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Show 1906.] OF THE THIRD TANGANYIKA EXPEDITION. 223 in all of which there is a skeleton of strongyles. In none of these, however, are there two kinds of strongyles. In S. loricata Weltner, in addition to large strongyles (220-260 p x 20 u) there is a smaller kind of megascleres (124 p X 7 p) with finely granular surface and swollen ends; here the very different sizes of the two kinds of spicules will at once serve to distinguish the respective species. Locality.-From stones dredged in a few fathoms, Niamkolo Harbour, Lake Tanganyika. SPONGILLA BISERIATA Weltner. 1895. Spongilla biseriata Weltner, Arch. Naturg. 1895, (1) p. 138. 1897. Spongilla biseriata Weltner, Deutsch-Ost-Afrika, Bd. iv. Die Coelenteraten und Schwamme des siissen Wassers Ost- Afrikas, p. 6. 1898. Spongilla biseriata Weltner, Mittheil. naturhist. Mus. Hamburg, xv. Beiheft, p. 1. Dr. Cunnington's collection contains an example of this species from Lake Nyasa. The specimen is in the form of an irregular clump about 4 cm. in diameter, growing round the stem of a reed. The sponge, which is in spirit, is dirty grey in colour, and is full of pale yellow gemmules. A n interesting additional fact to record is Dr. Cunnington's observation that the colour of this specimen was bright green when alive. The large dry type specimen from Cairo is described by Dr. Weltner as dirty white. Localities.-From swamp, Karonga, Lake Nyasa, 2/7/04 (Cunnington). From a pool at Cairo (Inez and Stuhlmann). SPONGILLA ROUSSELETII, sp. n. (Plate XVII. figs. 1-5.) Sponge in form of a whitish incrustation. Skeleton a network with longitudinal main and tranverse and oblique secondary fibres formed of bundles of oxeas with very little spongin. Spicules curved oxeas, 214 x 18*5^. Gemmules spherical, with one or several pore-tubes, with a thick coat of spongin and with gemmule-spicules in form of spined micro-strongyles arranged tangentially in one or two layers. Locality.-Above Victoria Falls, Zambesi. (Collected by Mr. C. F. Rousselet, Sept. 13, 1905.) Description.-The new species is represented only by some small fragments of dirty-white colour. Mr. Rousselet, who kindly entrusted m e with the material for description, informed m e that that the general surface of the spicules is not smooth, but fine-spined or granular all over, just as in S. bohmii. There are no amphidi.sk flesh-spicules in the tiny scrap which represents, I believe, the type specimen of Moore's species. S. bohmii and P. weltneri both come from the same region, the former from the Ugalla River, a tributary of Tanganyika, and the latter from the lake itself. It would be well, however, to wait till more material is available for examination before deciding whether Potamolepis weltneri is a good species or otherwise. |