These aren't mushrooms, they are toad stools - big enough for a toad (not a little frog) to sit on and have room left over. I don't know what it is with the weather lately, but several of the lawns in my neighborhood, mine included, have had some form of mushrooms growing in them. I guess we've had the perfect combination of rain and sun for the funny fungi to grow. The second photo shows the gills on the underside. The third and forth shots are macros - I wanted to bring out the details in the caps.