Habit and structure. Thallus stipitate with peltate blades, deep red in colour but iridescent in situ. Blades circular when young, becoming stellate with ligulate lobes when mature (to 10 cm in breadth and 200–300 µm thick), regularly anastomosing with blades of adjacent thalli or re-attaching to the substratum. Structure multiaxial, with a polystromatic medulla of several layers of large, hyaline cells grading into a cortex of 3–4 layers of pigmented cells.
Reproduction. Tetrasporangia occurring (primarily) in the mid cortex of the ventral surface, scattered or in dense clusters, transformed from intercalary cortical cells, cruciately-divided, ovoid and 20–30 x 15–25 µm. Spermatangia on outer cortical cells. Carpogonial branches four-celled, on inner cortical cells. Auxiliary cells from inner cortical cells attached to the supporting cells of the carpogonial branches. Cystocarps protuberant, when mature are about 1200 µm in diameter. Pericarps ostiolate, often with extended necks.
Distribution. Jurien Bay to the Dampier Archipelago, W. Aust.
Habitat. Epilithic in the subtidal. Generally grows on vertical surfaces in part shade.