iLet's not make this any more difficult than it should be. They're obviously collinista snails.
I'm just stating the obvious. And obviously, there is no way to come to any "obvious" conclusion" from those pics.
I was just throwing out the possibility that they could be limpets, which are quite common, and many, including the limpets in my tank, are very tiny and white. Without seeing them in person, or with a decent pic, there is no possible way to know for sure.