122 The Grayling and the Smelt 



the northern form (signijer) ; but the constancy of these charac- 

 ters in specimens from intermediate localities is yet to be proved. 

 Another very similar form, called Thymallus montanus, occurs 

 in the Gallatin, Madison, and other rivers of Western Montana 

 tributary to the Missouri. It is locally still abundant and one 

 of the finest of game-fishes. It is probable that the grayling 

 once had a wider range to the southward than now, and that 

 so far as the waters of the United States are concerned it is 

 tending toward extinction. This tendency is, of course, being 



FIG. 81. Michigan Grayling, Thymallus tricolor Cope. An Sable River, Mich. 



accelerated in Michigan by lumbermen and anglers. The 

 colonies of grayling in Michigan and Montana are probably 

 remains of a post-glacial fauna. 



The Argentinidae. The family of Argentinida, or smelt, is 

 very closely related to the Salmonida, representing a dwarf 

 series of similar type. The chief essential difference lies in the 

 form of the stomach, which is a blind sac, the two openings 

 near together, and about the second or pyloric opening there 

 are few if any pyloric caeca. In all the Salmonidcs the stomach 

 has the form of a siphon, and about the pylorus there are very 

 many pyloric caeca. The smelt have the adipose fin and the gen- 

 eral structure of the salmon. All the species are small in size, 

 and most of them are strictly marine, though some of them 

 ascend the rivers to spawn, just as salmon do, but not going 

 very far. A few kinds become land-locked in ponds. Most of 

 the species are confined to the north temperate zone, and a 

 few sink into the deep seas. All that are sufficiently abundant 

 furnish excellent food, the flesh being extremely delicate and 

 often charged with a fragrant oil easy of digestion. 



