Snails can be divided into two categories when discussing manners of breathing: those with lungs and those with gills. Pulmonate (lung) snails assimilate oxygen through the thin wall ("lung") of their mantel cavity. Other snails breathe using gills.
Snails like the Pond and Ram's Horn are pulmonate. Their mantel cavity is located directly behind the head on most snails. This thin wall is called the "lung" of the snail. Snails that breathe using gills, like the freshwater Common River Nerite and the Common Mud Snail, do so via the mantel cavity as well. However, in contrast to pulmonate snails, the mantel cavity actually contains small gill-like organs through which the snail breathes.