BONY FISHES. ORDER IV. THE ELECTRIC EEL. 205 
This genus comprises A. tobianus, the Sand Eel, and A. ldancea, the 
Sand Lance, species which burrow in the sand, and are supposed to consti- 
tute, in part, the food of salmon. 
Gyunotus. — The gills of this genus are partially covered by mem- 
branes, but opening before the pectorals; vent far forward; anal fin occu- 
pying the under line of the body. It has no dorsal. The true Electric 
Eels have no caudal or dorsal fin, nor visible scales ; moderate intestines, 
with several flexures, and numerous coca; stomach short, and plaited on 
its inner surface. One long air-bladder extends in a cavity of the abdomen ; 
the other, in two lobes, is placed over the gullet. Found only in the rivers 
and stagnant fresh waters of tropical America. 
G. Electricus. —The Electric Gymnotus, called from its form the Elec- 
trical Eel. It attains the length of five or six feet, and communicates shocks 
so powerful that men and horses have been stunned by them. This power 
is voluntary, and can be sent in a particular direction, and even through the 
water, the fish in which are killed, or stunned, by its shocks. By giving 
these, it is greatly exhausted, and requires both rest and nourishment before 
it can renew them. The immediate organ of this power extends along the 
whole under side of the tail, occupying about half its thickness. It consists 
of two large longitudinal fasciculi above, and two smaller ones below, rest- 
ing on the base of the anal fin. | Each fasciculus is composed of numerous 
parallel membranes, nearly horizontal, and close to each other, one end 
being attached to the skin, and the other to the mesial plane. They are 
joined by numerous transverse and vertical membranes ; and the canals and 
cells thus formed are filled with gelatinous matter. The whole apparatus is 
largely supplied with nerves, affording one striking instance of the intimate 
connection between electric or galvanic action in matter, and nervous action 
in animals. 
BONY FISHES. ORDER V. LOPHOBRANCHII. 
The name of this order (Lophobranchi?) signifies fishes with their gills 
in tufts. “ All the fishes of the preceding four orders not only have a skele- 
ton of fibrous bones, and the jaws complete and free, but their gills are 
always in fibres or fringes, like the teeth of a comb; but those of the pres- 
ent order, while they have the jaws complete and free, have the gills not in 
equal lamin along the arches, but in small round tufts, disposed along the 
arches in pairs—a structure of which there is no instance in other fishes. 
These are defended by a large operculum, attached by membranes on all 
sides, except one small hole for aliowing the water to escape ; and mere 
NO. XVI. 79 
