Hard thing on snail foot

[thumpersalley]

I see on a couple of my serith & margarita snails an either white or brown hard disc right on the foot. What is this & why is it happening? Kim

 

[alix2.0]

if youre thinking of what im thinking of (which can sometimes be a dangerous situation) then it might be the snail's "door".

 

[yosemite sam]

Its called the operculum. As alix said, it's the 'door' snails have that protects them when they curl into their shells.