2800 THE BONY FISHES AND GANOIDS 



The box-like coffer fishes (Ostraaon] 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 recognized by the inclosure of the angulated body 

 in a complete cuirass formed of six-sided bony plates with their edges in juxtaposi- 

 tion, 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 (O. quadricor- 

 nis) is figured in the colored plate. 



THE GLOBEFISHES AND SUNFISHES Family DIODONTID^L 



Unlike as they are in external appearance, the spine-clad globefishes and the 

 huge flattened sunfishes 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. In- 

 habitants 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 sunfishes. In 

 many of them the flesh is of a highly poisonous nature, at least during certain sea- 

 sons 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 ( Trio- 

 don 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 di- 

 vided by a median suture, while that of the lower jaw is continuous. The elon- 

 gate tail terminates in a forked fin, and the body is invested with spiny bony plates, 

 which do not overlap one another. The single species, which may attain a length 

 of twenty inches, ranges over the Indian and Malayan seas, and is of a general 

 brown color, with a spot of variable color on the sac, and the fins yellow. 



The essential characteristics of the globefishes, which form the sec- 

 ond subfamily, are that the tail and its fin are distinct and well devel- 

 oped, and that a portion of the oesophagus is highly distensible and capable of being 

 inflated with air. All the globefishes, or, as they are sometimes called, sea hedge- 

 hogs, are easily recognized by the short and cylindrical or rounded form of the 

 body, which is generally covered with a scaleless skin bearing a number of spines of 



