92 



Fig. ikQ. Nitzschia elliptica , (6), cells 13-22u long, 5-6[i wide; 

 carinal dots small, 16-20 in 10|a; striae indistinct; 

 frustule delicate. X 1000. At times abundant in the 

 Arkansas River. 



J 



■~\ 



'-■J 



valve view 



Notes: 



Fig. 1*4-9. Nitzschia filiformis , (5), cells 20-100u long, k-6^ wide; 

 8-11 carinal dots in lOu; about 36 striae in lOu. X 1000. 





valve view 



girdle view 



Notes : 



Fig. 150. Nitzschia fonticola, (5), cells ll-30u long, 2-k\i wide; 

 12-15 carinal dots in lOu; striae fine, but distinct, 

 28-30 in lOu. X 1000. In the Snake River. 



valve view 



Notes : 



