Fishes. 4779 



racterized by the presence of certain teeth, placed transversely on 

 the fore part (chevron) of the vomer, the rest of the bone being 

 edentulous. 



2nd. The forelle or Salmo Fario of all countries and localities may 

 at once be recognized and arranged by the presence of transverse 

 teeth on the chevron of the vomer, and by a single row of teeth 

 extending backwards along the body of the vomer, mesially. 



3rd. The trout of all localities is known by a double row of teeth 

 on the body of the vomer, the transverse teeth on the chevron or fore 

 part of the bone being absent or but little distinct {peu distincte). 



This arrangement is so simple, so clear, so seemingly practical, so 

 easily understood, that one feels a reluctance to disturb it : it reminds 

 me of the arrangement of serpents by their dentition, prior to the ex- 

 tension of the inquiry into the Indian species and those of the Japan 

 seas ; like it, the formula applied so well to certain genera of Europe 

 and perhaps of Africa that it was the most natural thing in the 

 world to believe it universally true; but it failed in presence of 

 a more extended inquiry, as the natural-history arrangement of 

 M. Valenciennes, in respect of the Salmonidae, will be found to do. 



I. Select a salmon of such a size, say 30fbs. weight, as to leave no 

 reasonable question of its adult condition, and the dentition will, 

 generally, be as follows : — 



Upper jaw. — Maxillary and intermaxillary teeth. . 35 + 35 = 70 



Palatal teeth 17 -j- 15 = 32 



Vomerine (called by some middle palatal) 

 on the chevron 4 ; on the body, mesially 

 and behind the others, 1 or 2 6 



Now these teeth of the vomer vary much, even in the adult, for 

 sometimes there are none on the body of the vomer, and the transverse 

 may be five in number or reduced to one or two. 



In the lower jaw and on the tongue there are, 



1st. Mandibular teeth. 18 + 18 = 36 



2nd. Lingual teeth 5 -\- 5 = \0 



As the teeth of fishes, like those of serpents, are constantly being 

 shed and replaced by others, the number of five d teeth becomes un- 

 important as a natural-history character. Not so the number of mu- 

 cous cavities destined to receive the teeth ; these, no doubt, are 

 constant and determined from the first. I reckon the dentition, there- 

 fore, by the number of these mucous cavities destined to receive 



