ICHTHYOLOGY. 



229 



Pleetog. 

 nathi. 

 Sclero. 

 dermi. 



degree of phosphoric splendour. We once came along- 

 side of one while swimming in the Mediterranean. It 

 got out of our way by sinking very slowly downwards. 

 The Diodon mola of Pallas {Spic. Zool.) is anotiier species 

 of the same genus. 



The only remaining genus of the first family of Plec- 

 TOGNATin is named Tbiodon by Cuvier, from a species 

 discovered in the Indian seas by M. Reinward.' 



FAMILY II._SCLEHODERMI. 



Easily distinguished by the conical or pyramidal form 

 of the muzzle, prolonged from the region of the eyes, and 

 terminated by a little mouth armed with a small number 

 of distinct teeth on each jaw. The skin is generally 

 rough, or covered by hard scales. The swimming blad- 

 der is large and robust, and of an oval form. 



Genus Balistes, Linn. Body compressed; eight 

 teeth upon a single row on each jaw, and generally of a 

 cutting kind ; skin scaly or engrained, but not absolutely 

 osseous ; first dorsal composed of one or more spines, ar- 

 ticulated on a special bone, which is attached to the cra- 

 nium, and presents a groove into which the spines are re- 

 ceived ; second dorsal soft and long, and corresponding in 

 its position to an anal fin of nearly similar form. Although 

 the ventral fins are wanting, we nevertheless perceive in 

 the skeleton a true pelvic bone suspended to those of the 

 shoulder. 



The species occur in vast numbers in the torrid zone, 

 among rocks nearly on a level with the surface of the 

 water, where they shine with a brilliant lustre resembling 

 that of the beautiful chsetodons, formerly described. 

 Their flesh, at no time much esteemed, is said to become 

 dangerous as food while they themselves are nourished 

 by the polypi of the coral reefs. Cuvier however states, 

 that in such specimens as he had occasion to dissect, he 

 found nothing but the remains of marine vegetation. The 

 generic name is derived from balisla, an ancient imple- 

 ment of war, to which the inclined dorsal spine has been 

 regarded as bearing some resemblance. In modern times 

 the oiiginal genus has been divided into the four follow- 

 ing groups. 



In Balistes (properly so called) of Cuvier, the whole 

 body is clothed by large, hard, rhomboidal scales, which 

 not being imbricated, or encroaching on each other, pre- 

 sent the appearance of compartments on the skin ; their 

 anterior dorsal has three spines, of which the first is much 

 the largest, the third being very small, and placed some- 

 what apart behind. The extremity of the pelvis is al- 

 ways prickly and projecting, and behind it are some spines 

 involved in the skin, which in the lengthened species have 

 been regarded as rays of the ventral fins. Some have no 

 particular armature on the sides of the tail ; others have 

 the lateral portion of that part armed by a certain num- 

 ber of ranges of spines curved forwards. 



In MoNOCANTHUS, Cuv., the scales are very small, and 

 beset by close asperities ; the extremity of the pelvis is 

 projecting and spiny, as in the preceding group, but there 

 is only one large dentated spine to the first dorsal, or, if 

 the second exists, it is almost imperceptible. 



In Aluteres, Cuv., the body is elongated, and covered 

 by scarcely visible, small, close-set grains ; there is a single 

 spine to the first dorsal ; and the pelvis is entirely sub- 

 cutaneous, not forming that spiny projection visible in the 

 other Balistes. See Plate CCCVI. fig. 12. 



In Triacanthus, Cuv., the species are distinguished by 

 possessing a kind of ventral fins, each sustained by a large 



single spiny ray, and adhering to an unprojecting pelvis. Chondrop- 

 The first dorsal, posterior to its principal spine, has three terypi. 

 or four smaller ones. The skin is covered by small, close- -"O"*^ 

 set scales, and the tail is more elongated than in the other 

 groups. There is only one species known, a small fish 

 from the Indian seas, figured by Bloch (148, 2) under 

 the name of Balistes bi-aculeatut. 



Genus Ostracion, Linn. Instead of scales, the species 

 of this genus have the head and body covered by regular 

 and bony compartments, soldered together so as to form 

 an inflexible cuirass, which leaves nothing moveable but 

 the tail, fins, mouth, and a small lip which borders the 

 gills. The majority even of the vertebral joints are also 

 as it were soldered. Each jaw is armed with from ten to 

 twelve conical teeth. The branchiae open only by a small 

 cleft, furnished with a cutaneous lobe ; but internally 

 they are provided with an opercle and six rays. Both the 

 pelvic bones and ventral fins are wanting, and there is 

 only a single dorsal and anal fin, each small of its kind. 



These anomalous-looking fishes are sparingly supplied 

 with flesh ; but their liver is large, and yields an abundant 

 supply of oil. Some are suspected of being poisonous. 

 The species are called tnmk-Jish by our English writers. 

 We here figure the horned trunk-fish, Ostracion cornutus 

 of Linn, and Bloch, a native, like most of the genus, of the 

 Indian and American seas. Plate CCCVI. fig. 13. 



SECOND great SERIES OF THE CLASS OF FISHES. 



THE CHONDROPTERYGII, OR CARTILAGI- 

 NOUS FISHES. 



This division of fishes, by the peculiarities of the organs 

 of hearing and generation in some genera, approaches to 

 the class of reptiles ; while others have a skeleton so de- 

 fective, and such simplicity of organization, that we might 

 almost arrange them with Vermes. We may thus consider 

 them, says Cuvier, as bearing the same relation to the 

 first series as the marsupial animals do to the other mam- 

 mifera furnished « ith claws. 



Their skeleton is distinctly cartilaginous, destitute of 

 true bony matter, as the calcareous portion is not dis- 

 posed into a fibrous structure, but is deposited in grains 

 in a substance essentially gelatinous. The skull is com- 

 posed of a single piece, and consequently is destitute of 

 sutures, but possesses foramina, prominences, and fossuls, 

 like the cranium of other fishes. The facial articulations 

 are also wanting ; and it forms one of their characteris- 

 tics to want the maxillary and inter-maxillary bones, 

 which ordinarily support the teeth of the upper jaw ; or 

 they have only vestiges of these parts, while their functions 

 are performed by bones analogous to the palatines or the 

 vomer. In some the vertebral column, as in the lamprey, 

 forms but a single piece ; in others, as in certain rays, 

 several vertebra are joined together. The gelatinous in- 

 ter-vertebral substance, which in other fishes communi- 

 cates from one to another through a small foramen, is in 

 several of this series a cord of equal thickness, perforat- 

 ing all the vertebrae. Yet their nervous system, connected 

 with the organs of digestion, is as complete as in other 

 fishes ; and some of them have organs of copulation and 

 generation quite as perfect as in the class of reptiles. 



This series is divided into two orders ; one distinguish- 

 ed by having the gills free, as in other fishes ; the other 

 with fixed branchia. 



' See Rigne Animal, t. ii. p. 370 ; and Buperrey's Voyage, Foistoru, No. 4. 



