195 WISCONSIN PHYTOPLANKTON 



PLATE 76. 



All figures x 500. 



Page 



Figs. 1-8. Staurastrum lacustre G. M. Smith 97 



Figs. 9-10. Staurastrum tetracerum var. validum W. & G. S. West 96 



Figs. 11-14. Staurastrum tetracerum var. evolutum W. & G. S. West 97 



Figs. 15-16. Staurastrum tetracerum var. trigonum Lund 97 



Figs. 17-20. Staurastrum contortum sp. nov 98 



Figs. 21-24. Staurastrum Chaetoce'ras (Schrod.) comb, nov 99 



