Genus Sessilogoga Grygier, 1990

Type species Sessilogoga elongata Grygier, 1990

Key to genera of the family Synagogidae and species of the genus Sessilogoga (based on morphology of females)

1 Carapace functionally bivalved, with long aperture, thorax without dorsal humps or horns, parasites of antipatharians or crinoids............................................................................................. 2

- Carapace functionally univalved, with restricted aperture (medium or short), thorax with dorsal humps or horns, mesoparasites of octocorals (unknown for Flatsia)....................................................................... 6

2 Epaulets on thoracomere 6 absent, frontal filament complex small, endoparasites of antipatharians.......... 3 ( Sessilogoga)

- Epaulets on thoracomere 6 present, frontal filament complex developed, ectoparasites of antipatharians or crinoids........ 5

3 Furcal rami length/height ratio 4.0–5.0............................................................. S. captiva

- Furcal rami length/height ratio 6.0–9.0.................................................................... 4

4 Furcal rami length/height ratio 7.5–9.0, telsonic spines denticulate...................................... S. elongata

- Furcal rami length/height ratio 6.0–6.5, telsonic spines smooth.......................................... S. perfuga

5 Ventral margin of carapace valves unflattened, without pair of big anterior pores, filamentary appendage of thoracopod 1 absent, ectoparasites of antipatharians.............................................................. Synagoga

- Ventral margin of carapace valves flattened, with pair of big anterior pores, filamentary appendage of thoracopod 1 present, ectoparasites of crinoids......................................................................... Waginella

6 Carapace with special superficial grapnels and antero-ventral anchoring protrusion, parasites of octocorals of genus Chrysogorgia ......................................................................... Thalassomembracis

- Carapace without special superficial grapnels and antero-ventral anchoring protrusion............................... 7

7 Thoracomeres with mid-dorsal dorsal humps, carapace aperture of medium length, host unknown................ Flatsia

- Thoracomeres with long dorsal horns, carapace aperture small, parasites of octocorals of orders Malacalcyonacea and Scleralcyonacea...................................................................................... 8

8 Dorsal horns present on thoracomeres 1–3, but never on thoracomeres 4 or 5, parasites of octocorals of families Paramuriceidae, Eunicellidae and Primnoidae ................................................................ Gorgonolaureus

- Dorsal horns present on thoracomeres 2–5, but never on thoracomere 1.......................................... 9

9 Females with uniramous penis, telsonic spines considerably shorter than furcal rami, parasites of octocorals of family Keratoisididae ................................................................................. Isidascus

- Females with bifurcate penis, telsonic spines comparable in length to furcal rami, parasites of octocorals of family Chrysogorgiidae ............................................................................ Cardomanica