150 



Clarence J. Elmore 



lO/A, extending nearly to the pseudoraphe ; striations indistinct, 

 about 22 in io/a. 

 In ditch, Thedford. 



7. Surirella ovalis Breb. Consid. 1838. (According to Kiits. 



BacilL, p. 61.) 



PI. 21, figs. 795-806. 



Ovate-elliptical or broadly ovate, sometimes subcordate, 27-80 fi 

 long, 9-24 fjb wide; costae short, marginal, perpendicular to the 

 margin, 5-6 in io/j.; striations very delicate, about 18 in 10 fx; 

 pseudoraphe narrow. Very variable, most of the specimens found 

 agreeing with the form called var. ovata. This form is often 

 twisted like 6'. spiralis, as in figs. 799, 801. Var. miniita is a very 

 small form, 12-25/* long. Fig. 806 is a form found in Devils 

 Lake, N. Dak. 



Common among luxuriantly growing algae : Alma, Andrews, Anselmo, 

 Arago, Ashland, Auburn, Benkleman, Blue Springs, Brock, Broken Bow, 

 Brownlee, Central City, Clear Lake, Cook, Crawford, Culbertson, Dismal 

 River, Emerald, Fairbury, Fremont, Gordon Creek, Grand Island, Hack- 

 berry Lake, Julian, Lakeside, Lincoln, Lodi,, Louisville, Mason City, New 

 Helena, Norfolk, North Platte, Omaha, Orleans, Ruby, Rupert, St. Paul, 

 Salem, Seneca, Seward, Stanton, Stromsburg, Talmage, Tekamah. Thedford, 

 Trenton, Valentine, Wahoo, Wann, Weeping Water, York. 



Blackpipe, Rapid City, Rosebud, S. Dak.; Cheyenne, Wyo. ; Chippewa 

 Falls, Wis.; Ft. CoUins, Colo.; Blackhand, New Concord, Rodney, Ohio. 



8. Surirella spiralis Kiitz. BacilL, p. 60, pi. 3, fig. 64. 1844. 

 PI. 21, fig. 807. 



Elliptical-lanceolate, 95-1 50 ju, long, 40-50/1 wide, twisted 

 around the longitudinal axis, resembling the figure " 8 " ; costae 

 2-3 in 10 /x, extending nearly to the center. 



In creeks, rivers, ponds, etc., also fossil : Anselmo, Callaway, Dismal 

 River, Snake River, Valentine. 



Fossil : Agate, Mullen. 



Rosebud, Turtle River, S. Dak. 



37. Campylodiscus 



Campylodiscus Ehr. in Bcr. Berl. Akad., p. 11. 1840. 



Calcodiscus Rabenh. ; Coronia Ehr. 



Etym., from Gr. Kafnrv\o<;, curved, and 8tWo9. disk, so named from 

 the cells being nearly circular and curved. 



