PISCES. 
326 
Gymnotus, the true Electric Eels, have no caudal or dorsal tin, nor visible scales ; moderate intestines, with 
several flexures, and numerous coeca ; stomach short, and plaited on its inner surface. One Ions' 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 ; and the most celebrated is,— 
G. electricus, the Electric Gymnotus, called from its form the Electric 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, resting ; 
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 3 
numerous transverse and vertical membranes ; and the canals and cells thus formed are filled with gelatinous j 
matter. The whole apparatus is largely supplied with nerves, [affording one striking instance of the intimate 
connexion between electric or galvanic action in matter, and nervous action in living animals.] j 
Campus, has the body compressed and scaly, and the tail much narrowed. They live in the South American rivers. | 
Sfenarchus, have the anal separated from the tail, and a caudal,— a soft filament along the back, lodged in a i 
groove, in which it is retained by tendinous threads, and reaching the whole way to the tail. It has some freedom J 
of motion, but the use of it is not known. The head is oblique, compressed, and naked, with the skin hiding the 
operculum and gill-rays ; the body scaly ; the teeth small and crowded, and scarcely discernible in the middle of 
the jaw. Like the rest of the genus, they inhabit the waters of South America. 
Gy mnarchus.— Body long and scaly ; gill-opening before the pectorals ; a soft-rayed fin along the back, but no 
anal, and the tail ending in a point ; head naked and conical; mouth small, and with a single row of cutting-teeth. 
G. niloticus, the only known species, inhabits the Nile. 
Leptocephalus.—Gi\\-oi>enmg before the pectorals ; body compressed and ribbon-like ; head very small ; snout 
short, and a little pointed ; pectorals nearly or totally wanting ; dorsal and anal obscure, but extending to the 
point of the tail ; the viscera occupying a small cavity along the under-part of the body. One species is found in 
the British seas. L. morrissii, the Anglesey Morris, is a very little fish, silvery, and semi-transparent, but with 
bright and prominent rays, and is very lively in its motions. It lurks in sea-weed ; and is one of those animals, 
exceedingly rare among Vertebrata, of which the internal structure can be seen without dissection, and its action 
understood accordingly. Other species have been found in the warm seas. 
Ophidmm, reseinbles the Eels in having the vent far backwai'ds, and the dorsal and anal meeting at the point of 
the tail ; and the body is so long and compressed, that the fish has been compared to a sword-blade. The skin 
has minute and buried scales, as in the Eels, but the gill-openings are large, and the gill-lids have free motion ; 
the dorsal rays are joined, not branched; some have small barbules, others none, and some short cirri ; some are 
flesh-coloured, with black fins ; some brown, and some large ones are rose-colour, with brown spots. 
[The species without cirri, the O. imberbis of Linnaeus, has been made a subgenus by Cuvier, under the name of 
Fierasfer, in which the dorsal seems a mere fold of the skin. A specimen, about three inches long, has been met 
with on the south coast of England]. 
Ammodytes, have the body like the former, a fin with simple-jointed rays along the back, an anal fin, and a forked 
caudal, and the fins are not united ; snout sharp ; upper jaw extensile, and shorter than the longer in the closed 
mouth ; stomach fleshy and pointed ; no coeca, or air-bladder. They burrow in the sand, and are captured by 
digging it at low water ; and are understood to contribute materially to the support of Salmon in the estuaries. 
There are two species : — A. tobianus, the Sand-eel ; and A. lancea, the Sand-lance. The latter is thicker in the 
body than the former, with the intermaxillaries larger, and the dorsal commencing farther forward. They are j 
both found on the sandy shores of Britain. li 
THE FIFTH ORDER OF BONY FISHES. | 
LOPHOBRANCHII (Fishes w^ith their Gills in Tufts). ; | 
All the fishes of the preceding four orders not only have a skeleton of fibrous bones, and i ^ 
the jaws complete and free, but their gills are always in fibres or fringes, like the teeth of a . 
comb ; but those of the present order, while they have the jaws complete and free, have the ■ . 
gills not in equal laminae along the arches, but in small round tufts, disposed along the arches j 
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 allowing the 
water to escape ; and mere vestiges of rays are shown in the substance of the operculum. \ \ 
These fishes are also distinguished by shields or small plates, which cover the body, and often; ' 
give it an angular form. In general, they are of small size, and almost without flesh. Their. | 
