75 
July 12, 1853. 
Dr. Gray, F.R.S., Vice-President, in the Chair. 
The following papers were read :— 
1. On some FISHES ALLIED TO GYMNOTUS. 
By Aurrep 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 
vertebree ; and by having a single row of short acute teeth in each 
aw. 
: 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, xo 
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 Lacépéde. 
These fishes were all found near the sources of the Rio Negro and 
