PLECTOGNATHI. 247 



Fam. 125. Triodontidae. Covered with small spiny bony laminae; 

 teeth fused into a beak ; without spinous dorsal and pelvics ; abdomen 

 with a dilatable sac ; Indian Ocean. Triodon. 



Fam. 126. Balistidae. .Covered with juxtaposed movable scutes or 

 with minute rough scales ; teeth incisor-like ; spinous dorsal with one 

 to three spines ; pelvics, if present, as short rough spine ; flesh of many 

 species poisonous. Balistes Art., file-fishes, trigger -fishes, trop. or sub- 

 trop., feed on corals and molluscs, enemies of pearl-fisheries ; to 3 ft. ; 

 B. capriscus has been taken off Britain ; Monacanthus, Paraluteres, Pseuda- 

 luteres, Pseudomonacanthus, Alutera, Psilocephalus. 



Fam. 127. Ostraciontidae. Trunk-fishes. Encased in a carapace 

 formed of large juxtaposed bony plates ; teeth incisor-like ; without 

 spinous dorsal and pelvics. Tropical seas, living near bottom ; about 

 20 species. Ostracion Art., coffer-fishes (Fig. 130) ; Aracana, Lactophrys. 



Tribe 2. GYMNODONTES. 



Supraclavicle oblique ; lower three somactids enlarged and immovably 

 united to the coraco-scapular cartilage, upper somactid small, suturally 

 united to the scapula. Anterior vertebrae with bifid divergent spines ; 

 suture between dentary and articular visible ; without spinous dorsal 

 and pelvics ; teeth fused to form beak ; trop. and sub- trop. seas, 

 a few in f.w. ; when taken they frequently produce sound by 

 expulsion of air from oesophagus ; flesh usually poisonous. 



Fam. 128. Tetrodontidae. Globe-fishes. Beak with median suture; 

 skin naked or with movable spines ; caudal fin present ; can inflate the 

 oesophagus with air and so distend the body ; when dilated the spines 

 of the scaleless skin become erected, and when in this condition they turn 

 over and float at the surface belly upwards ; in some cases the spines 

 about the head can be erected by cutaneous muscles. Tetrodon L. ; T. 

 lagocephalua has been taken off Britain ; T. psittacus (Brazil), T. fahaka, 

 (Nile), and T. ftuviatilis (E. Ind.) are in large rivers. Ephippion, 

 Tropidichthys, Xenopterus, Chonerinus. 



Fam, 129. Diodontidae. Porcupine-fishes. Beak without median 

 suture, belly inflatable ; trop. seas. Diodon Gthr. ; D. hystrix L. ; 

 Lyosphaera. 



Fam. 130. Molidae. Body compressed, very short, dorsal and 

 anal fins confluent ; no air-bladder, tail short, without caudal fin ; 

 beak without median suture ; body non-inflatable ; skin rough or 

 tesselated ; an accessory opercular gill ; fishes of the open seas ; appar- 

 ently composed of a huge head to which small fins are attached ; bask 

 at the surface in calm weather ; young very different in form to adult 

 and described as a distinct genus, Molacanthus. Orihagoriscus Bloch, 

 (Mola Cuv.) ; 0. mola Bl. Schn., sun-fish, attains a large size ; Tanzania. 



