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DescriptionThallus: endolithic or inconspicuously white and ecorticate or limited to occurring below the apothecia, with abundant algae within the limited thallus above substrate; Apothecia: usually irregular, rarely round, 0.3-0.7 mm wide, dispersed or contiguous; disc: red to blackish red (red or orange when wet), plane; margin: black, often very prominent, sometimes flexuous, often undulate, sometimes split or plicate and compressed, always persistent, always with rather distinct joint lines; true exciple: 18-30(-110) µm thick, with radiating hyphae, externally black, carbonaceous (the degree of carbonization varying), internally pale brown to hyaline; epihymenium: pale brown-orange, not carbonaceous, 8-10(-12) µm thick; hymenium: orange to pale yellow, 60-85(-110) µm tall; paraphyses: simple, conglutinated, basally 1.7-2 µm wide, apically expanded to 2.5-5 µm wide; subhymenium: hyaline, 20-50 µm thick; hypothecium: hyaline to pale yellow or very pale brown, 15-35 µm thick; asci: clavate, 45-55 x 10-12 µm, 100+-spored; ascospores: hyaline, simple, cylindrical or rarely ellipsoid, 3-5(-5.5) x 1-2 µm; Pycnidia: not observed; Spot tests: all negative; Secondary metabolites: none detected.; Substrate and ecology: on acidic and carbonaceous rocks, often in washes, drainages, the flood plains of rivers or on surfaces where it is inundated during storms; World distribution: Europe, North America, North Africa, and Saudi Arabia; Sonoran distribution: Arizona, southern California, and Baja California.; Notes: Sarcogyne privigna begins as small verrucae, which usually "unfold" the margin in sections, which become fused. This causes some morphological variation in S. privigna apothecia. Some apothecia do appear crenulate when unfolding sections of parathecium have not fully fused and then thickened. These specimens can be distinguished from S. clavus by its pale hypothecium. The ontogeny deserves fuller investigation. Sometimes the verrucae are elongated and develop a central slit, and hence appear plicate. Sarcogyne plicata H. Magn. is a synonym based on two plicate specimens from San Bernardino and Riverside Counties in southern California (FH!). This is not a stable or common morphotype. Regular or particle-filled flushing may induce the development of these variations and cause a roughening of disc surfaces, which may appear gyrose (but not be carbonized) and pruinose. The latter specimens may have been described as S. integra (de Lesd.) H. Magn (holotype missing). Unlike the carbonized exciple of S. clavus, the exciple of S. privigna hydrates quickly and has a shiny leather-like appearance in bright light. The carbonization of the pigmentation is midway between the very hard exciple of S. clavus and usually softer tar-like exciple of S. similis. Sarcogyne privigna is always smaller than S. clavus and does not have a black hypothecium. When carbonization is less well developed, it could be mistaken for S. similis, but can be differentiated by the occurrence of joint lines in margin. When the disc is orange hued (when wet), it has been confused with S. novomexicana which has larger apothecia (1 mm+ wide) and an entire, non-carbonized brown margin. The Acharius types are H-ACH No. 838 (labeled Lecidea strepsodina and Lecidea strepsodina var. privigna) and BM-ACH No. 426. Neither specimen appears to match the taxon we treat here as Sarcogyne privigna, nor do they appear to match the current concept of S. privigna in the European literature. Unfortunately we were not able to study types, except in photographs. Claude Roux annotated Lecidea strepsodina as Polysporina simplex and Lecidea strepsodina var. privigna, the most abundant specimen in H-ACH 838, as Acarospora cf. modenensis H. Magn., a distinctive species from Italy (1929b). BM-ACH No. 26 labeled Lecanora milvina var. privigna is apparently identical to H-ACH No. 838 with an abundance of Acarospora cf. modenensis. Further investigation is required. Most specimens we saw labeled in North America as Sarcogyne privigna were Lecidea species or Sarcogyne similis. The species we refer to as S. privigna is at least quite common in Sonoran area but is rarely collected because it usually occurs in unstable drainages on acid rocks, which overall are low in lichen diversity and sometimes it is only species in this microhabitat. It matches the general concept of this species as currently applied in Europe.