Semi-Centennial Volume. 167 



VIII. Frustules free, elonji:ated, valves linear, pointed; surface punctate 



or transversely striate Nitzschia. 



102. Navicula. Bory. Plate IV, fig. 36. 



Kansas: Very widely distributed, having been fourd 



eighty-five times. 

 Nebraska (1-2-3-24-25); Iowa (4). 

 lOS. Stauroncis Ehrbg. 



Kansas: Cedarvale, August, 1916. 

 Nebraska (1-2-3-24-25); Iowa (4). 



104. Plcurosigma W. Smith. Plate IV, fig. 35. 



Kansas: Found eleven different times during the sur- 

 vey. 

 Nebraska (1-2-3-24-25); Iowa (4). 



105. Gomphovema Agardh. 



Kansas: Cherryvale, 1915; Mound City, August, 1915; 

 Medicine Lodge, August, 1915; Burlingame, No- 

 vember, 1915, October, 1916; Jewell City, November, 

 1915; Horton, June, 1916. 



Nebraska (1-2-3-24-25); Iowa (4). 



106. Cymbella Agardh. Plate IV, fig. 34. 



Kansas: Rather generally distributed. Identified 



about 25 times. 

 Nebraska (1-2-3-24). 



107. Encyonema Agardh. Plate IV, fig. 32. 



Kansas: Waconda Springs, July, 1916; clinging to- 

 gether in gelatinous masses extending into filaments. 

 Nebraska (2). 



108. Amphora Ehrbg. 



Kansas: Identified ten different times. 

 Nebraska (1-2-24); Iowa (4). 



109. Nitzschia Hassall. 



Kansas: Chanute, November, 1915; Cherryvale, No- 

 vember, 1915; Independence, December, 1915; April, 

 1916; Ottawa, November, 1915; Burlington, April, 

 1916; Council Grove, April, 1916; Horton, April, 

 1916. 



Nebraska (1-2-3-24-25); Iowa (4). 



Tribe IV. Surirelloidese. 



110. SnH7-ella (Turpin). 



Oval valves with conspicuous transverse tubular striae 



between which are sometimes very pearled striae; 



wide pseudoraphe. 

 This genus was found only three times, i.e., Kansas: 



Chanute, November, 1915; Council Grove. April, 



1916; Emporia, April, 1916. 

 Nebraska (24): Iowa (4). 



