[1] It is found in the remote tropical island of Saint Helena, where it forms large patches on wet, overhanging rock ledges.

The type specimen was collected by the author on The Barn along God's Path at an elevation of 475 m (1,558 ft); there, it was found growing on basalt.

Thin-layer chromatography shows that the species contains erythrin; tiny translucent crystals of this lichen product encrust the hyphae of the medulla.

The photobiont partner, dispersed throughout the medulla, is an orange-coloured member of genus Trentepohlia, with cell diameters of about 10 μm.

The species epithet honours lichenologist colleague Mark Seaward, who encouraged the author to conduct the lichen survey at this location.