406 The Nematognathi, or Catfishes 
Order Gymnonoti.—At the end of the series of Ostariophysans 
we may place the Gymnonoti (yupvos, bare; v@ros, back). This 
group contains about thirty species of fishes from the rivers 
of South America and Central America. All are eel-like in 
form, though the skeleton with the shoulder-girdle suspended 
from the cranium is quite unlike that of a true eel. There is 
no dorsal fin. The vent is at the throat and the anal is ex- 
cessively long. The gill-opening is small as in the eel, and as 
in most elongate fishes, the ventral fins are undeveloped. The 
body is naked or covered with small scales. 
Two families are recognized, differing widely in appearance. 
The Electrophoride constitutes by itself Cope’s order of Glanen- 
cheli (yAavis, catfish; eyyeaAvs, eel). This group he regards 
as intermediate between the eel-like catfishes (Chlarias) and 
the true eels. It is naked and eel-shaped, with a short 
head and projecting lower jaw like that of the true eel. The 
single species, Electrophorus electricus, inhabits the rivers of 
Brazil, reaching a length of six feet, and is the most powerful of 
all electric fishes. Its electric organs on the tail are derived 
from modified muscular tissue. 
The Gymnotide are much smaller in size, with compressed 
scaly bodies and the mouth at the end of a long snout. The 
numerous species are all fishes without electric organs. FEzgen- 
mannia humboldti of the Panama region is a characteristic 
species. No fossil Gymnonoti are recorded. 
