Article: Calcifolium (Codiaceae) from the Upper Viséan of Scotland

Two species of the algal genus Calcifolium Shvetzov and Birina occur in two Upper Visean limestones in Ayrshire and Lanarkshire. At the lower horizon, that of the Hurlet Limestone, the characteristic form is C. punctatum Maslov; in the overlying Blackball Limestone, the species is replaced by C. okense Shvetzov and Birina. Both species are easily recognized in thin sections, and the genus appears to be an accurate marker for the P2-E1 stratigraphical interval.