Key to the identification of Agathotanaidae from the Iceland-Faroes-Shetlands sector of the North-east Atlantic.

1 Antennule three-articled; antenna one-articled; cuticle densely pitted.............................. Agathotanais ingolfi

- Antennule four-articled; antenna six-articled; cuticle shiny or weakly pitted....................................... 2

2 Uropods largely concealed beneath pleotelson, exopod very small or absent........................ Paragathotanais ...3

- Uropods visible from dorsal view, exopod a short or prominent fused process......................... Paranarthura ...5

3 Cephalothorax longer than pereonites 1–2....................................... Paragathotanais vikingus sp. nov.

- Cephalothorax shorter than pereonites 1–2.................................................................. 4

4 Pereonites 4–5 shorter than broad, pleotelson with pointed apex............................. Paragathotanais robustus

- Pereonites 4–5 as long as or longer than broad, pleotelson bulbous, with rounded apex............. Paragathotanais nanus

5 Uropod endopod two-articled, pereonites with distinct ‘shoulders’............................. Paranarthrura insignis

- Uropod endopod one-articled, pereonites without ‘shoulders’...................................................6

6 Cephalothorax as long as pereonites 1–2 combined; uropod endopod about twice as long as basal article; pereopod-1 with dis- tal propodal seta.................................................................... Paranarthrura borealis

- Cephalothorax shorter than pereonites 1–2 combined; uropod endopod only just longer than basal article; pereopod-1 without distal propodal seta................................................................... Paranarthrura subtilis