FILE-PISHES. 195 



pectoral fin is strongly geniculated. The gill-opening is above 

 the pectoral fin, instead of below or behind. There is no 

 conspicuous lure ; if present it is lodged in a depression below 

 the snout and serves presumably as a tactile organ. The skin is 

 provided with small tubercles or spines or bony warts. Most 

 Malthid fishes are found in deep seas of the tropical regions, 

 although the Bat-fish itself, Maltke vespertilio, 897, is a shallow- 

 water form. It occurs abundantly in the West Indies. When on Bat-fish, 

 the ground it stands upon its pectoral and pelvic fins and resembles 

 a Toad in general attitude. The skeleton of the Bat-fish (898) 

 shows the remarkable elongation of the basal bones of the pectoral 

 fins. Halieutaa (899) is 'allied to the Bat-fish, but the outline of 

 the head is more circular, and there are also differences in the 

 skeleton. 



Balistiformes (File-fishes and Sun-fishes). 



The suborder Balistiformes, or Plectognathi, includes aberrant 

 fishes, such as the File-fishes,, Trunk-fishes, Globe-fishes, and Sun- 

 fishes. The jaws are short, the maxillary and premaxillary bones 

 are often firmly united, and the teeth may be confluent into a beak. 

 The bones of the gill-cover are reduced and the gill-opening is 

 small. The vertebrae are comparatively few and there are no ribs. 

 The flesh of most of these fishes is poisonous, and if eaten 

 produces a disease of the nervous system known as " Ciguatera." 



In the first family, the Triacanthidae, the teeth remain separate ; 

 there is a spinous dorsal fin with one large and one or more 

 smaller spines, and the pelvic fins have each the form of a strong 

 spine, whence the name Triacanthidae or three-spined fishes. 

 They are fishes of the Indian and Pacific Oceans. Two species of 

 Triacanthus (900 and 902) are exhibited, also a skeleton (901). 

 A cast of Halimochirurgus from the Manaar Gulf, Ceylon, is 

 shown in the series of Deep-sea Fishes (Cabinet-case 44, specimen 

 977). It is a deep-sea genus of the family, remarkable for its long, 

 tube-like snout. 



The Triodontidae have the premaxillary bones confluent with the 

 maxillaries, and the teeth are fused to form a beak. The upper 



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