36 THE STORY OF LIFE IN THE SEAS. 



of Man I have seen the shore littered with Solens 

 scooped out of the sand by the force of the 

 waves and cast up with lacerated shells to fall 

 an easy prey to the Seagulls. 



The sandy bottoms in shallow waters are also 

 the haunts of many kinds of Fish that are speci- 

 ally modified in form and colour to resemble 

 their surroundings. The large family of the 

 Skates have their bodies compressed from above 

 downwards so that they can lie perfectly flat 

 upon the sand. Their upper surface is deeply 

 pigmented, giving them a general resemblance 

 to the ground on which they lie ; but to assist 

 them in escaping observation they have a habit 

 of shaking their fins in such a manner as to 

 scatter a considerable quantity of sand over their 

 bodies. Thus it can well be understood that in 

 the dim light of the sea-bottom the little Fish 

 and Shrimps, which form a large portion of their 

 food, may approach quite close to them without 

 being in the least aware of the danger into which 

 they are running. The upper side of the Skate 

 is also armed with a number of sharp and hard 

 spines, and in some forms called the Sting-rays 

 one of these, situated at the base of the tail, 

 is much larger than the others, and provided 

 with muscles so that it can be suddenly erected. 

 In connection with this spine there is a poison- 

 gland and duct. The wound that is inflicted 

 upon the arms or feet of the fishermen by this 

 formidable weapon of offence is said to be of a 

 very serious nature. 



Some of the Skates, too, show another very 

 interesting modification of structure, which, how- 



