Brown circular foliose lichen
A circular brown foliose lichen with folds growing on a pinkish rock. The lichen has numerous black circles (probably apothecia) on its thallus. My best guess is that this is _Umbilicaria phaea_. This lichen was found in Vasquez Rocks County Park in Los Angeles County. The scale bar is 5mm (contact me if you want a version of the image without the scale bar).