This key is corrected and modified from the key presented by Shear (1977). We include N. mexasca Shear, 1977 in the key, although it most probably does not belong to this genus (Benavides & Giribet 2007). Illustrations of all species can be found in Benavides & Giribet (2007) and the online catalog (http://giribet.oeb.harvard.edu/ Cyphophthalmi/).
1. Troglobitic; legs long and attenuate; color light brown; dorsum of abdomen without conspicuous transverse grooves; claw of leg II smooth, Mexico......................................................................................... N. mexasca Shear
- Not troglobitic; legs typically short and stout; color very dark brown to black; dorsum of abdomen with conspicu- ous transverse grooves; claw of leg II with small teeth............................................................................................ 2
2 (l). Adenostyle at base of tarsus or slightly removed from base, positioned before half length of tarsus..................... 3
- Adenostyle at half length of tarsus........................................................................................................................... 5
3 (2). Adenostyle at base of tarsus, Guyana........................................................................................... N. kartabo (Davis)
- Adenostyle slightly removed from base of tarsus; spermatopositor with distal prongs diverging at an acute angle................................................................................................................................................................................... 4
4 (3). Spermatopositor as in Fig 6 b, Brazil................................................................................................ N. immsi Hinton
- Spermatopositor as in Figs 4, 6 a, French Guiana............................................................................. N. virginie n. sp.
5 (2). Crown of spermatopositor with two long and sharply pointed spikes (Fig. 6 c), Guyana........... N. kamakusa Shear
- Crown of spermatopositor without long and sharply pointed spikes (Fig 6 d), Brazil...... N. microphaga (Martens)