These two and several more were found on a trail edge in a fairly open semi-grassy area. The cap size varied between 2.9 and 4.9 cm across. The stems were about 2 to 5 cm long and 0.70 to 1.0 cm thick. They all had the peculiar broad umbo that was flat in age and had an overall fragile nature. I didn't get a heavy spore print but they appeared brown to purple brown, smooth, medium sized and ellipitical to almost round. They don't seem to fit the description for any California Agaricus???