34 



Fig. 37. Diatoma elongatum. (5), cells 30-120u long, 2-k-\i wide; 

 internal costae narrow, 6-10 in lOu; striae delicate, 

 about l6 in lOu. X 1000. In Great Lakes and Columbia 

 River. 



girdle view 



valve view of var. 

 tenuis 



valve view 

 Notes : 



Fig. 38. Diatoma hiemale , ( 4) , cells 15-100u long, 7 - 20u wide; internal 

 costae robust, 2-4 in lOu; striae prominent, 18-20 in lOu. 

 X 1000. 



girdle view of valve 

 part of colony view 



girdle view 

 of part of 

 colony of var. 

 mesodon 



valve view 

 of var. mesodon 



Notes : 



