Cap 3.0-7.0 cm broad, obtuse-conic to convex, broadly convex in age; margin incurved, then decurved, striate when moist; surface more or less glabrous, hygrophanous, hazel-brown, dingy tawny-brown, drying from the disc to lighter shades, initially covered with sparse whitish fibrils or fine scales; context watery-brown, thin, up to 5.0 mm thick at the disc; odor and taste not distinctive.
Gills adnate-seceding, sometimes with a decurrent tooth, close, relatively broad, up to 7.0 mm in width, at first cream to pale-tan, eventually dull-brown, sometimes with a purplish or vinaceous tint; lamellulae in three to four series.
Stipe 3.0-9.0 cm long, 8.0-15.0 mm thick, more or less equal or slightly enlarged at the base, hollow, fragile; surface of apex white, fibrillose-squamulose, the lower portion fibrillose, to patchy squamulose, whitish pubescence at the base; partial veil white, floccose-tomentose, forming a membranous superior ring, the upper surface conspicuously striate.
Spores 7.0-9.0 x 4.0-5.0 µm, smooth, thin-walled, elliptical in face-view, inequilateral in profile; apical germ pore and hilar appendage inconspicuous; spore print dark-brown with a purplish tint.
In small groups in mixed-hardwood-conifer woods, coastal and lower elevations of the Sierra Nevada; fruiting from late fall to mid-winter; occasional.
Compared to most Psathyrella species, P. longistriata is distinctive. It is recognized when young by a glabrous, brown, striate-margined cap, adorned sparsely with whitish fibrils, and an annulus with a grooved upper surface. Another ringed species, Psathyrella ellenae var. yubaensis, is smaller, up to 4.0 cm broad, and has a membranous, non-striate ring. It fruits during the spring at mid to higher elevations of the Sierra Nevada. Also similar is Psathyrella barrowsii, known from under Aspens (Populus tremulloides) in New Mexico and Colorado. Like Psathyrella longistriata it has a brownish, hygrophanous cap and a well developed annulus, but the cap lacks whitish fibrils, striations on the margin as well as on the ring.