Macellicephala paucidentata – synonym of Diplaconotum paucidentatum
Macellicephala paucidentata Eliason, 1962 – synonym of Diplaconotum paucidentatum
Macrochaeta bansei Hartmann-Schröder, 1974 – synonym of Macrochaeta bansei
Macrochaeta clavicornis McIntosh, 1923 – synonym of Macrochaeta clavicornis
Macrochaeta helgolandica Friedrich, 1937 – synonym of Macrochaeta helgolandica
Macrochaeta polyonyx Eliason, 1962 – synonym of Macrochaeta polyonyx
Maea mirabilis – synonym of Magelona mirabilis
Maea mirabilis Johnston, 1865 – synonym of Magelona mirabilis
Magalia perarmata – synonym of Syllidia armata
Magalia perarmata McIntosh, 1908 – synonym of Syllidia armata
Magelona alleni Wilson, 1958 – synonym of Magelona alleni
Magelona filiformis Wilson, 1959 – synonym of Magelona filiformis
Magelona minuta Eliason, 1962 – synonym of Magelona minuta
Magelona mirabilis Kirkegaard, 1992 – synonym of Magelona mirabilis
Magelone papillicornis – synonym of Magelona mirabilis
Magelone papillicornis (non Müller) Auctt. – synonym of Magelona mirabilis
Malacoceros fuliginosus Hartmann-Schröder, 1971 – synonym of Malacoceros fuliginosus
Malacoceros tetracerus Hartmann-Schröder, 1971 – synonym of Malacoceros tetracerus
Malacoceros vulgaris Hartmann-Schröder, 1971 – synonym of Malacoceros vulgaris
Maldane arctica Detinova, 1985 – synonym of Maldane arctica
Maldane biceps – synonym of Chirimia biceps
Maldane biceps Michaelsen, 1896 – synonym of Chirimia biceps
Maldane sarsi Malmgren, 1865 – synonym of Maldane sarsi
Maldane? cincta Saint-Joseph, 1894 – synonym of Clymenella cincta
Malmgrenia alba – synonym of Malmgrenia arenicolae
Malmgrenia alba Augener, 1928 – synonym of Malmgrenia arenicolae
Malmgrenia andreapolis McIntosh, 1874 – synonym of Malmgrenia andreapolis
Malmgrenia castanea McIntosh, 1876 – synonym of Malmgrenia castanea
Malmgrenia furcosetosa Loshamn, 1981 – synonym of Malmgrenia furcosetosa
Malmgrenia lunulata Pettibone, 1953 – synonym of Malmgrenia lunulata
Malmgrenia marphysae Chambers & Muir, 1997 – synonym of Malmgrenia marphysae
Malmgrenia mcintoshi Chambers & Muir, 1997 – synonym of Malmgrenia mcintoshi
Malmgreniella andreapolis – synonym of Malmgrenia andreapolis
Malmgreniella andreapolis Pettibone, 1993 – synonym of Malmgrenia andreapolis
Malmgreniella arenicolae – synonym of Malmgrenia arenicolae
Malmgreniella arenicolae Pettibone, 1993 – synonym of Malmgrenia arenicolae
Malmgreniella castanea – synonym of Malmgrenia castanea
Malmgreniella castanea Pettibone, 1993 – synonym of Malmgrenia castanea
Malmgreniella lunulata – synonym of Malmgrenia lunulata
Malmgreniella lunulata Pettibone, 1993 – synonym of Malmgrenia lunulata
Malmgreniella marphysae – synonym of Malmgrenia marphysae
Malmgreniella marphysae Pettibone, 1993 – synonym of Malmgrenia marphysae
Malmgreniella mcintoshi – synonym of Malmgrenia mcintoshi
Malmgreniella mcintoshi Pettibone, 1993 – synonym of Malmgrenia mcintoshi
Manayunkia aestuarina Fauvel, 1927 – synonym of Manayunkia aestuarina
Manayunkia aestuarinus – synonym of Manayunkia aestuarina
Manayunkia aestuarinus McIntosh, 1923 – synonym of Manayunkia aestuarina
Marenzelleria viridis Maciolek, 1984 – synonym of Marenzelleria viridis
Marenzelleria wireni Augener, 1913 – synonym of Marenzelleria wireni
Marphysa sanguinea Fauvel, 1923 – synonym of Marphysa sanguinea
