(based on the characteristics of the dorsal armament and on the structure of coxa 1)
1. Body segments with strong dorsal teeth (fig. 1a,b, d–i)....................................................... 2
- Body segments without strong dorsal teeth (fig. 1c)............................. Neopleustes carinatus Margulis, 1963
2. Pereon segments 1–6 without carination, pereon segment 7 with strong dorsal tooth posteriorly (fig. 1a,b).............. 3
- Pereon with a large number of dorsal teeth (fig. 1d–i)........................................................ 4
3. Pereonal & pleonal segments without aesthetascs dorsally (fig. 1a)............. Neopleustes boecki boecki (Hansen, 1887)
- Pereonal & pleonal segments with submedial and sublateral groups of plumose aesthetascs dorsally (fig. 1b)................................................................................... Neopleustes boecki pacifica s sp. nov.
4. Pereon segments 1–4 without carination, pereon segments 5–7 with strong dorsal tooth posteriorly (fig. 1g,h,i).......... 5
- Pereon carinated posteriorly from segment 1 to segment 7 (fig. 1d,e,f)........................................... 7
5. Lower margin of coxal plate 1 rounded, without central ventral angle (fig. 4g)..... Neopleustes kussakini (Budnikova, 1995)
- Lower margin of coxal plate 1 with central ventral angle (fig. 4h,i).............................................. 6
6. Head, pereonal & pleonal segments without setae dorsally, lower margin of coxal plate 1 with acute central ventral angle (figs. 1h, 4h)....................................................... Neopleustes pulchellus pulchellus (Krøyer, 1846)
- Head, pereonal & pleonal segments with submedial and sublateral long pappose single setae dorsally, lower margin of coxal plate 1 with subquadrate central ventral angle (figs. 1i, 4i)................... Neopleustes pulchellus asiaticus s sp. nov.
7. Body, pereon segments 1–3 weak carinations, and strongly carinated from segment 4 to segment 7 (fig. 1d)..................................................................... Neopleustes columbianus Hendrycks & Bousfield, 2004
- Body, pereon strongly carinated from segment 1 to segment 7 (fig. 1e,f).......................................... 8
8. Head with anterodorsal crest, lower margin of coxal plate 1 with acute central ventral angle (figs. 1e, 4e)................................................................................ Neopleustes euacanthoides Gurjanova, 1972
- Head without anterodorsal crest, lower margin of coxal plate 1 without acute central ventral angle (fig. 1f)................................................................................... Neopleustes euacanthus (G. Sars, 1877)