360 



TROPICAL AND SOUTHERN FISHES 



Ox Eye. 



until it reaches the vent, when it immediately carls itself into a loop and thrusts 

 the tip of its whip-like tail into the aperture. When this is accomplished, the 

 fish straightens itself, and proceeds leisurely to insinuate itself, tail-first, into the 

 body of its host, the action being apparently assisted by the spines of the dorsal 

 and ventral fins. The whole process occupies only about half a minute. 



The last family of bony fishes to be mentioned here is that of the 

 Scopelidce, the members of the typical genus of which inhabit the 

 tropical and temperate zones where they come to the surface only at night, 

 remaining in the depths during the clay and also in stormy weather. To this 

 family belongs the so-called ox-eye (Scopelops hoops) of the Pacific, a fish remark- 

 able not only for its large, goggle eyes, but also on account of the presence of a 

 number of eye-like phosphorescent spots on the head and sides ; similar structures 

 being also developed in certain other members of the group. 



THE BLUE SHARK. 



Sharks. 



Among the cartilaginous fishes, mention may first be made of 

 the common blue shark (Carcharias glaucus), the largest member of 

 the family Carcha/riidce, in which the teeth are usually triangular in form, with or 

 without serrated edges, and sometimes provided with a pair of basal cusps. The blue 

 shark, which grows to five-and-twenty feet, inhabits both the Atlantic and Pacific 

 Oceans, representing a genus containing between thirty and forty species. Nearly allied 

 to the Garchariidm are the curious hammer-headed sharks (Zygoma, or Sphyma), 

 forming the family Zygcenidw, and characterised by the peculiar shape of the head. 

 A well-known representative of a third family, the Lamnidce, is the porbeagle 

 (Lamna comubica), the range of which extends from the North Atlantic to Japan 

 and New Zealand. This shark, which grows to a length of about 9 feet, is of 

 rather stout build, with the oval eyes situated above the sides of the mouth, and 

 carrying numerous formidable rows of spear-like teeth, armed with large basal 

 cusps, in both jaws. The large size of the first dorsal fin, which, like the second, is 

 devoid of a spine, as well as its stouter make, serve to distinguish this species- 

 at a glance from the blue shark, which has two small dorsal fins. To the same 



