behind it (except in WtimgUnis). The gill-membranes are con- 

 fluent with the skin of the isthmus. 



Group K. Rayed dorsal fin present. The anterior and posterior 

 nostrils are remote from each other. . Doradina, p. 191. 



Group L. The anterior and posterior nostrils are close together. 



Rhinoglanina, p. 216. 



Group M. Rayed dorsal fin none .... Malapterurina, p. 219. 



Sixth Subfamily. 



SILURID^ PROTEUOPODES. 



The rayed dorsal fin is always present and rather short ; the 

 ventrals are inserted below or in front of the dorsal. The gill- 

 membranes are confluent with the skin of the isthmus. Vent be- 

 fore or not much behind the middle of the length of the body. 



Group N. The anterior and posterior nostrils are close together, and 

 there is generally a short flap or barbel between them. The lower 

 lip is reverted, and much dilated, forming a broad flap, more or less 

 deeply notched in the middle Hypostomatina, p. 221. 



Group 0. The anterior and posterior nostrils are remote from each 

 other, without barbels. Lower lip not reverted ; humero-cubital 

 process much developed and prolonged. Aspredinina, p. 265. - 



Seventh Subfamily. 

 SILUPIDiE OPISTHO'PTEE^. 



The rayed dorsal fin is always present, short, being placed above 

 or behind the ventrals, which, however, in one genus are absent ; 

 anal short. Nostrils remote from each other ; if a nasal barbel 

 is developed, it belongs to the anterior nostril. Lower lip not 

 reverted. The gill-membranes are not confluent with the skin of 

 the isthmus. 



Group P. Dorsal fin above the ventrals. Nematogenyina, p. 271. 

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



Trichomycterina, p. 272. 



Eighth Subfamily. 



SILUPID^ BEANCHICOL^. 



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

 the ventrals ; anal short. Vent far behind the middle of the 



