MARINE GAMMARIDEAN AMPHIPODA 377 



5. Gnathopod 1 palm oblique Westwoodilla and Bathymedon 



Gnathopod 1 palm transverse Carolobatea 



6. Mandibular molar unridged, with a few setae Perioculopsis 



Mandibular molar large, ridged 7 



7. "Mandibular palp article 2 strongly curved" (fig. 137A;), article 2 of antenna 



1 as long as or longer than article 1 Arrhis 



"Mandibular palp article 2 straight" (fig. 1370 (type-species), article 2 of 

 antenna 1 shorter than article 1 Aceroides 



8. Uropod 2 reaching only to end of peduncle of uropod 3 9 



Uropod 2 reaching halfway or more along rami of uropod 3 (or rami of 



uropod 3 absent) 12 



9. Gnathopods 1-2 : article 5 strongly lobate 11 



Gnathopods 1-2: article 5 not lobate (figs. 138/,z) 10 



10. Gnathopod 2 simple (fig. 138i) Bathyporeiapus 



Gnathopod 2 subchelate Parhalimedon 



11. Eyes contiguous, appearing as one body, pereopods 1 and 2 with article 7. 



Halicreion 

 Eyes not contiguous, pereopods 1 and 2 lacking article 7 . . . Exoediceros 



12. Mandible lacking palp, uropod 3 lacking rami. 



Metoediceros (Incertae Sedis) 

 Mandible bearing palp, uropod 3 bearing rami 13 



13. Mandibular molar lacking triturating surface, often with articulate spine(s) 



(fig. 1370 14 



Mandibular molar bearing teeth and ridges (fig. 137A;) 19 



14. Lower lip: inner lobes coalesced (fig. 1370 15 



Lower lip: inner lobes separate (fig. 137m) 16 



15. Telson entire (fig. 136/) Perioculodes 



Telson emarginate (fig. 136a) Perioculopsis 



16. Gnathopods 1-2 structurally alike 17 



Gnathopods 1-2 structurally dissimilar Paroediceros 



17. Gnathopods lacking posterior lobe on article 5 Exodiceropsis 



Gnathopods bearing posterior lobe on article 5 18 



18. Gnathopods 1-2: lobe of article 5 long, fully guarding article 6 . Arrhinopsis 

 Gnathopods 1-2: lobe of article 5 short, scarcely guarding article 6. 



Oediceros 



19. Gnathopod 1, palm transverse Carolobatea 



Gnathopod 1, palm oblique 20 



20. Gnathopods 1-2: article 5 not distinctly lobate 21 



Gnathopods 1-2: article 5 grossly lobate 23 



21. Gnathopod 2 subchelate 22 



Gnathopod 2 simple (fig. 138i) Bathyporeiapus 



22. Eyes unpaired, coalesced; article 2 of pereopod 5 broadly lobed postero- 



distally Methalimedon 



Eyes paired; article 2 of pereopod 5 sharply narrowed posterodistally. 



Parhalimedon 



23. Back multicarinate Acanthostepheia 



Back not multicarinate, usually smooth, occasionally tuberculate ... 24 



24. Coxa 4 produced subacutely posterodistally 25 



Coxa 4 not produced posterodistally 28 



25. Eyes coalesced dorsally or absent 26 



Eyes paired and lateral Oediceropsis (typical) 



26. Article 1 of antenna 2 swollen 27 



Article 1 of antenna 2 not swollen . . Oediceroides and Paroediceroides 



