foliose, umbilicate, monophyllus or much divided in some forms with many lobules close together, the lobes 1-7 cm broad, flat or slightly rippled, reddish brown or gray-brown, gray pruinose, 0.3-0.5 mm thick; underside smooth to warty, not veined, light to dark brown; the upper cortex and lower cortex about the same thickness of paraplectenchymatous cells with diameter of 4-8.5 µ. Perithecia
immersed, pale with only the tips brownish, 200 µ diameter, the gelatin 14-blue; spores
8, hyaline, elongate elliptical 8-14 x 5-6 µ.
This species grows on calcareous rocks often in very dry habitats with much sunlight. It is circumpolar, arctic to temperate, ranging over most of North America where there are appropriate rock substrata.