From Carboniferous deposits exposed on the southern slope of the Cantabric mountain chain, 58 rugose coral species are described. The rugose coral fauna of this area is not yet completely known. 32 of the species are new, 13 are unnamed and 12 are identical with or closely related to Upper Middle Carboniferous species from the Moscow and Donetz basins of Russia. These species have a fairly long stratigraphie range and their occurrence is largely conditioned by favourable environment. Hillia is erected as a subgenus of Lithostrotionella. New genera have not been founded, existing genera have been interpreted rather widely. The species recorded belong to the following genera or subgenera: Rotiphyllum, Bradyphyllum, Amplexocarinia, Polycoelia, Sochkineophyllum, Ufimia, Cyathaxonia, Lophophyllidiurn, Stereostylus, Zaphrentites, Duplophyllum?, Euryphyllum, Lithostrotion, Arachnastraea, Clisiophyllum, Dibunophyllum, Koninckophyllum, Corwenia, Pseudozaphrentoides, Bothrophyllum, Lonsdaleia, Lithostrotionella, Hillia, Koninckocarinia, Carcinophyllum, Axolithophyllum, Lonsdaleoides, Amygdalophylloides, Ivanovia. The distribution of the corals in the Carboniferous of Palencia is shown on Tables I to III (p. 108). The age of the formations from which the corals were obtained ranges from the Namurian up into the Westphalian D, as established by goniatite and plant evidence, or from the Bashkirian to the Upper Moscovian on fusulinid evidence.