Synonyms: (basyonim) Melobesia caulerpae Foslie (1906) p. 16; Melobesia trichostoma Rosenvige (1917) p. 253; Heteroderma caulerpae (P. & H. Crouan) Adey (1970b) p. 16; Fosliella tenuis Adey & Adey (1973) p. 398 (pro parte); Pneophyllum rosanoffii Chamberlain (1983) p. 367; Pneophyllum zonale (P. & H. Crouan) Chamberlain (1983) p. 435.

VEGETATIVE FEATURES

Thallus habit: encrusting, adherent, flattened, more or less orbicular or lobed. Entire, thin without orbital ridges margin; smooth surface. Size: diameter up to 10mm; 0.13mm thick. Colour of living specimen: brownish, mauve, pink. Colour of dried specimen: from white to yellow ivory.

Basal filaments: unilayered, cells 7-16µm in diameter. Erect filaments: in epiphytic thalli absent; in epilithic thalli up to 8 cells thick present; cells 10-29µm long x 7-15µm in diameter. Epithallial cells: protuberant, elliptical. Cell connections: cell fusions. Other features: intercalary trichocytes, larger than the other cells of thallus present in basal filaments.

Gametangial conceptacles: spermatangial near carpogonial , with spout (B), flask-shaped chambers; carpogonial conceptacles with more or less circular chambers. Tetra/bisporangial conceptacles: uniporate, raised, with glossy pore due to protruding filaments (C); elliptical chambers and frequent presence of a central columella, 104-240µm in diameter x 70-164µm high. Pore canal surrounded by specialized cells in free unicellular filaments (C). Phenology: ---

Habitat: common species. Epiphytic particularly on Halopitys species, epizoic, epilithic also on glasses. Bathymetric distribution: littoral. Epiphytic thalli are generally littoral. Epilithic thalli have been recorded up to 20m deep. Geographic distribution (Babbini & Bressan 1997):

Western Mediterranean Sea (African shores) (B): Algeria; Middle Western Mediterranean Sea (C): Spain, Italy; North Western Mediterranean Sea (D): France, Italy; Middle Adriatic Sea (F): Italy; South Eastern Mediterranean Sea (H): Italy, Malta, Libya; Middle Eastern Mediterranean Sea (L): Greece; North Eastern Mediterranean Sea (M): Greece.