126 Clarence J. Elmore 



Chromatophores usually one or two large plates. Auxospores two 

 from two conjugating mother cells. 



A. Striations twice as numerous as the costae. 

 h. Valves arcuate. 



c. Striations coarsely granular. i. C. iurgida. 



cc. Striations finely granular. 2. C. sorcx. 



bb. Valves nearly straight. 



c. Elongated, slightly gibbous. 3. C. gibba. 



cc. Shorter, strongly gibbous. 4. C. ventricosa. 



AA. Striations at least four times as numerous as the costae. 

 b. Costae scarcely radiate, striations coarsely granular. 

 c. Costae with apices capitate in girdle view. 



d. Costae close. 5. C. ocellata. 



dd. Costae distant. 6L C. argns. 



cc. Costae with apices not capitate in girdle view. 



7. C. zebra, 

 bb. Costae radiate, striations finelj' granular. 



c. Ventral margin nearly straight. 8. C. gibberula. 



cc. Ventral margin curved. 9. C. musculus. 



I. Cystopleura turgida (Ehr.) Kuntze. Rev. Gen. Plant., II, 

 p. 8pi. iSpi. 



Navicula turgida Ehr. Ahh., p. 64. 18^0. 



Epithemia turgida (Ehr.) Kiitz. Bacill., p. ^4, pi. 5, fig. 14. 

 1844. 



PI. 17, figs. 646-648. 



Arcuate, 70-195 /* long, dorsal margin more curved than the 

 ventral, ends more or less capitate; costae distinct, perpendicular 

 to the margins, 3.5-4 in 10 /x; striations coarsely granular, 7-8 in 

 10 jx. Very variable, hence presenting many so-called varieties. 

 Fig. 647 agrees with var. vertagus. 



Very common in ponds, rivers, creeks, tanks, etc., attached to filamentous 

 algae, also fossil: Anselmo, Battle Creek, Bellevue, Brownlee, Burge, Cal- 

 laway, Cedar Creek, Central City, Cody Lake, Crawford, Culbertson, Dis- 

 mal River, Dunning, Johnson, Gordon Creek, Grand Island, Hackberry 

 Lake, Haigler, Halsey, Hyannis, Holt County, Lakeside, Lodi, Long Pine, 

 Nebraska City, New Helena, Newport, North Platte, Northport, Oakdale, 

 Orleans, Peru, Phalaris Lake, Ruby, Rupert, St. Michael, St. Paul, Scotts- 

 bltlff, Seneca, Snake River, South Bend, Stromsburg, Talmage, Tekamah, 

 Thedford, Tioga, Valentine, Wahoo, Wann, Whitman. 



Fossil : Agate, Cherry County, Greeley County, Loup City, Merriman, 

 Mullen, Thedford, Valentine, Wheeler County. 



