Unio monroensis Lea, 1843
Lea, 1843. [privately published sheet]: [1].
Lea, 1845. Trans. Amer. Phil. Soc. 9 [O. 4]: 279 [37], pl. 41, fig. 8.
Type(s): HOLOTYPE (MONOTYPY) USNM_85169, L. Monroe, Florida.

Unio (sec. Elliptio) monroensis — Simpson (1900), Simpson (1914)
Elliptio (s.s.) buddianus-monroensis — Frierson (1927)
Elliptio (s.s.) buddianus — Haas (1969)
Elliptio (s.s.) dariensis — R.I. Johnson (1970), R.I. Johnson (1972), Burch (1975)
Elliptio monroensis — Turgeon et al. (1998), Lee (2006), Graf & Cummings (2007), Bogan (2010), Cummings & Graf (2010), ... Graf & Cummings (2021), FMCS (2021), Hopper et al. (2023), MolluscaBase (2024), FMCS (2025)

Unio anthonyi Lea, 1861
Lea, 1861. Proc. Acad. Nat. Sci. 13: 41.
Lea, 1862. Jour. Acad. Nat. Sci. 5 [O. 9]: 197 [19], pl. 27, fig. 266.
Type(s): HOLOTYPE USNM_84986, Florida.

Unio (sec. Elliptio) pusillus — Simpson (1900), Simpson (1914)
Elliptio (s.s.) anthonyi — Frierson (1927)
— Haas (1969)
Elliptio (s.s.) fraterna — R.I. Johnson (1970), Burch (1975)
Elliptio monroensis — Williams et al. (2011), Williams et al. (2014)

Unio websterii B.H. Wright, 1888
B.H. Wright, 1888. Proc. Acad. Nat. Sci. 40: 113, pl. 2, fig. 2.
Type(s): LECTOTYPE USNM_125697 (by R.I. Johnson, 1967: 10), [Lake Woodruff, Volusia Co., Florida].

Unio (sec. Elliptio) websteri — Simpson (1900), Simpson (1914)
Elliptio (s.s.) buddianus — Frierson (1927), Haas (1969)
Elliptio (s.s.) dariensis — R.I. Johnson (1970), R.I. Johnson (1972), Burch (1975)
Elliptio monroensis — Williams et al. (2011), Williams et al. (2014)

Unio hartwrightii B.H. Wright, 1896
B.H. Wright, 1896. Nautilus 9(11): 121, pl. 2, figs. 4-6.
Type(s): HOLOTYPE USNM_151031, St. Johns River, Blue Springs, Fla.

Unio (sec. Elliptio) hartwrighti — Simpson (1900), Simpson (1914)
Elliptio (s.s.) buddianus-hartwrightii — Frierson (1927)
Elliptio (s.s.) buddianus — Haas (1969)
Elliptio (s.s.) dariensis — R.I. Johnson (1970), R.I. Johnson (1972), Burch (1975)
Elliptio monroensis — Williams et al. (2011), Williams et al. (2014)

Unio polymorphus B.H. Wright, 1899
B.H. Wright, 1899. Nautilus 13(4): 42.
Type(s): LECTOTYPE USNM_152060 (by R.I. Johnson, 1967: 8), Spanish Creek, Charleton Co., Ga.

Unio (sec. Elliptio) polymorphus — Simpson (1900), Simpson (1914)
Elliptio (s.s.) polymorphus — Frierson (1927), Haas (1969)
Elliptio (s.s.) crassidens crassidens — R.I. Johnson (1970)
Elliptio (s.s.) crassidens — Burch (1975)
Elliptio crassidens — Parmalee & Bogan (1998), Watters et al. (2009)
Elliptio monroensis — Williams et al. (2011), Williams et al. (2014)