ICHTHYOLOGY. 



313 



side, thus furnishing a good defensive armour. When 

 taken, the Gymnodonts produce a sound, doubtless by ex- 

 pulsion of air from the stomach. Tlieir air-bladder is deeply 

 bilobate, and their kidneys, placed hi^h up, have been mis- 

 taken for lungs. Differing from other fishes in the com- 

 paratively short tail, feeble as a locomotive organ, the mye- 

 lon of the Gymnodonts is particularly short, and instead of 

 being, as is usual in fishes, nearly as long as the spine, was 

 found by Professor Owen to be only four lines long in a 

 Diodon which measured 7 inches. It is still shorter in 

 Orthagoriscus, and the neural canal is chiefly occupied by 

 a long " Cauda equina." In this respect they agree with 

 Lophius, and they resemble that genus also in having only 

 three branchial arches. In Orthagoriscus the processes of 

 the pair of leaflets forming a gill are alternate, and not op- 

 posite as usual. Among the Diodons and Tetraodons 

 there are genera which have no external openings to the 

 nostrils, but merely cutaneous tentacles, on which the olfac- 

 tory nerve is finally expended. Tefraodon nar'dus (Rich.) 

 has only one nostril to each pituitary sac, but it is 

 nearly as wide as the sac itself, and its membranous border 

 can expand either in an infundibulifc)rm way, or contract 

 the orifice. The Tetraodons are remarkably tenacious of 

 life, and have a disagreeable odour, which they retain for 

 several years when preserved in alcohol. The Malays will 

 not use them even as manure. For the arrangement and 



Fig. 134. 

 Tetraodon solandri. 



generic characters of the Diodons, Ostracions, Balistes, and 

 Lophobranchs, we are indebted to the labours of Dr Kaup. 

 We refer to the Philosophical Transactions, vol. 76, for 

 an account of Tetraodon electricus. 



Order VI.— PLECTOGNATHI, Cuv. 



Endo-skeleton partially ossified; exo-skeleton as ganoid scales or 

 spines. Maxillaries and premaxillaries fixed together. Swim- 

 bladder without an air-duct. No pfincreatic ca.*ca ; merely vestiges 

 of ribs; and no distinctly developed ventrals. 



Family I.— BALTSTIDiE. 



Sclerodermic Cuv. ; Balistini, Miill. Snout conical. Teeth inci- 

 sorial, more or less conical, and few in number. Skin either with 

 shield-like scales or with small rough ones. Swim-bladder ovate, 

 strong. 



SUB-FAMILY I. BALISTINI, Kaup. 



Whole body mailed in a cuirass divided into rhomboidal disks by 

 cross lines, and commonly displaying varying tints of colour 

 that are generally lost in the preparation of the specimen. First 

 ray of the anterior dorsal very stout and bony, followed by one or 

 two small ones, all of them falling into a dorsal furrow ; pubic 

 bones more or less projecting, and carrying the spinules of linear 

 ventrals. 



Genus 1. Pyrodon, Rupp. (Xenodon, KUpp.) Profile slightly 

 convex, with the chin projecting. Four blunt front teeth, whereof 

 the middle pair are the broadest, and the side ones worn away inte- 

 riorly ; two longer red-coloured, conical corner teeth in the upper 

 jaw, and four with notched crowns in the mandible. A canal 

 before the eyes. Shields behind the gill-opening. No lateral caudal 

 spines. One species. F. niger. 



Genus II. Melichthys, Swain. The front teeth all equal in 

 VOL. XII. 



length standing in a semicircle, the middle ones broad and sharp- Classifica- 

 edged, like human incisors, as in Pyrodon, Profile arched, with a ^^^n — 

 broader forehead. Large scales at the gill-opening. Tail more or Plecto- 

 less forked. A canal before the eyes. Two species. gnaths. 



Genus III. Xanthichthys, Kaup. Naked furrows on the face ; ^'^^ ^y-*— ' 

 two rays in the first dorsal. No shields before the gill-opening. 

 One species. X. curassavicus. Fig. 127. (Squamation badly shown.) 



Genus IV. C'anthidermis, Swain. A canal before the eyes. 

 Teeth conical ; no separate corner teeth. Broad forehead ; arched 

 profile. Small shields behind the gill-opening. No sjjines on the 

 tail. Second dorsal and anal fins in the older fish very high ; 

 caudal slightly crescentic. Scales in the young very rough, but in 

 the old there are only traces of roughness in the fore angle of the 

 rhombs. One species, C maculatus. 



