The Treatise on Invertebrate Paleontology lists about 27 unionoid genera and subgenera for Africa, so the above species count is probably a bit low.  Lamprell and Healy 1998 list about 19 species for Australia.

The status of Corbicula is somewhat complex.  Fossil Corbicula occur in North Carolina and nearby states up to the end of the Pliocene or so, when it became regionally extinct.  Two varieties of Corbicula have been introduced.  Some molecular work suggests that the widespread form is actually C. leana, with fluminea represented primarily in the southwestern U.S.

No natural lakes occur in the North Carolina Piedmont (or the rest of the U.S. piedmont, but some coastal plain lakes in North Carolina are natural.

    Dr. David Campbell
    "Old Seashells"
    Biology Department
    Saint Mary's College of Maryland
    18952 E. Fisher Road
    St. Mary's City, MD  20686-3001 USA
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"Mollusks murmured 'Morning!'.  And salmon chanted 'Evening!'."-Frank Muir, Oh My Word!