MALACOPTERYGII 



567 



represented in the seas and freshwaters of Europe, Asia, and 

 North America, extending southwards to North-West Africa, 

 Asia Minor, Northern Persia, the Hindu Kush, the head of the 

 Gulf of California, and the Eio Grande ; Salvelinus, Charr, with 

 8 to 10 rays in the anal, and teeth on the raised head of the 

 vomer only, of the lakes of Northern and Central Europe and the 

 rivers of the northern parts of Asia and North America as far 

 north as 82° 34', sometimes descending to the sea. 



The changes in form and colour which these fishes undergo 

 when passing from fresh water into the sea or when artificially 

 transported from one place to another are very great, and this 

 plasticity, together with the connecting links which render the 

 naming of not a few specimens impossible, have caused most recent 

 students of the genus Salmo, in Europe at least, to reduce many 



Fig. 343.— Tront (Salmo trutta). 



(After Valenciennes. ) 



of the so-called species to the rank of local varieties, and even 

 our common Brown Trout or Brook Trout {S. fario) is now 

 generally regarded as not specifically separable from the ana- 

 dromous Sea Trout (>S'. trutta). The anadromous true Salmon 

 {S. scdar) may be distinguished by its somewhat larger scales, 

 there being only 11 or 12 in a transverse series running from 

 the posterior border of the adipose fin forwards to the lateral 

 line. Trout having 13 to 16. The Charr of the lakes of Wales, 

 the North of England, Scotland, and Ireland are also regarded 

 as mere varieties of the common Northern migratory Charr 

 {S. cdpinus), of which the " Omble Chevalier " of the Swiss lakes 

 and the " Saeblings " of the Alpine lakes of Germany and Austria 

 are likewise varieties. An allied species (S. fontinaUs) has been 

 introduced into England from North America, as well as a true 

 Trout (S. irideus). The large size of the eggs, their lack of 



