COMMON TROTJT. 
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the tail; the upper rays of this fin longest, nineteen in all; 
its action in a depressed direction; and the arrangement of 
hones at its root not as in other Trouts; the line of the vertebrae 
so arched as to cause the distortion. But a more remarkable 
distortion or deficiency is frequent in a Trout which is found 
in Malham Tarn, in Yorkshire, for the knowledge of which 
and the possession of examples I am indebted to W. Morrison, 
Esq., M.P. The situation is on a hill twelve hundred and fifty 
feet above the level of the sea; the rock near is limestone, and 
the water clear. The fish are termed Silver Trouts, from the 
brilliancy of their appearance; but there is another species in 
the same water, which I have no doubt of being the Lake 
Trout, ( Salnio ferox,) of which the colour has a strong 
impression of yellow. This Silver Trout is of the ordinary 
growth of its species, and is in good condition; but the 
deficiency consists in the entire absence of the posterior plate 
of the gill-cover, sometimes on one side and at others on the 
other; and in a specimen sent to me this deficiency was on both; 
so that in every case the fibres of the gills are bare and open 
to the water. About one in four or five of the Trouts caught 
in this place are found with this deformity; notwithstanding 
which the fish bore no marks of having been subject to any 
inconvenience, and were in good condition. Among the casual 
malformations a Irout was caught in Cornwall which had a 
second or smaller head, which appeared projecting from this 
natural part; and Mr. Yarrell mentions one, in which there 
was both a separate head and tail. Deformed Trout, some of 
them like those already mentioned, are also recorded by Mr. 
Thompson, in his “Natural History of Ireland;” so that in fact 
there is no fish so liable to these irregularities of structure as 
the Trout. 
