Cyrena salmacida var. subrostrata Fischer & Crosse, 1894
Fischer & Crosse, 1894. Miss. Sci. Mexique, Rech. Zool. 2(16): 643, pl. 61, fig. 7.
(intro'd as intra-sp. of Cyrena salmacida Morelet, 1851)

Sphaerium subtransversum Fischer & Crosse, 1894
“Prime” Fischer & Crosse, 1894. Miss. Sci. Mexique, Rech. Zool. 2(16): 652, pl. 69, figs. 5-5a.
(misidentified reference to Sphaerium subtransversum Prime, 1860)

Sphaerium yucatense Fischer & Crosse, 1894
Fischer & Crosse, 1894. Miss. Sci. Mexique, Rech. Zool. 2(16): 653, pl. 63, figs. 1-1a, pl. 64, figs. 1-1b.

Unio alienigenus Crosse & Fischer, 1894
Crosse & Fischer, 1894. J. de Conch. 41: 294.
Fischer & Crosse, 1894. Miss. Sci. Mexique, Rech. Zool. 2(16): 590, pl. 65, figs. 5-5a; pl. 66, fig. 3.
Type(s): SYNTYPE MNHN-IM-2000-1634, Coatzacoalcos, Vera Cruz, Mexico.

Unio computatus Crosse & Fischer, 1894
Crosse & Fischer, 1894. J. de Conch. 41: 295.
Fischer & Crosse, 1894. Miss. Sci. Mexique, Rech. Zool. 2(16): 601, pl. 67, figs. 2-2a.
Type(s): SYNTYPE MNHN-IM-2000-1662, Coatzacoalcos, Vera Cruz, Mexico.

Unio distinctus Crosse & Fischer, 1893
Crosse & Fischer, 1893. J. de Conch. 41: 110.
Fischer & Crosse, 1894. Miss. Sci. Mexique, Rech. Zool. 2(16): 579, pl. 69, figs. 2-2a.
Type(s): SYNTYPE MNHN-IM-2000-1676, Rio Cosamaloapan, Mexique.

Unio explicatus Fischer & Crosse, 1894
‘Morelet’ Fischer & Crosse, 1894. Miss. Sci. Mexique, Rech. Zool. 2(16): 594, pl. 61, fig. 1.
(reference to Unio explicatus Morelet, 1849)

Unio opacatus Crosse & Fischer, 1894
Crosse & Fischer, 1894. J. de Conch. 41: 295.
Fischer & Crosse, 1894. Miss. Sci. Mexique, Rech. Zool. 2(16): 592, pl. 66, figs. 1-1a.
Type(s): SYNTYPE MNHN-IM-2000-1755, Mexique.

Unio pensitatus Fischer & Crosse, 1894
Fischer & Crosse, 1894. Miss. Sci. Mexique, Rech. Zool. 2(16): 599.
(new name for Unio plicatulus Lea, 1859)

Unio pigerrimus Crosse & Fischer, 1894
Crosse & Fischer, 1894. J. de Conch. 41: 293.
Fischer & Crosse, 1894. Miss. Sci. Mexique, Rech. Zool. 2(16): 582, pl. 65, figs. 1-1a.
Type(s): SYNTYPE MNHN-IM-2000-1761, Mexique.

Unio popeii Fischer & Crosse, 1894
of Authors.
Fischer & Crosse, 1894. Miss. Sci. Mexique, Rech. Zool. 2(16): 605 [as ‘Unio (Graphonaias) popei’].
Martens, 1900. Biol. Centr.-Amer., Moll.: 504 [as ‘Unio (Nephronaias) popei’].
Simpson, 1900. Proc. U.S. Nat. Mus. 22: 738 [as ‘Unio (sec. Elliptio)’]. [in part]
Pilsbry, 1910. Proc. Acad. Nat. Sci. 61: 535. [in part]
Ortmann, 1912. Ann. Carnegie Mus. 8: 271 [as ‘Elliptio’].
Simpson, 1914. Descr. Cat. Naiades: 700 [as ‘Unio (sec. Elliptio)’]. [in part]
Frierson, 1927. Check List N. Amer. Naiades: 38 [as ‘Elliptio (Popenaias)’]. [in part]
Haas, 1929. Senckenbergiana 11: 330 [as ‘Elliptio (Popenaias)’]. [in part]
Haas, 1969. Das Tierreich 88: 201 [as ‘Nephronaias (Popenaias)’]. [in part]
Graf & Cummings, 2007. J. Moll. Studies 73: 308 [as ‘Popenaias’]. [in part]
Pfeiffer et al., 2019. Zool. Scripta 48: 504 [as ‘Popenaias’]. [in part]
(misidentified reference to Unio popeii Lea, 1857)

Unio sallei Crosse & Fischer, 1894
Crosse & Fischer, 1894. J. de Conch. 41: 179.
Fischer & Crosse, 1894. Miss. Sci. Mexique, Rech. Zool. 2(16): 619, pl. 68, figs. 3-3a.
Type(s): SYNTYPE MNHN-IM-2000-1776B, Mexique.

