INTRODUCTION. 13 



shell-fish; and when they are unable to penetrate the 

 shells with their beaks, they ascend with them to a consi- 

 derable height, and let them fall on some rough or craggy 

 place ; by which means the shells are broken, and the fish 

 becomes an easy victim*. 



Crabs, and other crustaceous animals, are known to 

 make serious attacks on the testaceous orders. The lar- 

 ger sort of crabs are able, by their great strength, to open 

 the valves of most shells by main force; but those of small- 

 er dimensions make their inroads in a different manner : 

 the pea-crab, in particular, is very destructive to bivalves, 

 especially to muscles; it enters their shells whenever it 

 has the opportunity of finding them open, and there re- 

 mains, preying upon the fish, till it has entirely consum- 

 ed it; at which period the shell opens, the crab takes his 

 departure, and proceeds to make similar attacks else- 

 where. 



Another species, called the hermit crab, is also suppos- 

 ed to be implicated in similar offensive operations among 

 univalves;- for it is frequently found housed in the vacant 

 habitation of a buccinum, turbo, or nerite, and is there- 

 fore suspected of having previously devoured the animal, 

 and afterwards to have secured a retreat for itself in the 

 empty shell. 



* Mr. Mawe states, in his Travels in Brazil, that he saw a spot 

 of bare granite, not more than one hundred yards square, cover- 

 ed with an immense number of mutilated shells; the whole 

 neighbourhood was rich in wood and verdure, and the sea at 

 least five miles distant. On inquiry he was informed, that large 

 flocks of birds every evening repaired to this place with shells 

 left by the tide, which they let fall on the rock, in order to ob- 

 tain their contents. 



