Cartilaginous, purplish brown fronds, often in dense tufts, arising from a discoid holdfast, to 200 mm high. Narrow compressed stipe expands into strap-like blade, usually rolled to form a channel, with thickened margins. Repeatedly dichotomously branched, with axils acute. Upper part of frond with papillae to 10 mm or more long on surfaces and margins on female plants. Male plants lack papillae and are generally rare. Tetrasporophyte a purplish-black crust (Petrocelis-phase). 

References: Guiry, M.D. & Guiry, G.M. 2013. AlgaeBase. World-wide electronic publication, National University of Ireland, Galway. http://www.algaebase.org; searched on 18 November 2013.