Collemopsidium elegans (R Sant.) Grube & B. D. Ryan
Pyrenocollema elegans R Sant.
Thallus superficial, very thin, translucent, turning green-brown and finally dark brown, scattered with irregular black excrescences or warts 0.1-0.2 mm diam., and black ridges up to 0.15-0.5 mm, radiating notably near the thallus margin. Perithecia scattered more or less abundant, prominent, ostiole hollowed, 0.1-0.4 mm diam., blackish or dark brown when moist. Ascospores oblong, 1-septate, not constricted at the septum, 12-20 x 4-7 µm. Pycnidia immersed in the ridges, visible as back dots. Photobiont : cyanobacteria (with brown-yellow cells). On siliceous rocks in the littoral zone of sea shores with Verrucaria (Wahlenbergiella) striatula and Verrucaria (Wahlenbergiella) mucosa. Sometimes difficult to macroscopically distinguish from some morphs of Verrucaria (Wahlenbergiella) striatula of which the ascospores are simple and the thallus markedly dark brown with angular perithecia and widely opened apices. See also Collemopsidium halodytes s.l. which is very similar but devoid of warted excrescences and black ridges. N.B. Recent molecular biology investigations indicate that this 'species' is still poorly defined and analysed and that several taxa would in fact be considered under this name. This is why the specimen presented here are restricted to those fulfilling the core criteria of this species. N.B. In the field, may also be defined as a Verrucaria (Wahlenbergiella) striatula with a brown thallus.