314 Div. 1. VERTEBRATE ANIMALS.-^PISCES. Class 4. 



Gymnotus, the true Electric Eels, have no caudal or dorsal fin, nor visible scales ; moderate intestines, with 

 several flexures, and numerous cceca ; stomach short, and plaited on its inner surface. One lonof 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, tlie Electric Gymnotus, called from its form the Electric Eel. It attains the length of five or six 

 feet, and communicates shocks so powerful tliat men iind horses have been stunned by them. This power is 

 voluntary, and can be sent in a particular direction, and even throuoh 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 

 numerous transverse and vertical membranes; and the canals and cells thus formed are filled with gelatinous 

 matter, 'llie whole apparatus is largely supplied with nerves, [aflJbrding one striking instance of the intimate 

 connexion between electric or galvanic action in matter, and nervous action in living animals.] 



Caraptis, has the body compressed and scaly, and the tail much narrowed. They live in the South American rivers. 



Ulenarchus, have the anal separated fiom the tail, and a caudal, — a soft filament along the back, lodged in a 

 groove, in which it is retained by tendinous threads, and reaching the whole way to the tail. It has some freedom 

 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. 



Gymiiarchiis. — 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. 



Lepiocephaltts. — Gill-opening 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. morrissU, the Anglesey Morris, is a very little fish, silvery, and serai-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 Vcrtebrata, of which the interna! structure can be seen without dissection, and its action 

 understood accordingly. Other species have been found in the warm seas. 



Ophidium, resembles the Eels in having the vent far backwards, 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. imherbis of Linnieus, 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 tlie south coast of England]. 



Ammodi/tes, 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 ; uj-per jaw extensile, and shorter than the lower 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. lancca, 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 

 'Hith found on the sandy shores of Britain. 



THE FIFTH ORDER OF BONY FISHES. 



LOniOBRANCHII (Fishes with their Gills in Tufts). 



All the fishes of the preceding four orders not only have a skeleton of fibrous bones, and 

 the jaws coTn])lctc and free, but their gills are always in fibres or fringes, like the teeth of a 

 comb ; but those of the jncsent order, while they have the jaws complete and free, have the 

 gills not in equal lamin.x 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 allowing the 

 ■water to escape ; and mere vestiges of rays are shown in the substance of the operculum. 

 Tliese fishes are also distinguished by shields or small plates, which cover the body, and often 

 give it an angtilar form. In general, they arc of small size, and almost without flesh. Their 



