Thallus gelatinous, non-stratified; non-filamentous; black to brown or dark gray, photobiont mostly blue-green
1a Habitat aquatic, submerged most of the year
2a Habitat freshwater; photobiont blue green; ascocarps apothecia
3a Lobes 2-15 mm broad, loosely attached; lower surface veined
3b Lobes < 2 mm broad, coalescing and tightly attached in dark, thin rosettes that are difficult to remove from rock; lower surface difficult to view
2b Habitat rocky intertidal; photobiont green; ascocarps perithecia
4a Spores elongate ellipsoidal, 11-18 x 3-5 μm; gelatinous matrix enclosing asci in center of ascocarp; thallus with short thin lobes to 1 cm wide, shiny greenish gray; algal partner Prasiola borealis, algal cells often in regular groups, the groups separated by fungal mycelium; Alas to s BC
4b Spores ellipsoidal, 10-13 x 3.5-7 μm; gelatinous matrix filling only the ostiole; thallus of tubular to flattened lobes; algal partner Blidingia minima var. vexata, algal cells irregularly arranged in surface view; fungal hyphae layered between algae; BC to Cal
1b Habitat mostly not aquatic but occasionally in seasonally wet habitats or seepage
5a Thallus glossy black, on rock, in section with a thick white central layer. Widespread, rare in PNW, common in SW.
5b Thallus brown, gray, or dull black, substrate various, in section completely dark or with a whitish paper-thin central layer
6a Thallus generally dull, black or olive-black, lacking a cortex, the surface of interwoven hyphae, lacking isodiametric cells in upper surface view under LM
7a Spores nonseptate; thallus tiny; upper surface of interwoven hyphae; rare spp
8a Apothecia lacking thalloid margin; thallus granulose to subfruticose
8b Apothecia with thalloid margin; thallus either of flat, interlaced lobes with fruiting warts or of small knobby clusters
7b Spores septate; thallus tiny to large; upper surface various; including common species
6b Thallus with a cellular cortex, generally of + isodiametric cells; thallus often faintly shiny, brown, gray or black
9a Hyaline hairs present on and near the lobe margin; thallus weakly stratified, a broken lobe showing a pale layer sandwiched between dark algal layers; on moss and soil or soil over rock.
9b Hyaline hairs lacking on upper surface or if present then thallus homogeneous at 10-40X; substrate various.