Key to species of Bathymunida Balss, 1914

1. Abdominal somite 4 with median posterior spine............................... B. avatea Macpherson & Baba, 2006

- Abdominal somite 4 without median posterior spine........................................................ ... 2

2. Sternite 3 with pair of prominent anterior spines................................... B. corniculata Macpherson, 2013

- Sternite 3 without anterior spines......................................................................... 3

3. Rostral and supraocular spines separated by oblique margins................. B. nebulosa Baba & de Saint Laurent, 1996

- Rostral and supraocular spines separated by concave or straight transverse margins................................. 4

4. Supraocular spines extending far beyond rostral spine......................................................... 5

- Supraocular spines slightly longer than or subequal to rostral spine............................................ 10

5. Rostral spine papilla-like or obsolescent.................................... B. frontis Baba & de Saint Laurent, 1996

- Rostral spine small but distinct........................................................................... 6

6. Rostrum with elevated ridge in midline.................................. B. dissimilis Baba & de Saint Laurent, 1996

- Rostrum without distinct ridge in midline.................................................................. 7

7. Maxilliped 3 merus gently narrowed distally.......................................... B. longipes Van Dam, 1938

- Maxilliped 3 merus rather truncate....................................................................... 8

8. Pereopod 2–4 dactyli without spine-like seta on flexor margin............................... B. balssi Van Dam, 1938

- Pereopod 2–4 dactyli with 1 or 2 spine-like setae on flexor margin............................................... 9

9. Ocular peduncles with tubercles along distal end proximal to cornea............ B. ocularis Baba & de Saint Laurent, 1996

- Ocular peduncles without tubercles............................................... B. brevirostris (Yokoya, 1933)

10. Rostral spine about as large as, or only slightly larger than, supraocular spines................................... 11

- Rostral spine much longer than supraocular spines.......................................................... 14

11. Branchial region with distinct transverse ridges.............................................. B. polae Balss, 1914

- Branchial region with tubercles or scale-like ridges......................................................... 12

12. Carapace with tubercles and elevated scale-like ridges; lateral marginal spines on branchial region sharp and prominent. Ros- tral and supraocular spines of moderate size, length about twice basal width........ B. rudis Baba & de Saint Laurent, 1996

- Carapace with scale-like granular ridges, lateral marginal spines on branchial region relatively small. Rostral and supraocular spines small, length about equal to basal width............................................................. 13

13. Anterolateral spine of carapace divergent anteriorly. Male pereopod 5 with fine setae on distal portion of propodus......................................................................... B. eurybregma Baba & de Saint Laurent, 1996

- Anterolateral spine of carapace directed straight forward. Male pereopod 5 with ribbon-like setae on distal portion of propodus..................................................................... B. recta Baba & de Saint Laurent, 1996

14. Anterior margin of rostrum straight between rostral and supraocular spines. Carapace with scale-like ridges.......................................................................................... B. quadratirostrata Melin, 1939

- Anterior margin of rostrum concave between rostral and supraocular spines. Carapace with distinct transverse ridges...................................................................................... B. sibogae Van Dam, 1938