THE SALMON 25 



(Morone), which belong to the marine family of the 

 Sea Perches (Serranidce) ; two species live in the sea 

 or in estuaries, two more ascend rivers to spawn, and 

 two have become permanent residents in fresh water ; 

 also, the Shad are fishes of the Herring family which 

 spawn in rivers, or may even spend their lives in 

 fresh water. 



However, this is only argument from analogy, and 

 more positive evidence is derived from the distribu- 

 tion of the species, which affords abundant proofs 

 of their marine origin ; the Salmon is not a European 

 but an Atlantic species, the Trout extends eastwards 

 to the Caspian and Aral Seas and their tributaries, but 

 is absent from the Siberian rivers to the north of 

 them, wherein our Roach, Pike, and Perch are found ; 

 with one or two exceptions, probably due to recent 

 geographical changes, the Char and Whitefish of the 

 Alps are found only in those lakes which do not 

 communicate with the Mediterranean. In short, 

 the distribution of the Salmonoids has been mainly 

 determined by the seas to which they resort, or 

 those from which they formerly came. 



The British members of this family belong to 

 four genera, namely, Salmo (Salmon and Trout), Sal- 

 velinus (Char), Coregonus (Whitefish), and Thymallus 

 (Grayling), the salient differences between which 

 are shown in the following synopsis : 



I. Mouth rather large, the maxillary extending at 

 least to below the middle of the eye ; teeth 

 well developed ; scales small or. moderate ; 

 dorsal fin with 10 to 16 rays. 



No depression behind the head of the 

 vomer, and a double or zigzag series of teeth 



