Key to genera of Entoniscidae, modified from Adkison (1990) and Shiino (1942)

1. marsupium formed by close adhesion of the oostegites to host membrane; males with segmented pereopods.............. 2

- marsupium formed entirely by host membrane, oostegites free, not adhering to host membrane, pleural lamellae absent, females lacking pereopods, males with unsegmented pereopods ( Entoniscinae)............................................ 3

2. parasitic in hermit crabs; females without pleural lamellae, female with heart tubercle in pleomere 1 ( Diogenioninae n. subfam.)..................................................................................... Diogenion

- parasitic in other decapods; females with well-developed pleural lamellae, female with heart tubercle in pleomere 3 (Entioninae)......................................................................................... 6

3. parasitic in hermit crabs; oostegite 1 largest with ascendant and recurrent lobes, oostegites 2–5 at posterior end of pereon; male with antenna not projecting beyond margin of head............................................... Paguritherium

- parasitic in other decapods.............................................................................. 4

4. female without maxilliped; terminal segment of male bifurcated...................................... Entoniscoides

- female with maxilliped; terminal segment of male undivided................................................... 5

5. more than 2 pairs of oostegites present; unpaired dorsal ovarian processes................................ Entoniscus

- oostegite 1 absent; only 2 pairs of oostegites forming brood pouch...................................... Synalpheion

6. males with five pairs of pereopods; female pereon with pairs of lateral ovarian processes and without unpaired ventral or dorsal processes................................................................................... Allocancrion

- males with six pairs of pereopods......................................................................... 7

7. female pereon without any ovarian processes............................................................... 8

- female pereon with at least 1 ovarian process................................................................ 9

8. female with two transverse lobes on oostegite 1 and fused oostegites 2–5; males with pair of lateral expansions on each of the first two pleomeres............................................................................. Pinnixion

- female with one transverse lobe on oostegite 1 and separate oostegites 2–5; males with pair of expansions only on pleomere 1............................................................................................ Entionella

9. mature female with dorsal ovarian processes of variable number, rarely absent.................................... 10

- mature female without dorsal ovarian processes............................................................. 11

10. mature female with two ventral ovarian processes....................................................... Entione

- mature female without ventral ovarian processes...................................................... Cancrion

11. female with dorsolateral ovarian processes................................................................ 12

- female without dorsolateral ovarian processes.............................................................. 14

12. female pereon with one unpaired dorsolateral ovarian process........................................... Micippion

- female pereon with paired dorsolateral ovarian processes..................................................... 13

13. female with one pair of dorsolateral ovarian processes................................................. Portunion

- female with two pairs of dorsolateral ovarian processes.................................................. Priapion

14. female with 1 unpaired ventral ovarian process........................................................ Xanthion

- female with 2 unpaired ventral ovarian processes............................................................ 15

15. female first oostegite without transverse lamellae................................................... Pinnotherion

- female first oostegite with transverse lamellae.............................................................. 16

16. female posterior oostegites reduced, not enclosing recurrent lamella of first oostegite......................... Tiarinion

- female posterior oostegites enclosing recurrent lamella of first oostegite.................................... Achelion