4784 Fishes. 



Leman trout, which has teeth on the chevron of the vomer. The 

 adult lake trout I speak of were dark spotted trout with pink- 

 coloured flesh. They all had a double row of teeth on the body 

 of the vomer, whilst the anterior group, called transverse and 

 teeth of the chevron by M. Valenciennes, had disappeared. That 

 they were once present no one can now doubt; the law therefore of 

 edentulation (for, in point of fact, it comes to this) in the lake trout of 

 the species I now speak of, is to lose the anterior group of the vome- 

 rine teeth and to retain the double row on the body of the vomer to the 

 last. • 



On the other hand, in a 4 lbs trout of Loch Leven, the largest of 

 that peculiar species I have yet examined, the anterior clustered 

 vomerine teeth were present, whilst those on the body were assuming 

 the form of a single undulating row, which possibly in time they 

 would have become. 



Lastly, M. Valenciennes admits, that in the mouth of the trout of 

 the Moselle, which he views as the type of the order, the clustered an- 

 terior teeth are distinct as well as the double row on the body of the 

 vomer, thus excluding the species forming the type of the order from 

 the law he intends shall apply to all. 



Thus, the law of M. Valenciennes does not apply to the trout 

 of British rivers nor to those of certain lakes, whilst it expresses the 

 dentition of others. It is not then a safe guide for the determination of 

 the subfamily, Salmo Trutta. Let us'now test its accuracy in respect 

 of the remaining subfamilies, the forelle or salmon trout and the true 

 salmon. 



If we trace the young of the forelle in its progress towards 

 the adult fish, we shall find that up to a certain weight it retains its 

 original generic dentition, that is, it resembles strictly that of all the 

 salmon kind. At this stage of its growth or metamorphosis it could 

 not be distinguished by the dentition alone from the Salmo Trutta or 

 from the true salmon of the same size : yet neither the salesman, nor 

 the naturalist, nor even the angler, lowest in the scale of observers, 

 experiences any difficulty in deciding on the nature of the fish before 

 him. They do not look at the teeth ; they have other much surer 

 characteristics, even at that age. Tracing the forelle until it attains 

 a considerable size, we find at last that the body of the vomer presents 

 a single row of teeth ; but the same edentulation has happened to the 

 salmon of the same size : in both, this single row is finally reduced to 

 one or two teeth, and may in both ultimately disappear; even the clus- 



