The species most overwhelmingly present on the chaparral in that area is N. laevigatum, which is supposed to have a yellow medulla, but all over Rancho Corral I found it where the yellow tones bled through the lower cortex, giving the lower surface a pale yellow cast. You can see this in the center of your main photo. Rarely I found N. helveticum.
JJ Johnson
2016-01-00
Sun Jan 10 2016 12:41:50 GMT-0800 (PST)
United States of America, California, Point San Pedro, Pacifica, CA
Smooth brown upper with light lower surface. orange apothecia coming from underside. No veins. Nephroma? On coyote brush - on coastal ridge near conifers. I was surprised to see it here, but then I saw it again and again....