[24 



A HISTORY OF FISHES 



So characteristic is the form of the teeth in many Sharks 

 that it is often possible to identify a species from one or two 

 teeth alone, and in the case of many extinct forms these are the 

 only parts of the fish which remain, all the rest of the skeleton 

 having disappeared. Further, in those species in which the 

 dentition is of more than one type, it is possible to state whether 

 a certain fossil tooth belonged to the upper or the lower jaw, 

 and whether it occurred in the front or at the side of the jaw. 

 The curious Elfin or Goblin Shark {Scapanorhynchus) was first 

 known from some teeth occurring in Upper Cretaceous strata, 

 but a living specimen of this supposedly extinct form was 



Fig- 53. ELFIN AND PORT JACKSON SHARKS. 



A. Elfin or Goblin Shark {Scapanorhynchus ozvstoni),X3\ (a, isolated teeth of 

 same) ; b. Port Jackson Shark (Heterodotitus phillippi), X ^V (^> lower jaw of same). 



found oflf the coast of Japan in 1898. It is remarkable for the 

 long, blade-like snout, separated from the jaws by a deep cleft, 

 and the teeth are of a characteristic pattern (Fig. 53A, a). 

 Recently the known distribution of the species was further 

 extended in an interesting manner. A "break" occurred in 

 one of the deep-sea telegraph cables lying at a depth of 750 

 fathoms in the Indian Ocean, and on its being brought to the 

 surface the damage was found to have been caused by a fish 

 which had left one of its teeth embedded in the cable; this tooth, 

 which had broken oflf short, was identified as belonging to an 

 Elfin Shark. 



All the Sharks so far mentioned are active predaceous forms, 

 and although they feed mainly on other fishes, the diet is some- 



