XV. SOME GASTROPOD MOLLUSCS FROM 

 THE GANGETIC DELTA. 



By N. ANNANDAI.E, D.Sc, F.A.S.B., Director, Zoological Survey 



of India, and B. Prashad, D.Sc, Superintendent of Fisheries, 



Bengal, Bihar and Orissa. 



(With Plate XX). 



The molluscs described or discussed in this paper live in the 

 waterways of the Gangetic Delta or lead an amphibious existence 

 on their shores. A large proportion of the species that do so in the 

 delta have already been described by Benson, Stoliczka, Blanford 

 or Nevill, or by more than one of these authors, to all of whom we 

 owe invaluable information about the brackish- water fauna of the 

 Indian estuaries It is much to be regretted that Nevill did not 

 live to complete his Hand List of the Molluscs in the Indian 

 Museum, in which work almost alone exact data as to localities 

 are to be found. We hope later to discuss the invertebrate 

 fauna of the lower part of the delta as a whole ; for the present we 

 will consider only those Gastropods about which we have some- 

 thing new to say from a strictly taxonomic point of view. 



We have figured the radular teeth of most of the species dis- 

 cussed, but it has seemed to us unnecessary to give elaborate 

 descriptions of these teeth. Our figures, if they are as correct as 

 we believe them to be, should prove much clearer than any 

 written description. We have to thank Babu D, N. Bagchi for the 

 accuracy with which he has drawn the figures under our super- 

 vision. The figures of the shells have been prepared with equal 

 care by Babu A. C. Chowdhury. 



We have also to thank Mr. T. Southwell, Director of Fisheries, 

 Bengal, Bihar and Orissa, for the facilities that he has given us in 

 collecting specimens. The majority of those on which we base 

 the following notes were collected by Mr. S. W. Kemp and our- 

 selves on a recent trip from Calcutta to Khulna on board the 

 Bengal Fishery launch " Kitty." 



Family NERITIDAE. 

 Genus Dostia, Gray. 



i8^n. Dostia, Gray, Syn. Contents Brit. Mus. 



1879. Neritaeae Mitrulae, von Martens, Neretina in Chemitz's Conch. 



Cab., pp. 16, 37. 

 1915. Septaria, Preston, Faun. Bvii. Ind., Freshivater Moll., p. 6 (in 



part). 



