242 CLASSIFICATION OF FISHES. 



semi-opaque fish, long celebrated for its richly silvered 

 swimming bladder ; it is so brilliant as to be seen 

 through the body, and has long been used in the manu- 

 factory of false pearls. Hitherto we have noticed only 

 such salmon as have a small, or, at least, only a mode- 

 rate sized mouth : but there is another race, whose food 

 must be entirely animal ; the mouth is excessively large, 

 the gape opening far beyond the eye; and the sides of 

 the jaws, as well as the inside, are armed with long 

 slender teeth, of different sizes, and moving backwards 

 at their roots : this gives them an appearance of being 

 flexible, but they are not so ; for if an attempt is made 

 to bend them forward, they become as firm and hard as 

 if they were rooted in the jaw : such is the nature of 

 the teeth in the genus Laurida of Aristotle, which was 

 the Sahno Saurus of Linnaeus.* The use of this struc- 

 ture seems to be, that the fish may swallow its prey at 

 once, and that it may glide down the throat without 

 being impeded by the numerous teeth it meets with in 

 the passage. The enormous gape, indeed, of these 

 fishes, shows that they swallow others of a dispropor- 

 tionately large size; and the teeth, being so very slender 

 and acute, are only used for the purpose of capture. 

 One species, the Salmo Saurus, of the old writers 

 {Laurida Mediterranea Sw.), is found in the Mediter- 

 ranean, and presents no very marked difference in struc- 

 ture from others found by Spix in the Brazilian seas : 

 the head is covered with strong bony plates, or, rather, it 

 appears to be naked; and the scales are firm and hard. 

 The Laurldce are also generally remarkable for the 

 smallness of the pectoral, and the great size of the 

 ventral fins. Although marine fishes, they have an 

 evident relation to Erythrinus, in their round and cy- 

 lindrical body, large mouth, and bony head; as well as 

 to the true salmons of Europe; the former being a 



* M. Cuvier has not only rejected the classic name given by no less a 

 naturalist than Aristotle to this group, but uses one {Saurus, a lizard), 

 which, under any circumstances, is totally inadmissible : we may just as \\ell 

 employ Avis, Amphibia, Reptilia, ice. to designate ichthyological genera. 



