Type-species. Synasterope implumis Poulsen, 1965
Composition. The genus Synasterope includes 34 species of which the following are known from the study area (Fig. 20): S. bassana Poulsen, 1965, S. mystax Kornicker, 1975, S. brachythrix Kornicker, 1975, S. polythrix Kornicker, 1975, S. empoulseni Kornicker, 1975, S. duplex Kornicker, 1975, S. arnaudi Kornicker, 1975, S. dimorpha (Hartmann, 1965), S. solox Kornicker, 1996, S. species 129 Hartmann, 1990.
Distribution. Members of this genus live between 44 °– 45 °N (Chavtur 1983) and 75 °– 76 °S (Kornicker 1975) and a depth range of 1–4450 m.
1. Lateral eyes present.................................................................................... 2
- Lateral eyes absent.................................................................................... 3
2. 2 or 3 midsetae on dorsal margin of mandibular basale.............................................. S. empoulseni
- Without midseta on dorsal margin of mandibular basale............................................... S. bassana
3. Ventral margin of basale of maxilla with 5 proximal setae...................................................... 4
- Ventral margin of basale of maxilla with 1 proximal seta....................................................... 5
4. Seventh limb with 18–22 setae................................................................... S. polythrix
- Seventh limb with 12 setae........................................................................ S.duplex
5. Length more than 2.2 mm............................................................................... 6
- Length less than 2.2 mm................................................................................ 7
6. Length more than 3.0 mm, 1 st segment of endopodite on 2 nd antenna shorter than 2 nd segment, endite of mandible basale with 3 spinous and 3 triaenid setae......................................................... S. pseudomystax sp. nov.
- Length less than 3.0 mm, 1 st segment of endopodite on 2 nd antenna subequal length of 2 nd segment, endite of mandible basale with 4 spinous and 4 triaenid setae................................................................. S. mystax
7. e-seta on 8 th segment of 1 st antenna about same length or shorter than a-claw of 7 th segment; medial seta on protopodite of 2 nd antenna absent.......................................................................... S. brachythrix
- e-seta on 8 th segment of 1 st antenna longer than a-claw of 7 th segment; medial seta on protopodite of 2 nd antenna present.. 8
8. Length of ventral margin of 6 th segment of 1 st antenna of female less than 60 percent of distance between base of sensory seta and base of proximal filament on sensory seta; 8 processes on posterior infold of carapace................... S. dimorpha
- Length of ventral margin of 6 th segment of 1 st antenna of female more than 70 percent of distance between base of sensory seta and base of proximal filament on sensory seta; 3–5 processes on posterior infold of carapace...................... 9
9. 4 – 5 processes on posterior infold of carapace; 5–6 setae forming row between ventral part of posterior ridge and posteroventral valve margin.................................................................................. S. arnaudi
- 3 processes on posterior infold of carapace; over 40 setae forming row between ventral part of posterior ridge and posteroven- tral valve margin................................................................................. S. solox