208 THE BOTTOM OF THE ;SEA. 



of the ajjimal seems to be furnished with no organ 

 by which oven the softest substance could be pierced. 

 It has two teeth, but they are so deeply seated that it 

 is impossible they could ever operate upon the walls 

 of tlie retreat which the creature bores out for 

 itself. Our attention is directed to the anterior part 

 of the shell, which appears to be set with hard points, 

 so arranged on the surfaces extending from the hinge, 

 forward, as to form a kind of file. At this end, a 

 short foot or tougiie is protruded, by which the ani- 

 mal holds on to the rock, while at the same time it 

 partly turns itself, and thus by the friction of the 

 serrated shell rasps away the chalk or rock. The 

 work conunences from the beginning of the creature's 

 life. It iu'st makes a slight hollow in the stone, in 

 which it ensconces itself. In that position the water 

 of the sea brings it sufficient food. Little by little, 

 as the animal grows, it enlarges the shell in which it 

 lives, and at the same time buries itself more deeply 

 in the stone. Their advance is made almost horizon- 

 tally at lirst ; but having reached a certain depth, 

 they suddenly change their direction, and bore out 

 their reti eat perpendicularly. It is at once theil 

 dwelling and their tomb, and in form resembles a 

 common lobacco-pipe — the stalk debouching in the 

 sea, and the bowl containing the animal. 



lu the regions frequented by pholades, the rocks 



