Two species of pearl mussels, Dahurinaia (Kurilinaia) laevis D. (K.) zatravkini, inhabiting fresh waters of Sakhalin, South Kurile and Japan Islands, were found in the upper Amur River drainage basin (Transbaikalye). Considerable likeness of morphological and morphometric shell characters with island species is shown. The problem of ancientorigin of pearl mussels of Transbaikalye is discussed.
