THE PIDDOCK OR PHOLAS 403 



were made of mother-of-pearl. And they are so sharp that the 

 whelk can bore through the shells of its victims with little difficulty. 

 But the hole having been made, the tongue now serves the 

 purpose of extracting the body of the owner of the shell which has 

 been pierced in this systematic, house-breaking sort of fashion. 



Tongue of Whelk ; general view, and enlarged view of detached Teeth 



Whelks are captured for the market in a very simple way. A 

 large basket is partly filled with pieces of decaying fish, and then 

 lowered by ropes to the bottom of the sea. The whelks soon 

 detect the feast, and come flocking in numbers to the basket, which 

 is then raised to the surface and its contents transferred to a tub. 

 In this way great numbers of the molluscs are often taken in a 

 short time. 



PELECYPODA 



This is the great group of bivalve creatures ; that is, of animals 

 whose shelly covering consists of two pieces. The Snails and 

 Whelks are representatives of the much greater group of univalve 

 creatures ; that is, creatures whose shelly covering is of one piece. 



These bivalves are all aqueous in habit. As we must know 

 what an oyster and a mussel are like, let us consider one or more 

 uncommon members of this great group. 



THE PIDDOCK OR PHOLAS (Family Pholadid^) 



In one respect the Pholas is not a good representative of the 

 bivalves, as its shell consists of one or more pieces, besides the 

 typical two " valves ". But it is a most interesting creature. 



