Wildlife Spotting

I think it looks like a buckeye seed. If you can find the tree you think it is from and there are no leaves, buckeye trees have opposite branching and chestnuts have alternate branching.

If it is a buckeye seed (nut) then don’t eat them unless you know specific leaching techniques because they’re poisonous.

I think this might be a California Buckeye, bulb like seed. http://en.wikipedia.org/wiki/Aesculus_californica http://www.stevenkharper.com/buckeye.html

For me it looks like a chestnut, as you are in california, perhaps the American chestnut, as i suggested above?