1. SALMO. 47 



tudinal series between the lateral line and the root of the ventral. 

 AU the scales are rounded behind, extremely delicate, very deciduous, 

 and loaded with a silvery pigment. 



Coloration silvery ; back with a greenish shade becoming darker on 

 the upper part of the head ; numerous distinct blackish spots of about 

 the size of two scales are scattered on the sides above the lateral line 

 and sparingly below it. Operculum with several black spots, no red 

 spots whatever. Dorsal with several rows of black spots. 



Caudal and pectoral blackish ; ventral and anal perfectly white. 



Hybrid between Sewin (S. cambricus) and River-Trout 

 (S. fario). 



Hybrids between the Sewin and Trout are of no uncommon oc- 

 eiu-rence, and in several parts of South Wales tliey have received a 

 distinct name, Twh-y-daU, Kterally FaU of the Leaf, indicative of 

 the reddish shade of coloiir and of the dark-brown sjjots of the 

 male. Most of these specimens have retained the instinct of an 

 annual migration to the sea, and are full of milt or spawn in the 

 autumn ; and we have never had an opportunity of observing a 

 naturally sterile individual. But W. Peel, Esq., of Taliaris Park, 

 has stocked, for years, with young individuals of this form a fresh- 

 water pond which has no communication with the sea : they live 

 for years, growing to a length of fi'om 15 to 18 inches, but remain 

 sterile throughout their lifetime. Males are much more numerous 

 than females. 



These fishes, when young, generally more resemble the Trout, and 

 when adult the Sewin. They have much more similarity one to 

 another when young than after their first return from the sea. The 

 young, from 4 to 11 inches long, are distinguished by their short, 

 trout-like appearance, having at the same time the tail considerably 

 less deeply forked than the true Sewin of the same age. The vome- 

 rine teeth are numerous, but rather placed alternately than side by 

 side. The colours are constantly the same, the back and the sides 

 densely covered with small, angular, black spots, and a series of 

 round red spots along the lateral line ; none of the spots are ever 

 ocellated. We have never observed a specimen changing from this 

 variegated colour into the bright silvery of the young true Sewin 

 before going down to the sea for the first time. The dorsal and 

 anal have a bright yellow antero-superior margin, the former with 

 numerous oval black spots ; pectoral, ventral, and anal light lemon- 

 coloured. 



After their first return from the sea, these fishes are generally 

 rather inferior in size to the Sewin, and, although scarcely differing 

 from it in general form, they may be readily recognized by the 

 reddish hiie of the coloration, by the caudal fin being less distinctly 

 emarginate, and by a more or less complete longitudinal series of 

 vomerine teeth, which is sometimes double ; generally, however, the 

 teeth are strongly bent towards the sides. 



After the second return from the sea, they have assumed the 



