206 MOLLUSKS: GASTEROPODS. 



They are all marine. On the coast of England the 

 Limpet is much used by fishermen for bait, and on 

 the coast of Berwickshire twelve millions have been 

 collected' yearly for this purpose. In the north of Ire- 

 land the people collect it for food. On the western 

 coast of South America there is a kind of Limpet which 

 is a foot across, and the natives use its shell for a 

 basin. 



LAND-SNAILS. 



Land-Snails are very numerous, more than four thou- 

 sand kinds being already known. Figures 409-414. 

 They all feed upon decaying plants. One of the 

 largest and one of the most common is the Helix albo- 

 labris, Figure 409. It is easily found by searching 

 under old logs, stumps, and leaves. In warm, damp 

 weather, snails of this and similar kinds come out 

 of their hiding-places, and may be seen crawling over 

 the leaves and up the trunks of trees. In early sum- 

 mer they lay their eggs in the loose soil beside logs 

 or stones, and in twenty or thirty days the young 

 hatch. When the cold weather of autumn comes they 

 seek a sheltered spot, close the mouth of the shell with 

 a thin membrane which they secrete, and at length 

 become torpid, and remain in that condition till the 

 warm days of the following spring. 



POND-SNAILS, OR LIMNJEIDS. 



These live in fresh waters, and lay their eggs in 

 transparent masses on aquatic plants and on stones. 

 They have a thin and horn-like shell. Figures 415- 

 417. They feed on plants, and glide along the sur- 

 face of the water shell downwards. They thrive well 

 in an aquarium, where they are also very useful, as 



