Collection location: Eastern San Francisco Bay Area, California, USA [Click for map]
Unknown milkcap. Found in mixed oak/hardwood/chapparal. Somewhat viscid to tacky pileus and stalk. Not staining when cut except Gills exude white milk slowing turning yellowish.
They look like maybe L. alnicola. The viscid cap and scrobiculations on the stalk match the description. The habitat and the latex also matches. I have been finding these ofter in the SCMs as well.