I 



PLATE IV. 



Fig. 23. Arcella vulgaris, reproduction, x 620, - - 17 



Fig. 24. Arcella V7ilgaris, reproduction, x 560, - - 17 



Fig. 25. Arcella discoidts, dorsal view, x 225, - - - 18 



Fig. 26. Arcella disco/des, lateral view, x 225, - - 18 



Fig. 27. Centropyxis aculeata, ventral view, x 310, - . 18 



Fig. 28. Centropyxis aculeata, lateral view, x 500, - 18 



