TRUXK-FISHES. 



197 



does not have large bony plates in the skin, but very small scales or 

 spines of uniform size ; five species are represented, also a 

 skeleton (922-927). 



The Ostraciontidae, commonly called Trunk-fishes or Coffer- 

 fishes (fig. 94) , are tropical fishes living near the bottom in shallow 

 water. The body is encased in a carapace formed of large bony 

 plates, mostly hexagonal in shape. There is no spinous dorsal fin, 

 and the pelvic fins are wanting. The chief genera are Ostracion 

 and Aracana. Some species of the former have strong, sharp 

 spines (e. g. Ostracion cor nut us, 932), a pair pointing forward in 

 front of the eyes and a pair pointing backward beneath the tail. 



Trunk- 

 fish. 



Fig. 94. — Coffer-fish, Ostracion quadvicorms. 



Globe- 

 fish. 



Six species of Ostracion are shown (929-934). Aracana differs 

 from Ostracion in that the bony carapace is not closed behind the 

 anal fin; three species are shown (935-937). 



In the Tetrodontidse the teeth are coalescent, forming upper and 

 lower beaks. The beaks are divided by a median suture, so that 

 there appear to be four large teeth, whence the name ' Tetrodont ' 

 (see skull 942). The skin is either smooth or with movable spines, 

 rarely with bony plates. There is no spinous dorsal fin, and pelvic 

 fins are wanting. The Tetrodont fishes can inflate their belly with 

 air, whence they are commonly termed ' Puffers ' or ' Globe-fishes.' 

 When thus inflated they float helplessly at the surface of the 

 water, belly upwards. The Tetrodont fishes occur in all tropical 

 and warm seas ; a few species are found in fresh water. Thirteen 

 species of Tetrodon are shown (941, 943-947, 949-955) and a 

 skeleton of Tetrodon stellatus (948). 



In the Diodontidse, as in the preceding family, the teeth are Porcu- 

 coalescent, forming beaks. The upper and lower beaks have no P me_l18 - 



