SILURID^E. 101 



Synopsis of Indian Genera. 

 First group. HYPOSTOMATINA. 



Gill-membranes confluent with the skin of the isthmus; gill-openings 

 small. The rayed dorsal fin, if present, belongs to the abdominal 

 portion of the vertebral column, being in advance of the ventrals. 

 Adipose dorsal present. Pectorals and ventrals horizontal. Air- 

 bladder partially or wholly enclosed in bone. 



i plates along the back. The adipose fin 

 ui the form of a short spine. Upper 



caudal ray very elongate 1. SISOB. 



An adipose fin. An adhesive apparatus form- 

 ed of transverse folds of skin situated on 

 the chest between the bases of the pec- 

 toral fins 2. PSEUDECHENEIS. 



No long caudal ray, osseous dorsal plates, nor 



adhesive apparatus. A low adipose tin. . 3. EXOSTOMA. 



Second group. CHACINA. 



Gill-membranes confluent with the skin of the isthmus ; gill-openings 

 small. Rayed dorsal and anal fins consisting each of two portions ; 

 a strong serrated spine in front of the first dorsal fin, while the 

 posterior portions of both fins are confluent with the caudal. No 

 adipose fin. Ventral with six rays. Air-bladder not enclosed in 

 bone. 



Mouth very wide. Eyes rudimentary 4. CHACA. 



Third group. PLOTOSIKA. 



Gill-membranes not confluent with the skin of the isthmus ; gill-open- 

 ings wide. Rayed dorsal fin in two portions ; the anterior with 

 few rays, and armed with a pungent spine, the posterior long and 

 confluent with the caudal, as is also the long anal. No adipose 

 dorsal. Ventral many (12) rayed. A dendritic post-anal organ. 

 Air-bladder not enclosed in bone. 



Teeth on the palate. Pectoral with a spine. 5. PLOTOSUS. 



Fourth group. CLABIINA. 



Gill-membranes not confluent with the skin of the isthmus ; gill-open- 

 ings wide. Rayed dorsal fin single, spineless and elongated, pos- 

 teriorly neither it nor the anal confluent with the caudal. No adi- 

 pose dorsal. A dendritic accessory branchial apparatus attached 

 to the convex side of some of the branchial arches, and received 

 into a recess above and behind the true gill-cavity. Air-bladder 

 transverse, lobed, and enclosed in bone. 



Teeth on the palate. A pectoral spine. Ventral 



with six rays 6. CLARIAS. 



Fifth group. SILURINA. 



Gill-membranes more or less separate from the isthmus, which they 

 overlap, their hind edges being freo even if united to ono another. 



