Four species of Thalassema are currently known from southern Africa of which T. jenniferae is here described as new to science. T. diaphanes and T. philostracum are redescribed and figured. The discovery of T. diaphanes from the Natal coast marks an extension of its geographic range. T. thalassemum is briefly diagnosed but material of this species was not available. The taxonomie positions of two specimens of Thalassema, examined from the University of Cape Town collection, remain to be resolved. Adequate descriptions of both these specimens were not possible as the internal organs were badly damaged. A key for the identification of all the species in the genus is provided and the distribution of the southern African forms is discussed