I assume your photo is for the dark brown disks with the radiating white starbursts? If you were to pop one of these off the rock, you would see that it's attached by only a single, central point, the "umbo". Verrucaria is a crustose species that looks like a dark film on a rock, looks incredibly insignificant.
Liam O'Brien
2013-08-00
Fri Aug 09 2013 12:06:59 GMT-0700 (PDT)
United States of America, Oregon, Steens Mountain Wilderness, Princeton, Oregon, US