Abstract
A new species to science of the genus Rivulus POEY, 1861 is described as Rivulus haraldsiolii
spec. nov. It comes from the lower Itapocú, state Sta. Catarina, Southeast-Brazil.
The investigations resulted in comparison to the hitherto known and related species clear
differences. These are based on the meristical dates, a unique colour-pattern and the presence in a hitherto one times collected (1911) area.
The description is an extract of the works from the stocks of the german research-collections.
Additional remarks to the knowledge and determination of Rivulus-species are added.