PLATE 10 



Fig. 14. Looking due south from Mellen, Arizona, and toward the group 

 of spire-pointed hills known as "The Needles." The Colorado Eiver in the 

 right distance. Typical rocky mesa in the immediate foreground, the scattering 

 plants being creosote bushes. The desert mesa is here seen to abut closely upon 

 the river, leaving only very narrow riparian strips. Mammals trapped on the 

 mesa at this point were Perognathus intermedins and Ammospermophilus harrisi. 

 Photograph taken February 28, 1910. 



Fig. 15. Photograph taken March 7, 1910, on the Arizona side, from upper 

 slope of The Needles. Channel of the Colorado Eiver at extreme left. The 

 chief vegetation on the steep rocky slopes is the creosote bush and Encelia 

 farinosa. The latter reappears so persistently upon such ground that its name 

 has been selected to apply to the association marked by its presence. Mammals 

 trapped on this slope were Neotoma intermedia desertorum, Perognathus inter- 

 medins and Ammospermophilus harrisi. 



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