^.o Clarence J. Elmore 



3. Cyclotella comta (Ehr.) Kutz. Spec, p. 20. 184Q. 

 Discoplea comta Ehr. in Ber. Berl. Akad., p. 26'/. 1842. 

 PI. I, fig. 18. 



End of cell plane with a distinct narrow ring of striations around 

 the margin; striations about 15 in 10 /x, each third or fourth stri- 

 ation much heavier than the others ; central portion with radiating 

 puncta, about ten rows in 10 /a at outside margin of central portion ; 

 diameter of cell, 7.5-40 /x. The form described as var. radiosa 

 Grun. in V. H. Diaf., p. 447, pi. 22, fig. 654, agrees fully with the 

 specimens found. 



In creek, Anselmo. 

 Devils Lake, N. Dak. 



4. Cyclotella meneghiniana Kiitz. BacUL, p. 50, pi. jo, fig. 68. 



1844. 



PI. I, figs. 19-21, 



End of cell undulate with robust marginal striations, delicately 

 punctate; central portion 5-10 ^u. in diameter, with fine radiating 

 dots and one or two coarse dots almost in the center ; striations 7-9 

 in 10 ft; diameter of cell, 10-24 /x. 



In springs, creeks, ponds, etc., with higher algae : Benkleman, Broken 

 Bow, Cedar Creek, Central City, Clear Lake, Cody Lake, Crawford, Dis- 

 mal River, Dunning, Emerald, Fremont, Gordon Creek, Grand Island^ 

 Hyannis, Halsey, Lakeside, Lincoln. Lodi, Louisville, Melia, Milford, New 

 Helena, North Platte, Northport, St. Paul, Scottsbluff, Seneca, Seward, 

 Stanton, Stromsburg, Talmage, Tekamah, Thedford, Valentine, Wann, 

 Weeping Water, West Point. 



Fossil: Cherry County, Hay Springs, Loup City, Thedford. 



Blackpipe, Kadoka, Norris, Rosebud, Weta, S. Dak.; fresh water near 

 Devils Lake, N. Dak.; Cheyenne, Wyo.; Stockton, Cal. ; Muskingum 

 River, Put-in Bay, pond on island in Lake Erie, Ohio. 



3. Stephanodiscus 



Stephanodiscus Ehr. in Berl. Akad., p. 80. 184^. 



Etym., Gr. o-re^ai'os, crown, and StWos, disk, from the crown-like 

 appearance of the cells. 



Valves circular, somewhat convex, marked with granules ar- 

 ranged radially ; spaces between the rows of granules hyaline ; 

 center hyaline or granular ; margin with a single row of spines. 



