| abstract | Ten new species (Unionicola (Unionicolides) bakeri, hoesei, poundsi, fulleri, conroyi, burchi, scutella, lasallei, calnani and stansberyi) are described for the first time. Ten species were previously known in the subgenus Unionicolides, a New World group that parasitezes fresh-water mussels. All North American species are re-evaluated. Unionicolides contains a large number of incipient species which may be diverging through sympatric host race formation. |