426 FISHES. 



ing to the species; in some they are exceedingly elongate, 

 twice as long as the iish, in others they are not longer or even 



Fig. 186. — Pentmiemus quinquarius, from the "West Coast of Africa and 

 the West Indies. 



shorter than the pectoral. It is evident from the whole 

 organisation of these fishes that they live on muddy bottom 

 or in thick water, such as is found near the mouths of great 

 rivers. Their eyes are large, but generally obscured by a 

 iilmy skin, so that those feelers must be of great use to them 

 in finding their way and their food. The Polynemoids are 

 very useful to man : their flesh is esteemed, and some of 

 the species are provided with an air-bladder which yields a 

 good, sort of isinglass, and forms an article of trade in the 

 East Indies. Some of these fishes attain to a length of four 

 feet. 



Fifth Division — Acanthopteeygii Scijjniformes. 



The soft dorsal is more, generally much more, developed than 

 the spinous, and than the anal. No pectoral filaments ; head 

 with the muciferous canals well developed. 



Also this division is composed of one family only. 



Family — Sci^nid^. 



Body rather elongate, compressed, covered vjith ctenoid scales. 

 Lateral line continuous, and frequently extending over the caudal 



