Not 100% on the ID, but I think that's it. Very small, common little guy, growing in partly shaded grassy areas, like the book says.
At this point, I pretty much expect to find some Calisogas in Briones this time of year, but despite their pugilist reputation, most of the individuals I encounter are pushovers. Not this one.
This species is threatened by habitat loss, so it was a bummer to find a dead one by one of the ponds. Usually I see couple live ones along the edges, but not today.