EXPLANATION OF THE PLATES. 
Fig. 6. Variety of fig. 3 ? 
7. Five-armed variety of fig. 4. 
8. a. b. Euastrum margaritiferum, a. b. different position of same individual. 
9. a. b, Euastrum-, a. b. two positions. 
10. Euastrum-. 
11 and 12. Euastrum-. 
13. Euastrum-, 
14. Euastrum-. 
15. Xanthidium-, a recent species from West Point. 
16. a. b. Xanthidium-, another species from West Point. . 
17. Arthrodesmus quadricaudatus. 
18. a. b. Arthrodesmus cutus? 
19. Micrasterias Tetras. 
20. Micrasterias Boryana. 
21. Micrasterias . 
22. Euastrum rota ? 
23. Euastrum Crux-Melitensis ? 
24. Euastrum-, possibly a young state of E. rota. 
25. Euastrum-. 
26 and 27. 27 a. b. c. d. Euastrum -, (Echinella oblonga of Greville ?) a- b. two 
positions of same individual, c. d. smaller individuals. 
28. a. b. Euastrum -, two portions. 
29. Euastrum-. 
30. Closterium lunula. 
31. Closterium moniliferum. 
32. Closterium trabecula ? 
33. Closterium digitus ? 
34. Closterium lineatum ? • 
35. Closterium striolatum. 
36. Closterium rostratum. 
37. Closterium tenue ? 
38. Closterium-. 
39. Scale, each division of which represents yloth of a millimetre magnified equally with 
the sketches. 
