Description.Thallus thin, dark grey to grey-brown, rimose becoming areolate; areoles to 0.50-0.80 mm wide; surface plane to scabrid, matt; margin mostly determinate; prothallus lacking; vegetative propagules absent. Apothecia innate, sometimes broadly attached, frequent, scattered or contiguous, to 0.40-0.45 mm in diam.; disc black, plane, rarely becoming convex; thalline margin absent, or concolourous with thallus, entire, persistent, ca. 0.05 mm wide; excipular ring absent. ApothecialAnatomy. Thalline exciple 40-80 µm wide; cortex 5-10 µm wide; epinecral layer lacking; crystals absent in cortex and medulla; cortical cells to 4.5-6.0 µm wide, pigmented or not; algal cells to 9.0-16.5 µm long; proper exciple hyaline, 5-10 µm wide, to 20-30 µm wide above; hypothecium hyaline, 45-50 µm deep; hymenium 70-90 µm high, not inspersed; paraphyses 2.5-3.0 µm wide, conglutinate with apices to 4.5-5.0 µm wide, pigmented brown forming a dark orange-brown epihymenium; ascus 65-70 x 18-25 µm. Ascospores 8/ascus, Type A development, Mischoblastia-type, (18.5-)21.0-22.0(-24.5) x (8.5-)10.5-12.0(-14.0) µm, average l/b ratio 2.0-2.1, often becoming inflated at septum when mature, markedly so when overmature; torus present at maturity; walls not ornamented. Pycnidia immersed in thallus; conidiophores type I; conidia bacilliform, 3.0-4.0 x ca. 1.0 µm.
Chemistry. Spot tests all negative; secondary metabolites not detected.
Substrate and Ecology. Siliceous on sometimes irrigated rocks by rivers and streams, and on lake shores according to Mayrhofer & Moberg (2002). The few North American records conform with this assessment. Collected once with R. oxydata.
Distribution. A new record for North America, the species is scattered in the northeastern part of the continent and probably belongs to the Appalachian-Great Lakes. Scattered in the British Isles, rare in southern Sweden and central Europe (Mayrhofer and Moberg 2002).
Notes. Characterized by the innate apothecia, lack of atranorin, and by the rather large spores that become inflated at the septum with age. However, the spores are not as large as reported from Europe. The habit is similar to that of R. cana but the thallus is darker, the spores larger, and its mesic habitat is different from the more xeric habitat of R. cana.
Specimens examined. CANADA. QUEBEC. Gatineau Co., Eardley, I.M. Brodo 16855, 24841 (CANL). U.S.A. NEW YORK, Clinton Co., Altona, E. Lay 660545 (personal herb.). VERMONT. Windsor Co., Quechee Gorge, B.D. Ryan 19747a, 19748 (ASU). WISCONSIN. Florence Co., Popple River, 1968, J.A. Jesberger (SASK).