48 THE SEA-SHORE 



shells lying about in numbers on almost any 

 part of the shore where the cliffs are made of 

 chalk or limestone. And if you look at the rocks 

 which are left dry when the tide goes down 

 you will see the entrances to its burrows 

 large, oval holes, several of which you may often 

 find quite close together. For the piddock is 

 a boring shell, which drives its tunnels through 

 and through the rocks, until very often they are 

 quite honeycombed by its tunnels. Sometimes you 

 may meet with a big block of chalk which only 

 weighs about half as much as it should, because 

 all the rest has been cut away by piddocks. 

 And if you could split it open you would find 

 several of these creatures lying in their burrows. 

 But how they manage to cut their way through 

 the hard chalk, or the still harder limestone, 

 nobody quite knows. Most likely, however, they 

 do so partly by means of the soft part of the body 

 which we call the "foot," and partly by means 

 of the shell, which they turn first a little bit 

 to one side, and then a little bit to the other 

 side, just like a man who is using a bradawl. 

 Every now and then, of course, the burrow gets 

 choked up with the material which has been 

 scraped away. But the piddock knows quite 

 well what to do in order to clear it. It just 

 squirts out a jet of water from the siphon tubes, 

 by means of which it breathes, and so washes 

 the burrow out! 



