134 Clarence J. Elmore 



TryhlioncUa ongustata W. Sm. Brit. Diat., I, p. ^6, pi. 50, 

 fig. 262. 185^. 



PI. 18, figs. 687-691. 



Narrowly linear to ovate-lanceolate, 80-90 ;u. long, about io/a 

 wide, apices attenuate ; keel marginal, dots corresponding with the 

 striations, about 13 in 10 /a. The form described as var. mrta is 

 smaller, 48-67 /x long, 7-1 i/x wide. 



In creeks, ponds, etc. : Culbertson, Fremont, Grand Island, Norfolk, 

 North Platte, Ruby, Trenton, West Point. 



5. Homoeocladia tryblionella (Hantz.) Kuntze. Rev. Gen. 

 Plant., Ill, p. 409. 1898. 



Nitzschia tryblionella Hantz. in Rabenh. Alg., No. 084. 18'ji. 



Pl.T 8, figs. 692-698. 



From elliptical to lanceolate, 20-1 10 /x long, 6-30 /a wid«, apices 

 more or less acute ; valves undulate with a sulcus making tTie stri- 

 ations appear broken ; keel marginal with indistinct dots elongated 

 to form costae or striations, 7-12 in 10 /a, very fine punctate stri- 

 ations mixed with the coarser striations. Var. levidensis is a form 

 more elongated and with finer striations, fig. 693. Very variable. 

 Grunow in CI. & Gritn. Arct. Diat., p. 6p, says : " This widely 

 distributed species includes a very large number of forms among 

 which it is very difficult to separate a single variety with certainty 

 as is here attempted. They vary in respect to form, length, and 

 width, the undulation of the valves, the distinct or indistinct pmic- 

 tation of the very variable striations which sometimes are very 

 much fainter in the middle than near the margins and sometimes 

 equally distinct over the entire valve. Many valves appear 

 strongly costate and many punctate with only indistinct striations." 



Common among higher algae where conditions are good : Alma, Arbor, 

 Ashland, Auburn, Blue Springs, Cherry County, Crawford, Culbertson, 

 Fairbury, Fremont, Grand Island, Hackberry Lake, Lincoln, Nemaha City, 

 North Platte, Omaha, Orleans, Pleasant Dale, Ruby, Rupert, St. Paul, 

 Stanton, Stromsburg, Talmage, Tekamah, Wahoo, Wann, Weeping Water. 



Belvidere, Rapid City, Rosebud, S. Dak. ; Court Lake, Devils Lake, fresh 

 water near Devils Lake, N. Dak. ; Stockton, Cal. 



3. Grunowia 



A. Valves with sinuous margins. 6. H. tahcUaria. 



AA. Margins of valves not sinuous." ' 7. H. obfusa. 



