IÇI5-] Fauna of the Chilka Lake : Polyzoa. 127 



hood of Port Canning in the Gangetic delta (where it is abundant with Victorella 

 bengalensis in pools of brackish water) and at Rambha on the Chilka Lake. We did 

 not find it in the lake itself, but in March, 1909, it was growing luxuriantly on water- 

 plants of the genus Nais in pools of slightly brackish water near the shore. These 

 pools have now become quite fresh, probably owing to the action of floods, and the 

 Polyzoon has disappeared from them . Bowerbankia caudata , though it shares with 

 other members of its genus the capacity of living in brackish water, is essentially a 

 marine species and can only have reached the pools via the lake, in which its 

 apparent non-occurrence is therefore somewhat remarkable. 



Division ALCYON ELLE A. 



Family Ai<cyonidiidae. 



Genus ALCYONIDIUM, Lamouroux. 



Alcyonidium mytili t Dalyell. 



1880. Alcyonidium mytili, Hincks, Brit. Marine Polyzoa, p. 498, pi. lxx, figs. 



2,3- 

 1905. Alcyonidium mytili, Thornely in Herdman's Ceylon Pearl Fisheries IV, 



p. 127. 



Specimens from the Chilka Lake agree well with Hincks' s figures. The poly- 

 pides have as a rule 12 to 14 tentacles ; Hincks says 15 to 18. 



We found the species fairly common on shells of Potamides (Tympanotonos) 

 fluviatilis at Satpara both in the fresh- and the salt-water season, and on those of 

 Purpura (Thais) carinifera near the south end of the lake at all times of the year. 

 So far as we could see it was always attached to shells that contained either hermit- 

 crabs or their own proper inhabitants. Mr. T. Southwell recently captured at Dia- 

 mond Harbour in the Hughli estuary a sea-snake (Enhydrina valakadien) to the skin 

 of which numerous small circular colonies of this Polyzoon were attached. It would 

 seem, therefore, that in the conditions prevalent in the Chilka Lake and in Indian 

 estuaries it is advantageous for the organism to be attached to animals possessing 

 the power of progression ; but in Europe A . mytili has been found — as its name indi- 

 cates—associated with sedentary molluscs, and also on algae, stones, etc. 



The species is cosmopolitan. 



ENTOPROCTA. 



Family Urnateujdae. 

 1856. Urnatellidae, Allman, Mon. Freshwater Polyzoa, p. 117. 



The family may be defined as follows : — 



Deciduous colonial Entoprocta of fresh or brackish water that produce resting 

 buds either by segmentation of the stalk or by the degeneration of a capi- 

 tulum; that have a vertical or sloping lophophore with a well-developed 

 web-like sphincter at its base, distinct tentacular retractors, a well-defined 

 cloaca and a distinct water- vascular system. 



