550 



THE OCEAN WORLD. 



that of the Picked Dog-fish, Acanthias vulgaris (Fig. 362), which 

 sometimes attains the length of between three and four feet, and is 

 exceedingly voracious. It feeds upon other fish, of which it destroys 

 great quantities ; it does not hesitate to attack even the fishermen, 

 and especially bathers in the sea. It places itself in ambush, like the 

 Rays, in order to attack its prey. The flesh of the Dog-fish is hard, 

 smells of musk, and is rarely eaten ; but the skin becomes an article 

 of commerce, and is kno\\'n as shagrin, being, like the skin of the 



Fig. 36c.— The Picked Dog-fish Acanthias vulgas is). 



shark, used for making spectacle-cases, and for 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 family Zygcenid(Z contains the strange Hammer-headed Shark, 

 Zygcena malleus (Fig. 363), which is chiefly distinguished by the 

 singular conformation of its head ; it 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 fish are placed at the 

 extremity of the lateral prolongations of the head ; they are grey. 



