Ochrostylon thompsonii, a member of the golden-brown algal order Chromulinales, is described from North America (Quivira National Wildlife Refuge, Kansas). Each organism consists of a basal disk and an elastic stalk at the end of which sits the markedly dorsoventral protoplast. The strongly concave heteroflagellate cell contains a single plastid and contractile vacuoles. The cell further contains a large chrysolaminarin (leucosin) droplet and numerous small droplets.