212 WISCONSIN PHYTOPLANKTON 



PLATE 27. 



Page 



Figs. 1-3. Tetraedron limneticum (x 1000) 123 



Figs. 4-5. Tetraedron planctonicum (x 1000) 123 



Fig. 6. Tetraedron enorme (x 1000) 124 



Figs. 7-8. Polyedriopsis spinulosa (x 1000) 124 



