152 



DR PARNELL'S LIST OF 



time they reach the sea to a month or six weeks after, they are not seen ; and 

 we can only infer their growth from the fact, that after the lapse of that pe- 

 riod we find them returning to the rivers in which they were bred, ha\ang acqui- 

 red a weight between a pound and three-quarters and two pounds and a-half ; 

 they are now named Grilses. These fish rapidly increase in size ; and by the 

 end of July are taken from five to six pounds in weight, when they have as- 

 sumed the appearance of perfectly-formed salmon. 



The characters by which the salmon is distinguished from the sea trout are 

 by naturalists ill-defined, and this seems owing to the fish not having been exa- 

 mined at the several stages of its growth. 



Mr Yarrell (in his excellent work on the British Fishes, vol. ii.) speaks of 

 " the teeth of the vomer in the salmon, seldom exceeding two in number, and no 

 other teeth extending along the vomer as in the sea trout." Now, if we examine 

 a young salmon of eight inches in length, we shaU find the teeth as numerous as 

 in a trout of equal size, as it has from twelve to fom-teen in number running back 

 the whole length of the vomer. (See Plate VIII.) In a young salmon of eigh- 

 teen inches in length, the teeth are from five to seven in number, placed on the 

 anterior part of the vomer ; and in a salmon three feet long the teeth on the vo- 

 mer are often entirely wanting. 



The principal character, which at once removes the salmon from the migra- 

 tory trout, is derived from the anatomical structure of the internal organs. 



The csecal appendages in the salmon I have never found less than fifty-eight 

 in number, the average number being sixty-two ; whereas in no instance have I 

 ever found the csecal appendages in the migratory trout more than fifty-seven in 

 number, the average number being fifty-four. 



By combining a number of external characters together, the experienced Ich- 

 thyologist finds no difiiculty in distinguishing the salmon from the trout at all 

 ages. 



The salmon has never more than six spots below the lateral line, and often 

 is without any. The lower third of the pectorals is always black, as well as the 

 intervening membrane between the first three rays of the ventral fin. The mid- 

 dle ray of the tail is never more than half as long as the longest ray in that fin. 



Mr Yarrell, in his extensive collection of prepared fishes, possesses a young 

 salmon about a pound weight. Dr Johnston of Berwick has a specimen in his 

 possession a pouad and a-half in weight ; and the young sahnon which I have 

 now the honour of exhibiting to the Society, measures eighteen inches in length, 

 the weight being a pound and a-quarter. 



Salmo eriox, Yarr. — BuU Trout. Common. 



Salmo trutta, Yarr. — Salmon Trout. Common. Most naturalists have con- 

 founded many species of migratory trout under the names of Sabno eriox and 

 Salmo trutta ; and I hope, at a future meeting of the Society, to shew, that, in- 



