CAT-FISHES. 563 



The great number of different generic types lias necessi- 

 tated a further division of this family into eight subdivisions : 



I. SiLURiD^ HoMALOPTER^. — The dorsal and anal fins are 

 very long, nearly equal in extent to the correspo7iding parts of 

 the vertebral column. 



a. Clariina. 



Clarias. — Dorsal fin extending from the neck to the caudal, 

 without adipose division. Cleft of the mouth transverse, 

 anterior, of moderate width ; barbels eight ; one pair of nasal, 

 one of maxillary, and two pairs of mandibulary barbels. Eyes 

 small. Head depressed ; its upper and lateral parts are osseous, 

 or covered with only a very tbin skin. A dendritic accessory 

 branchial organ is attached to the convex side of the second and 

 fourth branchial arches, and received in a cavity behind the gill- 

 cavity proper. Ventrals six-rayed ; only the pectoral has a 

 pungent spine. Body eel-like. 



Twenty species from Africa, the East Indies, and the inter- 

 mediate parts of Asia ; some attain to a length of six feet. 

 They inhabit muddy and marshy waters ; the physiological 

 function of the accessory branchial organ is not known. Its 

 skeleton is formed by a soft cartilaginous substance covered 

 by mucous membrane, in wdiicli the vessels are imbedded. 

 The vessels arise from branchial arteries, and return the blood 

 into branchial veins. The vernacular name of the Nilotic 

 species is " Carmoot." 



Heterobranchus differs from Clarias only in the structure 

 of the dorsal fin, the posterior portion of which is adipose. 



The geographical range of this genus is not quite co- 

 extensive with that of Clarias, inasmuch as it is limited to 

 Africa and the East-Indian Archipelago. Six species. 



b. Plotosina. 

 Plotosus. — A short dorsal fin in front, with a pungent 

 spine ; a second long dorsal coalesces with the caudal and anal. 

 Vomerine teeth molar-like. Barbels eight or ten ; one immedi- 



