(8 5 



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. 



i. 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 I 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. 



Artificial key to the families. 



I. Dorsal spineless. Anal very long. 



A. Dorsal many-rayed, 4 pair of barbels Clariidae p. 1 86. 



B. Dorsal very short, rudimentary or absent, 2 pair of 



barbels ; . 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 



10 12 rays Plotosidae p. 223. 



2. Anal short, free from caudal. Ventrals with 6 rays. Chaddae p. 245. 



B. Caudal forked, emarginate or truncate, without any 

 procurrent part. 



I. Anal long with 28 40 rays. Gillmembranes free 

 from isthmus. 



