MARINE GAMMARIDEAN AMPHIPODA 299 



10. Inner plate of maxilla 1 with large sickle-shaped setae (fig. 127d). 



Hirondellea 

 Inner plate of maxilla 1 with normal setae 11 



11. Mandibular molar obsolescent or absent, gnathopod 1 strongly chelate or 



large 12 



Mandibular molar well developed, ridged or setulose, gnathopod 1 weakly 

 chelate (fig. 129a) 13 



12. Gnathopod 1 very slender, chela long (fig. 129o), epistome acute anteriorly. 



Euonyx 

 Gnathopod 1 powerful, article 6 very broad, chela formed by deeply excavate 



palm (fig. 129e), epistome unproduced Opisa 



Gnathopod 1 powerful, article 6 very broad and distally expanding, palm 

 protuberant, not excavate (fig. 1290, epistome and labrum each with 

 shallow rounded lobe Cheirimedon latimanus Sars, 1895 



13. Epistome with anterior bulb separated from protrusion of upper lip by long, 



flat margin Aristiopsis 



Epistome rounded and appressed to protrusion of upper lip (exceptional) . 



Schisturella 



14. Mandibular molar well developed, cuboid or ovate, setulose or ridged . . 15 

 Mandibular molar conical and unridged, obsolete or absent 19 



15. Telson cleft Gainella 



Telson entire some species of Orchomene 



16. Gnathopod 2 tapering to a point (but minutely chelate) (fig. 131z). 



(alternate position) Gainella 

 Gnathopod 2 distally blunt 17 



17. Maxillipedal palp article 4 vestigial (fig. 128e) Pachynus 



MaxiUipedal palp article 4 normal, claw-shaped 18 



18. Outer plate of maxiUiped large, exceeding end of palp article 2 19 



Outer plate of maxiUiped small, not or scarcely exceeding palp article 1 . 20 



19. Eyes very large (losing pigment in alcohol) , accessory flagellum 4 + -articulate, 



telson longer than broad Koroga 



Eyes absent, accessory flagellum l-articulate, telson as broad as long. 



Figorella 



20. Spines on outer plate of maxilla 1 reduced to two or three fused members, 



outer ramus of uropod 3 uniarticulate Sophrosyne 



Spines on outer plate of maxilla 1 of normal number (9) and articulate, 

 outer ramus of uropod 3 biarticulate Kyska 



KEY D 



Most lysianassids have the primary cutting edge of the mandible 

 bearing at least one notch subtended by a tooth but these notches 

 are always lateral and never in the middle of the cutting edge; the 

 following species have teeth along the middle margin of the primary 

 mandibular plate. 



Valettia is also included in Key B, because of its slightly chelate 

 first gnathopod. Podoprion and Onesimoides in Key C and Aristiopsis 

 in Keys C and N also have a toothed incisor. Clepidecrella may have 

 an extremely minute incisorial dentition. NichoUs' (1938) figure of 

 Adeliella has a slight indication of incisorial teeth. 



285-135 O - 69 - 20 



