Collemopsidium foveolatum forme sur Chthamalus.
Form found on Cirripedia. Thallus usually not visible, perithecia endolithic, located at the bottom of a minnute 'crater' with edges flared out. This form is currently 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.