Flowers: sepals faintly 3-veined, scarious margins narrow. Heads of achenes 11-26 mm; outer face of achene narrowly rhombic. 2 n =16. Flowering late spring (May-Jun). Wet meadows, vernal pools and sloughs, bogs, muddy shores of lakes and streams; 1500-2900 m; Alta., Sask.; Ariz., Calif., Colo., Mont., Nev., N.Mex., N.Dak., Oreg., Utah, Wyo. The illegitimate name Myosurus aristatus subsp. montanus (G.R. Campbell) H.Mason has been used for this taxon.