5-62 THE DACTYLE PHOLAS. 



ralists in all ages. When divested of their shell 

 they are roundish and soft, with no instrument that 

 seems in the least fitted for boring into stones, which 

 they are known to do, or even for penetrating the 

 softest substance. They are, indeed, each furnished 

 with two teeth ; but these are placed in such a 

 situation as to be incapable of touching the hollow 

 surface of their stony dwellings. They have also 

 two 'corners to their shells, that open and shut at 

 either end ; but these are totally unserviceable to 

 them as miners. The instrument with which they 

 perform all their operations, and by means of which 

 they bury themselves in the hardest rocks, is only 

 a broad fleshy substance, somewhat resembling 

 a tongue, that is seen issuing from the bottom 

 of the shell. With this soft yielding instrument, 

 while yet young and small, they work their way 

 into the substance of the stone, and they enlarge 

 their apartment as their increasing size renders it 

 necessary. 



The seeming unfitness, however, of this animal 

 for penetrating into rocks, and there forming a 

 habitation, has induced many philosophers to sup- 

 pose that they entered the rock while it was yet in 

 a soft slate, and, from the petrifying quality of the 

 water, that the whole rock afterward hardened 

 round them by degrees. This opinion, however, 

 has been confuted, in a very satisfactory manner, by 

 Dr. Bohads, who observed that many of the pillars 

 of the temple of Scrapis at Puteolt were penetrated 

 by these animals. Whence he justly concludes 

 that the Pholades must, have pierced into them alter 



