Arrangement of the Family Salraonida?. 



407 



sliglitl}' notclied posteriorly, and correlated with this the 

 main frontal ridges are wide apart and parallel, whilst the 

 supraorbital flanges are narrow and taper anteriorly. In the 

 Pacific species the mesethnioid is much smaller and is forked 

 posteriorly, the frontal ridges converge anteriorly and the 

 supraorbital flanges are broad. Thus the genus OucO' 

 rhi/nchus, Suckley, can be no longer maintained, unless it be 

 considered that the cranial characters warrant its separation 

 from Sahno ; in tiiat case Oncorhynchas will include not 

 only the Pacific Salmon, but the Pacific Trout also. Onco- 

 rhynchus is said to have a longer anal fin than Sahno, but in 



Figr. 2. 



Skulls of a. Salmon (Salmo salar) and b. Qiiinnat {S. (juinnaf). As in 

 lig. 1, the skulk are seen from above and the jaws, facial bones, &c., 

 liave been removed. The skulls are those of adult fish. 



various forms of S. cJarkii I count 8 to 11 branched rays, and 

 in S. (Oncorhynchus) masou 10 to 12, so that there is no 

 generic distinction between these species. Nor is there any 

 justification for Berg's genus Sahnothymus (Ann. Mus. 

 8t. Petersburg, xii. 1907, p. 502), based on Salmo obtusi- 

 rostr'is, lleck., a species that agrees in its osteology with 

 S. trutta and S. salar, and may be regarded as the repre- 

 sentative of the latter in the rivers of Dahnatia. 



