680 LIEUT.-COL. J. BIDBTJLPH ON THE [JuilC 16, 



Both types of the North-American Sheep have a large dirty- 

 white posterior disk, which is very conspicuous except in the old males 

 in summer, wlien the whole of the body becomes nearly white; they 

 have also a dorsal stripe, which is more or less conspicuous. In O. 

 nivicoln there is no disk showing ahove the tail ', though the posteriors 

 are white and the dorsal stripe is wanting. There are other charac- 

 teristics in which 0. nivicola differs from the southern race of the 

 Bighorn, but which it shares with the northern race. In all three 

 the horn is smoother, less wrinkled, and more goat-like in character 

 than in other known species of true Wild Sheep ; but both 0. nivicola 

 and the northern race of the Bighorn have the horns less massive, 

 and in both the points turn out abruptly, so that the tips are sharp 

 and seldom broken, and point outwards ; while the southern race of 

 Bighorn has the horns massive at the base, the tips blunt, generally 

 broken, and pointing forwards. 



The ears in O. nivicola are very small and rounded, giving the idea 

 that they have been cut, and are thickly furred to the edges. In 

 the northern race of Bighorn the ears are also small and thickly 

 furred, but have blunt points instead of being rounded. In the 

 southern race of Bighorn the ears are broad, pointed, and deer- 

 like, moderately coated with hair, and are, if anything, rather larger 

 than in any of the known species of Asiatic Argali, measuring in 

 the dried skin fully an inch longer than those of the northern race. 

 Another point of distinction between the two races of Bighorn is 

 in the size of the skull, the southern race havina: a skull averagins; 

 from an inch to an inch and a halt longer, and from half an inch to one 

 inch broader than the northern race. There are also considerable 

 apparent differences in colour between the two races of Bighorn ; but 

 I have not been able to examine a sufficient number of specimens to 

 be sure how far these differences are constant. I have failed to find 

 any specimens of the southern race with the dark winter coat like 

 the specimen from Liard's River, nor can I find any mention of their 

 ever assuming it. There appear to be also slight differences in the 

 distribution of the colour on the legs. The northern race also has 

 the hair between the ears at the back of the horns growing into a 

 long curly tuft, which also happens in O. nivicola, but not in the 

 southern race of Bighorn, 



The subjoined table contains some comparative measurements of 

 specimens of the heads of the two races of the Bighorn. 



1 This is clearly shown in Escbscholtz's figure of 0. nivicola (Zool. Atlas). 



