The Diatoms of Nebraska 149 



3. Surirella saxonica Auersw. in Rahcnh. Alg. 1421. 

 PI. 21, figs. 790-792. 



Long-ovate, 75-200 //, long, 25-38 /a wide; costae 1.5-3 ""^ 10 i^- 

 extending to the distinct pseudoraphe ; striations indistinct ; dried 

 empty shells often brownish. Differs from 5*. rohusta mainly in 

 the more distinct pseudoraphe with costae extending to it. 



In springs and creeks, also fossil : Aspinwall, Brock, Brownville, Fair- 

 bury, Long Pine, New Helena, Talmage, Thedford, Wahoo, Weeping 

 Water, West Point. 



Fossil : Agate. 



4. Surirella striatula Turp. in Mcin. du Mus. d'Hist. Nat., XVI. 



1828. 



PI. 21, fig. 793. 



Broadly oval, sometimes spirally twisted, 95-160 ^n long, about 

 75 /A wide; costae robust, about i in 10 /x, reaching to the median 

 line; striations 14-15 in 10 ;u,; girdle face cuneate, showing mar- 

 ginal alae. 



Devils Lake and fresh water near Devils Lake, N. Dak. 



5. Surirella robusta Ehr. in Ber. Bcrl. Akad., p. 21^. 1840. 

 PI. 21, fig. 794. 



Long-ovate. 135-365 /x. long; pseudoraphe broad, alae distinct; 

 costae very distinct, 1.5-2 in 10 /x. reaching nearly to the pseudo- 

 raphe, nearly perpendicular to the margins ; striations indistinct, 

 IQ-14 in 10 yu,. Var. splcndida is a form somewhat smaller. 



Common among luxuriantly growing algae in creeks, rivers, ponds, etc., 

 also fossil : Alma, Anselmo, Burge, Cherry County, Crawford, Culbertson, 

 Dismal River, Dunning, Fremont, Gordon Creek, Grand Island, Hackberry 

 Lake, Halsey, Lakeside, Long Pine, Norfolk, North Platte, Oakdale, Or- 

 leans, Red Cloud, St. Paul, Seneca, Snake River, Stanton, Stromsburg, 

 Talmage, Tekamah, Thedford, Valentine, Weeping Water. 



Fossil: Greeley County, Mullen, Spalding, Valentme. 



Blackpipe, Little White River, Rapid City, Rosebud, S. Dak. ; Blackhand, 

 Ohio. 



6. Surirella elegans Ehr. Verb., p. 1^6, pi. Ill, i, fig. 22. 184^. 

 PI. 23, fig. 860. 



Oval, 180-240 ;a long, 60-76 /x wide; costae delicate, 1.5-2 in 



