58 PROCEEDINGS OF THE NATIONAL MUSEUM vol. 99 



5b. Under side of head normal, -without a pair of grooves -with a filament. 

 6a. Teeth present in both jaws; body compressed. 



Eigenmannia Jordan and Evermann 

 6b. Teeth absent in jaws; head and body compressed to rounded; 

 the length of head equal to or longer than greatest depth; 

 anterior nasal opening in front of upper lip and posterior nasal 

 opening rather close to front of eye; anal fin origin about under 

 tips of pectoral fins; prominent pores along "lateral line" canals 



on head; anal papillae well developed Hypopomus Gill 



3b. Snout tubular, produced; jaws without teeth. 



Rhamphichthys Miiller and Troschel 

 26. Tail rather short, caudal fin present sometimes minute; dorsal filament 

 present; orbital margin not free. 

 7a. Snout much produced (these genera not yet reported from Venezuela). 

 7b. Snout heavy and blunt, not produced or tubular. 



8a. Teeth present in both jaws; gill opening extending a little over halfway 

 down in front of pectoral fin base; posterior nostril a trifle closer to 



anterior nostril than to ej^e Apteronotus Lacepede 



8b. Teeth present in lower jaw; upper jaw without teeth; gill opening 

 barely extends halfway to opposite pectoral fin base; posterior 

 nostril closer to eye than to anterior nostril. 



Stemarchogiton Eigenmann and Ward 



8c. Teeth absent in both jaws; posterior nostril not quite touching the 



upper front margin of eye, anterior nostril midway between eye 



and tip of snout Adontostemarchus EUis 



lb. Lower jaw projecting in front of upper jaw; frontal fontanel absent; head 

 depressed; dorsal filament absent; teeth conical in sockets. 

 9a. Anal fin not continuous around end of slender tail; body scaled; no electric 



glands (family Gymnotidae) Qyranotus Linnaeus 



9b. Anal fin continuous around end of tail; body scaleless; electric glands 

 present (family Electrophoridae) Electrophorus GiU 



Family STERNARCHIDAE 



Genus STERNOPYGUS Miiller and Troschel 



Sternopygus Miller and Troschel, Horae ichthyologicae, pt. 2, p. 13, 1849. 

 (Genotype, Gymnotus macrurus Bloch and Schneider.) 



KEY TO THE SPECIES OF STERNOPYGUS 



la. Anal rays number more than 300; snout very blunt, upper profile distinctly 

 convex (Amazon) Sternopygus obtusirostris Steindachner 



lb. Anal rays fewer than 300 or the upper profile of the head concave or straight. 

 2a. A black blotch behind head just above gill opening; interorbital space equal 

 to distance from tip of snout to halfway between rear nostril and eye; 

 dorsal profile of head convex or nearly straight; interorbital space into 

 head 3.4 to 4 times and into length of pectoral fin 1.2 to 1.6 times; snout 

 to occiput 7.4 to 8.4 and postorbital length of head 9.3 to 10.5, both into 

 length of anal fin base; midaxis of body with a pale or yellowish streak 

 posteriorly; anal rays 250 to 279 as counted by me on specimens from 

 Venezuela Sternopygus macrurus (Bloch and Schneider) 



