Collemopsidium foveolatum forme sur Mytilus.
Form found on mussels (Mytilus). Two different aspects may be found: one is characterized by a greyish to olivaceous thallus. Thallus absent in the second form, visible only by its endolithic perithecia. Currenty under investigation.
See: Evolution and taxonomy of the marine Collemopsidium species (lichenized Ascomycota) in north-west Europe. MORH Fiona, EKMAN Stefan, HEEGAARD Einar. Mycol. Res. 108 (5) : 515-532 (May 2004). The British Mycological Society.*