The Diatoms of Nebraska 39 



Lake, Red Cloud, Seneca, Valentine. 

 Fossil: Thedford. 

 Turtle River, S. Dak. 



2. Cyclotella 



Cyclotella Kiitz. BacilL, p. 50. 1844. Syn. Diaf., p. y. 1833. 

 (Only as a division, not as a generic name.) 



Etym., diminutive of Greek kukAos, circle. 



Cells usually single or in pairs, not in filaments, short-cylindrical, 

 disciform, hence usually seen in end view, divided into two parts, 

 the outer with more or less fine, smooth or punctate striations, 

 sometimes with scattered spines, without dots, or irregularly punc- 

 tate; the central part sometimes swollen. Girdle face straight or 

 undulate. Auxospores formed asexually, single from one mother 

 cell. 



A. Margin strongly striate and center coarsely punctate. 



I. C. striata. 

 AA. Not with marginal striations and coarsely punctuate center. 

 h. Center with triangu'ar dots. 2. C. antiqua. 



bb. Center without triangular dots. 



c. Marginal striations mixed with heavier striations at regular 



intervals. 3. C. comta. 



cc. Striations all alike. 4. C. meneghiniana. 



1. Cyclotella striata (Kiitz.) CI. & Grun. Arcf. Diat., p. up. 



1880. 

 Coscinodisciis striatus Kiitz. Bacill., p. 131, pi. i , fig. 8. 1844. 

 PI. I, fig. 22. 



End of cell with distinct marginal ring, 5-6 /* wide, of coarse 

 striations, 7-12 in 10 /x; diameter of cells, 30-80 /x. 



In Devils Lake, N. Dak. 



2. Cyclotella antiqua W. Sm. Brit. Diat., I, p. 28, pi. 5, fiq. 4p. 



1853- 



PI. I, fig. 17. 



Cells 1 5-30 /i in diameter; end of cell with distinct marginal 

 ring of costae, 2-3 /a wide ; costae intermixed with spines or coars^ 

 dots, about 15 costae and 6 dots in lO/^ ; center finely granular with 

 6-15 triangular elevations. 



Grand Island. 



