The Diatoms of Nebraska 121 



margin, 38-100 /x, long, 10-14 /^ wide; ends obtuse or truncate; 

 raphe slightly curved toward the dorsal margin, its ends bent to- 

 ward the dorsal side, the ends at the central nodule bent toward 

 the ventral side; striations slightly radiate, finely granular, 7-10 

 in 10 /x in the middle on the dorsal side, closer elsewhere, extending 

 nearly to the raphe, scarcely shortened opposite the central nodule, 

 the central one or two on the ventral side interrupted, leaving a 

 dot at the end. Fig. 615 is from a specimen in Rahenh. Alg. En., 

 ' 1 168. The interrupting of the middle striations is not at all con- 

 stant in Rabenhorst's specimens. 



In creeks, etc., also fossil : Grand Island, Mason Citj'. 

 Fossil : Mullen, Wheeler County. 

 Cheyenne, Wyo. 



13. Cymbella cistula (Hempr.) Kirchn. Alg. ScJiles., p. i8q. 

 1878. 



Bacillaria cistula Hempr. EJir. Syuib. PJiys. Phyto., pis. II, IV, 

 fig. 10. 1828. 



PI. 16, figs. 616-620. 



Lunate with concave, slightly gibbous venti:al margin, 40-68 /x 

 long, 13-15 yu, wide (according to Cleve Syn. Nav. Diat., I, p. 17^, 

 up to 160 fx long and 25 /a wide) ; raphe arcuate, bent toward the 

 ventral margin near the central nodule, ends bent toward the dorsal 

 side ; striations extending nearly to the raphe, 6-9 in 10 fx on the 

 dorsal side in the middle, closer elsewhere; striations interrupted 

 on the ventral side of the central nodule, leaving a row of two to 

 five dots. These dots are mentioned in all descriptions as char- 

 acteristic of the species and are found in Nebraska specimens, but 

 do not appear in Rabenhorst's specimens, Alg. En., 1028. 



In rivers, ponds, lakes, etc., also fossil: Anselmo, Bellevue, Big Alkali 

 Lake, Broken Bow, Cedar Creek, Crawford, Dewey Lake, Dismal River, 

 Dunning, Gordon Creek, Grand Island, Hackberry Lake, Long Pine, Pel- 

 ican Lake, St. Paul, Seneca, South Bend, Trenton, Valentine, Wahoo. 



Fossil : Agate, Greeley County, Loup City. Merriman, Mullen, Spalding, 

 Thedford, Wheeler County. 



Blackpipe, S. Dak.; Devils Lake, N. Dak.; Ft. Collins, Colo. 



