NATURAL HISTORY OF BRITISH SALMONIDZ. 153 
somewhat rounder or more tapering than either of its con- 
geners, the form of the gill lids and proportions of the tail 
being intermediate between the two. The scales are also re- 
latively smaller. 
Indigenous in almost all salmon or bull-trout rivers, and 
frequently abounding in streams which produce neither the 
one nor the other, there is no fish that swims which, when in 
the taking mood, will rise so boldly at the fly, or make a 
pluckier or more brilliant fight. 
In the division which I have adopted between the white or 
migratory species of trout and the yellow or non-migratory 
species, the sea trout is the only one about which any difficulty 
of identification is likely to arise. The difference in colour 
between the /avzo and the ¢ru¢fa—the one being silver and the 
other golden or yellow—is usually too obvious to admit of 
doubt ; but, especially when confined for a long time in a lake 
or loch, sometimes the sea trout gets bronzed and acquires a 
colour not very unlike that of the common trout. If a doubt 
as to the species should thus arise a reference to the seeth on 
the vomer or central bone on the roof of the mouth will decide the 
point. These teeth in the common trout—as also in the great 
lake trout—run in ¢wo distinct rows, whilst in the sea trout they 
run only in a single row. It is to be observed, however, that 
teeth require to be closely examined, as in the case of the sea 
trout the points bend alternately to either side, so as to pre- 
sent rather the appearance of a thinly planted double row ; 
whilst in the common trout the two lines of teeth are placed so 
that a space in one row has a éoo¢h opposite it in the other, 
making the difference appear at first sight to be little more than 
one of comparative closeness in the setting of the teeth. 
In regard to the position of these vomerine teeth, the en- 
graving of the mouth of the common trout, given farther on in 
this article, is somewhat inaccurate, resembling, in fact, more 
nearly the appearance of the single row seen in the mouth of 
the sea trout. 
The usual weight of the sea trout runs from one to three or 
