ANTITHAMNION AMPHIGENEUM (CERAMIALES, RHODOPHYTA) FROM THE EUROPEAN ATLANTIC COASTS

For the first time a subtidal population of Antithamnion amphigeneum A . Millar has been found in the Atlantic (Basque coast, northern Spain) . Outside of its area of origin (eastern Australia), only three previo us records, all of unfertile material (described as Antithamnion alger iense M. Verlaque er Seridi) and collected in the western Mediterranea n Sea, have been reported. Details of the tetrasporangial structures, morphology, ecology and geographical distribution of this uncommon spe cies are given.