Synonyms: Corallium cretaceum lichenoides Ellis (1755) p. 27; Spongites confluens Kützing (1841) p. 32; Melobesia polymorpha Harvey (1843) p. 108; Lithothamnium polymorphum (L.) Areschoug (1852) p. 524; Lithothamnium depressum Crouan (1867) p. 151; Lithothamnion polymorphum f. confluens (Kützing) Vinassa (1892) p. 59; Lithothamnium incrustans Foslie (1895) p. 94; Crodelia incrustans (Philippi) Heydrich (1911) p. 16.

VEGETATIVE FEATURES

Thallus habit: encrusting, more or less smooth surface (knobbly on old plants); thalli becoming confluent and differently crested (A). Thickened edge. (A). Size: maximum diameter 4cm. Variable thickness due to overlapping thalli and age of plants. Colour of living specimen: pink-violet. Colour of dried specimen: from yellow grey or mauve grey.

Basal filaments: unilayered, well developed (up to 200-300µm thick); rectangular cells 18-22 (25)µm long x 5-10µm in diameter. Erect filaments: multilayered (B), loosely aggregated; cells (5) 7-12 (15)µm long x (3) 6-8 (10)µm in diameter. Epithallial cells: rectangular to flattened. Cell connections: secondary pit-connections.

Gametangial conceptacles: spermatangial smaller than carpogonial; carpogonial 150-250 (300)µm in diameter. Tetra/bisporangial conceptacles: uniporate (C), more or less immersed, visible only as diffused pin points pores on surface, frequent presence of a columella (C); 210-375µm in diameter x 250µm high. Phenology: April and from August-September till November.

Habitat: occurring in sites with very different environmental conditions: on rocks exposed to waves action, as a rodholith, sometimes recorded on pebbles, always submerged. Generally situated under “trottoir a vermetidi”, as in Laminaria zone. Bathymetric distribution: midlittoral to sublittoral. Geographic distribution (Babbini & Bressan 1997):

Alboran Sea (A): Spain, Morocco; Western Mediterranean Sea (African shores) (B): Algeria; 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, Albania; South Eastern Mediterranean Sea (H): Italy, Malta, Tunisia, Libya; Middle Eastern Mediterranean Sea (L): Italy, Greece, Turkey, Syria; North Eastern Mediterranean Sea (M): Greece.