Profundilycastis profundus, first described as Namalycastis by Olga Hartman (1965), is in the following redescribed. The genus Profundilycastis Hartmann-Schröder, 1977 is closely related to Rullerinereis Pettibone from which it is to be distinguished by: absence of superior dorsal ligule; absence of eyes; parapods of first 2 setigers uniramous; parapodial ligules long and slender