The Diatoms of Nebraska 105 



Gyrosigma delicatulum (W. Sm.) Elmore. 



Pleurosigiiia delicatidmn W. Sm. Anyi. Hist., 2d scries, vol. p, 

 p. 6, pi. I, fig. 5. 1S52. 



PI. 13, figs. 512-513- 



Narrow, lanceolate, 139-280 /x long, 14-30 /x wide, apices slightly 

 acute or rounded ; raphe nearly central, slightly excentric near the 

 ends; striations crossing in three directions, 18-25 in 10 /x. 



In creeks and rivers : Crete, Julian, Lincoln, North Platte 



2. Gyrosigma acuminatum (Kiitz.) CI. Syn. Nav. Diat., I, p. 



114. i8p4. 

 Frustulia acuminata Kiitz. in Linnaca, VIII, p. 555. 18^^. 



Syn. Diat., p. 2/, fig. jd. 18^4. 

 PI. 13. figs. 514-515- 



Lanceolate, 100— 180 /x long, 10-20 /x wide, tapering toward the 

 rounded ends ; raphe central ; striations running in two directions, 

 longitudinal and transverse equally distant, 18-20 in 10 /x. 



In creeks, rivers, etc. : Ashland, Crete, Julian, Lincoln. 

 Devils Lake, N. Dak. 



3. Gyrosigma kiitzingii (Grun.) CI. in CI. & Grim. Arct. Diat., I, 



p. 115. 1894. 



Plcurosigma kiitcingii Grun. J'crli., p. j6i, pi. 4, fig. 5. i860. 



PI. 13, fig. 516. 



Lanceolate, sigmoid, with acute ends, 80-120 /x long, 12-15/1, 

 wide ; raphe sigmoid, median ; central nodule somewhat elongated ; 

 longitudinal striations closer than the transverse ; transverse 20-23 

 in lO/x, longitudinal 25-26 in lO/i. 



In creeks, rivers, springs, etc. : Central City, Culbertson, Fairbury, 

 Julian, Lincoln, Louisville, Ruby, Stromsburg, Tekamah, Wahoo, Weeping 

 Water. 



Devils Lake, N. Dak.; Little White River, Rapid City. Rosebud, S. 

 Dak. ; Stockton, Cal. ; Muskingum River, New Concord, Ohio. 



4. Gyrosigma parkerii Harrison in Q. J. M. S., p. 104. i860. 

 PI. 13, fig. 517. 



Lanceolate, sigmoid, with long acuminate ends, 80-1 50 /x long, 

 14-25 /,(, wide ; raphe median except at the ends, where it is ex- 



