A moss-like plant with an irregularly and highly branched frond. The frond is constricted at intervals into different sized segments and the holdfast is a mass of tangled fibres. The plant is small (growing up to 2 cm tall) and is dark purple.

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Thallus small, inconspicuous, to 3-4 cm high, red-purple in color. Thallus uniaxial, segmented; branches primarily pseudodichotomous, attaching to mangrove roots by haptera. Segments elongated, oval or flattened, generally 3 to 5 times longer than wide, 0.3-0.5 µm diameter. Thallus consisting of a central axial cell filament surrounded by 5 to 6 pericentral cells that give rise to fine, thick-walled medullary filaments bearing small, spherical outer cortical cells. Tetrasporangial branches bearing tetrasporangia in swollen subapical areas.

Similar species: Gelidium pusillum

Dixon, P.S. & Irvine, L.M. (1977). Seaweeds of the British Isles. Volume 1. Rhodophyta. Part 1. Introduction, Nemaliales, Gigartinales. pp. xi + 252, 90 figs. London: British Museum (Natural History).

Basionym: Ulva caespitosa Withering

Type locality: "Side Rocks, Anglesey", Wales (Silva, Basson & Moe 1996: 280).

Holotype: OXF (Dixon & Irvine 1977: 190).