MOUNTAIN SHEEP NOTES 253 



Horn Sheep, here is a simple rule by which to reduce 

 each pair of horns to exact terms : 



Add together (i) the basal circumference, (2) the 

 circumference 18 inches from the base, (3) the circum- 

 ference one inch from the tip, and (4) the length on the 

 outer curve; and divide their sum by 4. 



It must be remembered that all sheep horns shrink 

 in circumference with age. A large horn will in two 

 years' drying shrink nearly or quite an inch in basal 

 circumference; and there is no way to prevent it, in a 

 mounted specimen. 



North America contains six species of mountain 

 sheep, which form two fairly distinct branches of the 

 genus Ovis. The Big-Horn (0. canadensis] forms the 

 stem of the first, and from it branch off the Mexican 

 Sheep (0. mexicanus), of northern Mexico, and Nel- 

 son's Sheep (O. nelsoni), of southern California. 



The stem of the other branch is formed by the White 

 Sheep (O. dall'i), and its branches consist of Fannin's 

 Sheep (O. fanning if it survives) and the Black Sheep 

 (0. stonei). 



It is interesting to note how much more persistent 

 in its desire to migrate is the mountain sheep (genus) 

 than the mountain goat. Here in British Columbia 

 we found them inhabiting the same mountains, and 

 on September n we actually saw sheep and goats in 

 the same moment. In its eastward range, the goat 

 now stops at St. Mary's Lakes, on the eastern slope 

 of the Rockies, in Northwestern Montana, but the 

 mountain sheep goes four hundred and seventy miles 



