120 



BACK'S GRAYLING. 



Thymallus sirjnifer, 



PLATE XL 



Coregonus signifer, BaclCs grayling ; Richardson in Frankliii's 

 Journal^ and in Noriliern Zool. voL iii. pi. 88. 



The beautiful dorsal fin of this handsome species is 

 so conspicuous, that it has been noticed by the natives 

 dwelling on the banks of its streams, and, in their 

 language, signifies " wiry-like fin." It inhabits the 

 rocky streams that flow through the primitive 

 country lying between Mackenzie's River and the 

 Welcome*. It was found only in the clear waters, 

 and, Richardson says, delights in the strongest 

 streams, taking eagerly at the artificial fly, and, 

 w^hen hooked, tugging strongly, and requiring as 

 much dexterity to land safely as a trout six times 

 the size. "We do not see clearly the organs from 

 which this great power arises, except in the large 

 size of the dorsal fin ; for, in our idea of the use 

 which we have assigned to this fin, we look upon it 

 as incapable of using much exertion. There is, how- 

 ever, no other organ to which to refer it ; and if it 



* N. Zool. vol. vi. 



