CLASS PISCES. 425 



They come from the rivers of South America. 



Anostomus, Cuv., 



Have, with the form of thymallus, and a range of 

 small teeth above and below, the under jaw raised in 

 front of the upper, and gibbous, so that the small 

 mouth has the appearance of a vertical cleft, on the 

 end of the snout or muzzle \ 



Gasteropelecus, Bl. Serpes, Lacep., 



Have the mouth directed upwards, like the anostomi, 

 but their belly is compressed, salient and trenchant, 

 because it is supported by ribs that end towards the 

 sternum ; their ventrals are very small, and very far 

 back ; their first dorsal is over the anal, which is 

 long ; there are some conical teeth in the upper jaw ; 

 in the lower, there are some trenchant and dentated 



ones 2 . 



Piabucus, Cuv., 



The small head and slightly cleft mouth of the curi- 

 mata, the body compressed, the keel of the belly tren- 

 chant, but not dentated, and the anal very long. Their 

 first dorsal corresponds to the commencement of their 

 anal 3 . 



1 Salmo anostomus, L., Gronov. vii. 2. 



2 Gastropclecus slernicla, Bl. 97. 3. 



3 Salmo argentinus, Bl. 382. 1 ; Marcg. 170. S. btmaadalus, 

 Bl. 16. S. gibbosus, Gronov. Mus. I. i. 4. S. melanurus, BL 

 381. 2. 



