68 Salmonidz 
museums. A species of Stenodus called Stenodus leucichthys 
inhabits the Volga, Obi, Lena, and other northern rivers; but 
as yet little is definitely known of the species. 
Oncorhynchus, the Quinnat Salmon.—The genus Oncorlyn- 
chus contains the salmon of the Pacific. 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 number of developed rays in the anal fin. These in Onco- 
rhynchus are thirteen to twenty, in Salmo nine to twelve. 
The species of Oncorhynchus have long been known as anad- 
romous salmon, confined to the North Pacific. The species were 
first made known nearly one hundred and fifty years ago by that 
most exact of early observers, Steller, who, almost simultaneously 
with Krascheninnikov, another early investigator, described and 
distinguished them with perfect accuracy under their Russian 
vernacular names. These Russian names were, in 1792, adopted 
by Walbaum as specific names in giving to these animals a 
scientific nomenclature. Five species of Oncorhynchus are well 
known on both shores of the North Pacific, besides one other 
in Japan. These have been greatly misunderstood by early 
observers on account of the extraordinary changes due to differ- 
ences in surroundings, in sex, and in age, and in conditions con- 
nected with the process of reproduction. 
There are five species of salmon (Oncorhynchus) in the waters 
of the North Pacific, all found on both sides, besides one other 
which is known only from the waters of Japan. These species 
may be called: (1) the quinnat, or king-salmon, (2) the blue- 
back salmon, or redfish, (3) the silver salmon, (4) the dog- 
salmon, (5) the humpback salmon, and (6) the masu; or (1) 
Oncorhynchus tschawytscha, (2) Oncorhynchus nerka, (3) Onco- 
rhynchus milktschitsch, (4) Oncorhynchus keta, (5) Oncorhynchus 
gorbuscha, (6) Oncorhynchus masou. All these species save the 
last are now known to occur in the waters of Kamchatka, as 
well as in those of Alaska and Oregon. These species, in all 
their varied conditions, may usually be distinguished by the 
