Fishes. 4785 



tered teeth are ultimately reduced in the very large salmon and sea 

 trout to two or three. 



The law of edentulation, then, in the Salmonidae is curious and inte- 

 resting, the result seemingly of generic and specific influences. Cer- 

 tain of these difficulties are removed by tracing its history from the 

 young, i.e. the generic fish, onwards. In it we find a type including 

 all ; it alone is perfect, the species being characterized by a loss 

 of parts and not by any superadded organs. To this conclusion I had 

 long ago arrived by other routes. What is true of the dentition we 

 shall find to hold good in respect of some other characteristics of the 

 generic animal, and to these, after a few additional remarks, I next 

 proceed. 



Up to the length of 13 or 14 inches, the dentition in, all the 

 subfamilies is nearly the same ; at 2 lbs weight the dentition of the 

 forelle and salmon is identical. They are both beginning to lose the 

 teeth of the body of the vomer, and often show a single instead of a 

 double row. At 6, 8, 10 or 20 lbs weight, both have lost the greater 

 number of the teeth on the body of the vomer, but still retain those on 

 the chevron. There may be certain species of the forelle or salmon 

 trout which retain, to a large size, a single row of teeth on the body 

 of the vomer, but I have not met with them. 



Throughout the preceding observations I have confined my remarks, 

 with but few exceptions, to species and subfamilies I have myself ex- 

 amined andean command; not that I distrust the observations of others, 

 for what observations can, for example, be more fully depended on than 

 the valuable contributions to Science of my most esteemed friend, Sir 

 John Richardson. If a reference be made to his admirable work, the 

 6 Fauna Boreali-Americana,' it will there be found, that the formula in 

 use by M. Valenciennes, will not, cannot be applied with any success 

 to the vast number of species of the Salmonidae which people the seas 

 and rivers of the great Continent of America. The Mackenzie River 

 salmon, for example, must be rejected altogether from the natural 

 family of the Salmonidae, if the dentition alone be regarded, for it has 

 the teeth en velours, or like the pile of velvet in narrow bands, and 

 the upper maxillary bones carry none. The Salmo Rossii has thirty 

 teeth on the tongue. Is Scouler's salmon (Salmo Scouleri) a salmon, 

 a Fario, or a trout? The palatine and vomerine teeth are implanted 

 in double rows, and there are none on the chevron of the vomer : here 

 is a true salmon, for such I esteem it to be, with a dentition wholly 

 peculiar. The great lake trout of North America has a cluster of 



