Key to species of Gyge Cornalia & Panceri, 1861 (based on characters of mature females; modified from Markham 2004)

l. Body with indistinct anterolateral corners, subrectangular, margins of barbula projections smooth; internal ridge of oostegite 1 smooth.............................................................. G. angularis Page, 1985 [New Zealand]

- Body smoothly rounded, oval; margins of barbula projections digitate; internal ridge of oostegite 1 digitate............. 2

2. Lateral margins on one side of body acutely angled........................ G. irregularis (Markham, 1985) [Thailand]

- Lateral margins on both sides of body smooth.............................................................. 3

3. Marsupium fully enclosed by oostegites............................ G. branchialis Cornalia & Panceri, 1861 [Europe]

- Marsupium not fully enclosed by oostegites................................................................ 4

4. Pleopods and uropods smooth, uropods visible in dorsal view................................ G. wimi sp. nov. [Iran]

- Pleopods and uropods tuberculate, uropods not visible in dorsal view...... G. ovalis (Shiino, 1939) [Japan, Korea, Taiwan]