Racomitrium norrisii sp nova (Grimmiaceae, Bryopsida), endemic of western North America

Racomitrium norrisii Bedn.-Ochyra & Ochyra (Grimmiaceae, Bryopsida) is described as a new species of subgen. Cataracta Vilh. and sect. Stenotrichum (Chev.) Bedn.-Ochyra, and its diagnostic features are illustrated. It is closely related to the European R. hespericum Sergio, Munoz & Ochyra from the Iberian Peninsula from which it differs in its leaves with bistratose marginal border of (1-)2-10(-13) rows of cells extending from the base to the apex; unistratose laminae in the upper part; shorter, 9-12-celled axillary hairs; and lacking or inconspicous papillae over the cell walls. Racomitrium norrisii is a hydrophytic moss endemic to western North America where it occurs in California and Idaho.