter hairs are almost absent, while in the other extreme, the 

 black hairs are decidedly in the minority, giving a poorly defined 

 dorsal area. This difference seems to follow neither season nor age. 

 Immatures are usually lighter on the back than are adults, but not 

 invariably so. Most of the skins taken during the last of August, and 

 all of the September specimens (from the southern Sierras), have the 

 general color tone, buff, with the dusky bases of the hairs showing 

 through and fewer black hairs in the dorsal area. There are no 

 examples taken later in the fall by which the significance of this 

 change may be judged, but the pelage is then usually shorter, and as 

 there is no evidence of new hairs, the duller shade may be due to 

 fading, wear, and general devitalization of the old hairs preceding the 

 change to the winter coat. 



Skull. — Typical alleni has the smallest bullae of any race in the 

 state. 



Measurements. — Average, in the flesh, of 10 apparently adult 

 specimens from Eldorado County, California: length, 228.3 mm.; tail, 

 134.5; foot, 31.5. Average of 4 apparently adult topotypes of Z. p. 

 pacificus: length, 235.3; tail, 140.7; foot, 32.8. 



Remarks. — Although alleni has usually been considered a sub- 

 species of trinotatus, it seems to be definitely separated from that 

 species geographically, and its characters certainly place it closer to 

 pacificus. Many more specimens from the mountains of Washington 

 and Oregon are necessary before this point can be considered settled, 

 but the inference is that pacificus and trinotatus are specifically dis- 

 tinct, separated as are their ranges by the topographical barriers pre- 

 viously mentioned. It is possible that alleni is specifically distinct as 



