Dioecious, floating or loosely rooted, aquatic herb, stoloniferous. Leaves basal, floating on surface of water, and rosulate; petioles terete, fleshy, 7-15 cm long (shorter on juveniles); blades oblong-oval to rounded-oval, 4-6 cm long, 3-3.5 cm wide, obtuse to rounded at apex, acute to truncate at base, entire, spongy-reticulate on lower surface. Flowers unisexual; staminate spathes pedunculate with 2 or 3 long-pedicellate flowers; sepals 3, lanceolate, spreading; petals 3; stamens 6-12; filaments subulate, shorter than the linear anthers. Pistillate spathes of 2 bracts, bearing a short-pedicellate flower; ovary 6-9-carpellate; stigmas as many as carpels, 2-parted. Fruits baccate, many-seeded. Shattuck 401. Shattuck 401 was reported by Standley (1933) as Hydrocleys nymphoides. The species was apparently overlooked by C. den Hartog in the Flora of Panama treatment (1973).