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COMB-GILLED GROUP. 
that, “both jaws are armed with eight strong incisor-like and obliquely truncated 
teeth, by means of which these fishes are enabled to break off pieces of the corals 
on which they feed, or to chisel a hole into the hard shells of molluscs, in order 
to extract the soft parts. They destroy an immense number of molluscs, thus 
becoming most injurious to the pearl-fisheries. The first of their three dorsal 
•spines is very strong, roughened in front like a file, and hollowed out behind to 
receive the second much smaller spine, which, besides, has a projection in front at 
its base, fitting into a notch of the first. Thus these two spines can only be raised 
or depressed simultaneously, and the first cannot be forced down unless the second 
has been previously depressed. The latter has been compared to a trigger, hence a 
second name—trigger-fish—has been given to these fishes.” Two Atlantic species 
of the genus are now and then met with on the British coasts. 
The box-like coffer-fishes ( Ostracion ), of which there are rather more than 
a score of species from the tropical and subtropical seas, alone represent the 
third and last subfamily, and are easily recognised by the enclosure of the 
angulated body in a complete cuii’ass formed of six-sided bony plates with their 
edges in juxtaposition, thus forming a mosaic-like pattern. Both the spinous 
dorsal and the pelvic fins are wanting, although their position may be indicated 
by prominences. In the whole backbone there are but fourteen vertebrae, of 
which the last five are very short, while those in the front of the series are 
much elongated; and the ribs are entirely wanting. In some of the species the 
cuirass is marked by three, and in others by four or even five ridges; but in other 
cases it is armed with long spines, which vary in length according to the age of 
their owner. A species (0. quadricornis ) is figured in the coloured Plate. 
The Globe-Fishes and Sun-Fishes, —Family Diodontidoe. 
Unlike as they are in external appearance, the spine-clad globe-fishes and 
the huge flattened sun - fishes are referred to a single family, distinguished 
from the last by the bones of the jaws being confluent and modified into a 
cutting beak, which may or may not have a median suture, the dentition taking 
the form of dental plates composed bf thin parallel layers. The body is more or less 
shortened; a spinous dorsal, anal, caudal, and pectoral fins are developed, but the 
pelvics are wanting. The external covering may take the form either of a number 
of small or large spines, or of plates; and the air-bladder may be either present or 
absent. Inhabitants of tropical and subtropical seas, with the exception of a few 
found in the fresh waters of the same regions, the members of this family are 
mostly small or medium-sized forms, although this is by no means the case with 
the sun-fishes. In many of them the flesh is of a highly poisonous nature, at least 
during certain seasons of the year. Like the preceding, the present family may 
be divided into three groups or subfamilies, the first of which is represented only 
by the sac-fish (Triodon bursarius ) of the Indian seas, which takes its name from 
the sac formed by the dilatable skin of the abdomen; this sac being supported by 
the pelvic bone, and filled with air at the will of the fish, although its lower portion 
consists merely of a flap of skin into which no air can enter. The dental plate 
of the upper jaw is divided by a median suture, while that of the lower jaw is 
