Plants robust, in greenish to yellowish tufts. Stems erect, simple, 3--12 cm. Leaves erect to erect-spreading and imbricate when dry, erect-spreading when moist, plicate, straight or falcate, seriate in 5 spiraled rows, ovate-lanceolate, 1.5--2 mm; margins plane or narrowly revolute, serrulate to denticulate nearly to base, teeth paired or simple; costa robust, percurrent to excurrent, rough abaxially throughout; laminal cells prorulose at proximal ends, prorulae mostly on adaxial side, distal cells narrowly oblong to linear, 25--45 × 4--6 µm, basal cells rectangular to elongate-hexagonal, 15--30 × 7--10 µm. Sexual condition dioicous; perigonia discoid. Seta erect, 3--5 (--7) cm. Capsule horizontal, furrowed when dry, 2--3 mm. Spores subreniform, 20--22 µm, papillose.

Capsules mature June--Sept. Acid seeps and springs, high mountains or at high northern latitudes; 10--3000 m; s Greenland; Europe; Asia (India; Iran, e, n and w Russia; n Africa).

Philonotis seriata is an Old World species that enters the flora area only in southern Greenland. It is allied with P. fontana, including having obtuse inner perigonial leaves, but differs in the seriate stem leaves and the costa that is scabrous on the back throughout. According to S. Flowers (1935), authentic P. seriata does not occur on the North American continent.