CLASSIFICATION 



369 



The common Salmon and Trout are species belonging to the 

 genus Salmo, and the species of Salmon and Trout found on the 

 Pacific coast of North America are included within the same 

 genus: the latter, however, form a group apart, distinguished 

 from their European . ^ , 



relatives by certain S^^^-^es - ^:^csa 



skeletal and other 

 characters, and the 

 mutual relationships 

 of all the species are 

 best expressed by 

 regarding the Pacific 

 forms as belonging to 

 a distinct sub-genus, 

 to which the name 

 Oncorhynchus is ap- 

 plied. Thus, the 

 Rainbow Trout of 

 America is known by 

 the scientific name 

 of Salmo [Oncorhyn- 

 chus) irideus, and the 

 Atlantic Salmon as 

 Salmo (Salmo) salar. 

 Genera are, in their 

 turn, grouped into 

 families, separated 

 from one another by 

 morphological feat- 

 ures of more funda- 

 mental importance, 

 with sub-families as 

 half- way groups 

 where necessary. 

 The Salmon and 

 Trout [Salmo) , the 

 Char [Salvelinus) , the 

 White-fishes [Corego- 

 nus, Leucichthys, Argyrosomus) , the Grayling [Thymallus), etc., con- 

 stitute the family Salmonidae. Families are grouped into sub-orders 

 and orders, orders into sub-classes and classes, classes into sub- 

 kingdoms and kingdoms. There are only two kingdoms, animals 

 and plants, but even here no sharp fine of distinction can be 



2A 



EROSOMATA 



A/EOPTERYCn 



PI5CE5 



Sub^Kinr^do:?7E. VERTEBRATA 



Fig. 133- 

 Diagram to show the systematic position of the 



Common Sole (Solea soiea), illustrating 

 principles of classification. 



the 



