428 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 cuirass 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 Diodontidje. 



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 of 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 



