188 POPULAR BRITISH CONCHOLOGY. 



limpet, or TrocJius that comes within reach of its terrible 

 proboscis. It will bring the aperture of its own shell op- 

 posite to that of its victim, and then introducing his appa- 

 ratus, never leaves it until all the soft parts are transferred 

 to his capacious stomach. But even where no aperture or 

 door leaves the smaller mollusc open to the attack of his 

 enemy in that way, he is by no means deterred by this 

 little difficulty ; for if the object of his attack be a limpet, 

 firmly attached to a stone, or a bivalve, tenaciously hold- 

 ing its shell closed, he will manage to perforate the shell, 

 and through the hole to draw forth the quivering substance. 

 Mr. Spence Bates related to the authors of the ' History of 

 British Mollusca/ that by way of experiment he placed a 

 Purjoura in a vessel of sea-water in company with a mussel, 

 and observed the result. In a short time the Purpiira, 

 finding that the mussel was not at all open to his advances, 

 and that the valves of the shell were so firmly drawn toge- 

 ther as to leave no chance of effecting an entry between 

 their edges, began to think of attacking him from without. 

 Seeking a portion of the outer surface free from epidermis, he 

 commenced boring. His human observer, repudiating the po- 

 licy of 'non-interference,' removed him and turned the mussel 

 over, placing that valve uppermost which was most covered 



