I found a bunch of spider funnels out in the grass, and I was able to entice this guy out by dropping bug-size oat husks on the outer lip of his funnel. But when I very carefully nudged some whisps of web suspended ~30 cms above his hole out of my shot, he bolted back in. Wiley little dude. Wish I knew what he was. I think I might need to make a trip to the library to make an ID.
Abdomen and cephalothorax about 2.5-3 cm long, observed near Alamo, CA.