Gammarus 461 



1 Antenna 1 shorter than antenna 2 — 3. 



\ Antemia 1 not shorter than antenna 2 — 5- 



{Antenna 2, ultimate Joint of x>eduncle shorter 

 than penultimate • 2. G. abbreviatus . . . p. 462 

 Antenna 2, ultimate Joint of pednncle longer 

 than penultimate — 4. 



I Gnathopod 2, 6tli Joint narrow, subcjlindric . 3. G. annulatus . . . . p. 4(53 

 \ Gnathopod 2, 6tlijoint not narrow, subrectangular 4. G. natator p. 463 



„ I Pleon Segment 4 without dorsal spinules - - 6. 

 \ Pleon segraent 4 with dorsal spinules — 16. 



( Pleon Segment 5 without dorsal spinules — 7. 

 \ Pleon Segment 5 with dorsal spinules — 14. 



I Uropod 3, outer ramuslittle longer than peduncle 5. G. obesus p. 464 



7 l Uropod 3, outer ramus much longer than 



l peduncle — 8. 



Uropod 3, inner ramus less than half as long 



as outer — 9. 

 Uropod 3, inner ramus fully half as long as 



outer — 13. 



Uropod 3, outer ramus with rather large 



2d Joint — 10. 

 Uropod 3, outer ramus with very small 2d Joint — 11. 



f Uropod 3, inner ramus scarcely \4 of outer . 6. G. macrurus .... p. 464 



^ j Peraeopods with very few setae 8. G. subnudus . . . . p. 465 



\ Peraeopods with numerous setae — 12. 



I Uropod 3, inner ramus nearly ^'a of outer . . 7. G. compressus . . . p. 465 



Peraeopods with very few setae 



Peraeopods with numerous setae — 12. 



{Pleon Segments 4 and 5 dorsally upraised, 

 gibbous 9. G. deminutus . . . p. 466 

 Pleon Segments 4 and 5 not dorsally upraised 

 or gibbous 10. G. similis p. 466 



j Mandibular palp of nonnal size 11. G. weidemanni . . . p. 467 



\ 3Iandibular palp abnormally large 12. G. maeoticus . . . . p. 467 



/ Peraeopod 5, 2d Joint produced behind 3d . 13. G. crassus p. 467 



\ Peraeopod 5, 2d Joint not produced behind 3d — 15. 



I Peraeopod 5, 2djointbroad, abruptly contracted 

 distally 14. G. warpachowskyi . p. 468 

 Peraeopod 5, 2d joint not broad, not abruptly 

 contracted 15. G. pauxillus . . . . p. 469 



/ Pleon Segments 2 and 3, postero-lateral corners 



.. J obliquely truncate 16. G. kietlinskii . . . p. 469 



1 Pleon Segments 2 and 3, postero-lateral corners 

 ' not truncate — 17. 



I Uropod 3, inner ramus less than half as long as 

 outer — 18. 

 Uropod 3, inner ramus not less than half 

 as long as outer — 24. 



j Uropod 3, outer ramus remarkably long — 19. 

 \ Uropod 3, outer ramus not remarkably long — 21. 



{Gnathopod 1, 6tli joint much broader than that 

 of gnathopod 2 17. G. andrussowi . . • p. 469 

 Gnathopod 1, 6tli joint not much broader than 

 that of gnathopod 2 — 20. 



