230 PISCES. 



men and horses are struck down by them. This power is dependent on 

 the will of the animal, which gives it what direction it pleases, and renders 

 it effective, even at a distance, killing fishes therewith, so situated. It is, 

 however, dissipated by use, and to renew it, the Gymnotus requires rest 

 and nourishing food. The organ which is the seat of this singular faculty, 

 extends along the whole under side of the tail, occupying about half its 

 thickness; it is divided into four longitudinal fasciculi, two large ones above 

 and two smaller ones below, and against the base of the anal fin. The lit- 

 tle cells, or rather the little prismatic and transverse canals formed by the 

 two kinds of laminae that unite the bundles, are filled with a gelatinous mat- 

 ter, and the whole apparatus receives a proportion ably large number of 

 nerves. 



GYMNARCHUS, Cuv. 



The body scaly and elongated, and the gills slightly open before the pecto- 

 rals as in Gymnotus; but a fin, with soft rays, occupies the whole length of 

 the back; and there is none behind the anus, nor under the tail, which ter- 

 minates in a point. The head is conical and naked, the mouth small, and 

 furnished with a single row of small trenchant teeth. 



G. niloticus. The only species known; discovered in the Nile by M. 

 Riffault. 



LEPTOCEPHALUS, Penri. 



The branchial aperture before the pectorals? body compressed like a riband; 

 head extremely small, with a short and somewhat pointed snout; pectorals 

 almost imperceptible, or totally wanting; the dorsal and anal hardly visible, 

 and uniting at the point of the tail. The intestines occupy but an ex- 

 tremely narrow line along the inferior edge. 



JL. morisii, Gm., inhabits the coast of France and England. Several other 

 species, however, are found in the seas of hot climates, all of them as thin 

 as paper and transparent as glass, so that even the skeleton is not visible. 

 The profound study of their organization is one of the most interesting to 

 which travellers can devote themselves. 



OPHIDIUM, Lin. 



Dorsal and anal fins united with that of the tail, and terminating the body 

 in a point; the body so elongated and compressed that it has been compared 

 to a sword, and invested like that of an Eel with small scales planted in the 

 thickness of the skin. The Opliidii, however, differ from Eels in their well 

 cleft branchiae, which are furnished with a very apparent operculum and a 

 membrane with short rays. Their dorsal rays are articulated, but not 

 branched. 



AMMODYTES, Lin. 

 An elongated body like that of the preceding- fishes, provided with a fin, 



