ICHTHYOLOGY. 



225 



MaUcop- 

 teryjjii 

 Apodcs. 



Anguilli- 

 fornies. 



Gibraltar, between three and four feet in lenptb. The 

 skin is beautifully marbled with yellow sub-anjjular mark- 

 ings on a rich brown ground. When captured in nets it 

 lives long out of the water, and is capable of biting very 

 severely, from the sharpness of its numerous teeth. A 

 very beautiful muraena with obtuse teeth, 31. cntenata, is 

 found in the rivers of Guyana ; its colours are brown and 

 white. In the same region is found 31. zebra, a species 

 beautifully marked, on a dark-brown ground, with trans- 

 verse, linear, distant bands, meeting irregularly beneath. 

 Other species are, 31. reticularis, 31. punctata, 31. unico- 

 Inr, 31. Haiii/, 31. pictn, 31. meleagrii, 31. grisea, M. afra, 

 31. gtdlata, M. wubdata, 31. sordida. 



Genus Sphacebranchus, Bloch. This genus differs 

 from Murcena chiefly in having the branchial apertures 

 close together, and beneath the throat, instead of being on 

 each side of the neck. The snout is sharp, and projecting 

 far beyond the mouth ; the dorsal and anal fins, when per- 

 ceptible, do not commence until within one third of the 

 length of the fish from the extremity of the tail. Some of 

 them h.ave no ajipearance of pectoral fins ; others have 

 slight vestiges of those parts. One of them, Sph. catcus 

 (Genus Apterichtes, Dumeril), is absolutely without any 

 fins at all. The stomach has a long cul-de-sac ; the intes- 

 tine is straight ; and all have a long narrow swimming 

 bladder placed towards the posterior extremity. 



The best known is Sphagehianclnis rostratus, first no- 

 ticed by Bloch. It grows to a length of nine inches. 

 Sph. imberhis was described by Laroche in Aim. du 3Ius. 

 xiii. as well as Sphag. cceciis, which he considered as a 

 murxna. 



Genus Synbranchus, Bloch. This division is distin- 

 guished from the last by having only a single branchial ori- 

 fice, which is placed under the throat, and communicates 

 with the gills on each side. The fishes included in it are 

 totally w ithout pectorals, and their vertical fins are almost 

 entirely adipose. Their head is thicker than any part of 

 the body, and short ; the mouth is wide, lips fleshy, teeth 

 small, conical, and in several rows. Their opercles are 

 partly cartilaginous ; their branchial rays are very strong ; 

 their swimming bladder is long and narrow. They have no 

 csBca to the intestine, which is straight, and can scarcely 

 be distinguished from the stomach except by a kind of 

 pyloric valve. The species inhabit the seas of the hotter 

 parts of America, especially Surinam. Two only are known, 

 Synbranchus marmoretus (Plate CCCVI. fig. 4) and Syn. 

 iynmacvlatus. They have much the habit of water-snakes. 

 In succession to the preceding generic subdivisions of the 

 Linnaean 3iur(p.ncB, Cuvier places a singular and recently 

 discovered species, the Saccopharynx flagdJam of Dr 

 Mitchell. Its body is capable of great inflation. It is a 

 large and voracious fish, measuring about six feet in length, 

 with a deep cleft mouth armed witli sharp teeth. It has 

 hitherto been found only in the Atlantic Ocean, where it 

 floats on the surface by means of the inflation just allud- 

 ed to.' 



Genus Gymnotus, Linn. The gymnotes, like eels, 

 have the gills partly shut up by a membrane, which, how- 

 ever, opens before the pectoral fins ; the anus is placed 

 near the head ; the anal fin nms along nearly the whole 

 under part of the fish, and generally reaches to the extre- 

 mity of the tail, but is not continued along its upper por- 

 tion. 



In Gymnotus, Lacep. properly so called, the skin is 

 without visible scales; the intestine, in several convolu- 

 tions, occupies but a moderate space, and has many csca ; 

 the stomach is r. short, blunt sac, with numerous ruga; 



A]ioile3. 



