lo Charles E. Besscy 



Order Eupodiscales. Cells in transection cylindrical, less com- 

 monly polygonal, elliptical, or irregular ; typically in filaments, but 

 more commonly isolated by fragmentation; ends of cells marked 

 concentrically or radially by dots, areolations, lines, or ribs; cells 

 often with spines, processes, or horns. "Round Diatoms," mostly 

 marine. 



Family 7. Coscinodiscaceae. Cells short, often in filaments, 

 transection circular, not divided into sectors by ribs. Lysigoniiim, 

 Coscinodiscus. ( Pf. I, ib, 58.) 



Family 8. Actinodiscaceae. Cells short, transection circular, 

 divided into sectors by ribs, without "eyes.'' Arachnoidiscns, 

 Actiiwdiscus, Astcrolanipra. (Pf. I, ib, 68.) 



Family 9. Eupodiscaceae. Cells short, transection circular, 

 with radial undulations, with "eves." Actinocycliis, Eut>odiscus. 

 (Pf. I, lb, 76.) 



Family 10. Soleniaceae. Cells long, often in filaments, tran- 

 section circular. Rhi::osolenia. (Pf. I, ib, 82.) 



Family 11. Chaetoceraceae. Cells short, usually in filaments, 

 transection circular to elliptical, with horns longer than the cells. 

 Chactoceras. (Pf. I, ib, 85.) 



Family 12. Biddulphiaceae. Cells short, often in filaments, or 

 loose chains, transection circular, polygonal, or commonly ellip- 

 tical, with horns shorter than the cells. Triceratiuni, Isthmia, 

 Biddulphia. (Pf. I, ib, 87.) 



Family 13. Euodiaceae. Cells short, transection lunate with- 

 out transverse septa. Hcmidisciis. (Pf. I, ib, 99.) 



Family 14. Anauliaceae. Cells short, transection not lunate, 

 with transverse septa, without spines. Anaiilus, Terpsinoc. (Pf. 

 I, lb, 97.) 



Family 15. Rutilariaceae. Cells short, transection not lunate, 

 without transverse septa, with a marginal row of spines. Eutil- 

 aria. (Pf. I, ib, 100.) 



Order Naviculales. Cells in transection narrowly elliptical to 

 linear, less commonly broadly elliptical, lunafe, cuneate, or irreg- 

 ular, typically in filaments, but more commonly isolated by frag- 

 mentation ; ends of cells marked pinnately or transversely by dots. 



