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: immersed or superficial, usually subgelatinous, the hyphae often vertically oriented photobiont: primary one a cyanobacterium (Gloeocapsa, Hyella, or Nostoc, the cells orange or blue-green), secondary photobiont absent Ascomata: perithecial, unilocular; exciple: light to dark brown; intercellular spaces in peridium normally melanized involucrellum: absent or present, hyphae arranged in a textura intricata; hamathecium of sparingly to richly branched and anastomosed and often irregularly thick hyphae, septate, I- asci: with two functional wall layers and an internal apical beak, fissitunicate, ovoid to subcylindrical, usually stalked, I-, usually 8-spored ascospores: colorless, oblong to ovoid-fusiform, 1-septate, the upper cell usually broader than the lower, a poorly defined gelatinous perispore sometimes present Conidiomata: pycnidial; conidiogenous cells ± cylindrical, phialidic conidia: bacilliform to ellipsoid Geography: cosmopolitan Substrate: on calcareous substrata in moist situations, on wet sand, or on calcareous to acid rocks in freshwater or marine habitats. Notes: In recent works, Pyrenocollema Reinke has been used as a genus for the species treated here, but in the current concept, this is a highly heterogeneous assemblage of species. The type of the genus seems to be a parasite on Nostoc. It has thin, tangentially flattened cell walls at the outer layers of the peridium, which are polygonal in surface view. Another old name under consideration is Magmopsis Nyl., but its type species with unclear biological relation to algae or cyanobacteria has rounded cells in the peridium. The peridium of Collemopsidium is constructed differently; it is composed of irregularly shaped, interwoven cells (textura intricata). In contrast to the type species C. iocarpum, marine species usually have strongly carbonized peridia, at least at the apical parts. At a glance, marine species may be confused with the lichenicolous fungus Stigmidium marinum [not definitely reported from the Sonoran region, but not unlikely] which occurs on littoral Verrucaria species; it has perithecia 0.15-0.2 mm diam., lacks hamathecial filaments, and has the spores constricted at the septum, 10-15 x 4-6 µm.