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TROPICAL AND OUTSHERN FISHES 



honey-badger, it claims a portion of the feast. Be this as it may, it is certain that 

 pilot-fishes accompany large sharks and ships in their course. This fish, which 

 is of medium size, is easily recognised by the broad dark blue vertical bands on 

 the sides of the body which extend upwards on to the unpaired fins. In the 

 abyssal depths of the North Pacific the Carangidce are represented, among other 

 species, by the one known as Anomalops p>alpebralis, which, like so many deep- 

 sea fishes, is probably self-luminous. Here may be mentioned two luminous fishes, 

 PlLotoblepharon palpebratus and Heterophtliahuus catoptron, from the Malay 

 Archipelago, both of which are of small size, and belong to the present family. 

 They are remarkable among luminiferous fishes in being shallow-water forms, 

 the first named dwelling among stones at the bottom, while the second is a free- 

 swimmer. Their light-organs, which are situated in the skin, resemble generally 



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Mackerel. 



those of deep-water luminous fishes, though they have certain structural peculiarities 

 of their own. The whole upper surface of these fishes appears to be luminiferous. 

 The familiar mackerel (Scomber vernalis) is the typical re- 

 presentative of a family (Scombridce) of pelagic fishes, most of which 

 carry a small series of finlets between the tail and the unpaired fins of both 

 surfaces. In the ordinary mackerel there are five such finlets both above and 

 below, but in the Spanish mackerel (S. colias), which differs by the possession of 

 an air-bladder, there may be either five or six. Mackerel, which are found in 

 every tropical and temperate sea, but more especially the western South Atlantic, 

 afford an excellent example of protective colouring, the barring of black and green 

 on the back harmonising when seen from above with the ripple amid which these 

 fishes swim, while the pinkish silvery sheen of the lower surface renders them as 

 inconspicuous as possible when viewed from below against the light of the sky. 

 Tunny and Scarcely less valuable as a food-fish is the tunny (Thynnus medi- 



Bonito. terraneus), which has eight or nine finlets, and ranges from the South 

 Atlantic to the South Pacific. It is occasionally taken on all parts of the British 



