Nash, T.H., Ryan, B.D., Gries, C., Bungartz, F., (eds.) 2007. Lichen Flora of the Greater Sonoran Desert Region. Vol 3.

Thallus: patchily developed or continuous, thin, without a prothallus surface: pale gray, dull anatomy: undifferentiated Perithecia: prominent, hemispherical, often fused in groups of 2-5; exciple: 0.30-0.35 mm wide, colorless to brownish; involucrellum: covering the upper half up to two-thirds of the exciple, 50-70 µm thick, appressed to the exciple or slightly arching away; periphyses 30-40 µm long, partly furcate asci: clavate, 8-spored ascospores: hyaline, simple, ellipsoid , 18-25 x 8-12 µm Pycnidia: unknown Spot tests: all negative Secondary metabolites: none detected. Substrate and ecology: thinly epilithic, on calciferous rocks World distribution: Europe Sonoran distribution: only one sample seen from Arizona. Notes: Verrucaria confluens is included in V. muralis by most authors, but differs in having its perithecia often in dense groups with fused involucrella, and the involucrella tend to be thicker. In the other species the perithecia are solitary or only occasionally adjoining.