314 U.S. NATIONAL MUSEUM BULLETIN 271 



KEY Q 



1. Mandibular molar distinctly triturative and usually columnar, cylindrical or 



cuboidal, bearing ridges or cusps for grinding (figs. 12Qd,g,m) .... 2 



Mandibular molar not triturative or absent, often setulose or bearing a few 



articulate spines (figs. 12Ge,h,i,j) 17 



2. Coxa 1 noticeably reduced and partially hidden by coxa 2 or coxa 1 tapering 



or triangular 3 



Coxa 1 large, visible, rectangular or distally expanded 7 



3. Mandibular molar with triturative girdle, molar immense and not columnar 



(fig. 126d) Eurythenes 



Mandibular molar normally columnar or adze-shaped and medium in size . 4 



4. Telson emarginate or cleft one sixth or less, maxilla 2 with setae reduced to 



one to four per lobe (fig. 127k) Adeliella 



Telson cleft one third or more, maxilla 2 with lobes strongly setose 

 (fig. 1270 5 



5. Inner ramus of uropod 2 simple. 



Tryphosella, Tryphosoides, and "Pseudotryphosa" {?=Uristes) 

 Inner ramus of uropod 2 constricted 6 



6. Epistomal region not dorsoventrally elongate Schisturella 



Epistomal region dorsoventrally elongate Aristiopsis 



7. Gnathopod 1 simple 8 



Gnathopod 1 subchelate 9 



8. Telson as broad as long, emarginate .... Onlslmus[ = Pseudalibrotus] 



Telson longer than broad, deeply cleft Menigratopsis 



Telson as broad as long, cleft halfway. 



Rifcus and Paronesimus (sec diagnoses) 



9. Inner ramus of uropod 3 vestigial or absent (fig. 132A;), always less than 



half length of outer ramus 10 



Inner ramus of uropod 3 subequal to outer ramus 11 



10. Inner ramus of uropod 3 present, article 1 of both flagella of antenna 1 



elongate and that of accessoi-y flagellum expanded .... Onesimoides 



Inner ramus of uropod 3 absent, article 1 of both flagella of antenna 1 of 



normal size Paronesimoides 



11. Accessory flagellum 2-articulate 12 



Accessory flagellum 3 + -articulate 14 



12. Spines on outer plate of maxilla 1 reduced to five or six Rifcus 



Outer plate of maxilla 1 with nine or more spines 13 



13. Hand of gnathopod 1 enlarged and expanding distally . . Cheirimedon (type) 

 Hand of gnathopod 1 of normal unexpanded dimensions . . . Tryphosoides 



14. Telsonic apices with seven or more spines each (fig. 128s). 



Hippomedon [=^ Paratryphosites] 

 Telsonic apices with three or fewer spines or telson entire 15 



15. Telson cleft halfway or more 16 



Telson cleft one third or less. 



Boeckosimus and Onisimus [="Onisimus" and "Pseudalibrotus"] 



16. Inner ramus of uropod 2 simple, epistome unproduced and slightly dominated 



by labrum (from lateral view) (fig. 125n). 



Hippomedon i and [Paracentromedon] ^ 



Inner ramus of uropod 2 deeply constricted, epistome acutely produced 



(fig. 125&) Tryphosites 



• And see Cheirimedon femoratus (Pfeffer) and C.fougneri Walker distinguished from tliese genera by the 

 transverse palm of gnathopod 1 (see pp. 334-335). 



