BIVALVE MOLLUSCANS. 253 



adheres to the rocks and other bodies which it 

 meets with at the bottom of the sea, and thus 

 they brave the agitation of the waters. They 

 seldom change their station, but they can unfix 

 their byssns, if any circumstance renders such 

 change imperative. In Sicily and Calabria this 

 byssus, which is very silky, is manufactured into 

 stuffs, stockings, and gloves, which are very fine 

 and warm, but it will take no dye : articles com- 

 posed of it are very dear, and the manufacture 

 is fast declining. Aristotle observed a little 

 crustaceous animal within the valves of the wing- 

 shell, which he thought was necessary to its 

 existence. Pliny says it is always accompanied 

 by a companion, the Pinnotheres or Pinnophylax, 

 that when the Pinna opens its shell, a number 

 of small fish boldly enter, and when it is full, 

 the crab gives the blind animal notice by a 

 slight bite, who immediately closes his shell, and 

 assigns a portion of the prey to his little useful 

 companion. Small Crustaceans indeed, both 

 crabs and shrimps, certainly do find their way 

 not only into the shells of the Pinna, but into 

 those of muscles and whilks, 1 but their object 

 is to defend themselves, especially when their 

 crust is soft, and not to tell the Pinna when to 

 close its doors upon its prey ; for its food is the 

 sea water or the animalcules it contains. 



1 Bucclnum. 



