CARTILAGINOUS FISHES. 523 



used for making spectacle-cases and for other other ornamental 

 purposes, for which its green colour and high polish recommend it. 

 There is a smaller species than the preceding, which haunts rocky 

 shores, where it lies in wait for its prey. Its spots are larger and 

 more scattered, and its ventral fins are nearly square. It feeds on 

 molluscs, crustaceans, and small fishes. 



The Hammerhead, Zyg&na malleus (Fig. 354), is chiefly distin- 

 guished by the singular conformation of its head, which is flattened 

 horizontally, truncate in front, and the sides prolonged transversely, 

 giving it the appearance of the head of a hammer. The eyes of this 



Fig. 354. The Hammerhead (Zygana malleus). 



fish are placed at the extremity of the lateral prolongations of the 

 head ; they are grey, projecting, and the iris is gold-coloured. When 

 the animal is irritated, the colours of the iris become like flame, to 

 the horror of the fishermen who behold them. 



Beneath the head and near to the junction of the trunk is the 

 mouth, which is semicircular, and furnished on each jaw with three 

 or four rows- of large teeth, pointed and barbed on two sides. 



The most common species in our seas is long and slender in the 

 body, which is grey, the head blackish. It usually attains the length 

 of eleven or twelve feet, weighing occasionally nearly five hundred 



