PLATE O. 



Fig. 1. Canthocamptus illinoisensis, antenna oMemale. 



Fig. 2. " " fifth foot of female. 



Fig. 3. " " antennule. 



Fig. 4. " '' firstfoot. 



Fig. 5. " " caudal stylet. 



Fig. 6. CantJiocamptus northumhricus^ var. americanus, fifth 



foot of female. 

 Fig. 7. " " antenna of female. 



Fig. 8. " '* maxilliped. 



Fig. 9. " " caudal stylet. 



Fig. 10. " " antenna of male. 



Fig. 11. " " first foot. 



Fig. 12. " " fourth foot. 



Fig. 13. '' " fifth foot of male. 



Fig. 14. " " frontal area. 



Fig. 15. CantJiocamptus tenuicaudis, stylets. 

 Fig. 16. " " fifth foot of female. 



Fig. 17. Cyclops serridatus, fifth foot. . 

 Fig. 18. '" " fourth foot. 



Fig. 19. " " outer ramus of first foot. 



Fig. 20. Cantliocamptus northumbricus, inner ramus of third 



male foot. 

 Fig. 21. " " beak. 



Fig. 22. " " maxilla. 



