THE SCYPHOMEDUS^E OF THE SOUTHERN -HEMISPHERE. By R. von Lendenfeld, Ph.D. Part I. — Introduction. Animals, which, as in the generative stages of the Scyphomedusse, live in the open sea, can hardly be studied in a small area. It there-fore appears advantageous to extend our investigation from the Australian shores over the whole of the Southern Hemisphere, and we have a good right to do so from Sydney, as the centre of scientific zoological research this side of the equator. Very few other fields of investigation look so promising as this. Although hardly anything is known of the southern Medusae in comparison to their better studied northern relatives, still nearly as many southern species have been described. In some groups there are already more southern than northern species. All families are represented here, while I have discovered a new family on our shores, which has no representative in the Northern Hemisphere. In consequence of the larger area of ocean in this hemisphere the Medusae are, as we might expect from the previous statements, much more numerous in the southern than in the northern seas, although at present there are of course not quite so many known as north of the line. In this paper I shall give descriptions of all known Scypho-medusse from this hemisphere. The description of species observed before will be brief ; on those alone seen by myself I intend to dwell more in detail. The classification of Haeckel will be adopted, and Haeckel's Diagnoses translated. The authors will be cited, and all papers on the species referred to.