An extensive survey for freshwater sponges was carried at the temporarely exposed rocky bottoms of river Corumbá at Goiás State and river Manso at Mato Grosso State. The exposure resulted from the closing of the dams for lake formation at the respective Hidreletric Power Plants. Drulia uruguayensis Bonetto & Ezcurra de Drago, 1968, Corvospongilla seckti Bonetto & Ezcurra de Drago, 1966 and Trochospongilla repens (Hinde, 1888) were seen to be common to both rivers. Eunapiusfragilis (Leidy, 1851), Oncosclera navicella (Carter, 1881) and O. petricola (Bonetto & Ezcurra de Drago, 1969) were yet found in river Manso and O. schubarti (Bonetto & Ezcurra de Drago, 1967) in river Corumbá. O. schubarti is redescribed and SEM illustrated.
Sponges; Oncosclera schubarti; Neotropical; river; benthic assemblages