Genus V. Balistes, Linn., Kaup. Canal before the eye. Shields 

 behind the gill-opening. Conical, elongated, cutting teeth; no jut- 

 ting corner teeth. 



(a.) Two to seven rows of spinules or elevated lines on the tail. 

 Face scaly, without naked streaks. Caudal round or blunt. Four 

 species. 



(6.) Face naked, above which a row of scales. Two species. 



(c.) A more or less hollow profile ; face scaly. Tail destitute of 

 rows of spines or raised lines. Second dorsal and anal more or less 

 falcate. Tail more or less forked. Four species. 



Genus VI. Balistapus, Tilesius. No furrow before the corner of 

 the eye. Two or three rows of spines on the tail. Traces of ven- 

 trals ; caudal round or truncated; the second dorsal containing 

 from twenty-three to twenty-seven rays \ the anal from twenty to 

 twenty-four. Six species. 



SUB-FAMILY II. MONACANTHINI. 



Very small scales which are scabrous, with stiff bristles as densely 

 crowded as the pile of velvet. The point of the pubic bone pro- 

 jects, and is spiny as in the Balistini ; but there is one spine in the 

 first dorsal, and it is large and denticulated ; or, if a second spine 

 exists, it is almost imperceptible. 



Genus VH. Monacanthus, Cuv. (a.) In one division the pelvis 

 is very moveable, and is connected to the belly by an extensible 

 dewlap ; these have often strong spines on the side of the tail. 



(b.) Another division is distinguished by a tuft of coarse bristles 

 on the side of the tail. 



(c.) A third group has the body covered with small pedicellated 

 tubercles. 



(d.) The skin in a fourth group is clothed throughout by slender 

 hairs, which are often branched. 



(e.) And there are some which have none of these distinguishing 

 characters. 



Genus VIII. Aluterius, Cuv. Body elongated ; densely and 

 minutely granular. A single spine in the first dorsal. The pelvic 

 bones entirely concealed beneath the integument, without any bony 

 projection. 



Genus IX. Triacanthus, Cuv. Profile subtriangular, Thefirst 

 dorsal placed on one angle, and the tail, which is more slender and 

 tapering than in others of the family, ending in a second, on which 

 is the crescentic caudal ; while the mouth occupies the third. 

 Scales small, rough, with sharp spinules. Ventrals each consist- 

 ing of a strong rough spine. Pubic bones long, narrow, not pro- 

 jecting, covered with scales like the rest of the integument. Two 

 species. Tr. aculealus. Tr. strigilifer, Cant. 



Family II.~0STRACI0NID^. 



Ostracionesj Miill. ; Ostracioid<T, Cant. Teeth ten or twelve, coni- 

 cal. Lips fleshy. Body mailed in a tuberculated cuirass, or " tes- 

 sellated quincuncial pavement of dermal scale bones,"' out of which 

 the lips and teeth, the pectorals, and three vertical fins, together 

 with the tail, protrude. Exteriorly the gill-opening appears as a 

 slit, bordered by a skinny edge, but interiorly composed of a gill- 

 cover with six branchiostegals. Ventrals and pelvis wanting. Little 

 muscular substance ; a large oily liver. Stomach large, membran- 

 aceous. Vertebrae mostly coalescent. 



Genus I. Cibotion, Kaup. (Ostracion a corps qua drangul aire 

 sans epines, Cuv. lierj. An. ; Ostracion, Swain.) Nostrils in a pit. 

 No trace of spines. The completely naked tail destitute of shields 

 or bony rings. Eight species. 



Genus II. Dohvophuvs, Kaup, (Lactopkrys, partim, Swain.; 

 Lactophrys, De Kay.) Nostrils on the points of two small projec- 

 tions. Cuirass four-cornered, with spines above the eyes and on 

 the edges of the belly. Three species. 



Genus III. Ostracion, Linn. (Rhinosomus and Tetrosomus, 

 Swain.) Body inclosed in a more or less quadrangular cuiras^s, with 

 an acute dorsal ridge, which commences near the eyebrow. Nostrils 

 situated in a flat membrane, also one or two prominences without 

 apertures. No bony rings on the tail. 1. Some are without long 



2r 



