574 FISHES, 



c. Malapterurina. 



Malapterurus. — One dorsal fin only, which is adipose and 

 situated before the caudal ; anal of moderate length or short ; 

 caudal rounded ; ventrals six-rayed, inserted somewhat behind 

 the middle of the body ; pectorals without pungent spine. 

 Barbels six : one to each maxillary and two on each side of the 

 mandible. The anterior and posterior nostrils are remote from 

 each other. No teeth on the palate. The entire head and 

 body covered with soft skin. Eyes small. Gill-opening very 

 narrow, reduced to a slit before the pectoral. 



The " Electric Cat- or Sheath-fishes " are not uncommon in 

 the fresh v^aters of tropical Africa ; three species have been 

 described, of which M. clectricus occurs in the Nile ; they 



Fig. 264. — Malapterurus electricus. 



grow to a length of about four feet. Although the first 

 dorsal fin is absent, its position (if it had been developed) is 

 indicated by a rudimentary interneural spine, which rests in 

 the cleft of the neural process of the first vertebra. The 

 electric organ extends over the whole body, but is thickest 

 on the abdomen ; it lies between two aponeurotic membranes, 

 below the skin, and consists of rhomboidal cells which con- 

 tain a rather firm gelatinous substance. The electric nerve 

 takes its origin from the spinal chord, does not enter into 

 connection with ganglia, and consists of a single enormously- 

 strong primitive fibre, which distributes its branches in the 

 electric organ. 



VI. SiLUEiD^ Proteropodes. — The rayed dorsal fin is 

 always present and rather short ; the ventrals are inserted heloiv 



