Thallus: endolithic or thallus reduced to zone beneath apothecia or forming an ecorticate white to brown areolate thallus on crumbling, uneven substrates, with variable algal development Apothecia: black but sometimes with a reddish tint, round, 0.5-1(-2.1) mm in diam., dispersed or contiguous, becoming irregular when dividing to form new apothecia, sometimes forming immarginate and pulvinate clusters up to 7 mm across; broadly attached with medullary hyphae becoming thickly umbilicate disc: black (reddish black when wet), plane to convex, rough and uneven, rarely appearing gyrose, not carbonized, epruinose but the surface may appear pruinose in flush zones from particle deposition margin: black, smooth to rough, sometimes splitting and appearing crenulate, edge often down-turned over disc, disappearing if disc becomes very convex true exciple: 50-100 µm thick, externally black and tarry but not carbonized, internally brownish yellow with orange or red tones or sometimes hyaline epihymenium: yellowish to dark brown, 15-25(-30) µm thick, in a thick gel hymenium: hyaline, though sometimes orange in thick sections, (70-)80-115(-125) µm; paraphyses: conglutinated unevenly, septate, basally 1.5-2.5 µm wide, apically not expanded or 3-4 µm wide subhymenium: hyaline or pale yellow, indistinct, 15-25(-40) µm thick hypothecium: hyaline or pale yellow, 10-40 µm thick but sometimes hard to distinguish from subhymenium asci: clavate, 75-85 x 7-14(-27) µm, 100+-spored;. ascospores: hyaline, simple, variable in size, 4-6 x 1.1-2.3 µm Pycnidia: not observed Spot tests: all negative Secondary metabolites: none detected. Substrate and ecology: primarily on acidic rocks and rarely on coarse-grained alluvium from sandstone and granite or on limestone World distribution: Europe and North America Sonoran distribution: Arizona and southern California. Notes: Sarcogyne similis is similar to S. regularis but occurs on acidic rocks, and differs with its usually tar-like exciple, in having a wide dark-colored zone in its inner exciple, and in having apothecia, which divide and sometimes become convex and immarginate. Both species can vary in characteristics, leading to some specimens being hard to determine. But substrate is a good species indicator, except rarely on sandstone. Besides substrate, S. similis has irregular shaped apothecia that regularly divide and the medulla often thickens beneath the apothecium becoming umbilicate. Both species occasionally produces a thallus on crumbling substrates or sandstone. Sarcogyne.magnussonii de Lesd. (holotype missing) appears to be described from specimens of S. similis with thalli on sandstone in Mexico. Sarcogyne athroocarpa H. Magn. appears to be a reduced form of S. similis common at high elevations in Rocky Mountains. Magnusson's annotation is missing and the type is uncertain (FH!). These reduced specimens generally have a less tarry exciple. We have seen at least two probably undescribed taxa from montane habitats in Califronia and Arizona that would key out to S. similis or S. novomexicana but would not match our descriptions. Sarcogyne californica H. Magn is a synonym of S. similis which differs only in being described as always immarginate and pulvinate. The pulvinate form is caused by the multiple division of an apothecium and is very striking when seen, but intermediates with apothecia dividing into a lesser degree are numerous. Divisions forming pulvinate clusters were observed on hard granite boulders, which may stimulate it through restricting the spread of endolithic hyphae; on crumbling granite, sandstone, pebbles and small rocks, or on soil, convex and immarginate discs are usually rare.