GEX. ANGUILLA. EELS. i257 



native fishes, little more need be added to convey 

 an idea of the general appearance of the species. 

 Differing considerably from each other in the details 

 of their structure, they possess in common a long, 

 narrow, serpent-like body, which, owing to the con- 

 formation of the vertebral column, is extremely 

 flexible; the greater part of the body surrounded 

 by a low nearly continuous fin; scales so minute 

 as to be for the most part almost invisible ; and the 

 surface frequently invested with a slimy mucus. 

 The caeca are wanting ; but all have an air-bladder, 

 which sometimes assumes a very peculiar form. 



Gen. XC Anguilla. — Our acquaintance with 

 the species of true Eels, composing the present 

 group, is by no means in a satisfactory state. It is 

 not long since all the Eels found in this country 

 were regarded as specifically the same ; in the best 

 and latest works three kinds are described as dis- 

 tinct. The differences consist chiefly in the form 

 of the head and the colours of the body. In the 

 former respect Eels seem subject to great variation, 

 and there is reason to think, that if this be assumed 

 as a mark of distinction, we might find grounds for 

 believing in the existence of even more than three 

 species. No one believes that there are two species 

 of Conger-Eel in our seas ; and yet we have seen 

 an example which presents nearly the same differ- 

 ence in the form of the snout, that there is between 

 the sharp-nosed and broad-nosed Eel. The ante- 

 rior part of the head of the Conger is usually elon- 

 gated and rather narrow; in the specimen alluded to 



