Kindly help me to identify this specimen collected from tropical monsoonal estuary, (2m depth, estuary 5-25 ppt salinity), 2 meter depth, 1.5 to 2 cm length.
It is a species of family Nassariidae, probably Nassarius dorsatus. This species has been occasionally mentioned as Nassa dorsata from Indian estuaries (e.g. http://www.iaees.org/publications/journals/arthropods/articles/2013-2(2)/biodiversity-of-cultivable-molluscan-resources.pdf or http://www.pmbc.go.th/web/webpmbc/ResearchBulletin/full/Bulletin_57_full4.pdf).
Nassarius sufflatus is another species from the Indian Ocean that looks like your specimen.