272 FISHES 



scutes united into an immovable carapace, and with slender 

 teeth ; and lastly the Gymnodontes, in which the teeth are fused 

 into a strong beak and the skin is either armed with spines or 

 is naked. The Sclerodermi consist chiefly of the trigger- 

 fishes and file-fishes which owe their names to the three dorsal 

 spines of which the anterior when erected is fixed by the action 

 of those behind it, and to the file-like character of the single 

 spine in the second family. The trigger- fishes, Batistes, have 

 strong teeth with which they break off corals and crush the 

 shells of molluscs : the greater number of species occur in 

 the East Indies extending to Japan and the Hawaiian Islands; 

 several species are common in the West Indies, others on the 

 Pacific coast of Mexico, and one occurs in the Mediterranean. 

 The tropical species are inedible, their flesh being, poisonous. 

 The File-fishes, Monacanthus, have a similar distribution but 

 differ in habits, being herbivorous. 



Batistes is known to devour numbers of pearl-oysters and 

 in its turn is preyed upon by large rays ; recent investigations 

 have shown that the pearl is deposited round the dead body of 

 a parasite which is probably the larva of a tape-worm, and it 

 has been suggested that the adult stages of this parasite live 

 either in the Batistes or in the rays, or perhaps different stages 

 in both. In consequence of the immovable carapace the move- 

 ments of the trunk or coffer-fishes are very slow. Some of 

 the species have the carapace developed into long horns pro- 

 jecting forwards above the eyes, and are hence known as cow- 

 fishes. They are absent from the Pacific coast of America, 

 common in the West Indies, extending across the Atlantic to 

 the Gulf of Guinea, and common in the East Indies as far north 

 as Japan. The Gymnodonts all have the curious habit of in- 

 flating the stomach with air and so distending the abdomen ; 

 they are thus called globe-fishes or puffers ; when inflated they 

 float at the surface belly upwards. In one family the beak is 

 divided by a median suture above and below and they are 

 therefore named Tetrodontidae, the skin is either naked or 

 spiny. In Diodontidai the beak is undivided and these are all 

 spiny ; the spiny forms are often called porcupine fishes. Some 

 species of Tetrodon live in fresh water, occurring in the Nile 

 and West African rivers ; many species are found on the east 

 coast of America and the West Indies, others on the Pacific 



