FILEFISHES AND COFFER FISHES 2799 



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

 mediately 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 filefishes 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 filefishes 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 char- 

 acteristics 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 filefishes {Batistes) 

 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 in- 

 cluding 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 Anacanthus, 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, if eaten, gives rise to symptoms of most 

 acute poisoning. Many of the species are beautifully ornamented with symmetrical 

 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 Dr. Giinther writes 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 mollusks, in order to ex- 

 tract the soft parts. They destroy an immense number of mollusks, thus becoming 

 most injurious to the pearlfisheries. The first of their three dorsal spines is very 

 strong, roughened in fro-nt 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 simul- 

 taneously, 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 trig- 

 ger fish has been given to these fishes. ' ' Two Atlantic species of the genus are 

 now and then met with on the British coasts. 



