SHARKS 361 



family belongs the gigantic Carcharodon rondeleti, which grows to 30 or '40 

 feet in length, and is met with in all the warmer seas. Even more widely dis- 

 tributed is the thresher or fox shark {Alopecias vulpes), since it also ranges into 

 colder seas, and not infrequently makes its appearance, like the porbeagle and the 

 blue shark, in British waters. The excessive length of the upper lobe of the tail 

 renders it impossible to mistake this species for any of its kindred. Here, too, 

 belongs the remarkable Japanese elfin or ghost shark, originally described under 

 the name of Mitsukurina owstoni, but subsequently found to be apparently 

 inseparable generically from the supposed extinct genus Scapanorhynchus. This 

 shark is notable on account of a strap-like prolongation from the crown of the head 

 overhanging the upper jaw. 



PORT JACKSON SHARK. 



Great interest attaches to the small Port Jackson, shark (Cestracion philippi} 

 and its relatives, of the Indian, Japanese, Australian, and New Zealand seas, on 

 account of their being the sole survivors of a once numerous family, the 

 Gestraciontidce. The typical species is a bulldog-headed shark, marked with 

 vertical blackish bars on a yellowish brown ground. The genus is specially 

 distinguished by the peculiar character of the dentition, the hind portion of which 

 forms an exquisitely beautiful fluted pavement, adapted for crushing the shell-fish 

 on which these sharks feed, while those in the front of the jaws are sharp- 

 pointed recurved cones. The egg-capsules of these sharks are in the form of cones, 

 with two spiral ridges. 



A couple of species of so-called basking-sharks, Cetorhinus (or Selache') 

 maximus and Rhinodon typicus, respectively represent two other families of the 

 order. These monstrous sharks take their name from their habit of basking on the 

 surface of the sea, and apparently feed on small fishes and still more minute lower 



