THE SUB-GENERA OF SALMO. 245 



ened : the two jaws are of nearly equal thickness, or, 

 rather, the under one is narrower and weaker than the 

 other: the mouth is wide, and cleft in nearly a hori- 

 zontal direction : the first dorsal fin is in the middle of 

 the back ; while the anal fin is so short, as rarely to be 

 longer than the breadth of its anterior. These charac- 

 ters may be seen in full perfection in the salmon (Salmo), 

 with which we include the smelts (Osmerus) and Co- 

 rygonus : Mallotus has them only in part; the chief devi- 

 ation being in the anal fin, which is more lengthened. 

 The true genus Laurida of Aristotle, as well as Ana- 

 stomus of M. Cuvier, complete the divisions of this genus. 

 We consequently do not adopt Thymallus, or admit that 

 the smelt is any thing more than an aberrant species of 

 Salmo, just as Aulopus is of Laurida. Thus circum- 

 scribed, the European salmons with short anal fins are 

 all referrible to the following sub-genera, viz. Salmo, 

 Laurida, Anastomus, Mallotus, and Corygonus; the 

 affinities and relations of which appear to be as follows. 

 (220.) The European salmons, forming the genus 

 Salmo, have a small sharp head, with a mouth so 

 large as to have the gape often extending beyond 

 the line of the eye. The first dorsal is nearly central, 

 and the ventral immediately under it; the anal fin, 

 in like manner, corresponds in its situation to the 

 second or adipose dorsal ; while the pectoral is small, 

 pointed, and placed very low down towards the throat. 

 The teeth are very numerous in all; being placed, 

 generally, on all the maxillary bones, the palatines, 

 and the vomer : in some species, like the smelt, there 

 are very few teeth in the latter part ; and the lower 

 jaw, in both sexes, is longer than the upper; but 

 as this is a typical group, such slight variations are 

 always to be expected. In the Salmo tumbil (Bloch, 

 436.), we have the first material deviation from the 

 typical characters. The pectoral is placed higher up 

 towards the back ; the ventral fin is before the first 

 dorsal; and although not greatly developed, is yet as 

 large as the pectoral : the lower jaw, as in the smelt 



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