Probably some type of beetle. Do you have any big beetles in your area?
You might try posting on the Gardening forum sister site. There are some pretty knowledgeable people over there that might take identifying this as a challenge. Make sure you tell them a bit about where you found it. Not just northern California but a bit about elevation and terrain.
You can get the link at the bottom of this page.
Just to make it easier, here's the link. They've improved the format of this forum so its kind of hidden down there.
Thanks Ridge. About the biggest bugs we have here in Northern California are Potato Bugs aka Mole Crickets or Dragonflies. I told my wife I was going to take it to China Town and sell it as a miracle aphrodisiac so we could retire. She's creeped out because I put it in a humid jar so it will hatch. I told her,"You never know. A human head might pop out and need a meal".
I visited my sister in the Eureka area a couple of years ago, man, those banana slugs you guys have just gross me out!! The nephews really enjoyed picking them out of the friends garden and chucking them down the gully, but ... eww ...