30 



Fig. 29. Stephanodiscus niagarae , (3), 

 cells 30-100u in diamete r ; 

 3-5 rows of punctae in marginal 

 region of striae, spines sub- 

 marginal and more robust than 

 in S_. astrea. X 900. Upper 

 Mississippi and Missouri Rivers, 



Notes : 



valve view 



Fig. 30. Stephanodiscus tenuis , (3), 

 cells 6-28u in diameter) 

 spines at end of each row 

 of striae. X 1000. 



Notes : 



valve view 



Notes on other species of STEPHANODISCUS. 



