SWORD-FISHES— HORSE-MACKEREL AND PILOT-FISH 



345 



retained in the shape of long tapering rods. The muzzle of the sail-fishes is also 

 more triangular, with a less sharp cutting-edge, so that on the coasts of Madras 

 and the South Sea Islands it is comparatively easy to capture them when young 

 in nets. In length these fishes may reach as much as fifteen feet, with a " sword " 

 of a yard long. In the young both jaws are of equal length, and carry small 

 pointed teeth, while the fin on the back is of medium length. With increasing age 

 the back-fin grows abnormally, and the remnants of the pelvic fins make their 

 appearance in the sail-fishes ; soon afterwards the upper jaw begins to lengthen, 

 and eventually assumes the characteristic adult form, while at the same time 

 the teeth disappear. These fishes, which are carnivorous and highly ferocious, 

 frequently ram whales with their formidable weapons, although the precise purpose 



SWORD-FISH. 



of such attacks is not definitely ascertained. Sometimes they make a mistake and 

 charge ships, when, in the old days of wooden vessels, they would drive their 

 swords a foot or more into the planking. 



Horse-Mackerel As interesting examples of another family, the Carangidce, of 



and PUot-Fish. th e mackerel section, reference may be made to the horse-mackerel, 

 or scad, and the pilot-fish. The former (Caranx trachurus) is an unmistakable 

 fish on account of the lateral mucus line on each side of the body being protected 

 by a series of seventy-three large bony plates, which become keeled on the tail. 

 On the coasts of the west of England scad sometimes make their appearance in 

 enormous numbers, which literally choke the smaller harbours. The pilot-fish 

 (Raucrates ductor), which is a truly pelagic tropical species, occasionally 

 accompanying vessels into British waters, takes its name from its reputed habit 

 of conducting sharks to their prey, when, like the honey-guide in the case of the 



