COMMON TROUT. 239 



tlie tail; the upper rays of this fin longest, nineteen in all; 

 its action in a depressed direction; and the arrangement of 

 bones 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, f Salmo ferox,J 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 Trout was caught in Cornwall which had a 

 second or smaller head, which appeared projecting from this 

 natural part; and ]\Ir. 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. 



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