Ans;uillU 



i'ormes. 



within. Some of them have two swimming bladders ; the Malacop. 

 anterior is ovate and bilobular, and lies on the oesophagus, terygii 

 at the top of the abdomen ; the posterior is cylindrical, 

 and occupies a sinus in the abdominal cavity. The true 

 gymnotes are confined to the rivers of America. The i^ 

 best-known species is Gymnotus electricus, or electric eel 

 (Plate CCCVI. fig. 5). This animal has been well de- 

 scribed by Dr Garden of Charlestown, by John Hunter, 

 and by Humboldt. It is remarkable for the violence of 

 its electric shocks, which are often so powerful as to stu- 

 pify a man or a horse. The researches of Hunter detect- 

 ed an organ in the posterior part of this iish, resembling 

 the electric apparatus of the torpedo. See Plate CCCVI. 

 fig. 6. This organ consists of four longitudinal fasciculi, 

 which occupy one half the thickness of the part in which 

 they occur, and about one third of the whole animal. The 

 larger pair lie above, the smaller below. Each fasciculus is 

 composed of flat partitions or septa, with transverse divisions 

 between them. The outer edge of the septa appear in nearly 

 parallel lines in the direction of the longitudinal axis of the 

 body, and consist of thin membranes, which ai-e easily torn ; 

 they serve the same purpose as the columns in the analo- 

 gous organ of the torpedo, making the walls or abutments 

 for the perpendicular and transverse dissepiments, which 

 are exceedingly numerous, and so closely aggregated as to 

 seem almost in contact. The minute prismatic cells, inter- 

 ce|)ted between these two sorts of plates, contain a gela- 

 tinous matter ; the septa are about one thirtieth of an inch 

 from each other, and one inch in length contains a series of 

 240 cells, giving an enormous surface to the electric or- 

 gans. The whole ai)paratus is abundantly supplied with 

 nerves from the medula spinalis; and these nerves are 

 seen coming out in pairs from between the vertebra:. In 

 their course they give out branches to the muscles of the 

 back, and to the skin of the animal. In the gj^nnote, as 

 in the torpedo, the nerves supplying the electric organs are 

 much larger than those bestowed on any part for the pur- 

 poses of sensation or movement. Hunter thinks, how- 

 ever, that these nerves are more considerable in point of 

 size in the torpedo than in the gymnote. These organs 

 are attached loosely to the muscles of the back which lie 

 between the larger, and they are immediately connected 

 with the skin by a loose cellular texture. Humboldt has 

 given a very interesting and lively description of the mode 

 of capturing the electric gymnote, as practised in South 

 America, near the town of Calabozo. 



These fish abound in the stagnant pools of that vicinity. 

 The Indians are well aware of the danger of encountering 

 the gymnote when its powers are unexhausted. They 

 therefore collect twenty or thirty wild horses, force them 

 into the pools, and when the fish have exhausted their 

 electric batteries on the poor horses, they are laid hold of 

 without difficulty. The horses at first exhibit ir.uch agi- 

 tation and terror ; they are prevented leaving the pool by 

 an enclosing band of Indians, who goad them with bam- 

 boos whenever they attempt to escape. " The eels," says 

 Humboldt, " stunned and confused by the noise of the horses, 

 defended themselves by reiterated discharges of their elec- 

 tric batteries. For some time they seemed likely to gain 

 the victory over the horses and mules ; these were seen 

 in every direction, stunned by the frequency and force of 

 the shocks, to disappear under water. Some horses, how- 

 ever, rose again, and, in spite of the active vigilance of the 

 Indians, gained the shore, exhausted with fatigue ; and 

 their limbs being benumbed by the electric explosions, 

 they stretched themselves out upon the ground." " I re- 

 member the superb ])icture of a horse entering a cavern. 



VOL, xii. 



' Ophiognalhut amfvUaceus of llr Ilariiwood, Pliil. Trans. 1827, seems to pertam to the same genus. 



2v 



