Abstract. Delforge, P.,  cicmir, R., Kranjcev, R. & Gˇvaudan, A.- Validation of the description of Epipactis rivularis Kranjcev & Cicmir, a Croatian species of the Epipactis albensis species group (Orchidaceae) [Natural. belges 87 (Orchid. 19) (2006): 69-84]. Small populations of a late-flowering, autogamous, very hygrophilous Epipactis have been found in 2003 alongside brooklets of the foothill of the mount Medvednica, near Zagreb, Croatia. It possesses the main differentiating characters and the ecology of taxa of the E. albensis species group, which are summarized. It combines the general appearence of E. fibri, endemic to the Rhone valley, south of Lyon, France, with some characters of the gynostenium of E. albensis, from Central Europa. Its flowers are unique notably in the prevalence of purple pigments, particularly on the petals and the labellum, the constant presence of a rostellar gland, and the structure of the epichile. A detailed diagnosis is provided for E. albensis and E. fibri. As Epipactis rivularis was provisionally described in 2005 without latin description nor designation of an holotype, it is formally described here as Epipactis rivularis Kranjcev &  Cicmir sp. nova.

Key-Words: Orchidaceae, genus Epipactis,  Epipactis albensis species group, Epipactis rivularis sp. nova; flora of Croatia, Zagreb, Mt. Medvednica.