MARINE GAMMARIDEAN AMPHIPODA 303 



KEY H 



These genera have gills bearing swellings or plaits. Since so many 

 lysianassids have not been investigated for this characteristic and 

 because gills of the following genera are not always clearly plaited 

 the genera have been added to subsequent keys. Hence key H simply 

 represents a quick way for the taxonomist to determine familiar 

 genera with obviously plaited gills. If this key is unsatisfactory one 

 must proceed to couplet 11 of the Basic Key. Many species of Hij)- 

 pomedon have indistinctly plaited gills. Gills of Socarnella are unknown. 



1. Coxa 1 reduced and hidden by coxa 2 (fig. 1236) Schisturella 



Coxa 1 of normal dimensions and not hidden by coxa 2 2 



2. Gnathopod 1 subchelate 3 



Gnathopod 1 simple 7 



3. Mandibular palp attached proximal to molar (fig. 126z) 4 



Mandibular palp attached level with molar (fig. 126e) 5 



4. Article 5 of male antenna 2 extremely tumid (like article 4 of fig. 124A;). 



Microlysias 

 Article 5 of male antenna 2 slender or not relatively stouter than article 4. 



Orchomene 



5. Mandibular molar imperfectly conical or attenuate, setulose, not ridged 



(fig. 126;) Anonyx 



Mandibular molar cylindrical or cuboidal, ridged (fig. 126g') 6 



6. Dactyl of gnathopod 1 very small, similar to dactyl of gnathopod 2, palp 



article 4 of maxilliped stout, short Pseudoanonyx 



Dactyl of gnathopod 1 and palp article 4 of maxilliped long and claw-like. 



Hippomedon 



7. Dactyl of gnathopod 1 setose or spinose on posterior edge (fig. 130z), upper lip 



poorly delineated (fig. 125gr), mandibular palp attached level with molar. 



Ichnopus 



Dactyl of gnathopod 1 not setose or spinose on posterior edge, upper lip 



strongly delineated (figs. 125a,c), mandibular palp attached distinctly 



proximal to molar 8 



8. Outer ramus of uropod 3 biarticulate or composed of one article and large 



terminal spine Socarnes 



Outer ramus of uropod 3 uniarticulate 9 



y. Telson emarginate; mandible long and narrow, palp article 2 about 5 times as 

 long as article 1 and more than 2 times as long as article 3 . . . Socarnella 

 Telson cleft more than halfway; mandible short and stubby, palp article 2 

 only 3 times as long as article 1 and about 1.5 times as long as article 3. 



Socarnopsis 



KEY I 



Genera of Key H are included here owing to possible confusion in 

 Key G concerning gills. Koroga is repeated in case its telson is con- 

 sidered as slightly cleft. 



1. Coxa 2 concealing anteroventral corner and most of coxa 1 (fig. 1196), coxa 1 

 slightly or strongly reduced in size or not quadrate 2 



