298 INTRODUCTION TO CONCHOLOGY. 



We learn^ however, from this example, the mode by 

 which the ojster may extend over every part of the ocean 

 where the crab wanders ; and if she is at length cast by the 

 waves on some coast where, instead of sand and pebbles, 

 spreads out a deposit of fine mud, the foundation of an 

 oyster-bank may be readily laid. Mussels in like manner 

 are conveyed to far distant regions, where they furnish a 

 supply of food to different kinds of fish, marine birds, and 

 animals. 



But are not the Mussels defended witli a testaceous 

 coating ? How, then, is it possible for a bird to open and 

 devour them ? These instinctive creatures pounce upon 

 their prey, when left uncovered by the efflux of the tide, 

 and mount with it to a considerable height ; they then let 

 go their hold, the shell is broken by the violence of the 

 fall, and the inhabitant is easily extracted. 



]\Ionkeys also devour Mussels, as well as other shell-fish, 

 in considerable numbers. They watch the ebbing of the 

 sea, and whenever an unfortunate Mussel opens his shell 

 for the purpose of imbibing or rejecting water, a stone is 

 immediately slipped in, which prevents the valves from 

 closing, and renders him an easy prey to his sagacious 

 adversary. Birds, also, occasionally avail themselves of this 



