SALMONIDjE. 



37 



system, from which after the fins, and the nmnber of vertebrae, the 

 specific distinctions are most easily ascertained. 



rx. -^ 



It will be seen clearly, at the slightest inspection of the beautiful 

 little fish which has been selected as the subject of this cut, and which 

 is a species of Lake Trout from the continent of Europe, that it has 

 eight fins in aU, including the tail, six of which are displayed in the 

 lateral view, two being on the farther side ; and seven in the view of 

 the back taken from above ; the eighth, which is indicated by a dotted 

 line, being on the under part of the fish. 



Of these appendages, by which the motion, position in the water 

 and direction of the animal are regulated; the two nearest the head, 

 one on either side, a a, are the pectorals; the two somewhat farther 

 back, one on either side, bb, are the ventrals; the one on the under 

 side, yet farther back, c, the anal; the tail, d, the caudal; and the 

 two on the ridge of the back, ee, the dorsal ; f is the lateral line. 



These are all the denominations of fins possessed by any fish, 

 although the number and size, as well as the structure, vary in the 

 various species, which are thus easily distinguished. 



Of these fins, all the classes of fish, concerning which this book will 

 treat, with one exception, the apodal Malacopterygii, one species of 

 which will be slightly mentioned, all possess the following : — 



