This supplement lists identified Costellariidae species from Mozambique, along with the description of 10 new species. The type locality of Thala adamsi and Mitra clathrata has been defined. A neotype for Voluta mucronata has been selected and Mitra nigricans Dautzenberg & Bouge, 1923 is renamed Vexillum nigripulchrum. The type locality of Mitra praetexta has been designated. Notes on the natural history of Mozambique are followed by a historical outline of the occurrence of the family Costellariidae.
New taxa: Austromitra mozambiquensis n. sp., Tosapusia kantori n. sp., Vexillum aideni n. sp., Vexillum anapaulae n. sp., Vexillum delstonei n. sp., Vexillum horroi n. sp., Vexillum kedrici n. sp., Vexillum nampulaensis n. sp., Vexillum rodriguesi n. sp., and Vexillum romanii n. sp.
