A fertile population of a Potamogeton (subsect. Pusilli, Potamogetonaceae) resembling P. xlongiligulatus is known from Beebe Pond, Canaan, New York. The population, which is closely related to P. hillii, was originally identified as P. xlongiligulatus and later as a hybrid between P. hillii and P. zosteriformis. Extensive studies of the plant’s morphological characters and paper chromatography analyses indicate it to be a new species, P. ogdenii.