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Show 1906.] OF THE THIRD TANGANYIKA EXPEDITION. 221 Moliro, 24/10/09 ; No. 161, from rocks, shallow water, Chamkaluki, 15/11/04 (gemmules plentiful); No. 173, from shells, dredged in 10 fins., Pembe, 23/11/04 ; No. 593, 10 fins., Mtondwe Bay. SPONGILLA TANGANYIKA Evans. (Plate XV. fig. 10.) 1899. Spongilla tanganyikce Evans, Quart. Journ. Micr. Sci. vol. xii. p. 481, pi. xxxviii. figs. 9, 10. There are several small specimens, whole and in fragments, of this species in Dr. Cunnington's Collection. Two of the specimens (Nos. 163 and 224) are associated with Polyzoa, and although there are, in each case, only a few crumbling fragments, they are interesting, because in some respects they show an intermediate condition between >$'. moorei and the present species. The inegascleres are spined as in S. tanganyikce, but more nearly resemble the form of those of >S'. moorei. There are no stron-gyles, for instance, their place being taken by spined tornotes. Plate X V . fig. 10 shows a tornote on the way to becoming a strongyle; the sharp point of the oxea still persists, though it has nearly disappeared ; its complete disappearance would result in the strongylate form. On account of the spined condition of the spicules I have classed the specimens under S. tanganyikce. The remaining specimens are in the form of small incrustations on broken fragments of the shells of the Gasteropod Neothanma tanganyicensis together with incrustations of S. moorei. Specimens of these two species so closely resemble each other externally that it is only possible to separate them by an examination of the spicules. The surface is uniformly level and finely granulated, the granular appearance being due here, as in S. moorei, to the minute projecting tufts of the main longitudinal spicule-bundles. The tufts only project the length of a spicule, and differ slightly from those of S. moorei in being composed of only 1-3 in place of 2-5 spicules, and in the spicules being adherent to each other along their whole length. As in S. moorei there is a basal spongin-lamella, but it is very thin, nor are the spongin-fibres arising from it developed to the same extent as in the first species; at the same time, there are here also distinct spongin-fibres enclosing a core of spicules. There are no gemmules in any of Dr. Cunnington's specimens. Those described by Evans in the type had only a thin chitinous capsule, and were apparently very like those of AS'. moorei. Localities.-Lake Tanganyika, No. 163, associated with a Polyzoan, from rocks, shallow water, Chamkaluki, 16/11/04; No. 224, with Polyzoan, on shells, 20 fms., Mshale, 6/2/05; No. 593, dredged in 10 fms., Mtondwe Bay. SPONGILLA CUNNINGTONI, sp. n. (Plate XVI. figs. 1-6.) Sponge in form of a thin spreading crust. Surface smooth and devoid of projecting spicules. Skeleton a network with triangular and polygonal meshes, without distinct main and secondary fibres ; dermal skeleton composed of a definite layer of horizontally |