Description: Coarse moss, forming deep turf, green to yellowish-green in color, occasionally reddish, brownish or blackish. Stems 1 - 4 cm (to 1.6 in.) high. Leaves costate, the costa (midrib) being stout, rough, red, and conspicuous at the back, abruptly excurrent (extending out beyond the lamina of the leaf), with hyaline, spinulose hair point. Leaves twisted when dry. Whorls of enlarged leaves mark annual growth increments of the shoot and form an interrupted verticil (ring arranged around central axis). This species is bisexual, found often with capsules that have a white, corkscrew peristome that arises from a basal tube.
Habitat: In pinyon-juniper community, specifically in soil that is shaded by boulders.
Range: Fairly common along the coast of California, Oregon, and Washington. In Clark County, Nevada, currently known only from sites in the Red Rock Canyon National Conservation Area and the Virgin Mountains.
Comments: S. princeps was previously known as Tortula princeps. It is a bisexual species and often with capsules (spore-containing sac), whereas star moss (Tortula ruralis), a closely related species, is dioicous (male and female parts not on same moss), and without capsules.