Vol. 31, pp. 105-106 November 29, 1918 



PROCEEDINGS 



OF THE 



BIOLOGICAL SOCIETY OF WASHINGTON 



GEOGRAPHIC VARIATION IN CITELLUS TERETI- 



CAUDUS. 



BY JOSEPH GRINNELL. 



(Contribution from the Museum of Vertebrate Zoology of the University of California.) 



In studying the ground squirrels of California for the purpose 

 of preparing a general synopsis of the same, it has been found 

 necessary to make comparisons with material from other regions. 

 In doing this with Citellus tereticaudus the writer has become 

 convinced of the desirability of recognizing by name a new sub- 

 species from Arizona, as follows : 



Citellus tereticaudus arizonae, subsp. nov. 



ARIZONA ROUND-TAILED GROUND SQUIRREL. 



Type. — From Tempe, Maricopa County, Arizona; no. 25485, Univ. 

 Calif. Mus. Vert. Zool. ; 9 aduit, in complete summer pelage; collected 

 by H. S. Swarth, May 30, 1917; orig. no. 10596. 



Characters. — As compared with Citellus tereticaudus tereticaudus, C. t. 

 chlorus and C. t. eremonomus, of the Colorado and Mohave desert regions 

 west of the Colorado River, coloration of upper surface more reddish, and 

 tail shorter. 



Color. — On back, top of head and tail, deep pinkish cinnamon, be- 

 coming paler on neck, shoulders and sides, due to the greater extent of 

 the minute white tippings to the hairs. Sides of head, lower surf ace, and 

 feet, dull white. 



Measurements. — Of type: Total length, 243 millimeters ; tail vertebrae, 

 76; hind foot, 35. Eight adults from the Arizona side of the Colorado 

 River valley average: Total length, 234.1: tail vertebrae, 76.0; hind 

 foot, 35.1. 



Remarks. — As material accumulates representing more generally the 

 range of Citellus tereticaudus, it becomes clearly apparent that at least 

 four subspecies are worthy of recognition, distinguished rather easily 

 from one another by tone of coloration. Citellus tereticaudus eremonomus 

 Elliot, of Death Valley, Inyo County, California, exhibits a wood brown 



29— Pkoc. Biol. Soc. Wash.. Vol. 31. 1918. (105) 



