Amphiblestrum Gray, 1848 (Bryozoa Cheilostomatida) from the Atlantic-Mediterranean area,with description of a new species

Several species, belonging to the genus Amphiblestrum Gray from the Atlantic-Mediterranean area are discussed. One species is described as new: A. frigidum sp. n., from Lower Pleistocene sediments of the Mediterranean area and from the Recent Northern Atlantic. Systematic affinities among species are discussed together with geographical, ecological and stratigraphical distributions. The climatic-palaeoclimatic significance of some species is stressed: A. lyrulatum and the fossil A. spaeleus and A. intermedius seem to be warm-temperate species whereas all the others are cool, boreal or boreal-arctic species. A. flemingi and A. frigidum sp. n., both Recent Northern Atlantic species known from Würmian submerged sediments and/or Lower Pleistocene outcrops of the Mediterranean area are considered as Boreal Guests.