ABSTRACTUltrastructural examination of the brachiopod Thecidellina from three different locations in the Caribbean and the Atlantic revealed that at least three cryptic species are present. One is the type species of the genus, Thecidellina barretti, which may only occur in Jamaica. The other two, previously lumped into T. barretti, are new to science, viz T. bahamiensis Lüter & Logan sp. nov. from the Bahamas and T. williamsi Lüter & Logan sp. nov. from Cape Verde. All three species clearly differ not only in their provenance, but also in specific shell characters, such as spiculation of the ventral valve, presence of a ventral median ridge, shape of two holes in the intrabrachial ridge of the dorsal valve and the structure of the interbrachial lobes. The identification of three instead of a single species and their supposed allopatric speciation is discussed with regard to the thecideide life cycle and independent models of larval dispersal in the Caribbean, based on oceanographic data.