The holotype of Hydraena pensylvanica Kiesenwetter was found in the De
utsches Entomologisches Institut (Eberswalde, Germany). Facts proving
its true identity are provided. The epithet ''pennsylvanica'', introdu
ced by Provancher (1877) is based on an unjustified emendation of the
name pensylvanica. Hydraena atlantica Perkins (1980) is a junior synon
ym of H. pensylvanica. Hydraena pensylvanica sensu Perkins (1980) is d
escribed as H. americana species nova.