248 University of California Publications in Zoology [Vol.. 12 



One thing is apparent, that the Mecca series includes more small 

 specimens, with narrow-snouted sknlLs, than series of like extent from 

 elsewhere. There is thus a tendency towards the existence of a race, 

 of the characters assigned by Osgood to his angustirostris, in Salton 

 Sink. But if the upper Colorado Valley specimens are penicillatus, so 

 also are those from all the way down to Yuma and Pilot Knob and 

 thence across to the east flank of the Coast Range in eastern San Diego 

 and Riverside counties. 



In view of the locally fluctuating variations through the region 

 under consideration, the inclusion of all under the one name penicil- 

 latus seems now the wisest course. Should the penicillatus of Wood- 

 house prove to represent a truly distinct race, occupying the elevated 

 north central deserts of Arizona, as hinted by Osgood, then angustiros- 

 tris would be the name to be used for the subspecies of penicillatus 

 occurring all along the Colorado Valley below the Grand Canon, and 

 through the Colorado desert. 



Perognathus intermedius Merriam 

 Intermediate Pocket Mouse 



A series of 82 specimens taken, nos. 9876-9955, saved as skins- 

 with-skulls, and nos. 10785, 10786, as alcoholics. The localities of cap- 

 ture were all on the Arizona side of the river, as follows : Mellen, 19 ; 

 foot of The Needles, 10 ; above Bill Williams River, 2 : Ehrenberg, 13 ; 

 twenty-five miles below Ehrenberg, 1 ; ten miles below Cibola, 27 ; five 

 miles northeast of Laguna, 10. 



The preferments of this pocket mouse are to all appearances iden- 

 tical with those of the Harris ground squirrel. Both rodents are 

 restricted to rocky hills and the hard-surfaced, coarse-graveled mesa. 

 In both situations scattering creosote bushes form the prevailing vege- 

 tation, though on the hills Encelia farinosa is an additional conspicuous 

 plant. Perognathus intermedius was in no case found so near the 

 river as the second bottom (see diagram, fig. E). In fact, only three 

 out of the 82 individuals caught were found in sandy desert washes, 

 and these could have readily reached the points of capture in foraging 

 down from home centers on adjacent hills or mesa. 



Our series of record stations, as above named, carry the known 

 range (see Osgood, 1900, pp. 52, 53) of P. intermedius to the west, 

 and mark its limits in that direction as being at the east side of the 



