220 MOLLUSKS : CASTKOPODS. 



Limpets. 



Limpets cling tightly to stones and shells, and move 

 about but little. They are all marine. In England, 

 they are used by fishermen for bait, and on the coast of 

 Berwickshire twelve millions have been collected 3'early 

 for this purpose. In the north of Ireland the people 

 collect it for food. On the western coast of South 

 America there is a Limpet a foot across, and the natives 

 use its shell for a basin. 



Air-breathing Snails. 



Land Snails. 



Land Snails are very numerous, more than four thou- 

 sand kinds being already known. Figures 407-412. 

 They all feed upon plants. One of the largest and 

 most common is the Helix albolabris. Figure 407, 

 easily found under old logs, stumps, and leaves. In 

 warm, damp weather. Snails of this and similar kinds 

 come out of their hiding places, and crawl over the 

 leaves and up tree-trunks. In early summer they lay 

 eggs in the loose soil beside logs or stones, and in 

 twenty or thirty days the }'oung hatch. When cold 

 weather comes they seek a sheltered spot, close the 

 mouth of the shell \\ith a thin membrane which the}' 

 secrete and become torpid, remaining so till the ■\\arm 

 days of spring. 



Pond Snails, or Limnseidse. 



These live in fresh waters, and la}' their eggs in 

 transparent masses on aquatic plants and on stones. 

 They have a thin and horn-like shell. Figures 413- 



