Calman, 1905
Generic diagnosis:
The eye is large and bilobed, with the width of the upper lobe broader than the width of the lower.
The 1st segment of the peduncle of the 1st antenna has an almost vertical lobe, scarcely or not overhanging the 2nd segment. The 3rd segment bears a small rounded keel.
The 3rd thoracic leg is greatly elongated (Nematobrachion-thoracic leg); the proximal part of the merus has a small v-shaped bend, and the dactylus is elongated and armed at the tip with five long, straight, serrated spines. The 7th leg is short, but has a full number of segments. The 8th leg is rudimentary.
The carapace has a distinct transverse cervical groove.
The terminal process of the petasma is short, upright, distally broad and receptacle-like. The proximal process is long and slender, with a proximal heel and a strong curvature of ca. 180°.
There are 3 species in this genus, each showing a different degree of spininess. N. boopis has no spines on the peduncle of the 1st antenna, no carapace spine, no abdominal spines, and is even without a rostrum. N. flexipes has a rostrum, a long spine on the 1st two segments of the peduncle of the 1st antenna, lateral carapace spines, and a mid-dorsal abdominal spine on each of segments 3-6. N. sexpinosum has a long rostrum, long spines on the 1st two segments of the peduncle of the 1st antenna, post-ocular and lateral carapace spines, multiple dorsal spine-like projections on abdominal segments 4 and 5, and tooth-like ventral angles on the abdominal pleura of abdominal segments 1-5.