Salmonidae 1 1 



it is doubtful if this fish breeds in our waters. It attains a length 

 of 18 feet. It feeds on small invertebrates, stirring up the sand 

 or mud with its snout and feeling for them with its barbels. A 

 specimen 6 feet long is exhibited ; it was taken in the Thames 

 before 1855, in which year it was presented by the Zoological 

 Society. 



SALMONIDAE. 



The Salmonidae are soft-rayed fishes with the pelvic fins far 

 behind the pectorals, and vvith the non-protractile moutii bordered 

 aliove by the praemaxillaries in the middle and the maxillaries at 

 tlie sides ; they are distinguished from other British fresh-water 

 fishes, except the closely related Osmeridae, by the presence of an 

 adipose fin — a small fleshy rayless tin placed on the hinder part 

 of the back. These features are illustrated in the diagTammatic 

 figure of a Trout on p. 8 (fig. 1b). This is a northern family ; 

 many of the species are marine, but ascend rivers to breed ; 

 others are permanently estalDlished in lakes or rivers. The 

 British Salmonidae belong to four genera, which may be shortly 

 characterized as follows : — 



1. Salmo (Salmon and Trout). — Mouth rather large ; a double 



or zig-zag series of teeth along the vomer (in the middle 

 of the roof of the moutli) present, at least in the young ; 

 dorsal fin i-elatively short, of 10 to 16 rays. 



2. Salvelinus (Char). — Differs from Salmo in that vomerine 



teeth are present only as a group at the anterior end of 

 the bone, which is raised and has a boat-shaped depres- 

 sion behind it. 



8. Goregonus (Powan, Vendace, etc.). — Differs from Salvio in 

 having the mouth small, without or with minute teeth. 



4. Thijmallus (Grayling). — Mouth small ; dorsal fin long, of 

 18 to 24 rays. 



5 — 12. Salmon, Salmo .^.a/ar. -This important fish is too 

 well known to need much description, but it is very closely related 

 to the Trout, and it is not always easy to distinguish between 

 them. In the Salmon the dorsal tin usually has more branched 

 rays (10 to 12) than in the Trout (8 to 10), the scales on the tail 

 number 10 to 13 in an oblique series from the adipose tin to the 

 lateral line (13 to 16 in the Trout), the maxillary is shorter, even 

 in large fish not extending far beyond the eye, and the tail is 

 more constricted at the base of the caudal fin, which is more 



