330 BULLETIN 188, UNITED STATES NATIONAL MUSEUM 



2&. Dorsal fin many rayed, extending nearly entire length of back ; 4 pairs of 

 barbels; a supplementary arborescent breathing organ in upper part of 



each gill cavity Clariidae 



Ih. Dorsal fin few rayed, with pungent spine. 



4a. No adipose dorsal fin; caudal fin confluent with the long anal fin and 



extending forward as a second dorsal fin Plotosidae 



46. Adipose fin present ; caudal fin forked, emarginate, or truncate. 



5a. Anal fin long, with 28 to 40 rays ; adipose dorsal fin small ; gill-membranes 



free from isthmus Schilbeidae 



56. Anal fin mostly short, with 8 to 22 rays ; adipose dorsal fin well developed. 

 6a. Gill membranes united to each other, free from isthmus. 

 7a. Nostrils close together ; dorsal and pectoral spines weak. 



Amblycipitidae 

 76. Nostrils widely separated; dorsal and pectoral spines strong. 



Bagridae 

 66. Gill membranes united to isthmus. 



8c. Nostrils close together, separated by a barbel Sisoridae 



86. Nostrils close together, separate by a valve Tachysuridae 



Sc. Nostrils well separated, the posterior with a barbel Akysidae 



Family SILURIDAE 



This family includes more genera than does any other family of 

 Thai catfishes, although the number of species is less than in the 

 Tachysuridae. 



The local members of the family are easily recognizable by 2 pairs 

 of barbels (maxillary and mandibulary, the latter often very feebly 

 developed), very small or altogether deficient dorsal fin (which has 

 no spine), deficient adipose fin, extremely long anal fin (with 50 to 103 

 rays) , and a weak or moderately strong pectoral spine with or without 

 denticulations. 



Recent revisions of the nomenclature have made necessary a number 

 of changes in long-established generic names in order to conform 

 to modern rules. The following genera are here recognized : 



la. Eyes with a free fold of skin, above level of angle of mouth ; vomerine teeth 

 in 2 separate patches or in a more or less continuous band; dorsal fin 

 with 4 or 5 rays ; ventral rays 9 to 11. 

 2a. Vomerine teeth always in 2 well-separated elongate patches; dorsal fin 

 with 5 rays ; caudal fin forked and entirely free from anal fin. 



Wallagonia 



26. Vomerine teeth in a transverse band, which may be either continuous or 



medianly separated or constricted; dorsal fin with 4 rays; caudal fin 



rounded and united to anal fin Parasilurus 



16. Eyes subcutaneous, above or behind level of angle of mouth. 

 3a. Dorsal fin with 3 to 5 rays. 



4a. Caudal fin unequally lobed or obliquely emarginate or truncate, broadly 

 united to anal fin ; eye above angle of mouth ; teeth on vomer in a 



single rounded patch; ventral rays 7 Silurichthys 



46. Caudal fin deeply forked, entirely free from or very slightly connected 

 with anal fin. 



