186 



TRANSACTIONS OF THE AMERICAN PHILOSOPHICAL SOCIETY 



Glanencheli (Gymnotids) 



The gymnotids or "electric eels" represent a group of four closely related families of 

 Ostariophysi from South and Central America, which collectively seem to deserve the rank 

 of a separate suborder (Glanencheli). They are all more or less eel-like in external appear- 

 ance but are peculiar in having no dorsal fin, a greatly elongate anal fin and a shortened 

 body cavity with the vent on the throat. Of the nine known genera only Electrophorus is 

 provided with electric organs, which are extended along the sides of the body. 



Distichodus langi 



Fig. 71. Distichodus langi. Side view. 



It was long since shown that this fish is not a true eel but a strongly xnodified, degraded 

 characin (Boulenger, 1904, p. 579). The form of the skull diflfers very widely within the 

 group, as shown in the monograph by Ellis (1913). In an American Museum specimen of 

 Eigenmannia macrops the head (Fig. 72A) is fairly deep and the skull top narrow, with a 

 long narrow median fontanelle extending forward to the very narrow, downwardly sloping 

 mesethmoid. The latter ends below in a transversely widened facet for the small trans- 

 versely placed premaxillas. The mouth (Fig. 73 A) is small, not protrusile, and bordered 

 laterally by the toothless maxillae. The premaxillae and dentaries bear minute teeth. A 

 cylindrical bone that seems to be the prefrontal forms a prominent, nearly vertical pillar. 



