The following is the original description of N. onychophora, from Horst (1918):[2] Among the plankton-worms, collected at the above-named station, I met with a male Heteronereis, that is characterized by having in the anterior (agamous) body-region, the notopodial fascicle represented by a single, stout, yellow bristle, with a dark brown, hook-shaped apex; the neuropodial fascicle has its usual appearance and contains in its dorsal part some homogomph setigerous bristles and some heterogomph falcigerous ones, whereas ventrally there occur only falcigerous setae, with a terminal piece, that is ciliated along its whole border.

The dorsal ligule is very small, papilliform and bears a cirrus, which is much longer, extending somewhat beyond the extremity of the notopodial lobe, that is large, obtusely conical.

The neuropodial lobe has a conical anterior lip and reaches beyond the extremity of the ventral ligule, that is club-shaped.

III = a transverse, crescent group of 3 rows of paragnaths (9 + 8 + 7), the anterior ones very tiny.

With regard to the uniformity of structure of the parapodium, presented by nearly all the Nereidae, this species shows a remarquable (sic) exception.