Aspicilia candida (aka “Chalky Sunken Disk Lichen”)
Description: Thallus chalky white, almost blue-white, more or less circular, sometimes producing webby white lobes, or the thallus margin can be edged with a bluish black prothallus. Apothecia sunken or somewhat prominent, under 1 mm in diameter, sometimes, scattered, with pruinose-scabrose disks; margins darkish but pruinose; sportes 14-24 x 10-16 Um, 4-8 per ascus. The thallus, like that of many arctic crustose lichens, can become eroded by sand & ice leaving only scattered patches & isolated apothecia.
Chemistry: All reactions negative (no lichen substances known).
Substrate: On calcarous rocks
Range: Subalpine to arctic
Bibliography: Lichens of North America, by Brodo, Sharnoff, & Sharnoff
Database Entry: Distance Everheart 12-26-13