GLOBE-FISHES AND PORCUPINE-FISHES — SUN-FISHES 355 



Both the spiny dorsal and the pelvic fins have disappeared, as they would be quite 

 useless to species which crawl about on the sea-bottom in shallow tropical seas. 

 Their typical representative is the coffer-fish (Ostracion quadricornis), which, in 

 addition to the bony plates, carries a pair of spines in front of the eyes, and a 

 second, backwardly projecting pair some distance in advance of the anal fin. 



There are about a score of species of these strange fishes, allied to which are 

 others constituting the genus Aracana, distinguished from Ostracion by the bony 

 panoply being open behind the anal fin. In these fishes the front teeth coalesce 

 so as to form a kind of parrot-like beak, but in the file-fishes (Balistidce) they 

 remain separate and have the form of ordinary incisors. Although pelvic fins are 

 lacking, or reduced to a single spine, the spiny front dorsal fin is retained. The 

 typical file-fishes, or trigger-fishes (Batistes), some of which grow to a yard in 

 length, frequent coral-reefs, breaking oft' fragments of branching corals for food 

 with their powerful front teeth, and likewise nibbling at shell-fish, especially 

 pearl-oysters. The allied genera are Monacanthus and Aluteres, which are likewise 

 tropical and subtropical. 



Triodon bursarius, of the Indian Ocean, alone represents a family (Triodont- 

 idce) in which the teeth form a beak, those of the upper jaw being divided 

 by a median groove, while those of the lower jaw are completely united; this 

 peculiar arrangement giving rise to the name of these fishes. Both the front dorsal 

 and the pelvic pair of fins are lacking. 



Globe-Fishes Akin to the foregoing are the tropical globe-fishes and porcupine - 



and Porcupine- fishes of the families Tetrodontidce and Biodontidce, in both of which 

 Fishes. ^ Q teeth form parrot-like beaks, while pelvic and the front dorsal 

 fins are wanting. The globe-fishes, as typified by the genus Tetrodon, take their 

 technical name from the retention of a median division between the upper and lower 

 teeth of both sides, and have the skin naked, covered with spines, or, more rarely, 

 protected by bony plates. They can pump air into the lower half of the body, and 

 when in this balloon-like condition float helplessly, back -downwards, on the surface 

 of the sea. A few have taken to a fresh-water existence. In the porcupine-fishes 

 (Diodon), on the other hand, the upper and lower teeth of opposite sides are 

 respectively fused completely together, and the body is invariably protected by 

 spines, which in some cases are of considerable length. These remarkable fishes,. 

 which feed on corals and molluscs, have likewise the power of converting themselves- 

 into living balloons. 



Although very different in appearance, the gigantic sun-fishes of.' 

 the family Molidce are cousins to the porcupine-fishes, having the 

 upper and lower teeth completely soldered into a beak, although they cannot 

 inflate the skin of their bodies. Their strange truncated form is too well known 

 to need description, and it will suffice to mention that while the lesser sun-fish 

 (Ranzania truncata), in addition to its curtailed hind region, has a smooth skin 

 with embedded hexagonal plates, the typical species (Orthagoriscus mola) has a 

 rough, granulated skin. These fishes are met with in all the warmer seas, 

 especially near the equator, and occasionally straggle so far north as the British 

 Isles. The typical species may grow to as much as eight feet in length, and weigh 

 as much as 1800 lb. 



