Nash, T.H., Ryan, B.D., Gries, C., Bungartz, F., (eds.) 2002. Lichen Flora of the Greater Sonoran Desert Region. Vol 1.
Life habit: lichenized Thallus: crustose, superficial or immersed, thin, becoming warty or areolate when well developed, homiomerious, effuse; prothallus: absent upper surface: pale lime to dark gray or brown-black, smooth photobiont: chlorococcoid green alga Ascomata: perithecioid, hemispherical to spherical, brown to black, + immersed, 0.1-0.4 mm wide; ostiole: minute, inconspicuous involucrellum: absent true exciple: brown to black, 20-30 µm wide hamathecium: periphyses: present; hymenial gel I- or I+ yellowish,K/I+ blue; paraphyses: absent or disappearing; hymenium: hyaline, hypothecium: hyaline to pale brown asci: Verrucaria-like, narrowly cylindrical, tapering apically, thin-walled, up to ca. 180 µm long, multispored ascospores: ellipsoid, hyaline, simple, 2.5-4.5 x 2-3 µm Conidiomata: not observed Secondary metabolites: none detected Geography: oceanic influenced parts of Europe and California, USA Substrate: species occurring on either on bark or rocks, including limestone and marl. Notes: The only other pyrenocarpous genus in the region with a large number of spores per ascus is Thelopsis, but its spores become one-septate and its photobiont is a trentepoid yellow-green alga. The genus has not been revised recently, in part due to lack of adequate collections. A fourth species (T. versipellis Zahlbr.) was originally attributed to the genus, but was transferred to Trimmatothelopsis in the Dermatocarpaceae (Zschacke 1934) due to the presence of paraphyses. As far as we know the latter genus does not occur in North America.