618 FOURTH REPORT— 1834. 



of the Clupecs to that of the Salmonidce, since the only differ- 

 ence between them consists in the presence or absence of an 

 adipose fin, an organ assuredly too insignificant to constitute 

 the distinctive character betwixt two families, and the less 

 so as there are some genera of the family which possess it, 

 whilst in others it is completely wanting, as, for example, in the 

 Siluridce. We may with equal truth affirm, that all the real 

 Salmones of Cuvier have not this adipose fin, for in many spe- 

 cies of the genera Sarrasalmus, Myletes, &c., it is composed 

 of rays which are truly osseous. 



Restricted to the limits which Cuvier has assigned to it, the 

 genus Salmo comprehends all the species of which the body is 

 somewhat lengthened, the mouth large, and supplied with teeth, 

 which are conical, pointed, and formidable, implanted into all 

 the bones of the mouth, that is to say, into the interior maxil- 

 lary bones, both superior and inferior, into the vomer and 

 palate bones, into the tongue itself, and into the branchial 

 arches. The margin of the upper jaw is formed by the interior 

 and superior maxillary bones, and constitutes only a single con- 

 tinuous arch, as in the higher classes of animals ; a conforma- 

 tion which in the class of fishes is found only in the Clupece. 



It is also singular that the number of branchial rays is seldom 

 exactly the same on the opposite sides of the head, the number 

 varying from ten to twelve. The pectoral and the ventral fins 

 are of a middling size ; the latter placed about the middle of 

 the belly, opposite to the dorsal, at their base, and along their 

 insertion there is a fleshy fringe, somewhat similar to the long 

 scales which are found on the greater number of the Clupecs. 

 The caudal fin is attached to a very fleshy root, and is moved 

 by very powerful muscles. 



This elastic tial is to these fishes a most powerful lever : 

 when wishing to leap to a great height, they strike the surface 

 of the water with a kind of double stroke. By this means they 

 overcome obstacles which appear insurmountable, and leap over 

 nets which are intended to confine them: the most formidable 

 waterfalls can scarcely arrest them. The several species of this 

 genus are found in the northern and temperate regions of Eu- 

 rope, Asia, and America. 



The fishes of this family are very ravenous, and feed princi- 

 pally upon the larvae of aquatic and other insects and of the 

 small Crustacea ; they also devour fishes of a smaller size. 

 Their alimentary canal is short, but the stomach is proportion- 

 ally long and strait. At its pyloric extremity may be observed 

 a great number of appendices, which are connected with the 

 pancreas, and to which is generally, but erroneously, applied 