Unio soledadensis Crosse & Fischer, 1893
Crosse & Fischer, 1893. J. de Conch. 41: 111.
Fischer & Crosse, 1894. Miss. Sci. Mexique, Rech. Zool. 2(16): 608, pl. 69, figs. 3-3b.
Type(s): SYNTYPE MNHN-IM-2000-1785, Mexique, La Soledad.

Unio sphenorhynchus Crosse & Fischer, 1894
Crosse & Fischer, 1894. J. de Conch. 41: 296.
Fischer & Crosse, 1894. Miss. Sci. Mexique, Rech. Zool. 2(16): 617, pl. 66, fig. 2-2a.
Type(s): SYNTYPE MNHN-IM-2000-1792, Mexique.

Unio tamaulipasensis Fischer & Crosse, 1894
Fischer & Crosse, 1894. Miss. Sci. Mexique, Rech. Zool. 2(16): 621.
(new name for Unio taumilapanus Conrad, 1855)

Unio tehuantepecensis Crosse & Fischer, 1894
Crosse & Fischer, 1894. J. de Conch. 41: 296.
Fischer & Crosse, 1894. Miss. Sci. Mexique, Rech. Zool. 2(16): 618, pl. 65, figs. 3-4.
Type(s): SYNTYPES MNHN-IM-2000-1799, Mexique, Santa Efigenia. lac formé dans le cratère d'un volcan éteint.

Unio yzabalensis Crosse & Fischer, 1893
Crosse & Fischer, 1893. J. de Conch. 40: 294.
Fischer & Crosse, 1894. Miss. Sci. Mexique, Rech. Zool. 2(16): 597, pl. 64, figs. 4-4b.
Type(s): SYNTYPES MNHN-IM-2000-1810, Lac Yzabal, Guatemala.

Unio calamitarum var. B prolongata Fischer & Crosse, 1894
Fischer & Crosse, 1894. Miss. Sci. Mexique, Rech. Zool. 2(16): 613, pl. 63, figs. 5-5a.
(intro'd as intra-sp. of Unio calamitarum Morelet, 1849)
Type(s): HOLOTYPE BMNH_93-2-4-2008, Baluntie, near Palenque.

Unio calamitarum var. D nephretica Fischer & Crosse, 1894
Fischer & Crosse, 1894. Miss. Sci. Mexique, Rech. Zool. 2(16): 612.
(intro'd as intra-sp. of Unio calamitarum Morelet, 1849)

Unio calamitarum var. G arcuans Fischer & Crosse, 1894
Fischer & Crosse, 1894. Miss. Sci. Mexique, Rech. Zool. 2(16): 612, pl. 64, figs. 5-5a.
(intro'd as intra-sp. of Unio calamitarum Morelet, 1849)
Type(s): HOLOTYPE BMNH_93-2-4-2009, Baluntie, near Palenque.

Unio crocodilorum var. B semipustulata Fischer & Crosse, 1894
Fischer & Crosse, 1894. Miss. Sci. Mexique, Rech. Zool. 2(16): 578, pl. 60, fig. 4.
(intro'd as intra-sp. of Unio crocodilorum Morelet, 1849)
Type(s): PARATYPES BMNH_1893-2-4-2032, River Usumacinta, Guatemala.

Unio crocodilorum var. G praestricta Fischer & Crosse, 1894
Fischer & Crosse, 1894. Miss. Sci. Mexique, Rech. Zool. 2(16): 578, pl. 60, fig. 5.
(intro'd as intra-sp. of Unio crocodilorum Morelet, 1849)
Type(s): SYNTYPES BMNH_1893-2-4-2031, River Usumacinta, Guatemala.

Unio pliciferus var. B minor Fischer & Crosse, 1894
Fischer & Crosse, 1894. Miss. Sci. Mexique, Rech. Zool. 2(16): 581, pl. 69, fig. 4.
(homonym of Unio margaritifer var. minor Rossmässler, 1835; intro'd as intra-sp. of Unio pliciferus Lea, 1838)
Type(s): SYNTYPE MNHN-IM-2000-1812, Rio Medellin, Mexique.