66 Clarence J. Elmore 



very heavy, 4-6 in 10 fi, slightly radiate in the center and converg- 

 ing at the ends, not reaching to the raphe, those around the central 

 nodnle shortened, leaving a round hyaline space. 



With luxuriantlj'-grovving Cladophora in creeks and ponds : Anselmo 

 Seneca. 



Blackpipe, S. Dak. 



5. Navicula borealis (Ehr.) Kiitz. BacilL, p. p6, pi. 28, figs. 68- 



72. 1844. 



Pinnularia borealis Ehr. Verb., pi. I, II, fig. 6. 1843. 



PI. 7, figs. 194-199- 



Linear-elliptic, sometimes slightly attenuate, 30-68 jx long ; apices 

 rounded or truncate ; costae slightly radiate in the middle, con- 

 verging at the ends, very heavy, 3-6 in 10 /a, reaching almost to the 

 raphe, except those around the central nodule, which are shorter, 

 leaving a round hyaline space. Differs from A^. lata mainly in its 

 more linear outline. 



In ponds, rivers, creeks, pools, ditches, etc. : Ainsworth, Columbus, 

 Crawford, Dismal River, Dunning, Fremont, Grand Island, Long Pin^ 

 Milford, Norfolk, North Platte, O'Neill, St. Paul, Stanton, Trenton. 



Fossil ; Valentine. 



Belvidere, Conata, Little White River, Norris, Rapid City, Rosebud, 

 Scenic, S. Dak.; Stockton, Cal. 



6. Navicula intermedia Lagerst. Spetc. Diat., p. 2^, pi. i, fig. j. 



PI. 7, figs. 200-205. 



Linear-elliptic with rounded ends, 18-42 /a long, 5-8 /x, wide; 

 striations heavy, radiating, 9-10 in 10 /x, lacking in the center, 

 leaving a transverse hyaline space. 



Fossil : Agate. 

 Belvidere, S. Dak. 



7. Navicula stauroneiformis Elmore. 



Pinnularia acstnarii (Breb.) CI. Nav. Diat., II, p. pj, pi. i, 



fig. 16. 1895. 

 Navicula acstnarii Breb. in Ki'it.':. Spec. Alg., p. 800, 1849, is 



Gyrosignia. 

 PI. 7, figs. 206-207. 



