PERCH-LIKE FISHES 15? 



habits, but the food seems to consist of minute animals and 

 oceanic plants. 



SPEAR-FISHES AND SAIL-FISHES. 

 (Family Istiophorid.e.) 



Scombroids with a long, compressed body, covered with 

 narrow scales which are more or less embedded in the skin. 

 The snout and upper jaw are together prolonged to form a 

 long, pointed rostrum, which is narrow, flattened on the edges, 

 and more or less round in cross-section. Both jaws are 

 provided with minute granular teeth, which are also present 

 on the rooi of the mouth. The gill-plates form a network. 

 The dorsal fin is either single or double, but, if divided into 

 two parts, the first is always much larger ; the first rays of the 

 dorsal fin are stiff and spine-like. The anal fin is usually 

 divided into two portions. The caudal fin is widely forked, 

 and there are two fleshy crests or keels on each side of its base. 

 The pectoral fins are placed rather low down on the sides of 

 the body. The pelvic fins are narrow, and each consists of 

 from I to 3 rays. There is a large air-bladder. 



These are nearly all large fishes, and are found at or near 

 the surface in most of the warm seas of the world, generally 

 moving northwards during summer. 



Fossil remains of Spear-fishes and Sail-fishes probably date 

 back to the Eocene period. 



SPEAR-FISHES OR MARLINS. 



(Genus Tetrapturus.) Fig. 54. 



The doisal fin is low and appears to change considerably 

 with age. In smaller individuals it forms a single continuous 

 fin, with the middle portion nearly as high as the front, which 

 scarcely forms a distinct lobe ; in full-grown individuals the 

 front lobe is well developed, with the first few spines greatly 

 thickened, and the remaining rays of this portion become 

 progressively shorter towards the back, so that the whole 

 dorsal fin is divided into two distinct parts. The anal fin 

 is also divided into two portions. The pelvic fins are at first 



