94 Clarence J. Elmore 



In tanks, etc. : Dunning, Grand Island, Hastings, Stromsburg. 

 Fresno, Cal. 



69. Navicula mutica Kiitz. BacilL, p. pj, pi. 3, fig. 32. 1S44. 



PI. 12, figs. 451-452. 



Valves elliptical or elliptic-lanceolate, margins sometimes undu- 

 lating, 1 3-33 /A long, 7-1 1 fi. wide; striations radiate, 18-20 in 10 fx, 

 several opposite the central nodule shortened, leaving a pseudo- 

 stauros. 



In rivers : Benkleman, Haigler, Long Pine, Orleans, West Point. 

 Fresno, Cal. 



20. Scoliopleura 

 Scoliopleura Grun. in Wien. Verh., X, p. 554. i860. 



Etym. from Gr. o-koAios, twisted, and irXevpd, side, referring to 

 the form of the valve. 



Like Navicula, but faces of the valves convex, spirally twisted, 

 making the raphe and connecting zone sigmoid. 



A. Large with coarse striations. i. S. tumida. 



AA. Smaller with finer striations. 2. S. pcisonis. 



1. Scoliopleura tumida (Breb.) Rabenh. Fl. Eu. Alg., p. 229. 



1864. 



Navicula tumida Breb. in Kiita. Spec. Alg., p. 77. 184^. 



PL 13, figs. 472-473- 



Lanceolate, 100-160 /a long, 20-25 ju, wide (one specimen found 

 was only 37 /x long) ; striations nearly perpendicular to the mar- 

 gins, extending nearly to the raphe, leaving a very narrow axial 

 area, the central striations shortened, leaving an irregular space 

 around the central nodule; cells twisted spirally, making the raphe 

 slightly sigmoid ; faces of the valves convex. 



Fossil : Agate. 



2. Scoliopleura peisonis Grun. Verh., p. 554, pi. 3, fig. 25. i860. 

 PI. 13. fig. 474. 



Elliptical with rounded apices, 35-80 /a long, ia-18/i, wide; 

 raphe sigmoid, enclosed between two longitudinal ridges which are 

 at the ends of the striations; striations transverse, punctate, 12-16 

 in \o jx. 



In Devils Lake, N. Dak. 



