306 U.S. NATIONAL MUSEUM BULLETIN' 271 



KEY L 



1. Pereopods 1-5 with long dactyl folded back on an inflated article 6, thus 



prehensile (fig. 130d) Metacyclocaris 



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



2. Maxilla 2: lobes gaping and/or inner much broader than outer (fig. 127j); 



mandible with molar, combined with nearly simple gnathopod 1 . Aristias 



Maxilla 2: lobes appressed and of similar shape, other characters not in 



combination 3 



3. Mandible lacking molar, gnathopod 1 simple 4 



Mandible bearing molar, gnathopod 1 subchelate (except in Metambasia) . 5 



4. Article 2 of maxillipedal palp as broad as or broader than outer plate. 



Ambasiella 

 Article 2 of maxillipedal palp less than half as broad as outer plate . Ambasia 



5. Inner plate of maxilla 1 with one or two immense, falcate setae (fig. 127rf). 



Hirondellea ' 

 Inner plate of maxilla 1 with small, slender setae 6 



6. Maxilla 1 : inner plate with five or more setae 7 



Maxilla 1 : inner plate with three or fewer setae 8 



7. Mandibular molar immense (fig. 126(i), inner plate of maxilla 1 setose only 



terminally, article 3 of gnathopod 1 not elongate Eurythenes 



Mandibular molar slender but strongly projecting, inner plate of maxilla 1 

 setose medially and terminally, article 3 of gnathopod 1 elongate [see 2 

 species of Cheirimedon] Paralicella 



8. Inner ramus of uropod 2 constricted 9 



Inner ramus of uropod 2 simple . 11 



9. Gnathopod 1 slightly chelate, epistomal margin dorsoventrally elongate. 



Aristiopsis 

 Gnathopod 1 subchelate or simple (Metambasia), epistomal margin dorso- 

 ventrally compressed even though lobate (normal) 10 



10. Mandibular molar poorly developed, weakly triturative or fuzzy, palp 



attached proximal to molar, gnathopod 1 subchelate. 



"Orchomenella" groenlandica (Hansen) 

 Mandibular molar strongly triturative, palp attached level with molar, 



gnathopod 1 subchelate Schisturella 



Mandibular molar weakly triturative or fuzzy but very large, palp attached 



level with molar, gnathopod 1 simple Metambasia 



11. Outer ramus of uropod 3 uniarticulate Tryphosoides 



Outer ramus of uropod 3 biarticulate 12 



12. Mandibular molar lacking setules Lepidepecreopsis 



Mandibular molar bearing setules 13 



13. Gnathopod 1 with article 6 enlarged and distally expanding, nearly twice as 



broad as article 2, palm protuberant, long, and slightly chelate. 



Cheirimedon latimanus Sars, 1895 

 Gnathopod 1 with article 6 unexpanded, palm not chelate 14 



14. Head very small,^ epistome and upper lip weakly developed and incon- 



spicuous Uristes [=Urisloides] 



Head of normal size, epistome and upper lip strongly developed, epistome 

 generally slightly lobate 15 



1 See note, Key N, couplet 23 (p. 310). 



2 Occasionally head ventrally extended and covering base of antenna 2 as in " Uristes" lepidus J. L. 

 Barnard (1964a). 



