The Grayling and the Smelt 345 
the northern form (signifer); 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 hada 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 
X: 
Fic. 250 — Michigan Grayling, Thymailus tricolor Cope. Au 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 Argentinide.—The family of Argentinide, or smelt, is 
very closely related to the Salmonide, 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 ceca. In all the Salmonide the stomach 
has the form of a siphon, and about the pylorus there are very 
many pyloric ceca. 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. 
