The genera Mactrella and Mactrinula, both described by Gray in 1853, have generally been considered synonyms. Additionally, five species had been included in Mactrella were later placed in the genus Mactrellona Marks, 1951. The diagnosis of type species of these genera, as well as the study of their type material, have clarified the taxonomic status of the three related genera. The genus Micromactra Dall, 1894, is added to the synonymy of Mactrella. The complete shell morphology of type species Mactrella striatula and Mactrinula plicataria, both introduced by Linnaeus, 1767, is described. An updated synonymy list of each species is provided. In addition, an expanded geographical distribution of the genus Mactrella is given. Illustrations of Mactrellona alata (Spengler, 1802), Mactrellona exoleta (Gray, 1837), Mactrellona clisia (Dall, 1915), Mactrella californica (Conrad, 1837), Harvella elegans (G. B. Sowerby I, 1825), and Mactrella janeiroensis (E. A. Smith, 1915) are included.