THE KALAI'TERURUt ELECTRIC US. 



109 



Other species of Silurus occur in Afghanistan, Cochin China, Malabar, China, Japan, and For- 

 mosa. The genera allied to Silurus, which form Dr. Guiither's second sub-family, or Heteropterse, are 

 all confined to the Old World. The third sub-family is South American. The genus Helogenes 

 IKTS the eye very small, and covered over with the skin, as is the case in ssveral other Siluroid 

 fishes. Hypophthalmus has the eye behind, and below the angle of the mouth ; the mouth is devoid 

 of teeth. 



The genus Amiurus is confined to North America, though one species ranges to China. 

 The palate is toothless, and there are only eight rays in the ventral fin. Many genera of 

 Siluroid fishes are covered in the i-egion in front of the dorsal spins with heavy armour, which 

 frequently has a granulated surface. This armour is well seen in the genus Rita, in ^Elurichthys 



MALAPTEllUllf S ELECTlllCt'S. 



nuchalis, and in the genus Doras, which has a series of about twenty lateral shields on each side of 

 the body, each with a prominent spine in the centre. There are also broad dermal plates on the neck. 

 All the species of the genus Doras occur in South American rivers which flow into the Atlantic. 

 Similar lateral plates characterise the genera Oxydoras and Rhinodoras, which have a like 

 distribution. The African genus Synodontis has broad dermal bones on the neck. The genus 

 Rhinoglanis is a small fish an inch and a half long, from Gondokoro, on the Upper Nile, which 

 has two dorsal fins, both formed of rays. It has six barbels, the two longest ones, from the 

 maxillary, reach to the origin of the second dorsal fin. The whole of the ne?k is covered with 



* * o 



a cuirass formed of three broad plates. The tail is forked. 



The electric Siluroid, Malapterurus electricus, is found in the Nile and the rivers on 

 the West coast of Africa. Its single dorsal fin is fatty, and placed in front of the caudal fin, 

 which is rounded. The pectoral fins want the strong, sharp spines which are so characteristic 

 of most fishes in this family. The body is covered with more or less small round black spots, and 

 the anal and caudal fins are margined with white. The electric organ extends over the whole 



