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Show 180 MR. EDGAR A. SMITH ON THE MOLLUSCA [Mar. 6, October, when sexually mature individuals swarmed, though none showed any tendency to form buds*), Dr. Cunnington's carefully collected material, on the other hand, showed that reproduction by budding was continued in August, September, December, and February, and that it might therefore reasonably be supposed that it went on during the greater part of the year-if, indeed, it ever ceased. The discovery of Limnocnida in other river-basins in Africa had materially weakened the case of those who considered that Lake Tanganyika was the last surviving remnant of a Jurassic Sea. The fact that this Medusa had been found in the Victoria Nyanza by M. Ch. Alluaud and Sir Charles Eliot, and also in the Niger by the late Mr. Budgett, proved that it was another instance of a member of the freshwater fauna characteristic of the Central-African Region, and that it wras not peculiar to this one deep-water lake as had been originally supposed. Mr. G. A. Boulenger, F.R.S., V.P.Z.S., read a paper entitled " Fourth Contribution to the Ichthyology of Lake Tanganyika. Report on the Collection of Fishes made by Dr. W . A. Cunnington during the Third Tanganyika Expedition, 1904-05." This paper will be published entire in the ' Transactions.' The following papers were also read :- 1. Zoological Results of the Third Tanganyika Expedition, conducted by Dr. W . A. Cunnington, 1904-1905. Report on the Mollusca. By E D G A R A. SMITH. [Received February 6, 1906.] (Plate X.f) The small collection of Mollusca obtained by Dr. W. A. Cunnino-- ton in Lake Tanganyika does not contain any important addition to the thalassoid series. There are some interesting specimens of Bythoceras iridescens, tending to show that, like most freshwater species, it is subject to considerable variation. In two cases, Edgaria and Giraudia, I have been enabled to describe the opercula, which hitherto were unknown, and the collection also affords one new species of the genus Anceya. The various localities furnished by Dr. Cunnington also add to our knowledge of the distribution of some of the forms. Another matter which may be referred to in these introductory remarks is the occurrence together, at the south end of the lake, of both the keeled and unkeeled varieties of Neothauma tang any icense, which, according * J. E. S. Moore, * Tanganyika Problem,' 1903, pp. 298-308. f For explanation of the Plate, see p. 186. |