Molluscs 127 



One of the commonest of univalves in 

 this country is the familiar Limpet, 

 whose shell attains great solidity, es- 

 pecially on rugged coasts where it is 

 exposed to violent seas. The animal 

 holds to the rocks with proverbial 

 tenacity and a pressure which has been 

 calculated at over 60 Ibs. The limpet 

 is further remarkable for its homing 

 instinct. When covered at high water 

 it will sally forth in search of adventure 

 and vegetable food, returning always to 

 exactly the same spot, at low tide. Its 

 home is a quite deep pit, formed in the 

 rock with the aid of the sharp edges of 

 its almost circular shell and an acid 

 secretion. The tongue of the limpet, 

 which exceeds the shell in length, is 

 coiled like a watch-spring, and when 

 protruded makes a distinct scratching 

 sound, audible through the thick glass 

 of an aquarium. 



Nearly allied to the limpets are the 



