CHAKACLNIDJL 175 



and epineurals mostly free, floating. Pectoral fins inserted very low 

 down, folding like the ventrals, which are formed of 10 to 13 rays. 

 Body covered with scales *. An adipose dorsal fin often present. 

 Fresh waters of Central and South America and Africa. 



Synopsis of the Genera. 



I. HydrocyoninjE. — Dentition powerful ; upper jaw immovable or slightly 



movable; maxillaries well developed, bordering the mouth; gill-membranes 

 free or very narrowly attached to isthmus; scales not ciliated ; lateral line 

 nearer ventral than dorsal outline. 



A. Teeth unicuspid. 



Teeth very numerous, unequal, conical, in two 



series ; dorsal fin well behind ventrals . 1. Sarcodaces, Gthr., p. 177. 

 Teeth not very numerous, compressed, uni- 



serial ; dorsal fin above ventrals ... 2. Hydrocrjon, Cuv., p. 179. 



B. Teeth pluricuspid, in 2 or 3 series in the upper jaw. 



1. A pair of conical teeth behind the pluricuspid teeth of the lower jaw. 

 Teeth in 3 series in the upper jaw, the inner 



with more or less molariform excavated 



crowns ; dorsal fin originating in advance 



of ventrals 3. Bnjconcetldops, Gthr , p. 187. 



Teeth in 2 series in the upper jaw, the inner 



with obliquely truncated or molariform 



excavated crowns ; dorsal fin originating 



above or behind ventrals 4. Alestes, M. & T., p. 190. 



Teeth in 2 series in the upper jaw, both simply 



compressed, the front side not concave ; 



dorsal fin originating above or behind 



ventrals 5. Micralestes, Blgr., p. 223. 



2. No conical teeth in the lower jaw. 

 Teeth in 2 series in the upper jaw, both simply 



compressed ; dorsal fin originating above 



or behind ventrals G. Petersius, Hilg., p. 231. 



II. Ichthyoborin^e. — Dentition various ; upper jaw freely movable upwards ; 



maxillaries much reduced ; gill-membranes free or narrowly attached to 

 isthmus ; scales ciliated ; lateral line along the middle of the side, 



A. Two series of teeth in each jaw ; dorsal fin above ventrals. 

 Teeth equal ; snout rounded ; a naked space 



between the suborbitals and the prse- 



operculum ; scales small ; a scaly process 



at the base of the ventral 7. Eugnathklithys, Blgr., p. 241. 



* Exceptions in America. 



