SWOEDFISH. 147 



formed by the upper as it descends from the cranium, and 

 ends in a point ; the opening of the mouth extends back- 

 wards beyond the line of the eye ; no teeth ; the branches of 

 the lower jaw only slightly rough ; mouth divided by a 

 transverse membrane, with a smaller similar membrane to the 

 lower jaw ; no true tongue ; pharyngeal bones furnished with 

 very minute teeth : skin of the body rough. The pectoral 

 fins are elongated, and attached very low down on the body ; 

 the first three rays are the longest, the last the shortest ; 

 no vestige of ventral fins : the dorsal fin commences on a line 

 with the gill -opening ; the first three rays spinous, the fourth 

 or fifth ray the longest ; the rays then diminish rapidly to the 

 tenth or eleventh, where they become very slender, and are 

 connected by a very slight membrane as far as the thirty- 

 ninth or fortieth. Through a great part of this length the 

 dorsal fin is only about half as high as the pectoral fin is 

 long ; the three or four last rays are rather longer, and the 

 fin attains more power. This is the state of the fin in a 

 young fish when it has been but little used ; but the portion 

 of the fin intermediate between the two ends is so slight that 

 it is easily torn, or even entirely worn away by use during 

 life ; and this will help to explain the representations of this 

 fish when adult, .which exhibit only the two extreme ends of 

 this fin, and make it appear like two dorsal fins separated. 

 The two portions of the tail are elongated. 



The whole of the body is covered with a rough skin ; the 

 operculum smooth ; lateral line scarcely visible ; on each side 

 of the tail a membranous projection. The whole of the 

 underpart of this fish is of a fine pure silver colour, shaded 

 with bluish black on the upper part. Very young specimens 

 of twelve or eighteen inches long have the body covered with 

 small tubercles : these inequalities on the surface disappear as 

 the fish increases in size, first on the back, afterwards on the 



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