72 A NATURAL HISTORY OF THE SEAS 



The upper shell may have a downward opening apex 

 pierced with a hole, through which passes a strong ligament, 

 anchoring the creature to rocks or reeds. Within the shell 

 one finds two coiled arms or feet which have respiratory- 

 functions, whilst the food is washed towards the mouth 

 by currents set in motion by lashing cilia. 



In the remote times Brachyopods, or " Lamp Shells ,: 

 as they are called, from the shape of the upper valve, 

 abounded in every sea. To-day the group is much reduced 

 and widely scattered in depths of water varying from less 

 than a hundred to nearly three thousand fathoms. The 

 majority are of a dead white, but certain tropical forms are 

 resplendent with beautiful greenish or peacock tints. 



