29 



Fig. 26. Stephanodiscus dubius , (3), cells 10-25u in diameter. 

 X 1000. In Great Lakes and Columbia River. 



valve view 



girdle view 



Notes 



Fig. 27. Stephanodiscus Hantzschii , (7), 

 cells «-20u in diameter; 8-10 

 striae in 10^; striae very light; 

 frustule often collapses during 

 incineration; may be confused 

 with Melosira Binderana . X 2000. 

 Widely distributed. 



Notes : 



valve view 



Fig. 28. Stephanodis cus invisitatus , (7), 

 cells 5-15U in diameter,* 15-20 

 striae in lOu; striae very light; 

 easily confused with _S_« Hantzschii . 

 X 2000. Ohio River Basin. 



valve view 



Notes : 



