SALMO CAMBRICUS. 283 



number is not quite constant, and may occasionally be sixteen in large fishes. 

 There are fifty-nine to sixty vertebrae, and forty-nine to sixty-one pylorie 

 appendages. 



The transverse Parr marks disappear when the fish is five or six inches long- ; 

 it then has a silvery brightness, and is greenish on the back, with a few small 

 round black spots on the head and sides. As the fish becomes older the back 

 may be greenish-brown, the sides silvery, and the belly dark-brown at spawn- 

 ing-time in the male, while in the female the silvery tone remains. The 

 spots become irregular and X -shaped, and are scattered over the sides, both 

 above and below the lateral line. The fins have a blackish tinge, and small 

 round black spots usually occur on the dorsal. The colour, however, of the 

 other fins in the Grilse is only slightly grey, while in the Smolt the ventral 

 and anal are perfectly white. 



When in the sea they are known to feed on marine Crustacea and fishes. 

 Sterile individuals are met with in Denmark. This fish breeds readily with 

 the River Trout (Salmo fario, var. ausonii] in Wales, where the people 

 distinguish it as Twb-y-dail, which signifies " fall of the leaf/' in allusion, as 

 Dr. Giinther says, to its reddish colour and the dark-brown spots of the male. 

 The hybrids are fertile, and migrate to the sea, but when kept in fresh-water 

 ponds they never breed, though growing to a length of eighteen inches. 

 Males are relatively numerous. 



When young the hybrid is very like the Trout, but in maturity it takes on 

 the characters of the Sewin. There is a series of round red spots along the 

 lateral line. They do not acquire their reddish tinge till after the second return 

 from the sea. The pectoral and ventral fins are yellow in many specimens, 

 and then the lower front margin of the anal, and the corresponding margin of 

 the dorsal may be yellow, while bright orange-coloured spots extend along the 

 lateral line and below it. In Denmark another series of hybrids is formed 

 with the other variety of the River Trout (S. fario, var. gaimardii}. There 

 are fifty- eight to fifty-nine vertebrae in the Welsh fish. 



Salmo argenteus (Cuvmi AND VALENCIENNES). 



Of? 



D. 14, A. 11, P. 15, V. 10. Scales : lat. line, 123, trans. 



30. 



This is a Sea Trout, which ascends the rivers of France, and, according to 

 Dr. Giinther, occasionally reaches the British coast. It attains a length of 

 two feet six inches, and is regarded by some modern authors as identical with 

 the Salmon Trout ; but we prefer to follow Giinther in making it a distinct 

 variety, because it has an extra ray in the dorsal and in the ventral fin, and 



