WISCONSIN PHYTOPLANKTON 201) 



PLATE 24. 



Page 



Figs. 1-4. Tetraedron trigonum var. setigerum (x 1000) 117 



Figs. 5-9. Tetraedron trigonum var. gracile (x 1000) 117 



Figs. 10-13. Tetraedron minimum (x 1000) 118 



Fig. 14. Tetraedron regulare (x 1000) 118 



Figs. 15-16. Tetraedron regulare var. incus (x 1000) 118 



Figs. 17-18. Tetraedron regulare var. torsum (x 1000) 119 



Figs. 19-22.. Tetraedron victorieae var. major (x 1000) 



14 



