3/7/22: For a variety of complex taxonomical reasons Harry Lee in posting to Conch-L has pointed out that the current valid name for what I presented as Cumingia tellinoides (Conrad, 1831) is C. sinuosa.  Here are his comments:

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"Cumingia tellinoides: The basionym, Mactra tellinoides Conrad, 1831, is considered permanently invalid since it is a primary junior homonym of Mactra tellinoides Pulteney, 1799; see <https://molluscabase.org/aphia.php?p=taxdetails&id=540826>. [Of peripheral interest is the fact that Mactra tellinoides Pulteney, 1799 is a junior synonym of Mactrotoma fragilis (Gmelin, 1791) according to several authorities; see <https://molluscabase.org/aphia.php?p=taxdetails&id=420850> and Huber (2015: 834)]

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Cumingia sinuosa  A. Adams, 1850 is the earliest available synonym of the Conrad taxon; see <https://molluscabase.org/aphia.php?p=taxdetails&id=507255>."