Menanetia minchini – synonym of Halichondria panicea
Menyllus ingalli – synonym of Iophon hyndmani
Menyllus ingalli – synonym of Iophon nigricans
Menyllus nigricans – synonym of Iophon nigricans
Mesapos stellifera – synonym of Hymeraphia stellifera
Microciona acanthotoxa – synonym of Clathria acanthotoxa
Microciona ambigua – synonym of Plocamionida ambigua
Microciona armata – synonym of Clathria armata
Microciona ascendens – synonym of Clathria ascendens
Microciona atrasanguinea – synonym of Clathria atrasanguinea
Microciona bihamigera – synonym of Phorbas bihamiger
Microciona carnosa – synonym of Phorbas plumosus
Microciona ctenichela – synonym of Clathria ctenichela
Microciona dives – synonym of Phorbas dives
Microciona duplex – synonym of Clathria duplex
Microciona elliptichela – synonym of Clathria elliptichela
Microciona fallax – synonym of Clathria fallax
Microciona fictitia – synonym of Phorbas fictitius
Microciona gradalis – synonym of Clathria gradalis
Microciona jecusculum – synonym of Hymedesmia jecusculum
Microciona macrochela – synonym of Clathria macrochela
Microciona osismica – synonym of Clathria osismica
Microciona plumosa – synonym of Phorbas plumosus
Microciona seriata – synonym of Clathria seriata
Microciona simplicima – synonym of Bubaris vermiculata
Microciona sp. 'A' – synonym of Clathria fallax
Microciona spinarcus – synonym of Clathria spinarca
Microciona spinulenta – synonym of Iophon hyndmani
Microciona strepsitoxa – synonym of Clathria strepsitoxa
Microciona toxitenuis – synonym of Clathria toxitenuis
Microciona tumulosa – synonym of Halichondria panicea
Mycale aegagropila – synonym of Mycale contareni
Mycale armata – synonym of Clathria armata
Mycale contareni – synonym of Mycale contareni
Mycale contareni – synonym of Mycale micracanthoxea
Mycale littoralis – synonym of Mycale minima
Mycale microchaela – synonym of Mycale contareni
Mycale placoides – synonym of Mycale lingua
Mycale subclavata – synonym of Mycale similaris
Myriastra lactea – synonym of Stelletta lactea
Myxilla albula – synonym of Crella albula
Myxilla banyulensis – synonym of Antho involvens
Myxilla barentsi – synonym of Myxilla incrustans
Myxilla exigua – synonym of Crella albula
Myxilla fasciculata – synonym of Phorbas lieberkuehni
Myxilla flabelliformis – synonym of Dendoricella flabelliformis
Myxilla forcipis – synonym of Forcepia forcipis
Myxilla gigas – synonym of Myxilla incrustans
Myxilla involvens – synonym of Antho involvens
Myxilla irregularis – synonym of Phorbas plumosus
Myxilla occulta – synonym of Hymedesmia occulta
Myxilla peachi – synonym of Hymedesmia peachi
Myxilla radiata – synonym of Eurypon radiatum
Myxilla thompsoni – synonym of Esperiopsis fucorum
Myxilla veneta – synonym of Hymedesmia veneta
Myxilla versicolor – synonym of Hymedesmia versicolor