The new species Cucumis omissus Thulin from Yemen, Oman and Ethiopia is described and illustrated. According to phylogenetic analyses based mainly on nuclear ribosomal ITS sequences and chloroplast trnG sequences, the new species is sister to C. hastatus in Somalia and Ethiopia. A map showing the distributions of both C. omissus and C. hastatus is provided and morphological differences between these two species are pointed out. Cucumis omissus has been confused with C. pustulatus and...