The Diatoms of Nebraska 91 



61. Navicula amphigomphus Ehr. Verb., p. I2p, pi. 5, I, fig. 8. 



1845. 



PI. 12, figs. 430-432. 



Broadly linear with cuneate ends, 68-150 /a long, 12-40 ;u, wide; 

 raphe straight, the central ends bent in opposite directions ; stri- 

 ations punctate, oblique, 15-18 in 10 /x, interrupted near the mar- 

 gin of the valve by a deep sulcus, shortened opposite the central 

 nodule, leaving a transverse hyaline space. Dried valves usually 

 brown. 



In creeks, ponds, rivers, etc., also fossil : Auburn, Cody Lake, Craw- 

 ford, Culbertson, Halsey, Lakeside, Norfolk, North Platte, Rupert, Seneca, 

 Stanton, Stromsburg, Trenton, Whitman. 



Fossil : Agate, Cherry County, Hay Springs, Loup City, Mullen, Spald- 

 ing, Thedford, Wheeler County. 



62. Navicula affinis Ehr. Amer., p. i2p, pi. 2, II, fig. 7. 1843. 

 PI. 12, figs. 433-437- 



Linear, margins straight or tmdulating, 30-60 /^ long, 8-1 5 |U, 

 wide, apices rostrate or capitate ; raphe straight, the central ends 

 bent in opposite directions; striations punctate, oblique, 16-18 in 

 10 ju,. interrupted near the margin of the valve by a deep sulcus, 

 slightly shortened opposite the central nodtile. leaving a small 

 rounded hyaline space. Dried valves usually brown. 



In creeks, ponds, rivers, etc., also fossil : Andrews, Auburn, Blue 

 Springs, Dismal River, Fremont, Grand Island, Hackberry Lake, Long 

 Pine, New Helena, Talmage, Thedford, Valentine. 



Fossil : Agate, Loup City, Mullen, Wheeler County. 



Blackpipe, Rapid City, Rosebud, S. Dak. 



63. Navicula iridis Ehr. Amer., p. 130, pi. 4, I, figs. 1-2. 1843. 

 PI. 12, figs. 438-439- 



Linear to elliptic, 26-1 70 /a long. 5-30 /a wide, apices rounded or 

 somewhat attenuate ; raphe straight, the central ends bent in oppo- 

 site directions; striations granular, oblique, 15-17 in 10 /a. inter- 

 rupted near the margin of the valve by a deep sulcus, shortened 

 opposite the central nodule, leaving a transverse hyaline space. 

 Dried valves usually brown. 



In creeks, rivers, ponds, etc., also fossil: Andrews, Anselmo, Ashland, 

 Atkinson, Auburn, Clear Lake, Culbertson, Dismal River, Dunning, Gor- 



