54 Contributions to Indian Malacology. [No. 1, 



been shewn to inhabit the estuaries of India or Burma. Our estuary- 

 lists have hitherto been almost as imperfect as our catalogues of marine 

 species ; almost all that is known of the molluscan inhabitants of our 

 deltas being due to the labours of Mr. Benson, who has described many 

 of the forms found in the Ganges. 



It is, of course, highly improbable that the present list is nearly 

 complete. Only a very small portion of the Irawadi delta was ex- 

 amined, and that imperfectly. Still the number of species is consider- 

 able, and probably includes all those which are most abundant. A few 

 forms since found by Mr. Theobald and Mr. Fedden will be noted in 

 their place. 



The classification employed is mainly that of Messrs. H. and A. 

 Adams, in the Genera of Recent Mollusca. I have not, however, fol- 

 lowed those authors in employing the obscure and forgotten generic 

 terms of Klein, Montfort and others I have only deviated from their 

 arrangement in one essential particular, viz., the transfer of Assiminia 

 from the vicinity of Helix, from which it differs in every point of 

 structure, to that of Littorina, to which it is closely allied. If it be 

 objected that Assiminia is as closely related to Cyclostoma as it is to 

 Littorina, I can only suggest that Cyclostoma be also relegated to the 

 same position in the neighbourhood of Littorina. 



Class GASTEROPODA, 



Sub-class Pbosobranchiata. 

 Family BTJCCINIDvE. 

 No. 1, !N"assa planicostata, A. Adams. 



Estuary of the Bassein river, creeping upon mud between tideinarks. 

 Scarce. 

 No. 2, Purpura bitubercularis, Lam. 



Not common. Found in the lower part of the delta, with the nest 

 species. 



Family MITRID^E. 

 No. 3, Colunibella Ducloziana, Sow. 



Found in abundance at one spot in the estuary of the Bassein river, 

 amongst stones with mud. The specimens were unusually fine. I 

 also met with this shell on the mud flats of Ramri Island, coast of 

 Arakan. 



