Mushroom

C. molybdites would be my first guess as well, but there are some differences that I'm seeing. The stalk should be discolored red to brownish in some areas, and a double-edged ring should be present (although from just this one angle it's hard to tell). The margin (edge of mushroom cap) of the false parasols I've seen in my area all are fairly smooth, in other words, no warts are on that area. Where it's growing (grassy lawn) is right, the location is right, but in the end it does not match C. molybdites completely. Lepiota would be a great genus to search in.