Plants gregarious and tufted, pale green, erect when dry, to 7 mm. Leaves slightly dimorphic; vegetative 2-2.5 mm; distal lamina oblong-lanceolate; margins 1-stratose to slightly thickened distally, irregularly serrate; costa in cross section absent well-defined stereid cells; medial cells distinct, 8-10 µm, bulging and 1- to pluripapillose adaxially, bulging to 1-papillose abaxially; teniolae distinct at leaf shoulders and above; cancellinae rounded or ending in acute angles distally, adaxial distal cells mammillose at least in part; gemmiferous leaves with narrowed apices, bearing gemmae mostly adaxially but also abaxially on apices.
The species can be separated from the other Southern African taxa by the presence of teniolae; although they are rather weak on the only collection seen from the Flora area. The Southern African specimen did not have gemmae, but they are reported to occur in clusters at the leaf apex and are clavate with a long tapering apex.
Plants small, in loose tufts, dark green; corticolous. Stems erect, irregularly branched; in section round, central strand absent, inner cortical cells in 4-5 rows, outer cortical cells in 1-2 rows, slightly smaller, brownish. Leaves contorted and exposing hyaline bases dry, erect-spreading wet; oblong to ungulate above obovate base, 2-3(4) mm long; apex rounded, apiculate; base sheathing; margins plane, serrate, strongly so at shoulders; teniolae present, occasionally weak above, in section forming intermarginal, multicellular knob; extrateniolar lamina 1-3 cells wide. Costa percurrent to just excurrent, ventral superficial cells quadrate to rectangular, smooth to weakly prorate above, dorsal superficial cells rectangular, sharply prorate; in section elliptical, stereids absent, guide cells 6-8, large, weakly thickened, ventral cells in 3-4 layers, smaller than guide cells, ventral surface cells slightly larger, mam-millose, dorsal cells in 6-7 layers, cells in 3 rows under guide cells similar to ventral cells, 3-4 outer rows with cells smaller, flattened, incrassate, dorsal surface cells larger, sharply mammillose. Laminal cells small, rounded-quadrate, ventral surface strongly mammillose, dorsal surface weakly mammillose or papillose; single row of juxtacostal cells slightly larger; cancellinae rectangular; teniolar cells rectangular to long-rectangular, smooth. Dioicous. Perichaetia terminal, leaves weakly differentiated, base somewhat longer. Seta 3-4 mm long, red-brown; capsule cylindrical, 2.0-2.5 mm long, yellow-brown; exothecial cells rectangular, weakly sinuolate, in zig-zaging rows, at mouth with 2 rows of quadrate cells and up to 7 rows of transversely rectangular cells below mouth; stomata present at base of urn, phaneropore; peristome absent; operculum long-rostrate, 0.7-1.2 mm long, cells not twisted; calyptra persistent, cylindrical-rostrate, clasping base of capsule, scabrous above, dehiscence of spores through longitudinal slits in upper calyptra; spores rounded, 15-25 µm, yellowish, smooth with scattered large granules.
Endemic to Africa, C. rabenhorstii is most commonly collected in west tropical Africa, however specimens have also been reported from Zaire and Angola. A single specimen, with sporophytes, is known from Southern Africa. The specimen was recently collected on Raphia palms at Kosi Bay, in north-eastern Zululand.