Arctoa Bruch & W. P. Schimper, 1846.

Arctoa is rarely encountered on moist alpine rocks in the extreme north of California. It is one of a group of high elevation petricolous mosses that have a strong resemblance to Dicranum. This latter genus is absent from high elevations in California, and all our species of Dicranum are markedly larger than any of the members of the four higher elevation genera of comparison: Arctoa, Cynodontium, Kiaeria, and Blindia. Arctoa differs from Blindia in lacking strong alar differentiation; unlike Cynodontium, Arctoa has smooth median laminal cells are smooth and the leaves are not markedly crispate when dry. The sporophytes of Arctoa are erect and symmetric; those of Kiaeria are inclined and asymmetric.
see key to Kiaeria Etc.

Species included:
Arctoa fulvella (Dickson) Bruch & W. P. Schimper
Arctoa hyperborea (Withering) Bruch & W. P. Schimper, not known from CA