Among water-plant material received on loan from the Western Australian Herbarium, South Perth, there was a very remarkable Nymphaeacea which did not fit in any of the 8 genera so far described in this family. Mr. R. C. Royce, the curator of the herbarium mentioned above, kindly gave his permission for me to work out this material. Fortimately, additional specimens of this taxon were received on loan from C.S.I.R.O., Canberra, through the kind collaboration of Miss Dr. N. T. Burbidge. Dr. R. C. Bakhuizen van den Brink, Leiden, rendered the diagnosis into Latin. Miss R. van Crevel prepared the drawing. Mr. J. Muller studied the pollen of the plant; his findings are given in an appendix to this paper.