Mediomastus fragilis Rasmussen, 1973 – synonym of Mediomastus fragilis
Meganerilla swedmarki Boaden, 1961 – synonym of Meganerilla swedmarki
Melinella macduffi – synonym of Axionice maculata
Melinella macduffi McIntosh, 1914 – synonym of Axionice maculata
Melinna cristata Hessle, 1917 – synonym of Melinna cristata
Melinna elisabethae McIntosh, 1914 – synonym of Melinna elisabethae
Mercierella enigmatica – synonym of Ficopomatus enigmaticus
Mercierella enigmatica Fauvel, 1923 – synonym of Ficopomatus enigmaticus
Microclymene acirrata Arwidsson, 1906 – synonym of Microclymene acirrata
Microphthalmus aberrans Eliason, 1920 – synonym of Microphthalmus aberrans
Microphthalmus bifurcatus Hartmann-Schröder, 1974 – synonym of Microphthalmus bifurcatus
Microphthalmus fragilis Bobretzky, 1870 – synonym of Microphthalmus fragilis
Microphthalmus listensis Westheide, 1967 – synonym of Microphthalmus listensis
Microphthalmus sczelkowii Mecznikow, 1865 – synonym of Microphthalmus sczelkowii
Microphthalmus sczelkowii var. cantabrica – synonym of Microphthalmus aberrans
Microphthalmus sczelkowii var. cantabrica Augener, 1940 – synonym of Microphthalmus aberrans
Microphthalmus similis – synonym of Microphthalmus aberrans
Microphthalmus similis (non Bobretzky) Banse, 1959 – synonym of Microphthalmus aberrans
Microphthalmus similis Bobretzky, 1870 – synonym of Microphthalmus similis
Microsamytha ryckiana – synonym of Alkmaria romijni
Microsamytha ryckiana Augener, 1928 – synonym of Alkmaria romijni
Microserpula inflata – synonym of Chitinopoma serrula
Microserpula inflataThorson, 1946 – synonym of Chitinopoma serrula
Microspio arctica – synonym of Spio goniocephala
Microspio arctica Söderström, 1920 part – synonym of Spio goniocephala
Microspio atlantica – synonym of Microspio mecznikowianus
Microspio atlantica Hannerz, 1956 – synonym of Microspio mecznikowianus
Microspio mecznikowianus Söderström, 1920 – synonym of Microspio mecznikowianus
Mugga wahrbergi Eliason, 1955 – synonym of Mugga wahrbergi
Myriochele danielsseni Hansen, 1879 – synonym of Myriochele danielsseni
Myriochele oculata Zachs, 1922 – synonym of Myriochele oculata
Mysta barbata – synonym of Eteone barbata
Mysta barbata Malmgren, 1865 – synonym of Eteone barbata
Mysta papillifera – synonym of Eteone barbata
Mysta papillifera Théel, 1879 – synonym of Eteone barbata
Mysta picta – synonym of Eteone picta
Mysta picta Wilson, 1988 – synonym of Eteone picta
Mystides augeneri – synonym of Hesionura elongata
Mystides augeneri Friedrich, 1937 – synonym of Hesionura elongata
Mystides bidentata – synonym of Eulalia mustela
Mystides bidentata sensu Southern, 1914; non Langerhans, 1880 – synonym of Eulalia mustela
Mystides borealis – synonym of Mystides caeca
Mystides borealis Southern, 1914 – synonym of Mystides caeca
Mystides caeca Langerhans, 1880 – synonym of Mystides caeca
Mystides elongata – synonym of Hesionura elongata
Mystides elongata Southern, 1914 – synonym of Hesionura elongata
Mystides limbata – synonym of Pseudomystides limbata
Mystides limbata Saint-Joseph, 1888 – synonym of Pseudomystides limbata
Mystides lizziae – synonym of Paranaitis kosteriensis
Mystides lizziae McIntosh, 1908 – synonym of Paranaitis kosteriensis
Mystides southerni Banse, 1954 – synonym of Mystides southerni
Myxicola infundibulum Fauvel, 1927 – synonym of Myxicola infundibulum