Potamogeton aff. P. gaudichaudii Cham. et Schlecht.
N. Vietnam, Prov. Quang Binh, distr. Minh Hoa, 72 km to NWW from Dong Hoi, municipalite Thuong Hoa, Yen Son village, limestone massif Ke Bang (N 17°40′ E 105°57′). In shallow water of small karst lake on alluvial valley bottom between limestone ridges and mesas at 200 m alt. Aquatic floating plant with shoots up to 2 m lg occurring on 0.3-2 m depth. Common and sometimes abundant. VH 4841 19.05.1997 International Botanical Expedition of the U.S.A. National Geographic Society (grant No 5803-96)