NATURAL HISTORY OF BRITISH SALMONIDE, 
157 
and more numerous than in the other two species, the bull trout 
possessing the longest and strongest of the three fish, and the 
salmon those of medium size—short, stout, and pointed. 
The shape and size of the tail fins are 
a less certain test in some respects than the teeth, as they vary 
Thirdly, as to fins. 
A, the Zectoral or breast fins (so called from their being placed on the breast or 
shoulder of the fish); EE, the dorsa/ or back fins; B, the ventrad fins (named 
from their position on the belly); c, the aad fin (placed close behind the anal 
aperture) ; D, the cazdad or tail fin ; F marks the lateral or side line. 
much in different stages of growth. They will, however, be 
found a great aid to other distinguishing characteristics. 
are usually as follows : 
SALMON. 
Tail fin: deeply forked 
when young, less so 
at third year; at fifth 
year nearly or quite 
square. 
BULL TROUT. 
Becomes square at an 
earlier period than in 
salmon, and _after- 
wards gradually con- 
vex, 
They 
SEA TROUT. 
Less forked than in 
salmon of same age; 
becomes _ ultimately 
square. Tail shorter 
and smaller than in 
salmon. 
The shape and position of the other fins likewise differ, as 
will be seen by a comparison of the descriptions which follow: 
SALMON. 
Dorsal fin: Hinder ori- 
gin about half-way be- 
tween 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. 
BULL TROUT. 
Commences about half- 
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. 
SEA TROUT. 
Hinder origin exactly 
half-way between point 
of nose and end of 
tail fin. Second ray 
longest ; same length 
as base of fin. 
Half-way between origin 
of last ray of back fin 
and end of tail fin. 
