12 SILUEID^. 



Group 0. Aspredinina. 



Anterior and posterior nostrils remote from each other, without 

 barbels. Lower lip not reverted. South America. 



a. Anal fin short. 



Head higher than the hind part of the tail. 105. Bunocephalus, p. 266. 

 Head lower than the hind part of the tail. . . 106. Bitnocephalichthys, p. 267. 



b. Anal fin long. 



Barbels not less than six 107. Aspredo, p. 267. 



Seventh Subfamily. 



SILURID^E OPISTHOPTERtE. 



The rayed dorsal fin is placed above or behind the ventrals ; 

 anal short. Gill-membranes not confluent with the skin of the 

 isthmus. South America. 



Group P. Nematogenyina. 

 Dorsal fin above the ventrals. 



Adipose fin present 108. Heptapterus, p. 271. 



Anterior nostril with a barbel i09. NemaTogenys, p. 272. 



Group Q. Trichomycterina. 

 Dorsal fin behind the ventrals, if the latter are present. 



a. Anterior nostril with a barbel ; two maxillary barbels on each side. 



Ventrals present . 110. Trichomycterus, p. 272. 



Ventrals none 111. Eremophilus, p. 275. 



b. No nasal barbel; two maxillary barbels on each side. 



Jaws with a single series of te"eth 112. Pariodon, p. 275. 



Eighth Subfamily. 

 SILURIDjE BRANCHICOLjE. 



The rayed dorsal fin is always present, short, and placed behind 

 the ventrals. Vent far behind the middle of the length of the body. 

 Gill-membranes confluent with the sMn of the isthmus. South 

 America. 



Group R. Stegophilina, 



A single maxillary barbel on each side. 

 Jaws with a broadish band of minute teeth. 1 13. Stegophilus, p. 276. 



Jaws toothless ; a series of long pointed teeth on the vomer. 



114. Vandellia, p. 276. 



