CATFISH AND BBL8. I79 



are met with in Oaleichthys, Arius, and Bagrus, the former 

 characterized by the high dorsal and pectorals. 



" South America exhibits some Siluroids of especial inte- 

 rest. Conspicuous among these are Arges cychpum, or Pime- 

 lodus cydopum of Humboldt, and Brontes prenadilla, which 

 inhabit the highest regions in which fish are known to live. 

 They are found in Quito, at elevations of more than 16,000 

 feet above the level of the sea, living in the streams running 

 down the sides of Cotopaxi and Tunguragua. The most 

 interesting fact in the history of these fishes is, that they are 

 frequently ejected from the craters of the above-mentioned 

 volcanoes, in immense numbers ; the supply being probably 

 derived from the subterranean lakes in the body of the 

 mountains. Our space will not permit us to mention any 

 other members of this interesting family, excepting the Ma- 

 lapterus ehdricits, the Silurus electricus of older authors. 

 This species is characterized generically by the absence of 

 the first dorsal, the adipose dorsal alone existing, as also by 

 the possession of an electric apparatus or battery, somewhat 

 intermediate in character between those of Oymnotus and 

 Torpedo, although of much finer texture. The whole body 

 beneath the integuments is enclosed by the apparatus in two 

 layers of great compactness, and at first sight suggesting a 

 deposit of fat. A dense fascia separates the battery from the 

 muscular system. The cells, formed by transverse and longi- 

 tudinal fibrous partitions, are rhombic in shape, and exceed- 

 ingly minute. The nerves of the outer organ come from 

 blanches of the fifth pair of nerves, the inner organ is sup- 

 plied by the intercostal nerves. The direction of the current 

 is probably from the head to the tail ; the cephalic extremity 

 being positive, and the caudal negative." 



