Amural arachnophyllid corals from the Silurian of the North Atlantic area

Species previously assigned to Arachnophyllum and related genera from the Silurian of north-west Europe and North America are revised and their phylogeny and biogeography are discussed. Intraspecific variation, particularly in the English sample of Arachnophyllum murchisoni, is described in detail. The genera Arachnophyllum and Prodarwinia are redefined on the basis of redescriptions of their type species, A. murchisoni and P. speciosa. In addition the species A. sinemurum, A. separatum, A. pentagonum, A. striatum, A. pygmaeum, P. striata, P. mamillaris, and P. distans are accepted as senior synonyms and revised. A new species of Prodarwinia is described and comments are made on species of doubtful status. Species removed from this group are assigned to lowaphyllum, ?Zenophila, Radiastraea, and ?Mazaphyllum.