Perennial. Rhizome slender, rooting at nodes. Sterile leaves fasciculate, long-petioled; blade of 2 contiguous pairs of opposite, obovate-cuneate leaflets with flabellate anastomosing venation. Sporocarp leathery, sessile or stipitate, globular-ovoid to compressed, with truncate base, divided by membranous partitions (indusia) into two series of transverse compartments, each with a single sorus. Macro- and microsporangia intermixed in the same sorus; mature sporocarp dehiscent under water along the ventral suture into 2 valves and liberating a gelatinous ring which opens and turns into a long filament, bearing the sori.