The Diatoms of Nebraska 135 



6. Homoeocladia tabellaria (Grun.) Kuntze. Rev. Gen. Plant., 



Ill, p. 409. iSgS. 



Denticnia tabellaria Grun. in IVien. Verh., p. ^^48. 1862. 



Nitsschia tabellaria Grim, in CI. & Grim. Arct. Diat., p. 82. 

 1880. 



Nitzscliia sinnata (W. Sni.) Grun. in CI. & Grun. Arct. Diat., 

 p. 82. 1880. 



Denticiila sinuata W. Sm. Brit. Diat., II, p. 21. 18 j6. 



PI. 18, fig. 699. 



Lanceolate with margins undulate, very much inflated in the 

 middle, 26-30 /* long, J-io fx wide, apices small, globose; keel 

 marginal with dots elongated into costae extending about to the 

 middle of the valve, 5-6 in 10 ju,; striations 18-20 in 10 ^a. The 

 specimen represented in fig. 699 seems intermediate between 

 Nitsschia sinnata (W. Sm.) Grun. and Nitsschia sinuata var. 

 tabellaria Grun. as figured in V. H. Diat., pi. 75, figs. ^16, 577, 



Fossil in limestone : Mullen. 



7. Homoeocladia obtusa (Lyngb.) Elmore. 



Echinella obtusa Lyngb. Hydrophyt. Dan., pi. 6p. i8ip. 



Frustidia obtusa Ag. Consp., p. 44. 18^0. 



Nitzschia denticiila Grun. in Cl. & M. Diat. E.vsic. N'o. 224. 

 1878. 



PI. 18, figs. 700-706. 



Narrowly lanceolate, 14-86 /a long, 6-9 /x wide, apices more or 

 less acute, not rostrate ; keel marginal with dots elongated into 

 costae which extend from half across the valve to entirely across, 

 4-8 in 10 /a; striations granular, 14-18 in 10 /a. 



In tanks, rivers, creeks, etc. : Crawford, Long Pine, Louisville, North 

 Platte, O'Neill, Rupert, Seneca, Stromsburg, Valentine. 

 Fossil : Agate. 

 Cheyenne, Wyo. ; Blackpipe, S. Dak. ; Stockton, Cal. 



4. SiGMOIDEAE 



A. Striations distinct; carinal dots round. 8. H. brchisso>\n. 



A A. Striations fine ; carinal dots somewhat elongated. 



&. Very large ; dots 4-7 in 10 i^. 9. H. sigmoidca. 



hb. Medium size; dots 7-9 in 10 m. 10. H veriiiicularis. 



