A collection of terrestrial and freshwater snails from the Late Eocene to earliest Early Oligocene Zalumah Formation at Wadi Darbat, near Salalah, Oman is of importance on account of its taxonomic composition, its palaeoecological indications and its biogeographic affinities which are clearly tropical African; these are very different from the extant non-marine snail fauna of Oman which is typical of the Mediterranean belt. In addition, these fossil snails are by far the oldest-known representatives of their respective genera. The Late Eocene Zalumah deposits which yielded the molluscs accumulated just above sea level, as revealed by the admixture of marine, brackish water and freshwater taxa as well as fully terrestrial gastropods. These deposits now vary in altitude from near sea level at Taqah (Wadi Darbat) to over 930 m at Thaytiniti. Uplift of the Dhofar Plateau therefore must have occurred later than the Early Oligocene. The biogeographic affinities of the snails confirms that the Arabian Peninsula was part of the African continent at the time of deposition and that the opening of the Red Sea and the Gulf of Aden occurred later than the Early Oligocene.