Fifteen new species of calcareous nannofossils of probable stratigraphic significance are described. Cyclococcolithus macintyrei, Discoaster neohamatus, D. quintatus, Helicopontosphaera sellii, Micrantholithus procerus, Sphenolithus anarrhopus, S. neoabies, Thoracosphaera prolata, Triquetrorhabdulus inversus are abundant with wide geographic ranges. Their usefulness in developing worldwide zonations has been evident during preliminary studies of Deep Sea Drilling Project cores; naming the taxa, therefore, is important. Helicopontosphaera papillata, Leptodiscus larvalis, Pemma snavelyi, Quinquerhabdus colossicus, Syracosphaera formosa, S. labrosa, presently known from restricted regions or forming a minor part of worldwide assemblages, also may prove useful because they are easily identified and seem to have restricted time ranges.