benthic facies present an unsolved ecological problem. Faunally they are more closely related to the generally finer textured massive and sparsely fossiliferous beds (Cl 6, etc.) than to coarser textured littoral shellbeds composed of thanatocoenotic elements. The highest bed on the coast, Cu 8, disappears under a mantle of blown sands at Castlecliff and is believed to reappear as unfossiliérous siltstone on the north bank of the Wanganui River near Castlecliff wharf. Still higher Castlecliffian beds occur at Putiki and Landguard Bluff on the south bank of the Wanganui, and as these are classic fossil localities, brief descriptions are given of the beds there exposed and their probable stratigraphic relation to the coast section. Conditions of Deposition. The general environmental picture is of relatively frequent repetitions, wholly or in part, of a succession of biotopes. Each succession commences with a shoreline phase of wave cutting, scouring and accumulation of beach deposits, and culminates in quieter, off-shore sedimentation below the local effective wave-base. Occasional gradual reversals of the sequence occurred prior to interruption and repetition of the succession. The controlling force has been the discontinuous diastrophic tilting of a geosynclinal margin, relative to successive base levels which determined the extent of erosion and deposition. Several of the stratigraphic breaks marked by bored or scoured surfaces are at least locally unconformable on the next underlying bedding plane. The angle of unconformity can seldom be seen or measured, but is calculable from the thinning of the underlying bed. Thus Cl 11 appears to thin from 25 feet to 18 feet in less than a mile; Cu 4 and Cu 7 also thin in the same direction* Since vertical measurements in the present work were all made by aueroid baromete, it is difficult to be certain of the differences in thickness involved.. In a few instances (Cl 1, Cu 6) coarsening and faunal changes within a bed up the dip suggest that the present attitude of the beds is merely an exaggeration of the original depositional slope. The increase in dip with age of beds and the observed thinning up the dip of individual beds, with other evidence, point to intermittent cumulative tilting during their depostion. Fossils characteristic of and in some cases confined (in a biocoenotic condition) to a particular zone are not infrequently found derived above the succeeding erosion surface in a bed 50–100 feet stratigraphically higher. Thus, erosion of a deposit along its landward edge occurred shortly after its deposition, while later sediments were accumulating seaward. Tilting occurred about axes close to the Castlecliffian shorelines, which fluctuated back and forth across the Wanganui section. When the axis of tilting lay seaward, negative movement of strand-line allowed wave attack on the landward margin of earlier sediments; when it lay inland, positive movement allowed accumulation of sediment at depths below the profile of equilibrium. The beds at Castlecliff lie on the margins of the Palmerston-Wanganui Basin (see Ongley, 1945, for map), a Pliocene geosynclinal area which subsided and allowed the deposition of over 3,000 feet of Castlecliffian sediment in its deepest parts (Superior Oil Co.,