CATECHISM OF CONCHOLOGY. 



and stones, and often to the bottoms of ships, in' 

 such numbers as to impede their sailing, whence 

 their name. 



Q. What is the generic character of the Pholas 

 or Stone-piercer ? 



A. The shell of the Pholas is spreading, and 

 differently shaped, but with several smaller acces- 

 sory valves, situated upon the hinge and posterior 

 slope. * Hinge recurved (curved back), furnished 

 with a tooth : the outer surface of the shell is 

 rough, with points somewhat like a file. 



Q. Where are the Pholades found ? 



A. In stones and wood, as their name, derived 

 from the Greek, implies. They perforate the 

 hardest substances by means of an instrument 

 resembling a tongue, having previously softened 

 them with a peculiar secretion which exudes from 

 the body of the animal.f 



* For a particular account of this curious shell-fish, 

 consult the " Conchologist's Companion." 



f See next Chapter for the meaning of th's word. 



