I believe that is what would commonly be called a "rider" snail or one of those "Free" snails that come on the plants labeled "SNAIL FREE". I have a bunch of them. They aren't an issue. If you overfeed, they will actually help you by cleaning up the excess. They also help stay on top of the algae that could grow in various places. I just vaccum them up as I see them when water changing. I still have some, but they aren't a ridiculous problem. My son enjoys looking at them.
If you don't like them, just suck them out when you change your water... or crush them up when you see them (your fish will love you for it!). Don't overfeed and they will just be happy inhabitants of your tank. If you do overfeed, the numbers will climb dramatically.
My numbers initially went up like crazy as they were able to feed on a fungus that came out of my driftwood. They have been a manageable number ever since. I also suck up a few every water change, but never more than a dozen at a time.