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 mercenaria, 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 
