MAMMALS OF THE MEXICAN BOUNDARY. 301 



was last seen about 10 miles west of Jacumba Hot Springs, in rocky 

 hills bordering a canyon near the Hayden ranch. On the plain called 

 Jacumba Flats the antelope ground-squirrel was very numerous, living 

 on level ground, digging its burrows under sagebrush, much as Citellus 

 tereticaudus does; but in the canyon at the head of Jacumba Creek it 

 lived in the most rugged mountain sides. When running, its tail is 

 always carried vertically; and it continually utters a trilling call that 

 sounded on the ear from various distances all through the days spent 

 in camp at Mountain Spring. The large cheek-pouches of those killed 

 were always found to contain seeds or green vegetation. Sometimes 

 it is verj' shy and seldom seen, while at other times it appears in 

 abundance and is very tame. Mr. Holzner made the following note: 



At Mountain Spring, California, in May, 1894, 10 small young individuals of uni- 

 form-size were caught from one hole. The mother was never seen; and, as the place 

 was very near the rock house (occupied by soldiers) and my tent, she could not have 

 passed in and out unnoticed. Did she have sufficient food in her nest, or did she 

 forage at night? 



AMMOSPERMOPHILUS LEUCURUS INTERPRES (Merriam). 

 EL PASO GROIIND-SaUIRREL. 



Tamias interpres Meeriam, North American Fauna, No. 4, Oct. 8, 1890, p. 21 



(original description). 

 Spermophilus interpres, Bryant, Zoe, III, Oct., 1892, p. 208. — Miller and Eehn, 



Proc. Bost. Soc. Nat. Hist., XXX, No. 1, Dec. 27, 1901, p. 51 (Syst. Results 



Study N. Am. Mam. to close of 1900). 

 ISpermophilus] interpres, Elliot, Field Col. Mus., Zool. Ser., II, Mar., 1901, p. 86 



(Synop. Mam. N. Am.). 

 lOitellus'] interpres, F.lliot, Field Col. Mus., Zool. Ser., IV, 1904, p. 143. 



Type-locality. — El Paso, Texas. (Type, skin and skull, No. ||^||, 

 U. S. National Museum, Biological Survey Collection.) 



Geographical range. — Sonoran Zone, in the Eastern Desert Tract of 

 New Mexico and Texas. 



Description. — Similar to typical Ammospermophilus leucurus., but 

 darker and more strongly colored, with the head grayer. The pelage 

 is much finer and longer. Tail bushy, the lateral hairs with two free 

 black bands. The general size and length of tail are almost exactly 

 the same as in typical A. leitcurus. Specimens from New Mexico, east 

 of the Painted Desert (the habitat of Ammospermophilus leucurus cin- 

 namomeiis)., in the collection of the American Museum of Natural His- 

 tory , New York, are intermediate between typical leucurus and interpres. 



Remarks. — All of our specimens were adults, taken during February 

 and March, when they were in complete winter pelage. 



As our survey proceeded westward from the initial monument near 

 El Paso, Texas, no representative of the Auimospennophilus leucurus 

 group was found until we had crossed all of the New Mexico section, 

 and a considerable part of the Arizona section of the Boundary, when 

 Aiiiviospermophilus harrinii appeared on the western border of the 

 Elevated Central Tract. Ammospermophilus leucurus was not encoun- 



