Thallus: appearing crustose, poorly developed, often confined to a continuous or +lacerate, narrow collar of granules, squamules and external cephalodia forming a spongy cushion 1-3 mm thick, occurring in patches 2-10 cm in diam. when well developed surface: gray-blue or rarely brown-black cephalodia: dark gray, +densely cor-alloid-warted or nodulose, gelatinous when wet, partially buried in substrate photobiont: primary photobiont: cuff around apothecia with Coccomyxa; secondary photobiont: external cephalodia with Nostoc, becoming dark and sponge-like when wet Apothecia: scattered, urceolate, 15 mm in diam. disc: pale to dark red-brown, dull margin: pale green or olivaceous, often white pruinose, 0.1-1 mm wide hymenium: hyaline, 160-200 µm tall asci: clavate, (2-)4-spored ascospores: hyaline initially and becoming brown, 1-septate transversally, ellipsoid, 30-50(-55) x (16)18-24(-26) µm; epispore: thickened and ornamented with pits. Substrate and ecology: in moist, calcareous habitats similar to those of S. saccata but less often in crevices and less strongly calciferous World distribution: circumpolar Arctic-alpine in Europe and North America, and also New Zealand Sonoran distribution: upper montane areas of Arizona. Notes: Solorina spongiosa resembles a reduced morphotype of S. saccata (L.) Ach., but is distinguished by its dark, external cephalodia, and the mature ascospores which appear smoother in optical section; ultrastructural differences in the spores help to support the separation at a specific rank. For nomenclatural problems see Laundon (1984).