FISH IN GENERAL. 47 



EXTERIOR OF FISHES 1 . 



Fish are without a neck, and their tails are usually of equal 

 thickness with the body at their insertion, giving them in 

 general simple forms. The body may be rounded as in the 

 diodon, cylindrical as in the eel, depressed as in rays, or 

 compressed as in most species ; the head may be larger than 

 the body, as in the angler, or smaller than the body, as in 

 many fishes. It may be round or variously shaped ; obtuse 

 as in cottus, more or less lengthened as we see it in fistularia 

 and centriscus. Both jaws may be prolonged as in orphia, 

 or the inferior jaw alone may be lengthened as in hemiram- 

 phus, or the upper one prolonged above the mouth as in rays, 

 sharks, and xiphias. The mouth may open below as in rays, 

 or at the point of the snout, as in most fishes, or upwards, as 

 it is found in uranoscopus. It may be more or less wide, from 

 a small opening, such as centriscus presents, to an enormous 

 gape, like that of the angler. 



Exteriorly only two organs of sense are visible, the orifices 

 of the nostrils and the eyes ; but the first may be simple, as 

 in rays and sharks, or double, as in most osseous fishes ; and 

 they may be placed further from or nearer to the eyes, the 

 jaws, or the point of the snout; the eyes vary exceedingly in 

 size, according to the species, and may be altogether con- 

 cealed beneath the skin, as in apterichti. They may be 

 directed laterally as occurs in most species, be raised or turn 

 altogether towards the sky. The whole genus pleuronectes 

 has these organs on one side, both eyes being placed on the 

 right or on the left side of the head. 



One family of fishes only, (the chondropterygians,) has the 

 external border of the branchiae fixed to the skin, and as many 

 openings for the escape of water as there are intervals between 



1 Cuv. Hist, des Poiss. vol. i. p. 288. et sequent. 



