THE GYMNOTID^ l6l 



o. Snout produced into a long tube; no teeth; vent below or in 

 advance of eyes ; anal fin beginning at throat; eye nearer 



gill-opening than end of snout Rhamphichthys^ 6. 



gg. Snout not produced into a long tube. 



//. No teeth; vent behind eyes; anal beginning below pec- 

 toral ; eye nearer tip of snout than gill-opening, minute. 



/. jMental region without adipose filament Ilypopoimis^ 7. 



ii. Mental region with a filament of adipose tissue in a 



groove along each side Stcatogeiiys^ S. 



Jih. Teeth present in both jaws. 

 j. Eye without a free orbital margin ; jaws equal or the 

 upper the longer; teeth feeble, in a patch or band; 

 anal beginning below or in front of pectoral ; snout 

 more or less compressed, conical ; eye large. 



Eigen7)ia7i7tia^ 9. 

 jj. Eye small, with a free orbital margin; teeth feeble, in 

 bands ; jaws equal or the upper the longer ; gill-open- 

 ing small ; anal beginning below pectoral or slightly 

 in front of it; vent in fi'ont of gill-opening; snout 



blunt, conical Gymnottts^ 10. 



^. No fontanel ; maxillary very small ; lower jaw projecting ; 

 teeth rather strong, in a single series in each jaw ; anal begin- 

 ning behind pectoral ; vent below gill-opening; gill-opening 

 comparatively large; head depressed in front; eye small. 



Giio7z, 1 1 . 



I. Sternarchus Bloch & Schneider. (Figs. 1-3.) 



Stcrnarchiis Bloch & Schneider, 497, tab. 94. (Type: Gym- 



notus albifrons L.) 

 Sternarcluis Cuvier, Regne Animal, II, 237, 1817 {albifrons). 

 Apteronotus Lacepede, II, 208 {j)assan = albifrons). 



Geographical distribution of the species : Amazons ; Rio San 

 Francisco, Paraguay and Parana. 



a. Scales small, a maximum of 16 rows between lateral line and 



middle line of back.^ 



b. A maximum of 1 1 to 16 scales between lateral line and middle of 



back; angle of mouth in front of eye; snout 3.35 in head; 



depth of snout just in front of eye less than length of snout; 



depth of head more than 1.5 in its length brasiliensis., i. 



' Not examined in ^S. bonapartii. 



