Ectoplaninae with two ventro-median gonopores, one leading into the male atrium and the other one into the bursal canal. Copulatory bursa opening to exterior through mid-dorsal pore. Oviducts with distinct tubae. Penis papilla provided with sclerotic spines. Adhesive papillae absent.
This genus contains only one species, Nesion arcticum Hyman, 1956.