Unionicola (Hexatax) similis (Viets, 1935)

Material examined. 0/1/0, Nong Chang Yai Reservoir, Ubon Ratchathani Province, 15° 23.874ʹ N, 104° 49.756ʹ E, 25-x-2010 ; 0/2/0, Rice field, Roi-Et Province, 16° 05.126ʹ N, 103° 37.048ʹ E, 23-x-2010 .

Remarks. Our specimen measures 356 in length and 186 in width, much smaller than the specimen of Viets (1935) from Java and Sumatra. Lundblad (1969) assigned morphologically similar specimens to U. chappuisi Walter, 1935, a species described from West-Africa. Indeed, both species are very similar, but molecular methods are needed to clarify the taxonomic status of both species. For the time being we prefer to use the name U. similis . The species was previously known from Java and Sumatra. The present record is new for the fauna of Thailand.