OF GREAT BRITAIN. 31 



i 

 vomer or central bone in roof of mouth when quite young 



(loses a large portion on first visit to salt water, and gradually 

 all, or all but one or two on most forward point of bone), one 

 line on each side of lower jaw, one line on each side of tongue 

 (occasionally two lines on each side of tongue). 



Shape and position of fins in Salmon, Bull-Trout, and Sea- Trout. 



SALMON. 



Tail- fin deeply forked 

 when young, less so 

 at 3rd year ; at 5th 

 year nearly or quite 

 square. 



BULL-TROUT. 



Becomes square at an 

 earlier period than 

 in Salmon, and 

 afterwards gradually 

 convex. 



SEA-TROUT. 

 Less forked than in 

 Salmon of same age ; 

 becomes ultimately 

 square. Tail shorter 

 and smaller than in 

 Salmon. 



Dorsal fin : Hinder Commences about half- Hinder origin exactly 



origin about half- 

 way between point 

 of nose and end of 

 tail-fin. Third ray 

 longest. 



Adipose fin : Hinder 

 origin half-way be- 

 tween origin of last 

 back-fin ray and end 

 of tail-fin. 



way between point 

 of nose and origin of 

 upper tail-fin rays. 

 Base of dorsal longer 

 than longest ray. 



Nearer to end of tail- 

 fin than to origin of 

 last dorsal fin ray. 



half-way between 

 point of nose and 

 end of tail-fin. Se- 

 cond ray longest, 

 same length as base 

 of fin. 



Half-way between ori- 

 gin of last ray of 

 back-fin and end of 

 tail-fin. 



To the above it may be added, that in the Salmon the pec- 

 toral fin equals two-thirds of the length of the head, whilst in 

 the Bull-Trout it equals little more than half, the anal fin also 

 in the former commences about halfway between the origin of 

 the ventral fins and the origin of the lower tail-fin rays, and in 

 the latter nearer to the tail. 



The teeth of the Bull-Trout are larger and stronger than in 

 the other two species, and those of the Sea-Trout are the most 

 numerous. 



Fin-rays: D. 13: P. 12: V. 9: A. 9 : C. 19. Vertebrae, 60. 



