GLOBE-FISH ; SUN-FISH. BALISTID^. 55 



fast as they are destroyed by wear ; and they constitute very 

 efficient instruments for grinding down the food on which these 

 animals live, which consists of Crustacea and sea- weeds. To this 

 family belong the Globe-fishes ; which are so named from their 

 power of distending themselves into a spherical form, by inflating 

 with air a large sac contained in the abdomen. When thus 

 distended, they float along the water with the back downwards, 

 swimming onwards by means of their pectoral fins ; and they are 

 covered with a series of large spines, which are raised up when 

 the body is thus inflated, so as to form a very efficient means of 

 defence. From this last circumstance, these Fishes have been 

 sometimes termed Porcupine-fish. There are three genera in 

 which this curious power exists ; the Diodon (two-toothed), in 

 which there is no furrow or division in the jaws, so that each 

 seems like a single tooth ; the Triodon (three-toothed), in 

 which there is a division in the centre of the upper jaw ; so as to 

 divide it, as it were, into two teeth ; and the Tetrodon (four- 

 toothed), in which there is a division of this kind in each jaw. 

 Besides these, this family contains the Orthagoriscus, or Sun-fish 

 (so named from its rounded form), which looks like the anterior 

 half of a fish cut in two in the middle. It has the power of 

 floating with its head and eyes above water ; but not of distend- 

 ing itself with air ; in this state it moves along sideways, very 

 slowly, however ; and appears like a dead or dying fish. The 

 Sun-fish (or Moon-fish, as it is sometimes called) attains a con- 

 siderable size ; of the short species, which is most remarkable 

 for its peculiarity of form, individuals have been frequently 

 caught measuring four feet in length, and nearly as much in 

 breadth, and weighing 400 Ibs. ; and it has been stated occa- 

 sionally to attain double that weight. 



580. In the second family, that of BALISTID.&J, or File-fishes, 

 the jaws are armed with a small number of distinct teeth ; the 

 skin is either rough, or covered with very hard scales, whence 

 their name, and the mouth is prolonged into a sort of pyramid. 

 In their general form, and in the brilliancy of their colours, they 

 bear a considerable resemblance to the Chaetodons ( 556) ; and, 

 like them, they inhabit the seas of warm regions, keeping near 



