Answer:
- The body is soft and unsegmented, usually covered by a hard calcareous shell (absent in some, e.g. slug, octopus).
- The body is divided into head, muscular foot and visceral mass, and is covered by a fold called the mantle.
- They are triploblastic and coelomate; aquatic forms breathe through gills and land forms through lung-like structures.
Examples: snail, Pila, octopus, oyster.