This partial revision of the genus Micromyrtus Benth., deals mainly with species that have a ten-ribbed hypanthium, but excludes the M. racemosa complex. All of the new species are endemic to the south-west of Western Australia. Eight taxa are named: M. acuta Rye, M. chrysodema Rye, M. clavata J.W. Green ex Rye, M. elobata subsp. scopula Rye, M. placoides Rye, M. navicularis Rye, M. redita Rye and M. triptycha Rye. A key is given for Western Australian members of the genus. Micromyrtus is compared with its close relative Corynanthera J.W. Green, and the morphological specialisations of both genera and their possible affinities to other genera in tribe Chamelaucieae are discussed. The compressed winged diaspore of Corynanthera, which has the peduncle fused to both the bracteoles and fruit, is of particular interest, and an illustration compares it with diaspores from five- and ten-ribbed species of Micromyrtus.