MARINE GAMMARIDEAN AMPHIPODA 309 



Coxa 1 unexpanded distally, unguiform dactyl of gnathopod 1 bearing inner 

 accessory tooth, epistome slightly protruding in front of upper lip, inner 

 ramus of uropod 2 simple, palp article 4 of maxilliped unguiform. 



type-species of Tmetonyx 



Coxa 1 slightly expanded distally, dactyl of gnathopod 1 with accessory 

 tooth but reduced to size of dactyl on gnathopod 2, prebuccal parts 

 apparently like Anonyx of triplicut 29, inner ramus of uropod 2 simple, 

 palp article 4 of maxilliped tumid, subclavate Pseudoanonyx 



30. Dactyl of gnathopod 1 very small and similar in size and morphology to 



dactyl of gnathopod 2 Pseudoanonyx 



Dactyl of gnathopod 1 long, claw-like, thus normal 31 



31. Article 5 of gnathopod 1 longer than article 6 32 



Article 6 of gnathopod 1 longer than or subequal to article 5 33 



32. Head without distinct lateral lobes, anterolateral margin convexly truncate, 



coxa 5 as long as coxa 4 Lepidepecreoides 



Head with small but distinct lateral lobes, coxa 5 shorter than coxa 4. 



Hippomedon [= Paratryphosites, ?Paracentromedon, ?Elimedon] 



33. Outer ramus of uropod 3 uniarticulate Tryphosoides 



Outer ramus of uropod 3 biarticulate 34 



34. Articles 5 and 6 of gnathopod 1 subequal in length, article 6 not expanded, 



palm obsolescent [Paracentromedon] and Paronesimus 



Article 6 of gnathopod 1 large, distally expanding, more than 3 times as long 

 as article 5 (fig. 1290, palm strong Cheirimedon (type) 



KEY N 



All lysianassid genera with coxa 1 distinctly reduced in size and/- 

 or often largely hidden by coxa 2 are assembled here for ease of com- 

 parison. Those species of Key F, in which both coxae 1 and 2 are small 

 and hidden by following coxae, are not included. See also notes on 

 Stomacontion. 



1. Pereopods 1-5 with long dactyls folded back on inflated article 6, thus pre- 



hensile (fig. 130d) Metacyclocaris 



Pereopods 1-5 normal, dactyls short and sixth articles unexpanded ... 2 



2. Upper lip strongly lobate and projecting in front of epistome (figs. 125c,d) . 3 

 Upper lip scarcely or not projecting in front of epistome, latter often large 



and dominating upper lip (figs. I25h,i,k) or epistome and upper lip not 

 distinct from one another 6 



3. Coxa 1 half as long as its second article (fig. 130A;) 4 



Coxa 1 as long as or longer than its second article (fig. 130gf) 5 



4. Gnathopod 1 subchelate even though weakly Schisturella 



Gnathopod 1 simple Metambasia 



5. Outer plates of maxilliped lacking spines, maxilla 1 with seven spines on 



outer lobe Ambasiopsis 



Outer plates of maxilliped spinose, maxilla 1 normal, with 9+ spines on outer 



lobe Schisturella 



Outer plates of maxilliped spinose, maxilla 1 with spines on outer lobe 



reduced to five Neoambasia 



6. Mandibular incisor multidentate (fig. 126^') 7 



Mandibular incisor not dentate 8 



7. Mandible lacking molar, gnathopod 1 chelate, article 2 of pereopod 3 deeply 



indentured (fig. 1316) Podoprion 



