68 Salmonidae 



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 Oncorhyn- 

 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: (i) 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 (i) 

 Oncorhynchus tschawytscha, (2) Oncorhynchus nerka, (3) Onco- 

 rhynchus milktschitsch, (4) Oncorhynchus keta, (5) Oncorhynchns 

 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 



