Key to the species of Ampelisca from the Brazilian coast (modified from Valério-Berardo et al. (2005))

1. Head with a long rostrum reaching to end of peduncle article 1 of antenna 1 ................................. A. paria

- Head lacking a defined rostrum.................................................................................................................. 2

2. Head strongly narrow anteriorly, anteroventral margin parallel to anterodorsal margin ............................ 3

- Head slightly narrow anteriorly, ventral margin oblique............................................................................. 6

3. Posteroventral corner of epimeron 3 without spine .................................................................................... 4

- Posteroventral corner of epimeron 3 with spine.......................................................................................... 5

4. Antenna 1 shorter than antenna 2 peduncle; uropod 3 rami very broad, distal margin rounded; urosomite 1 dorsal carina pointed .......................................................................................................... A. flabellicaudata

- Antenna 1 subequal in length to antenna 2 peduncle, uropod 3 rami foliaceous; urosomite 1 dorsal carina saddle-shaped ........................................................................................................... A. meridionalis sp. nov.

5. Pereopod 7 ventral margin of basis nearly transverse (in larger specimens can be rounded); urosomite 1 dorsal carina produced into a rounded process; posterior margin of epimeron 3 not bisinuate .................... ....................................................................................................................................................... A. cristata

- Pereopod 7 ventral margin of basis rounded; urosomite 1 dorsal carina produced into an acute process; posterior margin of epimeron 3 bisinuate ........................................................................... A. brevisimulata

6. Pereopod 7 merus posterior margin strongly lobed, lobe extending to distal end of carpus or more ........ 7

- Pereopod 7 merus posterior margin weakly lobed, lobe not extending to the middle of carpus ................ 9

7. Epimeron 3 postero-ventral corner without spine; telson distal margin blunt .............................. A.moreirai

- Epimeron 3 postero-ventral corner with a spine; telson distal margin pointed .......................................... 8

8. Pereopod 7 propodus longer than twice dactylus length; uropod 2 both rami with 1 long apical robust seta ............................................................................................................................... A. longipropoda sp. nov.

- Pereopod 7 propodus shorter than twice dactylus length; uropod 2 outer ramus with 1 long apical robust seta ............................................................................................................................................... A.pugetica

9. Pereopod 7 carpus with 1 notch on anterior margin .................................................................................. 10

- Pereopod 7 carpus without 1 notch on anterior margin............................................................................. 12

10. Antenna 2 longer than body length; pereopod 7 propodus twice longer than carpus; uropod 3 rami broad .......................................................................................................................................... A. youngi sp. nov.

- Antenna 2 shorter than body length; pereopod 7 propodus subequal in length to carpus; uropod 3 rami slender....................................................................................................................................................... 11

11. Antenna 1 reaching to middle of peduncular article 5 of antenna 2; urosomite 1 dorsal carina raised into a lens-shaped process; inner ramus of uropod 3 distally uncinate ................................................... A. romigi

- Antenna 1 reaching to end of peduncular article 4 of antenna 2, urosomite 1 dorsal carina rounded and without lens-shaped process; inner ramus of uropod 3 not distally uncinate ...................... A.subtropicalis

12. Antenna 1 subequal in length to peduncle of antenna 2; uropod 3 outer margin of inner ramus nacked, outer ramus notched at tip ........................................................................................................ A.rodriguesi

- Antenna 1 shorter than peduncle of antenna 2; uropod 3 inner ramus with 1 stout robust setae on outer mar- gin, outer ramus not notched at tip ........................................................................................................... 13

13. Uropod 1 peduncle with 1 large robust seta on distal margin and outer ramus lacking marginal robust setae; pereopod 7 merus weakly produced posterodistally ...................................................... A. aff. lobata

- Uropod 1 peduncle without 1 large robust seta on distal margin and outer ramus with marginal robust setae; pereopod 7 merus not produced posterodistally .................................................................. A. burkey