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 
