48 MOLLUSC A, 



will be seen scraping surfaces of the glass, and swallow- 

 ing the green growths which they have taken off.* 

 Often the land snails will in this way destroy the sur- 

 face of a paper-box if confined in one. Their favorite 

 food is wet bran or leaves of different kinds of plants, 

 though they will also eat animal food with avidity. 

 They can be successfully kept in earthen pots on bran, 

 if this is dampened, and a small piece of sponge intro- 

 duced to maintain the moisture. The bran must be 

 changed frequently, and only a few kept together. 

 Leaves, also, of various kinds, lettuce and cabbage, etc., ' 

 can be used to feed them, and they will live well in 

 Wardian cases. 



The strong jaw in the upper part of the mouth works 

 down and back over two cartilaginous pieces, one of 

 which is shown in Fig. 26, car. Just below these is the 

 true mouth, and in the back part of this the tongue. 

 (Fig. 26, to). This consists of an inner, stiff, cartila- 

 ginous part (Fig. 26, ca?-), which supports a membrane 

 carrying upon its outer surface a broad band of very 

 small but numerous teeth. These are in rows, and 

 slant so as to have their points directed inwards. This 

 whole apparatus is moved forwards to the opening of 

 the mouth, becomes stretched by this, and the teeth 

 erect and in proper position to receive the coarse 

 pieces cut off by the jaw. These it rasps into smaller 

 pieces against the top of the mouth and under side and 

 edge of the jaw, and passes them backwards into the 

 throat, the whole operation being performed by the aid 

 of numerous and powerful muscles. In moving for- 



* They are particularly useful in aquaria in keeping the sur- 

 face of the glass clear and clean on the inside. 



