EXPLANATION OF THE PLATES. 
ILLINOIS CRUSTACEA. 
1, 2, 3, 4, 5, 6, 7, Crangonyx mucronatus , Forbes. 
1. Head of female, with pedicels of antennae. 
2. Posterior abdominal segments of male, with their appendages. 
3. One of 1st pair of hands of male. 
4. One of 2d pair of hands of male. 
5. Telson and last pair of stylets of female. 
6. One of 1st pair of hands of female. 
7. One of 2d pair of hands of female. 
8, 9, 10, 11, Asellus brevicauda , Forbes. 
8. Hand of male, X 20. 
9. One of 1st pair of genital plates of male, X 38. 
10. One of 2d pair of genital plates of male, X 19. 
11. One of caudal stylets. 
12, 13, 14, 15, 16, Asellus intermedius , Forbes. 
12. Hand ©f male, X 45. 
13. Hand of female. 
14. Last segment of abdomen, with caudal stylets, X 17. 
15. One of 1st pair of genital plates of male, X 38. 
16. One of 2d pair of genital plates of male, X 38. 
17, 18, Asellus communis , Say. 
17. One of 1st pair of genital plates of male, X 13. 
18. . One of 2d pair of genital plates of male, X 13. 
19, 20, Asellus stygius , Pack. 
19. One of 1st pair of genital plates of male. 
20. One of 2d pair of genital plates of male. 
21, 22, 25, Eubranchipus serratus , Forbes. 
21. Abdomen, X 3. 
22. Frontal appendage of male, X 10. 
25. Claspers of male, from before, X 0. 
