512 



THE OCEAN WORLD. 



the soft, elastic, and retractile ^skin which covers the head. Imme- 

 diately hehind the eyes are two blow- holes, which communicate with 

 the interior of the mouth. The animal is able to open and close 

 these holes at pleasure, by means of an extensible membrane, which 

 acts as a sort of valve. Through these holes it ejects the superabundant 

 water beyond what is necessary for respiration. In its general colour 

 the animal is ashy grey on its upper surface ; white, with rows of 

 black spots, below. 



Its tail is long, flexible, and slender, acting at once as a rudder and 

 a weapon of offence or defence. When lying in ambush, nearly buried 

 in mud at the bottom of the sea, and it has no desire to change its 



Fig. 350. The Lump-fish (Raia clavata). 



position, a rapid and sudden stroke of this formidable weapon, armed 

 with hooked bones on its upper surface, arrests its victim by wounding 

 or killing it, without disturbing the mud or seaweed by which it is 

 covered. This species sometimes attains a very Considerable size, and 

 their flesh is firm and nourishing ; but the larger specimens rarely 

 approach inhabited shores, even when the female desires to lay her 

 These eggs have a very singular shape, differing from almost 



