Key to species of Niphargogammarus

1. Antenna 1 main flagellum as long as the first peduncular article ....................................................................... 2

- Antenna 1 main flagellum shorter than the first peduncular article ....................................................................... 3

2. Body size ca. 10 mm, gnathopod 2 propodus larger than gnathopod 1, telson lobes diverging and armed with 1 apical spine ............................................... N. quadrimanus

- Body size ca. 5 mm, propodi of both gnathopods similar in size, telson lobes not diverging and armed apically with 2 spines ........................................................ N. aequimanus

3. Body size ca. 13 mm, urosomite 1 bare, uropod 3 exopod external margin armed with many setae ... N. borodini

- Body size ca. 7 mm, urosomite 1 armed with small setae, uropod 3 exopod external margin armed with few distal setae ................................................... N. intermedius