33 



Fig. 35. Tabellaria flocculosa , (5), cells 12-50u long, 5-l6»i wide; 

 about lb striae in 10u; many intercalary bands. X 1000. 

 In Great Lakes and Columbia River. 



valve view 



girdle view 



Notes 



9b Frustules without septae 10 



10a Valves with thickened internal transverse ribs (costae), most 



of which extend completely across the valve face 11 



10b Valves without thickened internal transverse ribs 12 



11a Valves symmetrical about the apical plane - DIATOMA 



Fig. 36. Diatoma anceps , (5), cells 15-100u long, k-Q\i wide; internal 

 costae narrow, 3-6 in 10n; striae delicate, 18-20 in 10|i. 

 X 1000. In Colorado River. 



fipMLiliilllllTpJ 



rrwr 



valve view 



girdle view 

 colony 



Notes: 



