SHARKS. 



103 



viduals of from twelve to fifteen feet are of very common occurrence, 

 but some of the species attain a much larger size and a length of 

 25 or more feet. Such large specimens are very dangerous to 

 man. 



The species of Galeocerdo (Case 33 : two large specimens of 

 G. arcticus, fig. 91, in the middle of the Gallery) also attain to a very 



Fig. 91. 



Galeocerdo arcticus. (From the Indo-Pacific and Atlantic Oceans.) 

 The figure of the tooth is of the natural size, and taken from a specimen 



11 feet long. 



large size, and belong to the most dreaded of their kind. On the 

 other hand, the Tope (Galeus) is a diminutive form, spread over 

 nearly all the temperate and tropical seas, and common in California 

 and Tasmania; one species (G. cams) occurs in British seas. The 

 Hammerheads (Zygcena) (Case 34) have the same powerful den- [Case 34.] 

 tition as Carcharias, and although they do not attain to the same 

 large size, they belong to the most formidable fishes of the ocean. 

 The peculiar form of their head is quite unique among fishes, the 

 anterior part being produced into a lobe on ea'ch side, theextrerrity 

 of which is occupied by the eye. The relation of this singular 

 structure to the mode of life of the Hammerheads is not known. 

 By far the most common is Z. malleus, which occurs in nearly 

 all tropical and subtropical seas. The " Hounds " (Mustelus) are 

 small Sharks, abundant on the coasts of all the temperate and 

 tropical seas ; two of the five species known occur on the coasts of 

 Europe, viz. M. lavis and M. vulgaris. 



