MAMMALS ()!■' THE .MI'.XKAN BOUNDARY 



331 



CITELLUS SPILOSOMA ARENS (Bail. 

 EL PASO SPOTTED GROUND SQUIRREL. 



fipermophUus spilosoma arens Bailey, Proc. Biol. Sue. Washington, XV, p. 118, 



June 2, L902 (original description). 

 (Melius spilosoma arens Miller and Rehn, Proc. Bost. Soc. Nat. Ilist., XXXI, 



No. 3, Aug. 27, 1903, p. 75 (Syst. Results Study N. Am. Mam. during the 



years 1901 and L902). 



Tuza (gopher) or Vron (officer) of the Mexicans. 



Geographical rwnge.- Sonoran Zone, in southwestern Texas and the 

 adjacent parts of Mexico the Eastern Desert Tract. 



Description.— Size small: form slender. Tail terete at base, some- 

 what flattened and bushy at extremity. Feet (tig. 53) small. Ears 

 reduced to short rims. Length, 240 mm.; tail vertebrae, 80 (to end 

 of hairs, 100); hind foot, 35; head, 4.'>. 

 Skull, 39 by 23.5. Mammae, 5 pairs. 

 Iris hazel. Dichromatic, with reddish 

 and grayish color-phases. Pattern 

 spotted above, with ill-defined white 

 spots arranged in longitudinal series. 

 Ground color nearly uniform vina- 

 ceous-cinnamon, or rusty brownish 

 gray, according to the phase of color- 

 ation. Under surface and sides of 

 head, except a longitudinal infra- 

 orbital stripe, white. Tail vinaceous- 

 cinnamon above, except at the tip, 

 where the hairs are broadly banded 

 with black and tipped with yellow; 

 under surface of tail yellow. 



Cranial and a\ ntal characters. — 

 Those of the subgenus Xerosper- 

 mophihis, constituted by Doctor Merriam for the reception of the 

 spilosoma group, of which Citellus mohavensis (Merriam) is the type. 

 Skull with shortened rostrum, broad nasals, narrow interpterygoid 

 space, sharply elevated supraorbital rim. and heavy, obliquely-sel 

 teeth. The first upper premolar is much larger than in Ammo- 

 spermophilus, and about as in Citellus tereticaudus. 



Remarks. — The hair is short and coarse at all ^ea^ons. In winter 

 there is some under fur, and the under surfaces are well covered; but 



"The subspecific name spilosoma was restricted by Merriam i N. Am. Fauna, No. i. 

 p. 37, Oct. 8, L890) to the animal occurring in northern Mexico and extreme western 

 Texas. In describing " Spermophilus spilosoma marginatus," a new subspecies, from 

 Alpine, Texas, Mr. Bailey says that it is "Sumter to the dark, typical form of spilo- 

 soma fnun northeastern Mexico, but smaller and brighter colored," the inference 

 being that he has refixed the type-locality of dlellus spilosoma spilosoma to '•north- 

 eastern Mexico." 



Fig 53 . — Citellus spilosoma ireks. Fori 

 Hancock, Texas. (Cat No. 63385, t" s. 

 X M. i a. Forefoot; '<. Hindfoot. 



