• Ralfsia Berkeley, 1843
• Ralfsia E. O'Meara, 1875 (uncertain > nomen dubium)
• Ralfsia australis Skottsberg, 1921
• Ralfsia bornetii Kuckuck, 1894 accepted as Stragularia clavata (Harvey) Hamel, 1939
• Ralfsia californica Setchell & N.L.Gardner, 1924 accepted as Petalonia fascia (O.F.Müller) Kuntze, 1898
• Ralfsia ceylanica Harvey ex Barton, 1903 accepted as Lobophora ceylanica (Harvey ex E.S.Barton) C.W.Vieira, De Clerck & Payri, 2016
• Ralfsia clavata (uncertain > unassessed)
• Ralfsia clavata (Harvey) P.Crouan & H.Crouan, 1867 accepted as Stragularia clavata (Harvey) Hamel, 1939
• Ralfsia clavata f. laminariae F.S.Collins, 1907 accepted as Stragularia clavata (Harvey) Hamel, 1939
• Ralfsia confusa Hollenberg, 1969
• Ralfsia deusta (uncertain > unassessed)
• Ralfsia deusta (C.Agardh) Berkeley, 1843 accepted as Ralfsia fungiformis (Gunnerus) Setchell & N.L.Gardner, 1924
• Ralfsia disciformis P.L.Crouan & H.M.Crouan, 1867 accepted as Stragularia clavata (Harvey) Hamel, 1939
• Ralfsia endopluroides J.Tanaka & Chihara, 1981
• Ralfsia expansa (J.Agardh) J.Agardh, 1848 accepted as Neoralfsia expansa (J.Agardh) P.-E.Lim & H.Kawai ex Cormaci & G.Furnari, 2012
• Ralfsia extensa P.L.Crouan & H.M.Crouan, 1867 accepted as Pseudolithoderma extensum (P.Crouan & H.Crouan) S.Lund, 1959
• Ralfsia fatiscens (uncertain > unassessed)
• Ralfsia fatiscens (Areschoug) Gobi, 1878 accepted as Lithoderma fatiscens Areschoug, 1875
• Ralfsia fluviatilis Areschoug, 1930 accepted as Heribaudiella fluviatilis (Areschoug) Svedelius, 1930
• Ralfsia fungiformis (Gunnerus) Setchell & N.L.Gardner, 1924
• Ralfsia fungiformis Nagai, 1940 (uncertain > unassessed)
• Ralfsia hancockii E.Y.Dawson, 1944 accepted as Neoralfsia hancockii (E.Y.Dawson) D.Leon-Alvarez & M.L.Nunez-Reséndiz, 2014
• Ralfsia hesperia Setchell & N.L.Gardner, 1924
• Ralfsia huanghaiensis Li & Li, 1993
• Ralfsia hyalina (Kützing) O'Meara, 1875 accepted as Diatoma hyalinum Kützing, 1844
• Ralfsia hyalina (Kützing) O'Meara, 1876
• Ralfsia integra Hollenberg, 1969
• Ralfsia longicellularis Perestenko, 1980
• Ralfsia lucida S.Lund, 1967
• Ralfsia macrocarpa Feldmann, 1931 accepted as Hapalospongidion macrocarpum (Feldmann) León-Álvarez & González-González, 1993
• Ralfsia major Kützing, 1859 accepted as Sonderopelta capensis (Montagne) A.D.Krayesky, 2009 accepted as Sonderophycus capensis (Montagne) M.J.Wynne, 2011
• Ralfsia minima (Ralfs) O'Meara, 1875 accepted as Diatoma minimum Ralfs, 1846
• Ralfsia minima (Ralfs) O'Meara, 1876 accepted as Fragilaria hyalina var. minima (Ralfs) De Toni, 1892 accepted as Diatoma minimum Ralfs, 1846
• Ralfsia occidentalis Hollenberg, 1945 accepted as Ralfsia pacifica Hollenberg, 1944
• Ralfsia ovata Rosenvinge, 1893
• Ralfsia pacifica Hollenberg, 1944
• Ralfsia pangoensis Setchell, 1924 accepted as Hapalospongidion pangoense (Setchell) Hollenberg, 1942 accepted as Mesospora pangoensis (Setchell) Chihara & J.Tanaka, 1982
• Ralfsia pangoensis var. galapagensis Setchell & N.L.Gardner, 1937 accepted as Mesospora pangoensis var. galapagensis (Setchell & Gardner) Chihara & J.Tanaka, 1982
• Ralfsia pedicellata J.Tanaka & Chihara, 1981
• Ralfsia pusilla (Strömfelt) Foslie, 1892
• Ralfsia robertii M.I.Parente & G.W.Saunders, 2019
• Ralfsia spongiocarpa Batters, 1888 accepted as Stragularia spongiocarpa (Batters) Hamel, 1939
• Ralfsia tabellaria O'Meara, 1875 (uncertain > unassessed)
• Ralfsia tenebris M.I.Parente & G.W.Saunders, 2019
• Ralfsia tenuis Kylin, 1947 accepted as Stragularia clavata (Harvey) Hamel, 1939
• Ralfsia unimaculata M.I.Parente & G.W.Saunders, 2019
• Ralfsia verrucosa (uncertain > unassessed)
• Ralfsia verrucosa (Areschoug) Areschoug, 1845 accepted as Pseudoralfsia verrucosa (Areschoug) Parente, Fletcher & G.W.Saunders, 2020
• Ralfsia verrucosa var. cochlearum J.E. Areschoug, 1876 accepted as Ralfsia verrucosa (Areschoug) Areschoug, 1845 accepted as Pseudoralfsia verrucosa (Areschoug) Parente, Fletcher & G.W.Saunders, 2020
• Ralfsia verrucosa var. erythraea Piccone & Gunow, 1884
• Ralfsia verrucosa var. lignicola J.E. Areschoug, 1847 accepted as Ralfsia verrucosa (Areschoug) Areschoug, 1845 accepted as Pseudoralfsia verrucosa (Areschoug) Parente, Fletcher & G.W.Saunders, 2020
• Ralfsiaceae Farlow, 1881
• Ralfsiales