Nerites are also male OR female. At least the species I have is (horned or thorn nerite)
Those are definitely little ramshorns. Someone told me recently that their rams were as bad as our ponds had been. However, my rams are slow breeders, I don't have a population issue.
Luckily for you that they hitched a ride, for some reason, they cost a little more to buy than ponds. I've seen the generic ones for 50 cents a snail. I bought mine for 8 cents each, because our local fish store is derped, and doesn't know the difference between a ram or a pond, even if I explain it in small words. lol