MAMMALS OF THE MEXICAN I'.OS'XDAUV. 



243 



rum]) blended with the coloring of the Hunk, instead of being sharply 

 defined. The muzzle is abruptly whitish in the northern animal and 

 unicolor with the rest of the head in the southwestern desert form. 

 Besides these differences, the median dark line which divides the white 

 of the nun | > into two part-- is obsolete and noncontinuous in the south- 

 ern specimen, which also has more white on the inner side of I he heel, 

 opposite the tibio-tarsal articulation. The summer female of 0. c. 

 gaillardi (No. 21392, U.S.N.M.) from the Gila Mountains. Arizona, 

 is much paler than one in corresponding pelage from Wyoming i No. 

 11801, U.S.N.M.) the former differing l'rom the latter t<» aboul the 

 same extent that the winter skins just compared differed from each 

 other. The skull of an eld male from the Gila Mountains. Mexican 

 Boundary Line (No. 59907, U.S.N.M.), is broader across the fore- 

 head and has a stouter muzzle than an old male collected l>v 



Fig. 39.— Ovis canadensis. Skull of adult male. Three Buttes, Montana. Cat. No. 13962, 

 I'. s.x. m.i. a, Lateral view; &, dorsal vii « 



the Northern Boundary Survey in Montana (No. 13962, U.S.N.M). 

 The horns of the male of the Gaillard bighorn are curved in a closer 

 spiral than those of the northern typical form (fig. 30), and in 

 Oris stonei," 0. canadensis <I<illi, and 0. iuri<-<>I<i the tips of the 

 horns become more and more divergent. Two pairs of horn- of 

 adult males were measured at Tinajas Altas. Yuma County, Arizona 

 (Nos. 59907 and 59908, U.S.N.M.), which were 720 and 820 nun.. 

 respectively, in length, following the outer curves of the 1 horns, and 

 365 and 360 nun. in circumference at base. The first horns of the 

 young male are quite different in form to those of the female. 



Geographical range. — Low deserf ranges in the Austral Life Zone, 

 south of the Gila and east of tin Colorado River, ranging south into 

 Sonora. Mexico, a- far as Seriland, opposite Tiburon Island, in the 

 ( in 1 f of California. 



aOvis stonei Allen. Bull. Am. Mus. Nat. Hist.. IX. An. VII, April is. 1897, 

 pp. 1 1 l-l 1 1. pis. ii. in. Type from the headwaters of the Stikine River, British 



Northwesl Territory, near the Alaskan boundary, al an altitude of about 6,1 



feet. 



