Twenty-seven species of galeommatid bivalves from six genera have been collected at intertidal reef flats near Phuket Marine Biological Center, Thailand (Andaman Sea, Indian Ocean). Fourteen of the species are new to science and a new genus (Nudiscintilla gen. nov.) has been established. The species are defined by full morphological descriptions, drawings of shells and soft parts, and photographs of shells, and for some of them, the live animals. The known geographical distribution and habitat of each species is also given. While one species is probably commensal with a thallasinidean crustacean, the remainder hide under shale, rocks and coral blocks, often in small intra- or interspecific family flocks. The behaviour was also noted for some of the species. It is presumed that galeommatid species go through a lengthy planktonic phase.