Mertensiothuria, Subgenus (Holothuria)
Mertensiothuria leucospilota – synonym of Holothuria leucospilota
Mertensiothuria pervicax – synonym of Holothuria pervicax
Mesothuria murrayi var. parva – synonym of Mesothuria parva
Metriatyla, Subgenus (Holothuria)
Microthele, Subgenus (Holothuria)
Microthele guamensis – synonym of Actinopyga mauritiana
Microthese difficilis – synonym of Holothuria difficilis
Milleria lecanora – synonym of Actinopyga lecanora
Molpadia australis – synonym of Paracaudina australis
Mülleria echinites – synonym of Actinopyga echinites
Mulleria nobilis – synonym of Holothuria nobilis