36 Clarence J. Elmore 



cc. Rachis of valves with a keel. 



27. AmpJiiprora, page 107. 

 AA. Valves not parallel; ends approximating. 

 b. Cells straight in girdle view. 



28. Gomphoncma, page 107. 

 hb. Cells curved in girdle view. 



29. Rhoicosphenia, page 114. 

 AAA. Valves not parallel; edges approximating. 

 b. Valves without transverse ribs. 

 c. Girdle narrow, not striate. 



d. Terminal nodules near apices ; raphe more or less arcuate. 



30. Cymhella, page 115. 

 dd. Terminal nodules distant from the apices ; raphe straight. 



31. Encyonema, page 122. 

 cc. Girdle broad, striate. 



32. Amphora, page 124. 

 bb. Valves with transverse ribs ; raphe not evident. 



ZZ- Cystoplcura (Epitheniia) , page 125. 



Family 8. BACILLARIACEAE 



34. Homococladia (Nitsschia) , page 130. 



Family 9. SURIRELLACEAE 



A. Valve surface undulate. 



35. Sphincfocystis (Cymatoplcura) , page 145. 

 AA. Valve surface not undulate. 



b. Valves cuneate, reniform, elliptical, or linear. 



36. Surirclla, page 147. 

 bb. Valves sub-circular, sadd'e-shaped. 



37. Campylodiscus, page 150. 



Family i. COSCINODISCACEAE 



Cells short and disc-like, or the length sometimes three or four 

 times the diameter ; ends striate or punctate, not ribbed. Cells in 

 long filaments or separated into single cells ; often with short 

 spines, but no horns. Chromatophores of numerous minute plates. 



Lysigonium 



Lysigonium Link in Necs Hor. pliys. hcrol., p. 4. 1820. 



Etym., Or. Awtos, dissolving, and yoVia, joints, from the appear- 

 ance of the filaments which resemble filamentous algae, but break 

 apart early. 



