papers of the author cited below.* The variation of density and the ellipticities of strata of equal density within the Earth, Monthly Notices Roy. Astron. Soc. Geophysical Suppl., vol. 3, No. 9, pp. 395-401, 1936. The author also considered the question of the variation of gravity within the Earth; the solution of this problem arises out of the density solution, and was the subject of the paper in the Transactions of the Royal Society of New Zealand of September, 1939. Note on the density and pressure inside the Earth, Trans. R.S.N.Z., vol. 07, pp. 122–124, 1937. Composition of the Earth at a depth of 500–700 km., Nature, vol. 142, p. 071, 1938. On recent developments in knowledge of the Earth's interior, Acta Astronomica, ser. c, vol. 14, pp. 17–21, 1939. The Mollusca of Stewart Island. A. W. B. Powell. (Rec. Auck. Inst. and Mus. vol. 2, No. 4, pp. 211–238, 27th Oct., 1939). The paper provides a comprehensive list of the Stewart Island Mollusca, 383 species being recorded, 21 of which are described as new. Five new genera and a new subgenus are proposed. Two external influences affect the fauna—the cold water, west wind drift and, to a lesser extent, the East Australian warm water current. The Subantarctic element in the fauna is strengthened by eight additional records, the most noteworthy being a new species of Kerguelenia. Pollen Grains of New Zealand Trees. Lucy M. Cranwell, M.A., F.L.S. In introducing a detailed account of pollen-grain morphology in the Coniferae and the Fagaceae, the two most important families of wind-pollinated trees in New Zealand, the author summarised the characteristics of wind- and insect-pollinated types, and described the technique of pollen-analysis through which a study of pollen, wind-borne to growing bogs and preserved in their successive layers, made it possible to trace back the history of forests for thousands of years. Pollen grains of Nothofagus, Phyllocladus, Dacrydium, and Podocarpus had been found freely in our peats and lignites by the author, those of Agathis only once, while the preservation of Libocedrus pollen was considered doubtful. Distinct generic types existed, overlap occurring only between Dacrydium and Podocarpus because of the anomalous group created by D. colensoi, intermedium, and laxifolium. Nothofagus pollen was shown to be quite distinct from that of Fagus, and all species investigated from New Zealand, South America, and Australia fell either into the menziesii-moorei-obliqua group, or into the fusca-dombeyi group, the latter at present restricted to New Zealand and South America. There was no proof that Fagus grew in the Southern Hemisphere in Tertiary times. Cranwell, L. M., 1939. Southern-Beech Pollens, Rec. Auck. Inst. Mus., vol. 2, No. 4, pp. 175–196. — (in press). Pollen-grains of the New Zealand Conifers, N.Z. Journ. Sci. Tech.