4780 Fishes. 



the teeth, and not by the number of teeth actually present. So long 

 as these narrow mucous cavities are present, teeth either forming 

 or fixed will be found in connexion with them: their absence 

 implies that the dentition has been exhausted, and that the bone now 

 edentulous will carry no more. 



Now, examine the mouth of a true salmon of some 4 or 5 lbs. 

 weight, and, in addition to the transverse teeth on the chevron, you will 

 find a single undulating and somewhat irregular row of teeth extend- 

 ing backwards on the body of the vomer, varying in number, but 

 always present. Were this specimen to be classed by the method of 

 M. Valenciennes, it would be called a Forelle, Fario or sea trout, but 

 we know it to be a pure salmon, though with the dentition of 

 the Forelle. M. Valenciennes would no doubt say, " my formula 

 applies only to the adult salmon, and this is evidently not an adult." 

 I admit the force of the objection, so far as it goes, and shall proceed 

 with my inquiry, at the same time remarking that the natural-history 

 character, which not merely fails in recognising a salmon of 4 lbs. 

 weight to be a salmon, but which, if attended to, would lead the natu- 

 ralist to an entirely false view, cannot be viewed as one of any 

 value. 



Now, look into the mouth of a salmon about a foot in length, and 

 the dentition of the vomer will be found to consist of, 1st, transverse 

 teeth anteriorly on the chevron ; 2nd, posterior vomerine teeth con- 

 sisting of a double undulating row, as in the common river trout. 

 Lastly, as regards the true salmon, look into the mouth of a salmon 

 smolt a few inches in length, and the dentition will be found 

 such as I have just described it to be. 



Thus, the dentition of the salmon, from the smolt to the adult, 

 passes through a series of metamorphoses, representing the adult den- 

 tition of all the species of the Salmonidae I have yet examined. The 

 edentulatory process then, in the salmon, is not an accidental chapter 

 in its history, but a philosophical reading of its affiliations with all the 

 salmon kind. 



II. The practical history of the dentition of the Forelle or Fario, 

 the sea trout of British naturalists, is the same as in the salmon. 

 As a smolt, it resembles in its dentition, with all other species of the 

 Salmonidse, the common trout. At a pound weight it still retains a 

 double alternating undulating row of teeth on the body of the vomer, 

 together with a distinct cluster on the fore part of the bone. At 3 or 

 4 lbs. weight the mesial row of the vomerine teeth from being double 

 has become single ; when larger or heavier, and presumed to be older, 



