96 Clarence J. Elmore 



2. Stauroneis acuta W. Sm. Brit. Diat., I, p. 5p, pi. 19, fig. iSy. 



PI. 12, figs. 456, 460. 



Rhombic-lanceolate or gradually tapering from the middle to 

 the narrow obtuse ends, or elliptical, 80-1 50 lU, long, 15-40^1 wide; 

 margins thickened at the ends, leaving a distinct diaphragm or 

 lumen; raphe double for most of its length; stauros very broad, 

 wider at the margins of the valve; striations granular, radiate, 

 about I2"in 10 /x; cells usually imited in short bands. 



In spring, Brock; Dewey Lake, Hackberry Lake. 



3. Stauroneis parvula Janisch. Guano, p. 14. i(i6i. 

 PI. 12, figs. 461-462. 



Linear-lanceolate or oblong, 12-25 ^u, lo"?. 5-6 /* wide; apices 

 more or less rostrate ; stauros extending to the margins ; striations 

 radiate, granular, extending nearly to the raphe, 20-23 in lO/x,. 



In creek, Anselmo; in bottle in laboratory, Grand Island; St. Paul, 

 Valentine. 



Fossil: Agate. 

 Rosebud, S. Dak. 



4. Stauroneis anceps Ehr. Amer., p. 134, pi. 2, I, fig. 18. 1843. 

 PI. 12, figs. 463-468. 



Elliptical or elliptical-lanceolate with apices varying from ros- 

 trate to rostrate-capitate, 27-130^11 long, 6-1 7 /x wide; stauros 

 broad, usually extending to the margins of the valve, slightly 

 broader outward; striations radiate, granular, 14-20 in 10 ft, short- 

 ened, leaving a hyaline space along the raphe. Var. amphiccpJiala, 

 fig. 466, is more linear in form with capitate apices. Var. linearis, 

 fig. 465, has rostrate apices. This species shows all gradations 

 into S. phocnicenteron. 



In pools, tanks, creeks, springs, etc., also fossil : Ainsworth, Andrews, 

 Ashland, Auburn, Brock, Central City, Clear Lake, Columbus, Dismal 

 River, Dunning, Emmett, Fairbury, Grand Island, Hackberry Lake, Halsey, 

 Hemingford, Hyannis, Julian, Lincoln, Long Pine, Louisville, Milford, 

 New Helena, Norfolk, Omaha, O'Neill, Orella, Peru, Red Cloud, St. Paul, 

 Snake River, Talmage, Valentine, Wann, Weeping Water, West Point, 

 Woodlake. 



Fossil : Cherry County, Loup City, Merriman. Mullen. 



Belvidere, Interior, Little White River, Rapid City, Rosebud, S. Dak.; 

 Cheyenne, Wyo. ; Stockton, Cal. ; New Concord, Rio Grande, Ohio. 



