Leaves usually contorted when dry, lanceolate to broadly subulate from an ovate or oblong sheathing base, 1.5-4 mm, apex acute to narrowly obtuse, margins entire or with a few teeth apically; costa subpercurrect to excurrent as a subula; distal laminal cells subquadrate or short-rectangular. Perichaetial leaves distinctly larger than the cauline, convolute-sheathing. Seta elongate, 0.5-1.5 mm. Capsule long-exserted, cylindric with neck strongly differentiated, conic to long-cylindric; peristome absent or present, of 16 simple, forked or perforate teeth, vertically barred on external surface; operculum differentiated, obliquely long-rostrate. Calyptra cucullate. Spores medium-sized, 20-30 µm, papillose.
Species ca. 25 (6 in the flora): worldwide, mainly temperate areas.
Trematodon is clearly in need of revision, with more than 80 correct binomials extant but only about 25 species commonly accepted as well characterized. It clearly intergrades with Bruchia. Within the genus, only T. ambiguus and T. longicollis have strumose capsules.