398 Miscellaneous. 



On some Fishes allied to Gymnotus. By Alfred R. Wallace. 



My object is to call the attention of the Society to some curious 

 fishes allied to the Electrical Eel, which are abundant in the fresh 

 waters of South America. They present many modifications of form, 

 and will probably constitute a distinct family or subfamily. They 

 may be characterized as fishes of an elongate form, very slender 

 posteriorly, without dorsal or ventral fins, but with a very long anal 

 fin. The intestines are situated immediately behind the head, and 

 occupy a very small portion of the entire length of the fish. The 

 teeth are very small, or altogether wanting. The air-bladder is in 

 some species very long, in others almost obsolete ; and the scales are 

 very minute, ovate, concentrically striate, and often so imbedded in 

 mucus as to be invisible till scraped off. The gill-opening is gene- 

 rally very small, and the eyes and nostrils minute. 



There seems to be sufficient variety of form and structure to justify 

 the establishment of five genera. 



1 . The true Gymnotus (of which the Gymnotus electricus appears 

 to be the only well-known species), characterized by the anal fin 

 reaching the extremity of the tail, which is flattened ; by the air- 

 bladder extending almost the entire length, in a cavity beneath the 

 vertebrae ; and by having a single row of short acute teeth in each jaw. 



'2. The genus Carapus, to which five of my species belong. These 

 have the tail cylindrical and pointed, extending beyond the anal fin ; 

 a band of minute teeth in each jaw ; and a double air-bladder, gene- 

 rally of very small size. One of my species appears to be identical 

 with Carapus brachyurus of Bloch. 



3. A form, of which I have but one representative, which has a 

 deep body, a rather large mouth, but no teeth, and a small round 

 single air-bladder. 



4. Two long-jawed species, which have a very small mouth, no 

 teeth, and no air-bladder. The larger of these is probably the Gym- 

 notus rostratus of Schneider. 



5. The genus Apteronotus, which differs from all the preceding 

 in having a small, but perfectly-formed and rayed caudal fin, a rather 

 large mouth, with the lower jaw shutting within the upper, and the 

 teeth rather acute and prominent in a row on the sides of the jaws 

 only. My representative of this genus appears to be quite distinct 

 from Apteronotus albifrons of Lacepede. 



These fishes were all found near the sources of the Rio Negro and 

 Orinoco, one of the most central positions in South America. They 

 are most abundant in the smaller streams, and feed on minute aqua- 

 tic insects. None of them, except the common Gymnotus, have 

 any electrical properties. They are all eaten, though, owing to the 

 number of forked or branched bones in every part of their bodies, 

 they are not much esteemed. 



The situation of the vent in these fishes is very peculiar, the in- 

 testine passing forwards from th.3 stomach, instead of backwards, as is 

 usually the case, so that they have the anus situated under the throat ; 

 in one of the long-snouted species it is actually considerably in front 

 of the eyes, a peculiarity which I believe does not occur in any other 

 vertebrated animal. 



