- macro-oligogyral
- macula
- male
- mangrove
- mantle
- mantle cavity
- mantle gland
- marine
- maritime
- maximum width
- medial
- median footlobe
- median lip depression
- median tubercle
- Mediterranean
- meiosis
- membrane
- meroplankton
- mesoderm
- mesopelagic
- mesoplankton
- Mesozoic
- metabolism
- metamorphosis
- MHNP
- micro-oligogyra
- micropaleontology
- microplankton
- migration
- minute stage
- Miocene
- mitosis
- MOM
- monograph
- monogyra
- monophyletic
- monospecific
- monotypic
- morpha
- morphology
- morphometric
- mouth
- muciparous
- mucus feeder
- mud
- MY