SALMONID^. 



8i 



a distinct and well-developed lower limb ; b is that of 5. brachypoma, which at b* has scarcely 

 a trace of a lower limb. This character may be said to be constant, and I have always 



Fig. 1. (After Giinther.) Fig. 2. 



found it a safe guide in discrimination. It should be remembered, however, that in the 

 young of all the Salmonoids the prseoperculum has a short lower limb, and that whilst "in 

 some species it lengthens with age, its development in a horizontal direction is arrested in 

 others." 



2. "The width and strength of the maxillary of the adult fish." This character is well 

 shown in the accompanying woodcuts. a is the maxillary or upper jaw of the Common 

 Trout, b that of the Lochleven Trout, each fish being of the same size, namely, twelve 



n. Common Trout- 



^, Locblcven Trout. 



(After Giintlicv.) 



inches long. I have before me a young specimen of the Common Brown Trout with, parr 

 marks distinct, from Ellerton Hall ; it is about four inches long. I have also before me a 

 parr Salmonoid from the Dee, near Min-yr-Afon, the residence of Mr. Bigge, caught in 

 August, 1878; it is about five inches in length. The young parr state in all the Salmon 

 family is very similar, and a general examination of the young of the different species would 

 fail to detect any difference. Now in the first of these two specimens [S./ario) the maxillary 

 reaches almost to a level with the posterior orbit of the eye ; in the Dee Salmonoid the 

 maxillar}' reaches only to the centre of the eye. Here is a most important character, for I 

 know at once that this young Dee Salmonoid is the parr stale of the Sal/no caiiibriciis. There 

 are other indications as to this being the species, but I pass over them for the present. 



3. "The size of the teeth, those of the intermaxillaries excepted." 



4. "The arrangement and the permanence or deciduousness of the vomerine teeth." This 

 is a character of some importance ; in some species the teeth are arranged on the vomer in 

 a double series, in others in a single one ; but as the teeth forming a single series are often 

 arranged alternately, or in a kind of zigzag way, presenting somewhat the appearance of a 

 double series, and other irregularities also occur, a definite arrangement is not always evident. 

 In some fish these vomerine teeth are persistent, in others deciduous. 



