312 



ICHTHYOLOGY. 



pedicellated, as in Lopltms, by the elongation of the radius and ulna, 

 which are mostly concealed by the skin. Twenty-eight species. 



Genus 111. MaLth.ea, Cuv. Body anteriorly, and the head 

 much depressed ; very wide at the pectorals, chielly from expansion 

 of the subopercula; posteriorly tapering and more or less compressed. 

 Pectorals pedicellated. Giil-opening a small orifice in the axilla of 

 the pectoral. liody covered with a tubercular skin ; many cuta- 

 neousfilaments. Mouth small, opening beneath theprojectingsnout, 

 horizontal and protractile ; a peculiar ])edicel witii soft tips at- 

 tached to the snout, represents the three free rays of Lopkius. This 

 genus is the only one of the family in which a.suboibitar scale-bone 

 is present. Seven species. 



Genus IV. II.^lieutea, Yalenc. Body very flatly depressed, 

 orbicular. Snout not prolonged. Palate smooth, tootliless. Skin 

 studded with small conical, acute, bony spines, having radiating 

 bases. Branchiostegals six. One species. 



Genus V. Batrachvs, Schneid. A large flat head and wide 

 mouth, bordered by cutaneous filaments. A very small first dorsal ; 

 pectorals ])edicellated on short flat arms ; ventrals jugular, of three 

 rays, the first elongated and lanceolate. Teeth on the jaws, vomer, 

 and palatines. Six branchiostegals. Gill-openings not extending 

 quite under the throat. A long and low dorsal and anal. Suboper- 

 culum as large as the operculum, and emitting strong spines; pre- 

 operculum unarmed. No suborbitar ; no caxal dilatation of the 

 stomach ; no pancreatic ca?ca ; air-bladder deeply forked anteriorly ; 

 and muscular laterally. Seventeen species. 



Genus VI. Ceiiatias, Kroy. Form high and much compressed. 

 IMouth cleft nearly vertically. Gill-opening below the pectorals, 

 pretty large, round. Branchiostegals six. Teeth of moderate size, 

 coni(!al, moveable, slightly curved on the preniaxillaries and man- 

 dible ; none on the vomer or palatines ; three branchial arches with 

 two layers ; the third pair of arches adherent to the gullet by their 

 interior border. No ventrals ; pectorals very small but supported 

 on long arms ; anterior dorsal of two free moveable rays, one on 

 the head, tiie .second near the middle of the back ; i)osterior dorsal 

 and anal very short, and close to the caudal fin. Tips of all the 

 rays free from the connecting membrane, especially those of the 

 caudal and ventrals, cartilaginous, not jointed, and with soft extre- 

 mities. No true scales, but innumerable recurved spines rising 

 from bony bases. No air-bladder. Two small pyloric CEeca. Skele- 

 ton soft and cartilaginous. Greenland. C. llolholi. 



Genus VII. Ciiaunax, Lowe. Body oblong, tetraedral, subin- 

 flatible, naked ; skin of the belly lax. Tail abruptly attenuated, 

 subcompressed. Head large, somewhat tetraedral, flat on the dor- 

 sal aspect. iSIouth very large, transverse. Teeth on the premaxil- 

 laries, vomer, and palatines, small granular. Nostrils neither tu- 

 bular nor pedicellated. Branchial openings behind the pectorals. 

 Dorsal solitary; ventrals pedicellated, fleshy, jugular; analfarback. 

 A single barbel in the internasal pit ; no other elsewhere. 



PLBCTOGNATnS. 



