27 



CHAPTER Y. 



EXCAVATIONS IN STONE, WOOD, WAX. — SUMMARY OF OPINIONS. — THE 

 ' rasping' PROCESS DESCRIBED. — DIPPICULTIES IN EVERY THEORY. 

 — VIEWS OF THE WRITER, AND A HOMELY EXPERIMENT. 



THE BORING POWER OP PHOLADID^. 



The great peculiarity from which this family of moUusca de- 

 rives its name, is the astonishing power possessed by all the 

 species, of scooping out dwelling-holes in various kinds of 

 stone, wood, sand, hard mud, and even wax. These holes 

 invariably correspond to the size of the creature which 

 makes them, and when the latter is quite mature, the hole 

 generally fits it so closely as to leave it no room to move. 

 The way in which this close fitting is effected is probably 

 by means of various supplementary growths on the edges or 

 back, or end of the shell. But the grand difficulty has 

 always been to account for the power of perforating in the 

 hard substances which they burrow. 



