1. Eyes absent.......................................................................................... 2
– Eyes present.......................................................................................... 3
2. Dorsal carination of pleon segments 1–3 without produced central tooth, lateral teeth more than submedial teeth................................................................................. Megamoera pallida (G. O. Sars, 1879)
– Dorsal carination of pleon segments 2–3 with produced central tooth each; pleon segment 1 without dorsal carination........................................................................... Megamoera lignophila (Barnard, 1961)
3. Head, lower margin of anterior lobe without accessory processes (Fig. 23 a)........................................ 4
– Head, lower margin of anterior lobe with accessory processes (Fig. 1 c)........................................... 7
4. Dorsal carination of pleon segments 1–3 without strong central tooth................... Megamoera aequidentatum sp. n.
– Pleon segments 1–3 with another combination of dorsal teeth................................................... 5
5. Pleon segment 1 with strong medial tooth dorsally; pleon segments 2 & 3 without strong medial tooth dorsally (medial tooth equal to lateral teeth in size); pleon plate 3 without strong processed tooth at the posterior-distal corner................................................................................... Megamoera borealis Jarret & Bousfield, 1996
– Pleon segments 1–3 with strong medial tooth dorsally; pleon plate 3 with strong processed tooth at the posterior-distal corner..................................................................................................... 6
6. Pleon segments 1 & 2 with 1–3 lateral denticles each side dorsally, pleon segment 3 with 3 lateral denticles each side dorsally........................................................................ Megamoera dentata (Krøyer, 1842)
– Pleon segments 1 & 2 without lateral denticles dorsally, pleon segment 3 with only one lateral denticle each side dorsally.................................................................... Megamoera unimaki Jarret & Bousfield, 1996
7. Urosomite 1 with 5 + dorsal teeth......................................................................... 8
– Urosomite 1 with 3 dorsal teeth.......................................................................... 9
8. Pleon segments 1 & 2 with 4 + lateral denticles each side dorsally, pleon segment 3 with 3 lateral denticles each side dorsally...................................................................... Megamoera subtener (Stimpson, 1864)
– Pleon segments 1 & 2 with 3 lateral denticles each side dorsally, pleon segment 3 with 4 + lateral denticles each side dorsally......................................................................... Megamoera falsomikulitschae sp. n.
9. Pleon plate 3 without strong processed tooth at the posterior distal corner........................................ 10
– Pleon plate 3 with strong processed tooth at the posterior distal corner........................................... 11
10. Pleon segments 1 & 2 with central tooth and 3–4 minute lateral denticles each side; pleon segment 3 with central tooth and 2– 3 lateral denticles................................................... Megamoera kodiakensis (J.L. Barnard, 1964)
– Pleon segments 1 & 3 with central tooth and 2 minute lateral denticles each side..................................................................................................... Megamoera glacialis Jarret & Bousfield, 1996
11. Pleon segments 1 & 2 with central tooth and 3 minute lateral denticles each side; pleon segment 3 with central tooth and 5 lat- eral denticles each side.............................................. Megamoera mikulitschae (Gurjanova, 1985)
– Pleon segments 1–3 with another configuration of dorsal armament............................................. 12
12. Pleon segment 3 without central tooth, with 3 lateral teeth each side........ Megamoera bowmani Jarret & Bousfield, 1996
– Pleon segment 3 with central tooth, with 2–3 lateral teeth each side............................................. 13
13. Pleon segment 3 without strong medial tooth dorsally (medial tooth equal to lateral teeth in size).......................................................................................... Megamoera rafiae Jarret & Bousfield, 1996
– Pleon segment 3 with strong medial tooth dorsally.......................................................... 14
14. Pereopods 5–7, bases regular, narrowed distally; sculpture of surface without points........ Megamoera similidentata sp. n.
– Pereopods 5–7, bases expanded, rounded posteriorly; sculpture of surface pointed............... Megamoera striata sp. n.