32 Memoirs of the Indian Museum. [Voi,. V, 



various kinds, but this is not so commonly the case in the Chilka Lake as in some 

 other localities. We found in them, however, at least two species of Nematode worms 

 (Dorylaimus sp. and Oncholaimus chilkensis, Stewart 1 ) as well as Polychacta of the 

 family Nereidae. Molluscs of the genus Modiola are often overwhelmed by the 

 growth of the sponge, but we did not find in sponges from the lake the shells of 

 Corbula a so common in those from the ponds at Port Canning. 



One of the most striking illustrations of admixture of marine and freshwater 

 fauna that the lake provides is the occurrence on the same rocks, and often even 

 intermingled, of Spongilla alba and a sponge of the marine family Suberitidae 

 (Laxosuberites lacustris, p. 49 postea). When they come in contact the Spongillid, 

 being the more vigorous species of the two, usually overwhelms the other. 



Spongilla nana, sp. nov. 

 (Plate iv, fig. 3.) 



The sponge forms spherical or cushion-shaped masses that do not exceed and 

 indeed rarely reach 5 mm. in diameter. The colour (in life as in spirit) is pale 

 yellowish or buff. The whole structure is extremely fragile. There is as a rule a 

 single osculum and in some specimens a cylindrical central cavity can be detected, 

 extending downwards almost to the base of the sponge (pi. iv, fig 3). The sub- 

 dermal cavity is ample and the general arrangement of the canals and apertures 

 resembles that found in Spongilla alba. There is little or no horny matter at the 

 base of the sponge, which is attached lightly to its support. 



The skeleton has a distinctly radial arrangement, but contains very little horny 

 matter. The radial spicule-fibres are distinct but slender and feebly coherent. They 

 can frequently be traced from a point near the centre of the sponge to its surface, 

 where they project as spines. The transverse fibres are, however, imperfectly 

 differentiated and in many places represented merely by an irregular network of 

 single spicules. No distinct subsidiary skeleton can be detected. 



The spicules in many respects resemble those of 5. alba, but are as a rule more 

 attenuated and irregular. The macroscleres in particular are remarkable in the 

 latter respect. Some are sparsely and minutely spiny, but their irregularity of 

 outline, the precise nature of which is best indicated by a figure (fig. 3, p. 31), is often 

 of a more general nature. The spicules of this type are sharply pointed at both ends 

 and as a rule slightly and regularly curved. 



The gemmtile-spicules are slender and also exhibit a slight and regular curvature. 

 As a rule they are distinctly mucronate at both extremities, but sometimes one 

 end is blunt. They bear short, straight, sharp spines, which are fairly numerous at 

 and near the extremities and sometimes a little retroverted in this region. The 

 middle of the shaft is often bare or has only a few isolated spines. 



1 Rec. Ind. Mus. X, pp. 245, 247 (1914). 



* See Preston, Ann. Mag. Nat. Hist. (7) XIX, p. 215 (1907) and Antiandale, Faun. Brit. Ind., 

 Freshw. Sponges, etc., p. 78 (191 1). 



