This chapter reports recent malacological research on Chetumal Bay, and particularly on the data from Oxtankah, Quintana Roo. The author collected species present in Chetumal Bay and compared these with archaeological collections from a series of excavations around Oxtankah. He notes that relatively few species are found in the muddy bay bottom itself and, while these were exploited for food, most of the broad range of species identified from archaeological remains stemmed from the Caribbean. A few Pacific species, obvious imports at Oxtankah, are also represented in the collections. Technological use wear studies of tool scars on worked shell objects and replication analysis of worked shells documents shell manufacturing techniques used at the site.