Brandt [7] recognized two subgenera from Thailand, Gabbia and Digoniostoma, containing 3 species each, with Bithynia (Digoniostoma) siamensis containing 2 subspecies B. s. siamensis and B. s. goniomphalos. Gabbia has now been raised to generic status [12] and [13]. Brandt [7] indicated that future studies would be likely to alter this taxonomic situation as many species in the family Bithyniidae were still anatomically unknown