340 University of California Publications in Zoology [Vol. 10 



in desertornm. The pelage of this example is slightly harsher, 

 however, and the skull is as in inU rmi ilia. These Vallevista wood 

 rats average smaller than inU run ilia proper, in this respect again 

 resembling the topotypes of gilva. 



The name gilva was applied (Rhoads, 1S04. p. 70) to a white- 

 footed wood rat from Banning. Our series of twenty-five from 

 that locality are thus topotypes. They bear out the single 

 assigned character of gilva (as compared with intermedia), 

 namely, general paleness of coloration. They show in additiou 

 an average smaller size than San Diego County intermedia, a 

 sligb.1 resemblance to desertornm. An analysis of the color char- 

 acters shows also in all respects an approach to desertornm: As 

 compared with intermedia there is less of the black admixture 

 mid-dorsally ; the brown tones are paler, more huffy; ventrally 

 the white is more extensive, in other words, the plumbeous occu- 

 pies a less space on the individual hairs, and there is more 

 frequently a pure white pectoral patch; the upper side of the 

 tail is less black, more brownish. Contrary to Goldman's state- 

 ment ( 101(1, p. 45) that cranially gilva is like intermedia, we find 

 that Banning old adults have visibly smaller and lighter skulls 

 than intermedia from the vicinity of San Diego, and the rostrum 

 and nasals are shorter. Thus far the resemblance is towards 

 desertornm, hut the audita! bullae are notably smaller than in 

 thai form, and no larger than in intermedia. 



Cabezon, farther down the San Gorgonio Pass towards the 

 desert proper, furnishes twenty-three examples for our study. 

 These are apparently identical in color with the Banning series, 

 and hence the same general remarks apply. Cranially, too, the 

 two series are practically alike. In measurements, the Cabezon 

 males are larger, and the females are smaller, respectively, than 

 in the Banning animals. These differences are likely therefore to 



Pig. A (on opposite page). Diagram showing individual and geographic 

 variation in total length (in millimeters) of certain adult white-footed wood 

 rats. Solid lines, males; broken lines, females; figures at left and right 

 of these lines, respectively, indicate numbers of individuals measured; 

 length of lines shows range of individual variation; points connected by 

 solid and broken lines, respectively, mark positions of averages. Note 

 general reduction in the dimension geographically from the San Diegan 

 district (at left) through the San Jacinto region to the desert. 



