68 Clarence J. Elmore 



Valves linear with rounded ends, 64-100 /x long, 10-14 /u, wide; 

 striations radiate in the middle and converging at the ends, grad- 

 ually shortened toward the middle, where they are entirely lacking, 

 9-10 in 10 IX. 



In pool, Long Pine. 



10. Navicula parva (Ehr.) Elmore. 



Stauroptcra parva Ehr. Verb., p. i^^f,, pi. ?, fig. ip. i8-j^^. 



Navicula stauroptera Grun. in Wicn. Vcrh., p. ^16, pi. 2, fig. 18. 

 i860. 



PI. 7, figs. 231-246. 



Linear or oblong, sometimes elliptical, often slightly swollen in 

 the middle, 36-100 /x long, 7-13 yu- wide; apices rounded or slightly 

 swolleil ; costae radiate in the middle and converging at the ends, 

 8-12 in 10 /A, shortened, leaving a broad hyaline space along the 

 raphe, becoming shorter toward the center, where they are usually 

 entirely lacking. 



Common where conditions for algae are good, in creeks, rivers, lakes, 

 etc.: Alma, Anselmo, Arago, Broken Bow, Brownlee, Clear Lake, Craw- 

 ford, Crete, Culbertson, Dismal River, Dunning, Fremont, Gordon Creek, 

 Grand Island, Hackberry Lake, Halsey, Julian, Lincoln, Lodi, Long Pine, 

 Louisville, North Platte, O'Neill, Orleans, Red Cloud, Seneca, Stanton, 

 Talmage, Thedford, Valentine, Weeping Water, West Point. 



Fossil : Agate, Loup City, Mullen, Thedford. 



Belvidere, Blackpipe, Little White River, Rosebud, S. Dak. ; Devils 

 Lake, N. Dak.; Stockton, Cal. 



11. Navicula decurrens (Ehr.) Kiitz. Bacill., p. pp. 1844. 

 Pinnularia decurrens Ehr. Verb., p. 1^2, pi. 5, i. 5. 184^. 

 Navicula gibba Ehr. AbJi., 18^0, and Inf., p. 184, 18^8, is 



Cystopleura gibba (Ehr.) Kuntze. 



A^avicula gibba Kiitz. Bacill., p. p8, pi. 28. fig. "jo. 1844. 



Pinnularia gibba Ehr. Verb., 184^. 



PI. 7, figs. 247-253. 



Linear-elliptic, swollen in the middle and at the ends, the median 

 inflation extending a considerable distance toward the ends, 50-95 fj. 

 long, y-i2 jx wide; costae slightly radiating in the center and con- 

 verging at the ends, usually extending nearly to the raphe, but in 

 the form var. brevistriata V. H. very much shortened and some- 

 times entirely lacking around the central nodule, 9-12 in 10 /a. 



