296 U.S. NATIONAL MUSEUM BULLETIN 271 



relationships and obviates the use of a long key with more than 100 

 couplets. Key N is provided as a separate entity for a special group of 

 genera. 



BASIC LYSIANASSID KEY 



1. Telson absent (figs. 122a, 124a) Key A 



Telson present 2 



2. Mandible without distinct incisor (fig. 126c) Kerguelenia 



Mandible with distinct incisor (figs. 126a,6,d) 3 



3. From lateral view, mouthparts group strongly and conically projecting below 



head, more or less styliform (fig. 123e) Key B 



Mouthparts group usually not strongly or conically projecting below head, 

 parts not styliform [if so, uropod 3 lacking rami (fig. 132j)] 4 



4. Gnathopod 1 chelate (figs. 129a,e,h,o) Key C 



Gnathopod 1 subchelate or simple, rarely appearing parachelate .... 5 



5. Mandibles: middle of incisor sharply dentate (fig. 126o) Key D 



Mandibles : middle of incisor not dentate 6 



6. Maxilla 1 lacking palp (fig. 1276) Key E 



Maxilla 1 bearing 1- or 2-articulate palp (fig. 126a) 7 



7. Both coxae 1 and 2 (and occasionally 3) very small or distinctly smaller 



than following coxae, largely hidden by following coxae (fig. 122c). 



Key F 



Neither coxae 2 nor 3 distinctly reduced, both visible (fig. 122d) (occasionally 



coxa 1 reduced alone) choose either couplet 8 or 21 ' 



8. Telson entire or emarginate, no apical slit (figs. 128p,M;) Key G 



Telson cleft enough to provide slit or facing edges at angle of less than 



45 degrees (figs. 128n,o,0 9 



9. Article 2 of pereopod 3 deeply indentured (fig. 1316) Glycerina 



Article 2 of pereopod 3 not deeply indentured . . use either couplet 10 or 11 



10. [Branchiae with large plaits (fig. 127s) (use Key H for rapid identification of 



select group of genera only, otherwise continue to couplet 11) . . Key H] 

 [Branchiae lacking plaits (if in doubt use this couplet) 11] 



11. Article 7 of gnathopod 1 minute, shrouded among a large and long tuft of 



setae or cirri attached to either or both propodus and dactyl (figs. 129n, 



130m) Key K 



Article 7 of gnathopod 1 clearly visible, not shrouded. 



use either couplets 12 or 19 



12. Upper lip produced forward lobately and usually conspicuously in front of 



epistome (epistome occasionally also projecting forward alongside dorsal 



edge of labral lobe) (figs. 125a-(i) Key I - 



Upper lip not conspicuously produced forward lobately, or epistome and 

 upper lip coalesced even if produced 13 - 



13. Epistome produced forward acutely and separately from upper lip (fig. 1256) . 



14 

 Epistome, if produced, not acute or conical or epistome and upper lip co- 

 alesced even though produced 16 



' Couplet 8 leads to characters of ease i n identification whereas couplet 21 leads to a possible natural group- 

 ing by use of mandibular structures. 



- Key I generally contains taxa with produced upper lip (labrum) even if coalesced with epistome as long 

 as labral portion recognizable by its position; couplet 13 generally contains taxa with epistome and upper 

 lip together lobate and separated by a notch even though some of these taxa occur in key I for comparative 

 purposes. 



