oblique cockle (Acrosterigma cygnorum)
oblique nutlet-shell (Ennucula obliqua)
oblique sinistral-creeper (Inella obliqua)
oblong olive (Amalda oblonga)
obtuse olive (Amalda obtusa)
obtuse urchin-snail (Curveulima obtusa)
ochraceous margin-shell (Alaginella ochracea)
octona top-shell (Leiopyrga octona)
octopleuron tusk-shell (Dentalium octopleuron)
oily top-shell (Archiminolia oleacea)
olivaceous false rice-shell (Pisinna olivacea)
olive margin-shell (Mesoginella olivella)
omicron keyhole-limpet (Amblychilepas omicron)
open fossarina (Fossarina patula)
opulent creeper (Glyptozaria opulenta)
orange-edged limpet (Cellana solida)
orange-red pyramid-shell (Syrnola aurantiaca)
oriental file-shell (Limaria orientalis)
ornate false-turrid (Filodrillia ornata)
ornate sea-slug (Austraeolis ornata)
ornate slit-shell (Scissurella ornata)
orthopleura urchin-snail (Melanella orthopleura)
orukta chiton (Rhyssoplax orukta)
oval trough-shell (Mactra antecedens)
ovate lepton (Lepton ovatum)
ovate lepton (Mysella ovata)
overlooked margin-shell (Austroginella praetermissa)