348 FISHES WITH CONJOINED JAWS. 



of beak, internally divided into plates which form a 

 grinding surface. To this family belong 



The Globe Fishes (Diodori)* so called because their 

 jaws being undivided have each but a single tooth- 

 like piece, and the Tetradons/j- in which both jaws 

 are divided in the middle, so as to present the 

 appearance of four teeth, two above and two below. 



FlG. 230. GLOBE-FISH. 



I 



These two genera of fishes have the faculty of swelling themselves 

 up like a balloon by swallowing air ; this peculiarity has obtained 

 for them the common names of Swell-fish, Porcupine-fish, Balloon- 

 fish, &c. f and furnishes them with a means of defence, for when the 

 skin is distended, the spines with which it is armed become every- 

 where erect, and project from the whole surface of the body; when 

 thus swollen, they turn over, the belly coming uppermost, and thus 

 they float on the surface _of the sea. They are found in tropical 

 climates. 



The Sun Fishes (Orthagoriscus^ Mola ), sometimes also 

 called Moon-fishes, resemble the Diodon in the arrange- 

 ment of their jaws, but the body is compressed and of a 

 strange shape ; it has no spines, nor is it susceptible of 

 inflation, and their tail is so short and so high vertically, 

 that they look like fishes with the hinder part cut off. 

 One species, which sometimes attains more than four feet 

 in length, weighing about three hundred pounds, is oc- 

 casionally taken off our own coasts. 



* Sis, dis, double ; 6$6vs, o5<Wos, odous, odontos, a tooth. 

 j- rerpa, tetra, four ; oSous, o5<Wos, odous, odontos, a tooih. 

 % opdayopio-Kos, orthagoriscos, a sucking-pig. 

 Mola, a mill-stone. 



