38 THE SEA-SHORE 



PLATE XIII 

 THE SADDLE OYSTER (2) 



This is a very curious oyster; for in its flat 

 lower valve, just below the hinge, is a large oval 

 hole. Through this hole passes a strong band of 

 muscle, to which is fastened a kind of shelly knob 

 which looks just like a button. By means of this 

 the animal fastens itself down to some object at 

 the bottom of the sea ; and very often indeed it is 

 found attached to the shells of other molluscs, 

 looking something like the saddle on the back 

 of a horse. That is why it is called the " saddle 

 oyster." 



Another curious fact about this creature is 

 that very often its shape completely alters as 

 it grows older. While it is quite small it 

 looks very much like an ordinary oyster. But 

 as time goes on it generally takes the form 

 of the object on which it rests. So you might 

 easily find half-a-dozen shells of the saddle 

 oyster, not one of which would be shaped like 

 any of the others. 



