More snails

I found this little specimen in North Andover, MA. I think it’s Oxyloma retusum, the blunt ambersnail.

This is a fairly similar animal, but I’m not sure it’s the same species since the shell is not glossy or amber. What do you think? I found this one on Nantucket, MA. Is that snail turd there?
Meanwhile, this is an operculum. It’s the door, essentially, to a snail, attached to the bottom of the foot so that when the snail draws inside the shell, it can seal itself in. Not all snails have these, but the mystery snails of Green-Wood Cemetery do. Something scarfs these snails up around the edges of the Valley Water, but the predator does not like the thin shells, which are usually shattered. A couple of these operculum were recently lying around as well. I still think these are Cipangopaludina chinensis, formerly known as Viviparus malleatus, but I’m happy to be schooled if I’m wrong.