Abstract
The temporarily exposed rocks of the Dobrotivá Formation (Middle Ordovician, upper Darriwilian) accessible, due to lower water levels, in Džbán water reservoir (Praha-Vokovice area) have produced common fauna. The newly obtained trilobite-dominated fossil associations enable a more detailed discussion of faunal changes in the lower and lower-middle portions of the Dobrotivá Formation - a transition from the Placoparia Association to the newly recognized Degamella-Zeliszkella Association, dominated by mesopelagic forms.