228 



Plectog- 

 nathi- 



Gyninu- 

 dontes. 



ICHTHYOLOGY. 



ORDER VI.— PLECTOGNATHI. 



The fishes of this order approach the great chondrop- 

 terygian division in the imperfection of their jaws, and 

 the slowness with whicli their skeleton hardens ; yet that 

 skeleton is fibrous, and its general structure resembles 

 that of the ordinary or osseous fishes. The principal dis- 

 tinctive character, however, of the Plectognathi, consists 

 in the maxillary bone being soldered or firmly attached 

 on the side of the inter-maxillary, which alone forms the 

 jaw, and in the palatine arch being connected by suture 

 with the cranium, which consequently renders it immove- 

 able. Moreover, the rays and opercles are concealed be- 

 neath a thick skin, which permits only a small branchial 

 cleft to be visible externall}'. The vestiges of ribs are 

 very slight. The true ventrals are wanting. The intes- 

 tinal canal is ample, but without ca;ca, and almost all the 

 species are provided with a rather large swimming blad- 

 der. 



The order comprises two very natural families, cha- 

 racterised by the different armature of the jaws. 



FAMILY I._GYMN01)0NT£S. 



Instead of apparent teeth, the jaws are furnished with 

 a substance like ivory, divided internally into lamina? or 

 plates, the totality of which resembles the beak of a par- 

 rot, and is essentially composed of true teeth united to- 

 gether, and succeeding each other as they become used 

 by trituration. The opercles are small, their rays five in 

 number on each side, and the whole greatly concealed. 

 The species live on Crustacea and Fuci. Their flesh is 

 in general mucous, and slightly esteemed. Some indeed 

 are even poisonous, at least during certain seasons. 



Two of the genera {Tetraodon and Diodon), commonly 

 called orbs or balloon-fish, possess a singular facult)' of 

 inflating their bodies by swallowing great quantities of 

 air. When thus swollen, they roll over and float upon 

 the surface, belly uppermost, apparently unable to direct 

 their course. They are not, however, defenceless, for the 

 spines with which their skin is armed project in all di- 

 rections. Their swimming bladder has two lobes, and 

 their kidneys, which arc placed very high up, have been 

 sometimes mistaken for lungs. There are but three bran- 

 chiae on each side. Each nostril is furnished with a 

 double fleshy tentaculum. 



Genus Diodon, Linn. The undivided jaws exhibit 

 but one piece above and another below, — from whence 

 the generic name, which signifies two teeth. Behind each 

 cutting edge is a rounded portion, transversely grooved, 

 and forming a powerful instrument of mastication.' The 

 skin is armed on all sides by strong, pointed spines, so 

 that, when inflated, these creatures bear a resemblance to 

 a gigantic burr of a chestnut tree. 



The species are numerous in the warmer seas. One of 

 the most common is the Diodon atinga of Bloch, which 

 measures about a foot in diameter. It inhabits the seas 

 of India, America, and Southern Africa, and feeds on the 

 smaller fishes, Crustacea, and shell-fish, the calcareous 

 covering of which it breaks with great facility, by means 

 of its robust and bony jaws. It is a dangerous species 

 to meddle with, owing to the sudden and hedgehog-like 

 manner in which it bristles up its spines. It seems s3'no- 

 nymous with D. hystrix of Linn., commonly called the 

 sea-porcupine, and ivas formerly a frequent and dusty ap- 



pendage in the shop of the apothecary. (See Plate CCCVI. Plectog- 

 fig. 8.) Diodon liolocanthns inhabits almost all the seas nathi. 

 between the tropics. When taken by means of a hook, Gymno- 

 it exhibits the most ungovernable movements, — alter- '""'^s- 

 nately inflates and compresses its body, ascends and de- 

 scends with rapidity and violence, and is extremely dan- 

 gerous to lay hold of. It is fished for both in the Red 

 Sea and along the coast of Japan ; and, according to Du- 

 tertre, the hooks are baited with Crustacea. The bait, it 

 appears, is first approached with caution, then tasted, 

 left, returned to, and finally svvallowed. It no sooner, 

 however, finds itself fairly hooked, than it swells itself 

 up like a balloon, utters a dull sound like that produced by 

 a turkey-cock while making its wheel, and then becomes 

 exceedingly furious. It next has recourse to an opposite 

 mode of action, by lowering its spines, disinflating its 

 body, and becoming as loose and flabby as a wet glove.* 

 It resumes its activity, however, as soon as it perceives 

 the fisherman drawing towards it, or feels itself being 

 drawn towards the fisherman. In short it has a particu- 

 lar dislike to being killed. 



Genus Tetraodon, Linn. Jaws divided in the centre 

 by a suture, so as to exhibit the appearance of four teeth 

 (from whence the name), two above and two below. 

 The skin is armed merely by small spines, which project 

 but little. Several species are regarded as poisonous. 



The most anciently known is an Egyptian species, T. 

 lineatus, Linn., which is thrown by the floods in vast num- 

 bers over the prolific banks of the Nile, where it is after- 

 wards gathered as a plaything by the children. According 

 to Hasselquist, however, the Egyptians hold it in abhor- 

 rence, and believe that the use of its flesh as food is fol- 

 lowed by death. The prickles of its skin produce a sen- 

 sation like the stinging of nettles. In many iMahommedan 

 countries another species, called T.hispidushy Lacepede, 

 is fully inflated, then carefully dried, and afterwards sus- 

 pended from the pinnacle of the minarets, where it serves 

 the purpose of a weathercock. The hare tetraodon, as it 

 is called ( T. lagocephalus, Linn.), appears to have been 

 described by Pennant under the title of Globe Diodon. 

 Though a tropical species, it has occurred occasionally 

 along" the British coasts, particularly near Penzance in 

 Cornwall. We here figure a curious Indian species, the 

 Tetraodon patocaoi'Yitiia.mWto'n Buchanan. Plate CCCVI. 

 fig. 9. 



Baron Cuvier has separated from the preceding, under 

 the generic title of Orthagoriscus (imposed by Schnei- 

 der, and synonymous with genus Cepltatus of Sliaw), the 

 peculiar species known to English readers under the 

 name of sun-Jish, the Poissons-ltmes of our continental 

 neighbours.^ The jaws are undivided, as in Diodon, but 

 the body, compressed and without spines, is unsusceptible 

 of inflation, and the tail so short, and vertical in its poste- 

 rior outline, as to convey the idea of an artificial trunca- 

 tion. The form is in consequence extraordinary and cha- 

 racteristic. The dorsal and anal fin, each high and point- 

 ed, seem to unite with the caudal. The swimming blad- 

 der is wanting, the stomach small, and penetrated direct- 

 ly by the ductus chokdocus. Beneath the skin we find a 

 thick layer of a gelatinous nature. The European seas 

 produce a species which sometimes measures more than 

 four feet in length, and weighs, in consequence of its 

 bulky proportions, above three hundred pounds. It is of 

 a fine silvery hue, and is named Tetraodon mola by Lin- 

 niEus, and the short sun-Jish by British writers. (See Plate 

 CCCVI. fig. 11.) It often exhibits during the night a high 



' Baron Cuvier observes, that the jaws of these fishes are by no means unfrequent among pelrifactionB. 

 - Griffith's Animal K'tvijdotn^ vol. x. p. r)yl. 



^ The title of Poisson-lune is however bestowed also on other .'jpecies by French writers, for ex.iniple on Lamprh gi'Uatus <i{ Ret- 

 zius, which is the Zcua liim of Gmeliji, and the Ojiah of Pennant. 



