1922.] Fauna of the Chilka Lake : Observations in Rambha Bay. 699 



thyra blanfordiana Nevill, S. minima (Sowerby) and S. (Astenothyra) miliacea (Nevill). 

 No change in the numbers of these abundant forms, comparative or actual, was 

 observed in April, 1920. 



Pelecypoda. — All the bivalve molluscs taken in Rambha Bay in 191 4 were abun- 

 dant forms. 



The Mytilidae were represented by two closely allied species of Modiola, M. undu- 

 lata (Dunker), which was found attached to algae and other floating objects, and 

 M. striatula Benson, which was taken on stones and other solid fixed objects. Both 

 were extremely abundant, as they still are. Practically every stone at the edge of 

 the bay, if not buried in mud, has several or many individuals of M. striatula 

 fixed to it tightly, while in stormy weather innumerable shells of M. undulata 

 are washed ashore. In suitable situations masses of living individuals are found 

 attached to weeds. There has certainly been no diminution in the numbers of these 

 speeies. M. striatula, an extremely plastic species, is known to be very tolerant of 

 changes in salinity and allied forms are found in freshwater lakes in the centre of China. 



The Veneridae include certain species of the genus Meretrix that are eminently 

 characteristic of estuarine and similar waters and M. casta Chemnitz is abundant in 

 a subfossil condition with Area granosa (Linn.) at several places on the shores of 

 Rambha Bay. The only species of the family found living in the bay in 1914 was, 

 however, one of the genus dementia, which is also characteristic of brackish water 

 but differs from Meretrix in having an extremely delicate shell. This species (C. 

 annandalei Preston) was one of the commonest molluscs all over the main area of 

 the Chilka Lake. In September, 1919, I found many dead shells and a few living in- 

 dividuals, the latter all of small size. In December of the same year only dead 

 shells were found, while in the following April very few even of these were left. 



The Solenidae, a marine family with one freshwater genus, Novaculina Benson, 

 were also represented by a single species, which was identified by Mr. Preston as 

 possibly a form of Solen fonesi Dunker. We, therefore, referred to it as ? Solen fon- 

 esi, being doubtful as to the identification. Dr. Ekendranath Ghosh 1 has recently- 

 shown that it belongs to a new genus and species, which he has called Neosolen aquac- 

 dulcioris. This was another very common mollusc in the bay in 1914, and nearly 

 every haul of our nets brought up, if not complete specimens, at any rate fragments 

 of the very characteristic double siphon, which is segmented and very readily cast 

 off. In the rainy season of 1919 no specimens were obtained ; in December a couple 

 of broken siphons were observed, while in April, 1920, no specimens of any kind were 

 seen. 



Theora opalina (Hinds), belonging to the family Scrobiculariidae, was the most 

 abundant of all the bottom-haunting molluscs of the bay in 1914. It survived m 

 greatly diminished numbers at any rate till April, 1920, when a few small individuals 

 were taken with many dead shells. 



The Cuspidariidae also were represented in 1914 by one abundant species, Cuspi- 



Ghosh, Rec. Ind. Mus. XIX ; p. 57 (1920). 



