Collemopsidium sublitorale (Leight.) Grube et Ryan

    Thallus immersed in the substratum, spreading out in patches, sometimes inconspicuous, beige-greyish, beige-pink, brown-yellow, scattered with globose perithecia, usually sessile and protruding (the most reliable charateristic), or slightly immersed in the shell, hardly visible to the naked eye as minute black dots, size and aspect irregular, 0.15-0.6 mm across (sometimes even larger), after falling down they leave discontiguous irregular 'holes' without distinct margin, ostiole distinct, crater-shaped at perithecia apices. Ascospores oblong, 1-septate, 15-25 x 6-9 µm (according to our measures). Pycnidia absent or abundant, smaller than perithecia. Photobiont: cyanobacteria. Common species on the shells of Balanus, Chtamalus where it is particularly well developed, but also on limpets (Patella) where it is difficult to distinguish from Collemopsidium halodytes; less common on limestone rocks but see: Collemopsidium sublitorale forme saxicole. May be found with Collemopsidium foveolatum as seen on one picture below.

   Can be distinguished only for canonical morphs of Collemopsidium foveolatum by its bigger, irregular and prominent perithecia. All the species of Collemopsidium are difficult to identify due to the fact that many intermediate specimen exist as well as crypto-species almost impossible to identify with the current morphological tools. Preliminary molecular biology analyses demonstrate that many undescribed taxa exist but they cannot be distinguished using the classical macroscopic and microscopic investigation tools.