1906.] OF THE THIRD TANGANYIKA KXPEDITIOX. 223 



in all of which there is a skeleton of strongyles. In none of these, 

 however, are there two kinds of strongyles. In S. loincata 

 Weltner, in addition to large strongyles (220-260 ju x 20 /.t) there 

 is a smaller kind of megascleres (124^ X 7yu) with finely gra- 

 nular 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 iew fathoms, Nianikolo 

 Harbour, Lake Tanganyika. 



Spongilla biseriata Weltner. ' 



1895. Spongilla 6zserm^« Weltner, Arch. Naturg. 1895, (1) p. 138. 



1897. Spongilla biseriata Weltner, Deutsch-Ost-Afrika, Bd. iv. 

 Die Coelenteraten una Schv/amme des siissen Wassers Ost- 

 Airikas, p. 6. 



1898. Spongilla biseriata Weltner, Mittheil. naturhist. Mus. 

 Hamburg, x%-. Beiheft, p. 1. 



Dr. Ounnington's collection contains an example of this species 

 from Lake Kyasa. 



The specimen is in the form of a^n irregular clump about 4 cm. 

 in diameter, growing round the stem of a reed. The sponge, 

 which is in spirit, is dirty gi'ey in colour, and is full of pale yellow 

 gemmules. 



An interesting additional fact to record is Dr. Ounnington'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 StuJilmann). 



SPO^fGILLA ROUSSELETII, sp. n. (Plate XYII. 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 18'5ju. 



Gemmtdes spherical, with one or several pore-tubes, v/ith a 

 thick coat of spongin and with gemmule-spicules in form of spined 

 micro-strongyles arranged tangentially in one or two layers. 



Locality. — Above Victoi*ia Falls, Zambesi. (Collected by 

 Mr. C. F. Rousselet, Sept. 13_, 1905.) 



Description. — The new species is represented only by some small 

 fragments of du-ty-white colour. Mr. Rousselet, who kindly 

 entrusted me with the material for description, informed me that 



that the general surface of the spicules is not smooth, but fiue-spined or granular 

 all over, just as in S. hdlimii. There are no amphidi.sk flesh-spicules in the tiny 

 scrap which represents, I believe, the type specimen of Moore's species. S. hoJimii 

 and P. tveltneri 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 tveltneri is a good species or otherwise. 



