Key to species of the Eriopisa group in Japan (excluding Eriopisa elongata sensu Nagata)

1. Antenna 2 flagellum almost fused......................................................................... 2

- Antenna 2 flagellum not fused.......................................................................... 3

2. Eyes present, merus of pereopod 7 greatly expanded....................................... Victoriopisa ryukyuensis

- Eyes absent, merus of pereopod 7 moderately expanded.................................. Victoriopisa wadai sp. nov.

3. Carpus of gnathopod 1 longer than propodus, palm transverse.................. Paraflagitopisa excavata gen. et sp. nov.

- Carpus of gnathopod 1 shorter than propodus, palm oblique.................................................... 4

4. Posterodistal corners of bases in pereopods 5–7 rounded or weakly incised................. Psammogammarus mawatarii

- Posterodistal corners of bases in pereopods 5–7 projected.......................... Psammogammarus lobatus sp. nov.