185 
lacking suboperculum and sometimes operculum. The anterior 
four vertebrae modified and often co-ossified. Their ribs and neural 
arch forming a chain of bones connecting the air-bladder with 
the auditory organ (Weberian ossicles). Pectoral arch suspen- 
ded from the skull. Mesocoracoid generally present. Fin-rays 
articulated, the dorsal and pectorals sometimes with a spine. 
Pectorals inserted low down, folding like the ventrals, which 
are abdominal, by exception absent. 
1. Suborder Siluroidea. 
(Nematognathi Gill). 
Skin naked or with bony scutes or plates, never with scales. 
Parietals generally united with supraoccipital. Mouth not 
protractile, superiorly bordered by the intermaxillary, which 
is generally toothed, the maxillary being reduced, nearly 
always toothless, bearing a barbel. Nearly always 1—4 pairs 
of barbels. Adipose fin generally present. Symplectic and 
suboperculum absent. Vomer and pterygoids usually with 
teeth. Pharyngeal bones with small conical or villiform teeth. 
Branchiostegal rays 4—17. No pseudobranchiae. Anterior ver- 
tebrae co-ossified. Ribs attached to the lower surface of long 
parapophyses. Fin-rays articulated, the second dorsal ray and 
the exterior pectoral ray generally transformed into spines by 
co-ossification of their segments. Lateral line may be ramified. 
Actiretal key to the fanvi lies. 
I. Dorsal spineless. Anal very long. 
A. Dorsal many-rayed, 4 pair of barbels......... Clariidae p. 186. 
B. Dorsal very short, rudimentary or absent, 2 pair of 
SETASENS S15 G Silchrec’ OOucnt Spo sonOacridsoecegmromciaced Siluridae p. 195. 
II. Dorsal with a pungent spine. 
A. Caudal pointed, united with the socalled second 
dorsal or procurrent caudodorsal., 
1. Anal long, united with caudal. Ventrals with 
HOF, TES Bo. a: Suge ch, Cleo Ce ONG NOLOMORSIRDE EO-CECICEy Plotosidae p. 223. 
2. Anal short, free from caudal. Ventrals with 6 rays. Chacidae p. 245. 
&. Caudal forked, emarginate or truncate, without any 
procurrent part. 
1. Anal long with 28— 4o rays. Gillmembranes free 
from isthmus. 
