Figure 3. Biddulphia laevis (arrow), a very large diatom characteristic of 

 brackish water. (UOOX) 



/ 





t 







Figure U. 



Pinnularia subcapitata var. paucistriata (arrow), a diatom prefering 

 water of low mineral content and an anomaly in the Yellowstone River. 

 (1000X) 



■14- 



