578 FISHES. 



Hypoptopoma. — Differing from Chcetostomus in the peculiar 

 formation of the head, which is depressed, spatulate, the eyes 



Fig. 267. — Bypoptopoma thoracatum, Upper Amazons. Natural size. 



being on the lateral edge of the head. The movable gill-covers 

 are reduced to two bones, neither of which is armed, viz. — the 

 operculum small and placed as in Chmtostomus, and a second, 

 larger one, separated from the eye by the narrow sub-orbital 

 ring, and placed at the lower side of the head. 



LomCAEiA. — One short dorsal fin ; anal short ; the outer 

 ray of each fin thickened, but flexible. Head depressed, with 

 the snout more or less produced and spatulate. Mouth situated 

 at the lower side of the snout, remote from its extremity, trans- 

 verse, surrounded by broad labial folds ■jvhich are sometimes 

 fringed ; a short barbel at each corner of the mouth. Teeth in 

 the jaws small, bent, with a dilated, notched apex, in a single 



