Synontms: (bayionim) Corallina membranacea Esper (1791) pl. XII; Hapalidium roseum Kützing (1843) p. 385; Melobesia corticiformis Kützing (1849) p. 696; Hapalidium roseum Kützing ex Areschoug (1852) p. 509; Hapalidium coccineum P. & H. Crouan (1859) p. 285; Melobesia rosea Rosanoff (1866) p. 77; Hapalidium hildebrandtioides P. & H. Crouan (1867) p. 149; Epilithon membranaceum (Esper) Heydrich (1897) p. 408; Lithothamnium corticiformis (Kützing) Foslie (1898b) p. 7; Lithothamnium membranaceum (Esper) Foslie (1898) p. 7; Melobesia hildebrantioides (P. & H. Crouan) Foslie (1898b) p. 11; Epilithon corticiforme (Kützing) Heydrich d’après Van Heurk (1908) p. 92.

VEGETATIVE FEATURES

Thallus habit: encrusting without protuberances, rounded, regular (rarely elliptical) (contiguous thalli ever overlapped). Continuous margin (A) without orbital ridges which is confused with the substratum, lobed, crenate edge. Size: 0.5-1cm in diameter; thickness up to 0.06mm. Colour of living specimen: wine-pink (even translucent). Colour of dried specimen: wine-pink to white. 

Monostratose thallus sometimes multilayered, up to 4-5 layers near conceptacles (conceptacles’ cells: (3) 5-7 (12)µm long x 10-15 (18)µm diameter). Basal filaments: rectangular cells: 8-12 (15)µm long x 7-10µm in diameter. Erect filaments: absent or reduced to few cells. Epithallial cells: triangular or elliptical (partially covering the mother cell lying beneath). Cell connections: cell fusions.

Gametangial conceptacles: spermatangial same as carpogonial but a little smaller; carpogonial spread, not confluent, slightly domed. Tetra/bisporangial conceptacles: multiporate (7-18 (30) pores), hemispherical with flat roof, numerous, raised, spread on surface or grouped and confluent. Old conceptacles break leaving small oval cavities with raised edge: (80) 110-130 (150)µm diameter x 50-80µm high. Other features: spore germination with 56 small central cells (B). Phenology: from May to August.

Habitat: epilithic, epizoic or epiphytic (more frequently) on different algal species; not growing on Zostera. Bathymetric distribution: from upper littoral to sublittoral 45m deep. Geographic distribution (Babbini & Bressan 1997):

Alboran Sea (A): Spain, Morocco; Western Mediterranean Sea (African shores) (B): Algeria, Tunisia; Middle Western Mediterranean Sea (C): Spain, France, Italy; North Western Mediterranean Sea (D): Spain, France, Italy; North Adriatic Sea (E): Italy, Slovenia, Croatia; Middle Adriatic Sea (F): Italy, Croatia; South Adriatic Sea (G): Italy; South Eastern Mediterranean Sea (H): Italy, Tunisia; Middle Eastern Mediterranean Sea (L): Italy, Greece, Turkey, Syria; North Eastern Mediterranean Sea (M): Turkey..