138 THE LIFE OF THE MOLLUSCA 



of rock, which it held ready, between the valves to 

 prevent them closing, when it easily devoured its 

 defenceless victim. The same animal was also seen 

 to watch by the side of a big Gastropod till the latter 

 emerged from its shell, when the Octopus pounced 

 on it. 



The uses to which Mollusca and their shells both 

 have been and are put seem almost endless. 

 Primarily they have served from prehistoric times 

 as articles of diet. The shells of Oysters, Mussels, 

 Cockles, Periwinkles, and other edible kinds, mixed 

 with bones of beasts and birds that had shared their 

 fate, are found in the refuse-mounds known as 

 " kitchen - middens," which range from 100 to 

 1,000 feet in length, and from 3 to 10 feet high, and 

 which occur along the coasts of Denmark, and are 

 even represented by small deposits in places in these 

 islands. Later-date counterparts of these refuse- 

 heaps are met with in North America, formed 

 principally of the valves of Venus mercenaries, in 

 Brazil, Tierra del Fuego, Australia, New Zealand, 

 etc. In caverns in Liguria enormous accumulations 

 of Limpet shells tell a like dietary tale. 



To-day nearly all the marine Bivalves are eaten in 

 one quarter of the world or another, as well as many 

 of the marine Gastropods and even Chitons. Cuttle- 

 fish are esteemed in Italy, Provence, Spain, China, 

 Japan, and the East generally. 



The freshwater molluscs, being less tasty, are not 



