FISH AND FISHERIES. 9 



collections, will find themselves so aided by the named species, that instead 

 of a difficult study the whole process of learning will be a delightful 

 recreation. 



In the wood-cut at the end of this chapter, fig. 1 represents — A, the 

 vomerine teeth ; B, the palatine ; C, teeth on the tongue ; D, supra- 

 maxillary ; E, maxillary. These terms will be frequently used. 



Fig. 2. Gill-cover of Salmo salar. A, pre-operculum ; B, opercu- 

 lum ; C, sub-operculum ; D, inter-operculum. 



Fig. 3. Gill-cover of Salmon trout ; letters the same as above. 



Fig. 4. Salmo salvelinus. 1, pre-operculum ; 2, operculum ; 3, 

 sub-operculum ; 4, inter-operculum ; 5, branchiostegal rays ; 6, fixed 

 plates forming immovable posterior margin of the gill-cover ; 7, root of 

 pectoral fin. 



These figures are adapted from *•' Freshwater Fishes of Central 

 Europe," by L. Agassiz. 



OD C 



Fig. 1. — Mouth of Trout, Salmo fario. 

 Fig. 2. — Gill cover of Salmo salar, Salmon. 

 Fig. 3. — Ditto of Salmo trutta, Sea-trout. 



Lower Figure — Salmo, head of Salmo salvelinus of Central Europe. 

 B 



