The history of the Waitotaran and Nukumaruan Stages (including the Waipipian and Mangapanian, Hautawan and Marahauan Substages) is described, The difficulty of applying the Lower Nukumaruan (Hautawan) substage concept is illustrated with reference to sections in the Wanganui and Te Aute Subdivisions, The origin of the term “lower Nukumaruan”, which was first applied to theChlamys delicatulabeds of Tahoraiti Survey District, southern part of Dannevirke Subdivision, is then examined more closely. Utilising evolutionary stages ofPhialopectenandPelicariafor correlating the Taohoraiti sequence with those in the Te Aute Subdivision and on the Wanganui coast, the type locality of the Waitotaran and Nukumaruan Stages, the writer concludes that the so-called Lower Nukumaruan beds of Tahoraiti are largely Upper Waitotaran beds that happen to containChlamys delicatulaand associated species, whose distribution is inferred to have been climatically controlled and geographically limited to regions under the influence of subantarctic waters.