Artedi constituteil an order named Branchiostegi, in 

 which lie included the Plectognatlis with the addition of 

 Cyclopteras and Lopliiii-s, attributing to the latter as well 

 as to Batistes and Ostracion the want of a branchiostegotis 

 membrane. Lophius, however, has as ample branchio- 

 stegous membranes as any fish possesses, and six long 

 branchiostegals ; while Batistes and Ostrrfcinu have gill- 

 covers and branchiostegals, though the thickness of the in- 

 tegument keeps them concealed. In Diodon, the oper- 

 cuhmi is not connected with the prcoperciilum, but is 

 suspended to the outer angle of the c])itynipanic. The real 

 cause of his assembling these genera into one group would 

 appear to have been the tardy ossification of their skeletons, 

 for which reason he placed the order between the osseous 

 and the cartilaginous fishes. But though the bones of the 

 Plectognalhs differ in some degree from those of the great 

 mass of osseous fishes, and there are fewer pieces in their 

 skeletons, they belong to that division of the class by the 

 fibrous character of their bones, as Cuvier mentions in his 

 Beijiie Animal;" and M tiller has shown that they agree 

 with other osseous fishes, in having two valves at the origin 

 of the arterial trunk, differing in that respect from the 

 Choudroplen/gii or Plagiostomcs, and fiom the Ganoids, 

 all of which have many valves. The want of mobility in 

 the upper jaw, through its union by suture with the cranium, 

 is the character that distinguishes the Plectognatlis most 



distinctly from the ordinary osseous fishes, though even Classifica' 

 this character is not universal in the group. Their dermal tion — 

 productions, scales, spines, roughness, and osseous plates, 

 differ from ordinary fish scales. By Agassiz, they were on 

 that account considered to be Ganoids, but Cuvier has as- 

 signed them a more correct place in our systems. 



Plecto- 

 gnaths. 



Fig. Vi\ 

 Xanthichthys curassavicus. 



The Sclerodermids, or Batistiiti, are distinguished by 

 the conical snout, a small terminal mouth, and distinct 

 but not numerous teeth. In Batistes the first dorsal spine 

 is articulated by ring and bolt to the broad interneural os- 

 seous plate. Wiien the spine is raised, a depression at the 

 back ])art of its base receives a corres|ionding projection 

 from the contiguous base of the second ray, which fixes it 

 like the hammer of the gim-lock at full cock, and it cannot 

 be let down until the small spine has been depressed, as by 

 pulling at the trigger ; it is then received into a groove on 

 the supporting plate, and offers no impediment to the pro- 

 gress of the fish through the water. (Owen.) This trigger- 

 like fixing of the spine takes place also in the dead fish ; 

 and when a Batistes is removed fioni a bottle for examina- 

 tion, it is generally necessary to release the spine by press- 

 ing on the small trigger-ray. The spine of the Batistes is 

 roughened with ganoid or enamel grains like a file, and the 

 teeth of this fish consist of true dentine, with a thick 

 layer of denser tissue that difft'rs little from enamel. 



In the Gymnodonts, or Diodontidw, the niaxillaries coa- 

 lesce wholly or in part with the preniaxillaries, and the 

 teeth are incorporated with the bone of the jaws, so that 

 the whole looks like one or two great teeth ; but the teeth, 

 individually small, are developed from pulps, are arranged 

 in lamellte, and approach the cutting edge of the compound 

 tooth or jaw as their predecessors are worn away, much as 

 in Seams. The dental plates consist of hard or unvascular 

 dentine. This kind of dentition is adapted to cut and 

 bruise the food on which these fishes live — fiici and Crus- 

 tacea. None of them are used as food for man, and they 

 are generally considered to be poisonous. An instance 

 occurred a i\j\v years ago at the Cape of Good Hope of two 

 sailors being poisoned by eating a Tetraodon, and dying 

 fiom the effects thereof. A detailed account of the symp- 

 toms was drawn up by a surgeon in the Dutch navy, who 

 attended them till they died, which was in less than half an 

 hour after eating the deleterious fish. The Tetraodons and 

 Diodons have the power of inflating their bodies by filling 

 their stomachs with air. Thisviscus is very large, occupying 

 the whole length of the abdominal cavity, and has very thin 

 coats. When thus blown up into a globular form, the fins cease 

 to play, and the fisli turns over, and floats belly upwards, 

 driving before the wind and waves, without being able to 

 direct its course, until it has resumed its former shape, by 

 expelling the wind. The inflation of the Diodons, how- 

 ever, causes the strong spines with which the skin is studded, 

 and which resemble those of a hedgehog, to radiate on every 



