PLATE XXXIII. 



FIGS. PAGE 



1-3. .Euastrum ventricosum Lund. All x 430 . 4 



4-6. E. crassum (Breb.) Kiitz. 4 and 6, x 430; 5, 

 x 400. The upper semicell of fig. 6 shows a 

 common variation in which there is a median 

 rounded protuberance on the sides of the semi- 

 cell . . . . .5 

 7-8. E. crassum var. scrobiculatum Lund. All x 430 . 7 



