1 Gubernaculum (whole length) much longer than a half of spicule length···················································································· 2
– Gubernaculum either almost equal to or shorter than a half of spicule length ············································································ 3
2 Body shorter than 2.0 mm, spicules approximately 1.5 abd long······································································ G. mediterraneum
– Body longer than 2.5 mm, spicule length equal to abd··································································································· G. arcticum
3 Spicules shorter than 30 µm ······································································································································· G. parafricanum
– Spicules equal to or longer than 40 µm ··············································································································································· 4
4 Tail 7–9 abd long in both sexes ································································································································· G. northumbriae
– Male tail either equal to or shorter than 6 abd··································································································································· 5
5 Gubernaculum thin, weakly developed ·············································································································································· 6
– Gubernaculum and lateral pieces well-developed····························································································································· 7
6 Spicule length almost equal to abd ······································································································································· G. georgei
– Spicules twice as long as abd·················································································································································· G. vulgare
7 Proximal end of spicules with a set-off capitulum········································································································· G. amokurae
– Proximal end of spicules with a not set-off capitulum························································································································ 8
8 Gubernaculum without tiny projections at distal end····································································································· G. scampae
– Gubernaculum with tiny projections at distal end···························································································································· 9
9 Body shorter than 1.5 mm, lateral differentiation absent ························································································· G. metuliferum
– Body equal to or longer than 2.0 mm, lateral differentiation present······················································· G. antarcticum sp. nov.