THE SALMON FAMILY. 



45 



longer head, rather smaller scales, and the dorsal 

 fin rather lower than in the northern form (sig~ 

 nifer) ; but the constancy of these characters in 

 specimens from intermediate localities is yet to be 

 proved. 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 con- 

 cerned, it is tending towards extinction. This 

 tendency is, of course, being accelerated in Michi- 

 gan by lumbermen and anglers. The colonies of 

 grayling in Michigan and Montana are probably 

 remains of a post-glacial fauna. 



The genus Oncorhynchus contains those species 

 of Salmonidce which have the greatest size and 

 value. They are in fact, as well as in name, the 

 king salmon. The genus is closely related to 

 Salmo, with which it agrees in general as to the 

 structure of its vomer, and from which it differs in 

 the increased number of anal rays, branchiostegals, 

 pyloric cceca, and gill-rakers. The character most 

 convenient for distinguishing Oncorhynchus^ young 

 or old, from all the species of Salmo, is the num- 

 ber of developed rays in the anal fin. These in 

 Oncorhynchus are thirteen to twenty, in Salmo nine 

 or ten. 



The species of Oncorhynchus have long been 

 known as anadromous salmon, confined to the 

 North Pacific. The species were first made known 

 one hundred and thirty years ago, by that most 

 exact of early observers, Steller,who described and 

 distinguished them with perfect accuracy, under 

 their Russian vernacular names. These Russian 

 names were, in 1792, adopted by Walbaum as 



