130 Clarence J. Elmore 



toward the acute ends; costae 3-4 in lO/x, radiate; striations 

 granular, about 16 in 10 /x; in girdle view broadly elliptical to 

 lanceolate-elliptical. Var. prodncta Grun. is, a smaller form with 

 ends of valves attenuate. 



In creeks, etc.: Crawford, Fremont, Grand Island, Norfolk, Valentine, 

 Woodlake. 

 Fossil : Hay Springs. 



9. Cystopleura musculus (Kiitz.) Kuntze. Rev. Gen. Plant., II, 

 p. 8pi. i8pi. 



Epithemia musculus Kiitz. Bacill., p. 33, pi. 30, fig. 6. 1844. 



PI. 17, figs. 670-671. 



Valves nearly semicircular, 27-50 /x long, 7-9^1 wide; dorsal 

 margin strongly convex, ventral margin concave ; ends acute and 

 somewhat produced; costae radiate, about 4 in 10 /x; striations 

 granular, about 16 in 10 fx; in girdle view broadly elliptical. 



In creeks, lakes, ponds, etc., also fossil : Anselmo, Ashland, Clear Lake, 

 Crawford, Emerald, Fremont, Grand Island, Lakeside, New Helena, 

 Orleans, Pleasant Dale. Ruby, Rupert, Scottsblufif, Stanton, Talmage, Thed- 

 ford, Trenton, Valentine. 



Fossil : Cherry County. 



Blackpipe, Little White River, Turtle River, S. Dak.; Cheyenne, Wyo. 



Family 7. BACILLARIACEAE 

 Cells usually very much broader than long (rod-like), usually 

 free-swimming, but some enclosed in gelatinous tubes and a few 

 adhering in filaments. Rachis lateral, hence not interrupting the 

 fine striations ; containing an elongated slit. 



34. Homoeocladia {Nitcschia) 



Homoeocladia Ag. Flora, II, p. 629. 1827. 



Etym., from Gr. ojxoio'i, siiuilar, and KXaSos, branch, from the 

 fact that some of the species to which the name was first given 

 grow in branching tubes of uniform diameter. 



Nitzschia Hassall. Brit. Frcslnv. Algae, p. 43^. 184^. Gru- 

 nozvia Rabenh. ; Oscillaria Schrank. ; Pritchardia Rabenh. ; 

 Sigmatella Kiitz. 



Cells mostly free, rarely in tubes or chains, sometimes stalked ; 

 elongated or linear, rhombic in cross-section ; valves linear to 

 lanceolate or elliptical, pointed, with the ol)lique. bordered keel at 



