1914] Grinnell: Mammals and Birds of th( Colorado Valley 255 



Vulpes macrotis arsipus Elliot 

 Desert Kit Fox 



This fox appeared to be a characteristic element in the purely desert 

 fauna. The five specimens taken were all trapped on the desert mesas 

 back from the river. In fact, no evidence at all was forthcoming to 

 show that kit foxes ever visit the river or even the bottomlands. Their 

 presence was generally detected in sandy tracts, especially around 

 colonies of Dipodmys deserti. It is to be inferred that this rodent 

 constitutes the main food-supply of the l:it fox in localities where 

 both occur. 



The accompanying table shows the data appertaining to the speci- 

 mens caught. Although a xerophilous species, examples from opposite 

 sides of the river do not differ appreciably, in either cranial or external 

 characters. 



The two females taken at Pilot Knob showed evidence of having 

 recently suckled young, though this stage was well passed. 



LIST AND MEASUREMENTS IN MILLIMETERS OF VVLPES MACEOTIS AESIPVS 

 PROM THE COLORADO VALLEY 



Locality 

 Mellen, Ariz, side 

 Ehrenberg. Ariz, side 

 Opposite Cibola, Calif, side 

 Near Pilot Knob, Calif, side 

 Near Pilot Knob, Calif side 



Urocyon cinereoargenteus scotti Mearns 

 Arizona Gray Fox 



The Colorado River bottom and nearby desert proved to be well 

 populated with a form of gray fox. Specimens were taken, as .shown 

 in the accompanying table, on both sides of the river. Besides the 

 localities represented by specimens, gray foxes were also seen on the 

 California side near Pilot Knob; so that the species doubtless occurs 

 continuously the whole length of the portion of the river explored 

 by us. 



Our Colorado River material added a subspecies to the known 

 mammal fauna of the state. Urocyon c. scotti is well distinguished 

 from U. c. calif ornic us, of the San Diego district, on the basis of 



