THE PEA CRAB 73 



PLATE XXV 



THE PEA CRAB (i) 



This is a very odd crab indeed. In the first 

 place it is extremely small. Even when it reaches 

 its full size it is scarcely ever so much as half- 

 an-inch across, while its body is so round that 

 it really does remind one very much of a pea. 

 Only it is not quite the right colour for a pea, 

 for it is creamy yellow instead of green. 



And, in the second place, this crab lives in 

 a very odd place namely, inside the shells of 

 living mussels, or pinnas, or even cockles ! What 

 it does there nobody seems quite to know. It 

 does not appear to injure the animal to whom 

 the shell belongs, although it is very fond of 

 the flesh of mussels, and if it finds one of those 

 creatures lying dead will certainly devour it. 

 Perhaps it only creeps inside its shell for the 

 sake of safety. At any rate, it is a very timid 

 little crab, and if you open a mussel and find a 

 pea crab lying hidden inside it, it will tuck up 

 all its legs quite close to its little round body 

 and lie perfectly still for several minutes in the 

 hope that you will think that it is dead. 



On some parts of the coast pea crabs are so 

 plentiful, that three out of four mussels are found 

 to have one of these odd little creatures inside it. 



