A full systematic account is given of the Scleractinians collected between the tidal zone and abyssal depths in the Mediterranean (deepest samples from about 2,500 m, fossil) and in the north-eastern Atlantic (deepest samples from about 4,800 m, alive), from the coasts of Europe and Africa to Iceland, the Azores and the Cape Verde Islands. This includes a detailed discussion of their intraspecific variability due both to phenotypic variations and to environmental factors. Some modifications of the conventional classification are suggested. There are 9 new species in a total of 85: Madracis profunda, Caryophyllia foresti, Caryophyllia alberti , Trochocyathus spinosocostatus, Trochocyathus mediterraneus, Deltocyathus conicus , Aulocyathus atlanticus, Balanophyllia thalassae, Leptopsammia chevalieri. The distribution, ecology and biology are discussed for each of the 85 species.