4. Cinclidium subrotundum Lindberg, Bot. Not. 1868: 72. 1868.
Plants 3-8(-12) cm. Stems dark reddish brown. Leaves green, reddish brown, or black when old, erect-spreading, ± flat, not strongly reflexed when moist, broadly elliptic, ± orbicular, spatulate, occasionally ovate or obovate, 3.5-6 mm; base short-decurrent; margins plane or weakly recurved, 2- or 3-stratose; apex rounded, obtuse, or rarely retuse, apiculate or sometimes not, apiculus blunt; costa percurrent, excurrent, or rarely subpercurrent; medial laminal cells elongate, (40-)70-110 µm, in diagonal rows, weakly collenchymatous; marginal cells short-linear or linear, in 3 or 4 rows. Sexual condition synoicous. Seta yellowish, 4-6 cm. Capsule yellowish, subglobose, 1.5-2.5 mm. Spores 25-70 µm. mature summer. Peat and deep organic soil to shallow wet mineral soil on rock in fens, along river banks; low to moderate elevations; Greenland; Alta., B.C., Man., Nfld. and Labr., N.W.T., Nunavut, Que., Yukon; Alaska, Mich.; Europe.
Cinclidium subrotundum is distinguished by its broadly elliptic, nearly orbicular or spatulate leaves usually ending in a small, blunt apiculus. When present, the subglobose capsules are also diagnostic.