Murchisonia megathanae (FOSSIL) Blodgett & Johnson,1992 †
Hormotoma meryenorfi (FOSSIL) E.F.R.K. Koken, 1897 †
Hormotoma meyendorfi (FOSSIL) E.F.R.K. Koken, 1897 †
Murchisonia micula (FOSSIL) Miller, 1877 †
Murchisonia minerva (FOSSIL) d'Archiac & de Verneuil 1841 †,
Aclisina minima (FOSSIL) (Shumard & Swallow,1858 †)
Hormotoma minnesotensis (FOSSIL) (Ulrich & Scofield,1897 †)
Aclisina minuta (FOSSIL) (Stevens, 1858 †)
Murchisonia minuta (FOSSIL) A.W. Grabau & Sherzer,1910 †
Hormotoma moderata (FOSSIL) Flower, 1968 †
Cyrtostropha monoliniformis (FOSSIL) (Lindström, 1884 †)
Cyrtostropha morinensis (FOSSIL) (Horný, 1952 †)
Hormotoma multivolvis (FOSSIL) (Billings, 1857 †)
Lodanaria munda (FOSSIL) Dahmer, 1925 †
Murchisonia mylitta (FOSSIL) Billings, 1865 †
Micrentoma nana (FOSSIL) (de Koninck, 1881 †)
Hormotoma neglecta (FOSSIL) (Ulrich & Scofield,1897 †)
Murchisonia nerinea (FOSSIL) C.L.F. von Sandberger& C.L.F. von Sandberger, 1855 †
Catazone nevadana (FOSSIL) Blodgett & Johnson,1992 †
Hormotoma nigra (FOSSIL) Longst, 1924 †
Morania nixonforkensis (FOSSIL) Rohr & al., 2008 †
Arribazona nodolira (FOSSIL) Mazaev, 2003 †
Wuxuanella nodusa (FOSSIL) Cook & Pan, 2004 †
Aclisina northviewensis (FOSSIL) R.M. Branson, 1938 †
Murchisonia obesa (FOSSIL) Whidborne, 1892 †
Cyrtostropha obscura (FOSSIL) (Portlock, 1843 †)
Mesocoelia obstipisutura (FOSSIL) E.G. Linsley, 1968 †
Cheilotoma obtusa (FOSSIL) (Klipstein, 1843 †)
Murchisonia obtusangula (FOSSIL) Lindström, 1884 †
Murchisonia oegensis (FOSSIL) Heidelberger & Koch,2005 †
Coelocaulus oehlerti (FOSSIL) Ulrich & Scofield, 1897 †
Leptorima oehlerti (FOSSIL) (J. Perner, 1903 †)
Murchisonia oehlerti (FOSSIL) Blodgett & al., 1999 †
Hormotoma ordosensis (FOSSIL) Yü, 1961 †
Murchisonia ordovicia (FOSSIL) Yü, 1961 †