THE FAMILY OF " ROUND-MOUTHED " FISH. 403 



body smooth and eel-like ; head rounded ; mouth circular, 

 armed with hard tooth-like processes ; tongue (which moves 

 backwards and forwards like a piston, and causes the suc- 

 tion) with two longitudinal rows of small teeth; seven 

 apertures on each side of neck, leading to seven branchial 

 or gill-cells ; the skin, towards the tail, extending in a fold 

 above and below, forming the back-, anal-, and tail-fins, 

 which are without rays. 



The Eels are the last of the Bony Series of British fresh- 

 water fish (in which are embraced all the species of which 

 the sportsman takes cognizance) ; and we now commence 

 the Cartilaginous Series, or those in which the skeleton is 

 composed of gristle or cartilage. To the last family of this 

 series belong the Lampreys, which, with one or two allied 

 species, are, in reference to their skeleton and in some 

 other respects, the lowest in the scale of creation amongst 

 vertebrate animals, or animals possessing a { back-bone/ 



A few remarks here upon the habits of Lampreys and 

 Lamperns generally, may prevent the necessity of repe- 

 tition under each individual species. 



In all these fish the swimming-bladder is absent; and 

 as they are also without any pectoral fins, they usually 

 swim at or very near the bottom of the water, where, in 

 order to resist the current, they attach themselves by the 

 mouth to stones or rocks, and have been consequently 

 named Petromyzonida* or " Stone- suckers." 



The shape of this mouth or sucker will be best explained 

 by a reference to the annexed engraving of the head of the 



