THE SHIPWORM 51 



rocks in which it lives. But there is another kind 

 of piddock which is very much smaller, for its 

 shells hardly ever measure more than an inch and 

 a half in length, and are a good deal narrower in 

 proportion to their size. This creature is called 

 the Little Piddock. It is generally of a brownish 

 yellow colour, and you may often find its burrows 

 in great numbers in limestone rocks. 



PLATE XVIII 



THE SHIPWORM (i and 2) 



This creature certainly does not look in the 

 very least like a mollusc; and I do not think 

 that anybody who had never seen it before 

 would ever guess that it is really quite a near 

 relation of the piddocks. It looks much more 

 like a kind of worm, for it has a soft round 

 body no larger than an ordinary drawing pencil, 

 though it is often as much as ten or even twelve 

 inches in length. But if you were to look at the 

 head end of its body you would see its bivalve 

 shells, though they are so very small that they 

 might easily be mistaken for jaws. And these 

 would show you that the animal is really a shell- 

 bearing mollusc. 



The shipworm is a most mischievous creature, 

 for instead of burrowing into chalk or limestone 



