Key to species of Niphargoides

1. Posterior margin of pereopod 6 basis armed with a few short setae proximally ................................... N. grimmi

- Posterior margin of pereopod 6 basis armed with long setae along its entire length .............................................. 2

2. Ventral margin of coxal plate 4 armed with setae shorter than 1/2 of its length ....................... N. corpulentus

- Ventral margin of coxal plate 4 armed with setae longer than 1/2 of its length ......................................................... 3

3. Uropod 3 exopod bares a well-developed setal fan ..... ............................................................................ N. caspius

- Uropod 3 exopod lacks setal fan, armed with strong spines ........................................................... N. boltovskoyi