AbstractTwo new species of Acaulon,A. chrysacanthumandA. leucochaeteare characterized by lamellae on the adaxial surface of the nerve and are placed in a new subgenus,Alaticosta. Acaulon chrysacanthumhas leaves with the nerve excurrent as a stout reddish-gold arista, and brown papillose spores, 30–35µm in diameter.Acaulon leucochaetehas the nerve excurrent as a long colourless flexuose hair point and buff-coloured spores, more finely papillose and 23–25µm in diameter. Both are species of semi-arid areas usually growing on red sandy soil in mallee scrub.