610 



FISHES. 



Fig. 278. — Megalobrycon cephalus. 



Megalobeycon. — Dorsal fin placed in middle of the length 



of the body, immediately behind 

 the ventrals. Anal long. Ab- 

 domen rounded in front of, and 

 somewhat compressed behind, 

 the ventrals. Cleft of the mouth 

 of moderate width. Teeth 

 notched, in a triple series in 

 the intermaxillary, and in a 

 single in the maxillary and man- 

 dible ; no other teeth behind 

 the mandibulary teeth or on the 

 palate. Scales of moderate size, 

 with the free portion striated. 

 One species from the Upper Amazons (M. cepludus). Speci- 

 mens more than one foot long have been obtained. 



Gastropelecus. — Dorsal fin placed behind the middle of the 

 length of the body, above the anal ; anal long ; pectoral long ; 

 ventrals very small or rudimentary. Body strongly compressed, 

 with the thoracic regioh. dilated into a sub-semicircular disk. 

 Scales of moderate size. Lateral line descending obliquely 

 backwards towards the origin of the anal fin. The lower profile 

 compressed into an acute ridge. Cleft of the mouth of moderate 

 width ; teeth compressed, tricuspid, in one or two series in the 

 intermaxillary, and in a single in the mandible ; maxillary with 

 a few minute conical teeth ; palate toothless. 



Three specimens of this singular form are known from 

 Brazil and the Guyanas ; they are of very small size. 



The majority of the other genera belonging to this group 

 are South American, viz. Piabucina, Scissor, Pseudochalceiis, 

 ApJiyocharax, Chalceus, Brycon, Chalcinopsis, Bryconops, Crca- 

 grutus, Chalcinus, Pialuca, Paragoniates, and Agoniates ; two 

 only are African, viz. NanncetMops, which represents the South 

 American Tetragonopierus, and Bryconcethiops, which is allied 

 to Brycon. 



VII. Hydrocyonina. — A short dorsal and an adipose fin; 



