The snail is a slow-moving gastropod noted mainly for its shell. It is sometimes more fully blazoned a “house-snail” in period, as in the canting arms of Shelley, 1610 [Guillim1 154].
The snail faces dexter by default. As the snail has no limbs, one can hardly blazon it as “statant”, “passant”, or whatever.
Society armory also has examples of the “slug”, essentially a snail without its shell. It follows the same conventions as the snail.
Peridot of the Quaking Hand bears: Azure, a snail guardant argent.
Alana O’Keeve bears: Vert, three snails Or.
Justinian the Sluggard bears: Checky gules and argent, a slug guardant contourny sable.