FILE-FISHES AND COFFER-FISHES. 427 



spines appear as if they were actually a part of the vegetable growth. These 

 species are of relatively large size, attaining a length of as much as a foot. 



File-Fishes and Coffer-Fishes, — Family Balistidje. 



With the file-fishes and their allies we come to the first of the two families 

 constituting the suborder Plectognathi, of which the following are the distinctive 

 characters. In the head the bones are completely ossified, while in the rest of the 

 skeleton they are incompletely hardened ; the number of vertebrae being few. 

 The small gill-openings are situated in front of the pectoral fins, and the gills 

 themselves are pectinate ; the mouth being narrow, with some of the bones of the 

 upper jaw united, and in certain cases both jaws prolonged to form a beak. There 

 is generally a single soft-rayed dorsal fin, placed far back on the body, and situated 

 immediately above the anal ; and there may be remnants of a spinous dorsal ; 

 while the pelvic fins, when retained at all, take the form of simple spines. The 

 skin may be either entirely naked, covered with rough scales, invested in a 

 complete cuirass of plates composed of true bone, or dotted over with bony spines. 

 There is no duct connecting the air-bladder with the pharynx. As a family, the 

 file-fishes and their allies are specially distinguished by the presence of a small 

 number of distinct teeth in the jaws. Their bodies are either compressed or 

 angulated, with a somewhat produced muzzle ; more or less distinct vestiges of a 

 spinous dorsal and pelvic fins generally occur ; and the skin may be either rough 

 or spiny, or the whole body invested in a bony cuirass. These fishes, which are 

 of medium size, range over all tropical and temperate seas, although more numerous 

 in the former than in the latter, and may be divided into three subfamilies, in each 

 of which we notice an example. Extinct generic types date from the period of 

 the lower Eocene, while the file-fishes themselves are recorded from the middle 

 Eocene of Monte Bolca. 



The first subfamily is typically represented by Triacanthus brevirostris, from 

 the Indian Ocean, the other genera being from the Australian seas. The special 

 characters of the group are to be found in the compressed form of the body, and 

 its covering of rough, scale-like plates, as well as in the presence of a pair of strong- 

 spines representing the pelvic fins ; the type genus being distinguished by having 

 from four to six spines in the spinous dorsal fin. The typical file-fishes (Bal ist( s) 

 belong to a group of three genera in which the body is compressed, and covered 

 either with a rough skin or movable scale-like plates; and the pelvic fins are either 

 wanting or represented merely by a single median swelling on the abdomen. These 

 fishes are distributed over all tropical and subtropical seas; the first two genera 

 including a very large number of species. Whereas in the typical genus there are 

 three spines to the dorsal fin, and the chin is devoid of a barbel, Monacanthus 

 differs in the reduction of the dorsal spines to two or one, and .1 nacanthu8, which 

 has a single dorsal spine, is distinguished from both the others by the barbel on the 

 chin. In many districts the flesh of these fishes, it eaten, gives rise to symptoms 

 of most acute poisoning. Many of the species are beautifully ornamented with sym- 

 metrical markings; and while the majority are of small size, some attain as much as 

 a couple of feet in length. Of the members of the typical genus \)\: Gunther writes 



