TJie Diatoms of Nebraska 67 



Linear with parallel margins and rounded ends, 100-120 /a long, 

 about 16 fjL wide; raphe flexuose ; striations parallel, shortened, 

 leaving a moderately wide hyaline space along the raphe, entirely 

 lacking in the middle, forming a pseudostauros, 7-10 in 10 /x. The 

 specimens shown in figures 206 and 207 are 82 /a and 37 ,u long, 

 respectively, but appear to belong to this species. 



Clear Lake. 



8. Navicula brebissonii Kiitz. Bacill., p. pj, pi. 2, fig- 49; pi- 30, 



fig. 3p. 1844. 



PI. 7, figs. 208-229. 



Linear-elliptic, oblong, or elliptic, sometimes constricted in the 

 middle, 14-68 /x long, 6-13/* wide; apices varying from obtuse to 

 slightly rostrate-capitate ; costae radiating in the center, but toward 

 the ends suddenly becoming convergent, either shortened or en- 

 tirely lacking around the central nodule, 9-12 in 10 /a; the empty 

 valves usually of a brownish color. Very variable. The follow- 

 ing forms have been described : var. angustafa Grun., very narrow, 

 ends attenuate; var. linearis O. Miiller, margins straight, ends 

 broad, round ; var. diminuta V. H., narrower than the typical form, 

 ends always narrowed ; var. notata Heibrand and Peragallo, a 

 small form with cuneate ends ; var. ornata O. Miiller, a form with 

 dots more or less regularly arranged in the hyaline area, especially 

 along the raphe; var. suhproducfa V. H., broader and shorter with 

 apices slightly rostrate. 



In creeks, ponds, pools, rivers, etc. : Andrews, Anselmo, Arago, Ash- 

 land, Auburn, Benkleman, Brock, Broken Bow, Brownlee Callaway, Cen- 

 tral City, Chadron, Clear Lake, Cook, Crawford, Culbertson, Dismal River, 

 Fairbury, Grand Island, Hackberry Lake, Halsey, Johnson, Lodi, Louis- 

 ville, Mason City, Milford, New Helena, North Platte, Northport, O'Neill, 

 Orella, Peru, Roca, St. Paul, Scottsbluff, Seneca, Seward, Sheridan 

 Countj^ Snake River, Stanton, Stromsburg, Talmage, Trenton, Valentine, 

 Weeping Water, West Point, Whitman. 



Fossil : Agate, Cherry County, Hay Springs, Merriman, Thedford. 



Belvidere, Blackpipe, Cutmeat, Little White River, Rapid City, Rosebud, 

 Scenic, Turtle River, S. Dak. ; Devils Lake and fresh water near Devils 

 Lake, N. Dak. ; Cheyenne, Wyo. ; Rodney, Ohio. 



9. Navicula rangoonensis (Grun.) Elmore. 

 Pinnnlaria rangoonensis Griui. in Ms. 

 PI. 22, figs. 823-824. 



