FISHES PHENOMENAL AND ECONOMICAL. 189 



Ostracion cornutum. In addition to the two horn-like frontal spines, two pairs are 

 developed on the back, a single pair from the centre of the side, and two or three 

 pairs on each side of the abdomen, making from twelve to fourteen in all. The 

 supremely restless habits, bright colouration, and grotesque shape of the little Tas- 

 manian Cow-fish, rendered this species a highly popular attraction at the writer's 

 Hobart fisheries establishment, where a tank was temporarily devoted to the reception of 

 a selected series of individually varying specimens. Among the more bizarre aspects 

 exhibited by this Cow-fish reference may be more especially made to that presented 

 in an end-on view as delineated in the two figures opposite the letter C in Chromo- 

 Plate VII. In its young condition Ostracion cornutum is common in Summer in the 

 shallow inshore waters of the innumerable coves and bays of the southern coast-line 

 of Tasmania, while the larger, adult, individuals are frequently taken in the " grab-all " 

 nets set by the fishermen in deeper waters for the capture of Silver Trumpeter. 



The Leather Jackets or Trigger-fishes, referable to the genus Monacanthus, 

 are among the most abundant of the representatives of the Plectognathi in Aus- 

 tralian waters. They take the first of their popular titles with respect to the 

 texture of their scaleless, finely granulated or hispid skins, which may be stripped 

 from their bodies with the greatest ease in a form highly suggestive of a piece 

 of fine kid leather. The second title of "Trigger-fishes" has been bestowed upon 

 them with reference to the peculiar construction of the anterior dorsal fin, which 

 in Monacanthus, as its technical name implies, consists of a single large sharply- 

 pointed spine and its attached membrane. This spine is capable of elevation and 

 depression at the will of its owner, and when erected is so rigidly held in its place 

 that it will break before it can be pressed into its recumbent position by main force. 

 There is, however, a small bone behind and at the base of this spine, which, on being 

 moved mechanically or by the muscles of the animal, immediately causes the spine to 

 drop down in a manner suggestive of the trigger and hammer arrangement of a gun- 

 lock. In the allied genus Balistes, with which the name of Trigger-fishes is more 

 exclusively associated, this mechanical peculiarity is most conspicuously developed. 

 Behind the large anterior spine there are two shorter and relatively slender ones, and 

 the pressure of one of these when the fin is erected causes the immediate collapse of 

 the larger spine. Several representatives of this genus frequent the coral reefs of the 

 Northern tropical Australian sea- board. 



Of the more cosmopolitan single-spined Leather Jackets, genus Monacanthus, 

 no less than forty Australian species have been described. These may vary in size 



