ACANTH'CUS. 159 



remarkably characterised by the strength of their 

 external coverings, whether it be developed in the 

 form of spines or plates. The dorsal and abdominal 

 plates are connected Avith the vertebral column and 

 move with it, or they are mutually dependent ; in 

 some degree the skeleton becomes external, and sup- 

 ports or assists the Aveaker arrangements which in 

 these cases prevail internally. They inhabit the 

 fresh waters of the new world, attaining an eleva- 

 tion of five thousand feet, and in nearly all the 

 species the mouth is placed underneath, is used as 

 a sucking apparatus for attachment to rocks or 

 trunks of trees, and the teeth are numerous but 

 minute, and have more the appearance of hooks 

 than true teeth. They swim near the bottom, and 

 sometimes leave their element to advance by the 

 rocks on the river side, in which they are assisted 

 hy the strong spines of their pectoral fins ; and for 

 this purpose also they are endowed with a powder of 

 lengthened vitality. 



ACANTHICUS. 



The first fish to which our attention will be 

 directed is one of a very remarkable form among 

 the single finned Loricarinoe ; it belongs to the 

 genus Acanthlcus of Spix and Agassiz, * but in the 

 last volume of the " Histoire Naturelle des Pois- 

 eons" it has been included in the genus Rkiiielcpisf 

 ol the same authors; and although ^e have re- 

 tained the generic name, we must acknowledge that 

 * 'Akkv^ikos, spined. + Vm, file ; Xstr/s, a scale. 

 I 



