Identification of fifty photographs is a lot to ask. I would be much more inclined to try to help if you had tried to provide your own identifications first. That way, you would learn a lot more from the identifications given freely by experts than simply receiving a list of names. Also a scale bar and locality data would be useful.
I understood that your point. I have herewith attached the list of tentative identification for the specimens. Most of them were juveniles and less than 15 mm in size. These were found from shallow water depths with the bottom sediments from coastal areas (marine) of Sri Lanka. I hope that would be difficult to identify and give positive identifications for these juvenile mollusc by using photographs which lack much more details like hinge details , but I hope it won't be too difficult for you as you are an expert on this field. Thank you very much for your response.