IÇI5-] Fauna of the Chilka Lake : Polyzoa. 123 



of the zooecium completely covered by a membranous upper or dorsal wall. They 

 are readily distinguished by the following characters : — 



M. bengalensis forms a slightly foliaceous colony with a faint silvery lustre and 

 is by no means hyaline. The lip of the zooecium bears a pair of very long 

 and slender bifid spines. 



M. hippopus forms an entirely flat colony that is transparent and hyaline; 

 unless the polypides are gorged with food or forming brown bodies, 

 all that is usually visible to the naked eye is a delicate network produced 

 by the armature of the lateral walls of the zooecia; the lip bears no 

 spines. 



Membranipora bengalensis, Stoliczka. 

 1869. Membranipora bengalensis, Stoliczka, Journ. As. Soc. Bengal XXXVIII 



(2), p 55, pl- xii. 

 1907. Membranipora bengalensis , Thornely, Rec. Ind. Mus. I, p. 186, fig. 4. 

 19 11. Membranipora bengalensis, Annandale, Faun. Brit. Ind., Freshw. Sponges, 



etc., p. 175, fig. 33. 



This species has not been found in the Chilka Lake, but is abundant in pools of 

 brackish water in the Gangetic delta, within the limits of which it also occurs in the 

 Salt Lakes near Calcutta. It has also been taken in creeks near Bombay, but 

 Miss Thornely' s record from Mergui is due to the misreading of an almost illegible 

 label. 



Membranipora hippopus, Levinsen. 

 1854. Membranipora lacroixii, Busk, B. M. Cat. Polyzoa II, p. 60, pl. lxix, pl. 



civ, fig. 1. 

 1880. Membranipora lacroixii, Hincks, Brit. Marine Polyzoa, p. 129, pl. xvii, 



figs. 5-8. 

 1909. Membranipora hippopus, Levinsen, Morph. Syst. Studies Cheilost. Polyzoa, 



pp. 144, 146. 

 19 11. Membranipora lacroixii, Annandale, Faun. Brit. Ind., Freshw. Sponges, 



etc., pp. 23, 175. 



There has been considerable confusion about this species, but L,evinsen has 

 given good cause for considering it distinct from the one described by Audouin as 

 Flustra lacroixii. 



The armature of the lateral wall of the zooecium is very slight, consisting of two 

 parallel calcified bands of no great depth, one situated at the base of the wall and the 

 other superficial. The area between them remains membranous. Both margins may 

 be either smooth, irregular or minutely denticulate ; when denticulate they have a 

 beaded appearance. In the numerous specimens I have examined I have failed to 

 find a single ovicell, but in one a "tower-cell" was present. The small triangular 

 abortive zooecia figured by Hincks (op. cit., pl. xxii, fig. 6) occur rarely in Indian 

 examples. The polypides have 12 very long and delicate tentacles. 



