Plants bright green in loose to dense tufts, rufous-tomentose proximally. Stems 1--3 cm, simple or forked. Leaves crowded, laxly erect to erect, sometimes secund when dry, erect-spreading when moist, 1--2.5 mm, narrowly triangular-lanceolate, acuminate; margins narrowly revolute, serrulate nearly throughout; costa excurrent; laminal cells prorulose throughout, prorulae projecting forward over distal ends of cells; distal cells linear, 30--65 × 5--7 µm, basal cells shorter and broader. Sexual condition autoicous ; perigonia gemmiform, lateral and just proximally perichaetia. Seta 1.5--3.5 cm. Capsule 1.8--2 mm. Spores reniform, 26--33 µm, papillose.

Capsules mature Feb.--Dec. Soil or rock, often on wet embankments; Ala., Ark., Fla., Ga., Iowa, Kans., La., Miss., Mo., N.Y., Ohio, Okla., Penn., S.C., Tex., Va.; Mexico; West Indies (Puerto Rico); Central America (Guatemala, Costa Rica): South America (Venezuela).

Philonotis longiseta can be recognized by the flat, narrowly triangular leaves with forward projecting prorulae at the distal ends of the laminal cells throughout the leaf.