54 SALMONID.E. 



and E E, to the outside row on the maxillary bones of the 

 lower jaw. 



Now it will readily be understood what is the importance of 

 examining carefully this system of teeth^ in the different 

 varieties of the Salmon family, whether called Salmon, Salmon 

 Trout, Lake Troutj Bi'ook Trout, or any other local name 

 whatsoever ; when it is stated that the distinct species are very 

 strongly and permanently indicated by the number of teeth 

 found in each upon the vomer, or central bone of the roof of 

 the mouth. 



In the true Salmon, the teeth on the vomer very rarely 

 exceed two ; and sometimes there is but one. 



In the Bull Trout, the teeth are longer and stronger than 

 those of the true Salmon ; but, like that fish, he has but two, 

 or at most three teeth on the vomer; he is distinguished, 

 according to the authorities, by the different formation of his 

 gill-covers, and the convex form of his caudal fin, whence he is 

 said to be termed the Round-tail in the River Annan, in 

 Scotland. This fish is unknown in America, and is merely 

 mentioned for the sake of example and illustration. 



In the Salmon Trout of Great Britain {Salmo Trutta, Lin.), a 

 migratory fish, growing to a very large size, the teeth extend 

 nearly the whole length of the vomer, thereby establishing a 

 distinction between this and the two aforenamed species. 



Of the Common Trout, we have already seen the dental 

 arrangement in the two distinct varieties of Lake Trout, recog- 

 nised by authorities in Great Britain, whicli are non-migratory, 

 and analogous to our Lake Trout. 



In the Great Grey Ti'out or Loch Aavc Trout [Salmo Ferox), 



