AIR-BREATHING SNAILS. 



221 



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

 face of the water, shell downwards. They thrive well 



Fig. 407. — Helix albolabris. 



Fig. 411. — Succinea. 

 Western States. 



Fig. 409. — Clirj'salis 



Shell, or Pupa. 



Florida. 



Fig. 408. — Bull- Fig. 410. — Slug, or Fig. 412. — Helix. North- 

 mus. California. Limax. New England. ern States. 



Fig. 414. — Planorbis. 

 United States. 



Fig. 413. — Physa. Fig. 415. — Limnjea. 



United States. United States. 



