336 CLASSIFICATION OF FISHES. 



SO small a group into sub-genera; yet as this has already- 

 been done, in part, by MM. Spix and Agassiz, we shall 

 adopt their divisions. Nearly all the types or sub-genera 

 of Loricaria appear to be discovered; and the addi- 

 tional interest that attaches to them from this cir- 

 cumstance, renders it advisable to designate them by 

 sub-generic names. One of the most remarkable of these 

 is Acanthicus Sp., where the whole head and body are 

 covered with short acute prickles^ placed on the surface 

 of the osseous plates, and even on the first ray of the 

 fins : the caudal fin is very large, deeply lunated, and 

 has the outermost rays greatly lengthened : the cirri are 

 only two, and very short ; but even these are sHghtly 

 barbed, on one side, with setaceous hairs. This extraordi- 

 nary fish was discovered in the great river of Amazons. 

 ■Rhinelepis of the same author is entirely without these 

 prickles ; but the edges of the plates are crenated ; the 

 two cirri very short and fleshy ; and the tail moderate 

 and only slightly lunate. The Plecostomus of Gronovius* 

 is another, and a most interesting form, at once dis- 

 tinguished by the great length of its tail; while the 

 caudal fin has one of its external rays prolonged into 

 a filament, as in Acanthicus: this singular fish is 

 probably an aberrant type for it has no cirri ; and it 

 thus opens an immediate passage'to the next genus, Hy- 

 postoma, where it is met by the Hy. etentaculata of Spix, 

 equally characterised by the absence of cirri, yet having 

 an adipose dorsal fin, which is the peculiar distinction 

 of this genus. There are only two species of these 

 double-finned Loric'arifE yet known from South America. 

 Following this, we now first characterise the genus Hop^ 

 lisoma (^H. punctata Sw.,fig. 81.), the type of which is 

 the Cataphractus punctatus of Bloch. Unlike all the 

 mailed silures, the mouth is terminal, as in the generality 

 of fishes : but, it differs from all the others, in having the 

 the body compressed: the cirri are well developed; and 

 although the anal fin is' short, the tail is long, so that 

 the vent is very close to the ventral fin : this is, in short, 



* Zooph. pi. 2. fig. 1, 2. 



