We are in Florida this week. And a snail genus of interest is Melampus.
I have identified this species tentatively as Melampus coffeus. It is a semi-terrestrial snail in the family Ellobiidae, subfamily Melampinae. All ellobiids are air breathers. The little hole that I marked with an arrow in the next picture is the pneumostome, the opening of the lung of Melampus coffeus.
Although they breathe air, the majority of the ellobiids, including Melampus coffeus live very close to the sea. They in fact spawn in the sea and at least some species go thru a planktonic larval stage before becoming terrestrial snails. This is an almost incontrovertible evidence that they evolved from marine snails.