Two recently discovered late Cenozoic faunas from the western Turkana Basin. north Kenya, have yielded a gastropod clearly referable to Potadoma (Swainson), a genus hitherto known only from west and central Africa. This first record of Potadoma from eastern Africa is of interest in demonstrating a drastic recent reduction of the range of the genus, particularly as the Turkana material has strong affinities with a sub-group of Potadoma known only at present from a restricted area of Cameroun, some 1800 miles to the west. The recent reduction in the range of Potadoma offers some interesting parallels with the late Cenozoic reduction in range of the mutelid bivalve Pleiodon, which also has a west and central African distribution at present, but which was also widely distributed in eastern Africa until recently. This record of Potadoma from the western Turkana basin may also provide useful paleoecological information regarding the important hominid-bearing deposits of the area.