I was curious to see if the mushroom had changed since yesterday. It looked like it either split open or someone or something pulled a piece of it open. A Puffball Mushroom would have exploded with powdery spores.
Disclaimer: The Corralitas Red Car Property Blog prefers to quote reliable sources, such as CalFlora and California Poison Control on the issue of toxicity. MykoWeb is the resource everyone seems to refer to for mushrooms. The Los Angeles Mycological Society has a recommended reading list.
If you are eating your way through the Red Car Property, we DO NOT recommend you eat any plant you find in the Red Car Property neighborhood without first doing your own research.