Key to species of Petalosarsia

1. carapace with distinct dorsolateral carina................................................................... 2

- carapace without or with faint dorsolateral carina........................................................... 6

2. carapace with sharp dorsolateral carina running entire length on each side....................................... 3

- carapace with short or dull dorsolateral carina on each side..................................................... 5

3. dorsolateral carina without tooth........................................................ P. declivis (Sars, 1865)

- dorsolateral carina serrated with about 10 teeth............................................................. 4

4. pseudorostrum short and truncated, 0.09–0.12 times as carapace length...................... P. brevirostris Gamô, 1986

- pseudorostrum long and acute, 0.21–0.25 times as carapace length................................. P. g a m o i sp. nov.

5. dorsolateral carina dull, run entire side surface.................................................. P. ovalis sp. nov.

- dorsolateral carina only at anterior portion of carapace...................................... P. ryukyuensis sp. nov.

6. carapace with faint dorsolateral carina..................................................................... 7

- carapace without dorsolateral carina.......................................................................8

7. carapace with faint dorsolateral carina with a few teeth on anterior portion..................... P. longicaudata sp. nov.

- carapace with faint dorsolateral carina without teeth for entire length.............................. P. australis sp. nov.

8. inner distal corner of pereopod 1 carpus forming rectangular angle................................ P. suluensis sp. nov.

- inner distal corner of pereopod 1 carpus forming obtuse angle.................................................. 9

9. pereonite 3–5 with brunt spines on dorsal surface....................................... P. longirostris Jones, 1973

- pereonite 4 with a spine directed forward on dorsal surface........................................ P. j o n e s i sp. nov.