1871.] MR. HARPER PEASE ON POLYNESIAN LAND-SHELLS. -4-19 I have now little doubt that the figure of the skeleton by Cuvier and the skull which my son-in-law brought from Para, on which I founded A. problemuticiis, belong to A.flaccidus. We have also a skeleton which appears to belong to the same species in the British Museum. 5. Catalogue of the Land-shells inhabiting Polynesia, with Remarks on their Synonymy, Distribution, and Variation, and Descriptions of New Genera and Species. By W. Harper Pease, C.M.Z.S. [Eeceived April 4, 1871.] The geographical limits of Polynesia may be determined from the distribution of its land-shells, as distinctly as by that of its marine mollusca and zoophytes. They characterize it as being a distinct zoological province, separate from the East-Indian. It is not only the largest in extent, but the most isolated in posi-tion of any on the surface of the earth. Stretching over nearly one fourth of the whole circumference of the globe, and from one extreme of the tropics to the other, it is separated by a wide expanse of ocean on three of its sides, north, east, and south, from the nearest pro-vinces. On the extreme west, at the Pelew Islands, it comes into con-tact with the Philippines, and a short distance south, at the Samoas, with the Papuan Islands. I do not propose to enter into a critical examination of the distri-bution and variation of the several genera and species, their relation to those inhabiting the neighbouring provinces and their probable origin, as it would involve the discussion of several collateral ques-tions, such as the origin of the islands, their topography, formation of valleys, &c, which I am not at present prepared to enter on. As to general distribution I note the following facts. In West Polynesia, comprising the Pelews, Ladrones, Caroline, Ralick, and Radack groups, a few East-Indian types have entered, but do not prevail, the Polynesian predominating. Of Helices two species of the large Philippine forms occur, viz. H. pelewana, Pfr., at the Pelews, and H. sowerbyana, Pfr., at Hogoleu. All the others are of Polynesian types. The genus Pitys, so prolific in species throughout all other parts of Polynesia, is not represented by a single species. Partulce occur on all the islands. Of operculated genera the East-Indian Diplommatinacea are re-presented by the genus Palaina at the Pelews, and one species at Ponape ; they extend no further. All the species of Omphalotropis are of the East-Indian type, carinate at the umbilicus, and more or less varied with colours. One species referred to Cyclophorus and one to Cyclostomus, both of doubtful genera, have been found at Proc. Zool. Soc— 1871, No. XXIX.