1906.] OF THE THIRD TANGANYIKA EXPEDITION. 225 



considerably longer and more slender, viz. 314x12 ^; likewise 

 the microstrongyles are longer and thinner, being 80-96 x 4 /x. 



The multiporal condition of the gemmule is found also in 

 Spongilla lacustris var. niuUiforis Carter from British Columbia 

 and the Yellowstone ; at first Carter based a new species {Spongilla 

 ■multiforis) on this character, but later considered the multiporal 

 condition to be only of vai-ietal importance. 



Spongilla? zambesiana, sp. n. (Plate XVII. figs. 6-10.) 



Sponge in form of a thick, nodulated, hard crust or cake with 

 irregular upper surface. 



Skeleton a dense network with very thick main fibres and 

 with secondary fibres. 



Spicules. — Megascleres of two kinds, viz. (1) thick, smooth, 

 slightly curved strongyles (180x24yu), slightly and gradually 

 swollen at the ends, forming the mass of the skeleton ; and (2) a 

 few slender, curved, smooth oxea, 170x7^. Microscleres 

 amphidisk flesh- spicules, with slender stem ending in disks with 

 usually four sharp recurved prongs ; avei"age dimensions : — leng-th 

 33 jjL, diameter of disks 13'5 ^u, thickness of stem in centre 1'6 /i, 

 at the ends 2-8 /i. 



Gemimdes ? 



Locality. — Above Victoria Falls, Zambesi. (Collected by Miss 

 Gibbs ; presented to the British Museum by Prof. A. Dendy.) 



The specimen on which the new species is based is in the form 

 of a thick hard crust, 2"5xl'8 cm. in area and about 8 mm. 

 thick. The rough surface is covered with a closely applied dermal 

 membrane, in which, however, no pores are visible. Thei-e are 

 several oscules 1 mm. in diameter scattered about. 



The great main fibres of the skeleton are visible under a lens. 



Permeating the sponge are several little white Chironomid 

 larvee, each surrounded by a sheath of spongin, which the sponge 

 has secreted in self-protection. The spongin- sheath is crowded 

 Avith the amphidisk flesh-spicules, and often has strongyles partly 

 embedded. Sometimes the sheath encloses a mass of decayed 

 sponge-tissue containing innumerable amphidisks. Some of these 

 chitin-tubes are slightly branched, but they do not resemble true 

 spongin-fibres, and do not seem to be proper to the sponge itself ; 

 but on this point I am not at all certain. 



Affinities. — The hard consistence of the sponge and the pos- 

 session of a dense skeleton constructed of thick smooth stronoyles 

 are characters of Uruguaya rather than of Spongilla ; but in its 

 skeletal arrangement and megascleres the new sponge closely 

 resembles Spongilla nitens Carter ; the latter species, however, 

 has no amphidisks and its strongyles are longer and more 

 slender, being 306 x 20-5 ji. Further, the new species comes 

 near Spongilla loricata Weltner and Spongilla bohmii Hilgend., in 

 both of which there are strongylate megascleres and amphidisk 

 flesh-spicules. 



The new form difiers from all species of Uruguaya in possessing 

 amphidisk flesh-spicules with toothed disks. 



