1 46 Hillside. 



snail shell is, of course, a univalve, that is, it is all in one 



FIG. 31. GROUP OF POLMO-GASTEROPODA OR LAND SNAILS. 

 1. Helix /ruticum. 2. Helix nemoralis. 3. Helix hortensts. 4. Helta; arbiwtorum. 



piece, but bivalves secrete the two pieces of their shell in 

 a very similar way. 



