The new sp. is described and diagnostic characters lor adults and larvae are illustrated (hololype 6. allotype 9; Wisconsin. Burnett Co., Saint Croix River, resp. 6 & 23- VI-1991; deposited at NMNH, Washington, D.C.). Placement within the genus is problematic since it shares characters with the subgcncra Ophionuroides Carle and Ophionurus Carle. Larvae are known only from large, rapid rivers with pristine water quality. Adult emergence is highly synchronized and takes place in late May.