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University of California Publications in Zoology [Vol. 12 



removed, leaving a surface of firmly packed gravel or pebbles. The 

 burrows of the Harris ground squirrel are most often to be found 

 opening out beneath a creosote bush (see pi. 12, fig. 18), which plant 

 occurs throughout the range of the squirrel. Up to the last date of 

 capture, April 9, no young had been observed, although on March 5, 

 at Mellen, a female taken contained six embryos. 



In no instance was this rodent found to have strayed on to any 

 part of the river bottom, even on to the edge of the sandy second 

 bottom. But where the river passed among the steep-sided hills, as at 



LIST AND MEASUREMENTS IN MILLIMETERS OP AMMOSPEBMOPHILUS 



EABBISI HABB1S1 FROM THE ARIZONA SIDE OF THE 



COLORADO RIVER 



1 Not averaged, tail defective 



