TJic Diatoms of Nebraska 95 



21. Stauroneis 



Stauroneis Ehr. Amer., p. 134. 1843. 



Etym. from Gr. o-rav/so's, cross, the transverse central nodule 

 forming with the racliis, a cross. 



Cells as in Navicula, but the central nodule broadened trans- 

 versely into a " stauros " (cross). Frequently also with a trans- 

 verse hyaline area bordering the stauros. Girdle with or without 

 interzones ; free or in a gelatinous envelope. Chromatophores as 

 in Navicula. Auxospores single from two mother cells. 



I. stauroneis phoenicenteron Ehr. Verb., pi. II, 5, fig. i. 184^. 



Bacillarla phoenicenteron Nitz. Beitr., pi. j, figs. 12, 14. i8iy. 



PI. 12, figs. 453-455. 457-459- 



Lanceolate, slightly attenuate, 62-266 /x long, 13-40 /a wide; 

 apices obtuse, rounded, often slightly constricted ; raphe consisting 

 of a double line for the greater part of its length; stauros broad, 

 extending to the margins of the valve, usually slightly dilated out- 

 ward; striations granular, radiate, 14-18 in lO/x, shortened, leav- 

 ing a broad hyaline space along the raphe. A sporangial condition 

 is shown in fig. 456. 



In creeks, rivers, ponds, ditches, springs, tanks, etc., usually with other 

 algae, also fossil : Andrews, Anselmo, Ashland, Atkinson, Broken- Bow, 

 Central City, Cherry County, Clear Lake, Crawford, Dismal River, Dun- 

 ning, Grand Island, Hackberry Lake, Hemingford, Johnson, Lincoln, Lodi, 

 Louisville, New Helena, North Platte, Oakdale, Orella, Pelican Lake, Peru, 

 Plattsmouth, Ruby, St. Paul, St. Michael, Seneca, Snake River, Talmage, 

 Tekamah, Thedford, Valentine, Wahoo, Wann. 



Fossil : Cherry County, Greeley County, Loup City, Mullen, Valentine. 



Rapid City, Rosebud, S. Dak. ; Cheyenne, Wyo. ; Sully's Hill, N. Dak. ; 

 New Concord, Rio Grande, Ohio. 



