Calvatia booniana A.H. Sm.
Thanks...Hadn't had time to ID it before you did... You're fast! Thanks for the Genus suggestions... Helped me narrow the search. I think this is it, but I'll leave it open, because I do not know fungi well at all :-)
Verbatim Date: 2014-05-10 5:41:42 PM PDT
United States, California
37.526577 -122.458129 +-6m.
about 10 cm wide, grown out of a drainage cut off the trail
Rights Holder: © held by the observer (listed as 'Collector') at iNaturalist.org, with some rights reserved (CC BY-SA)
Record Id: 9a55677d-26bf-43ab-bfe0-b19e46a92574