Bot. J. Linn. Soc. 158(1): 165 (2008).

Type: St Helena, Prosperous Bay Plain, north slope of Dry Gut, on basalt, altitude 280 m, 17 October 2006, A. Aptroot 66263 (holo. B; iso. ABL).

Thallus: Initially shrubby, soon becoming pendant with age, up to 80 cm long but usually much smaller (c. 10 cm), without distinct holdfast, relatively richly largely dichotomously branched, mostly terete to angular, never contorted, not canaliculate, never perforate, relatively slender, up to 2 mm wide, but generally c. 0.2–0.5 mm thick, with at most few inconspicuous warts, greenish-grey, most parts with conspicuous whitish linear pseudocyphellae, the overall colour therefore pale grey. Branches generally linear. Branch tips often minutely curved, usually not blackened. Thallus with irregular, terminal or lateral soredia bearing schizidioid, more or less corticatesoredia.Thallus section with conspicuous, rounded to angular strands of cartilaginous tissue in the medulla and at the surface, which are mostly hyaline, but brownish in section when reaching the surface. Cortex indistinct. Apothecia not observed. Conidia not observed.

Photobiont: Algal cells in irregular groups throughout the medulla.

Chemistry: Usnic acid with norstictic and connorstictic acids (by TLC).

Ecology: It occurs on boulders and cliffs in the Prosperous Bay Plain and almost everywhere else on the island, even on the walls of High Knoll Fort.

Molecular data: Genbank

Distribution: Database

Note: : This species is characterized by an angular, richly irregularly branched thallus with linear pseudocyphellae-like lines and lateral to terminal tiny schizidioid soredia. The thallus contains norstictic and connorstictic acids. This may be a relative of R. arabum (Dill. ex Ach.) Meyen & Flot.