SYNOPTICAL ARRANGEMENT 



BRITISH DIATOMACE^. 



Class CRYPTOGAMIA. 



Sub-class XLGM. Natural Order DIATOMACEiE. 



Plant a Frustule ; consisting of a unilocular or imperfectly septate cell 

 invested with a bivalve siliceous epidermis. Gemmiparous increase, by 

 Self-Division ; during which process the cell secretes a more or less siliceous 

 Connecting Membrane. Reproduction, by Conjugation and the 

 formation of Sporangia. 



Tribe I. Frustules naked; not imbedded in gelatine nor enclosed in mem- 

 branaceous tubes. 



Sub-tribe 1. Connecting membrane deciduous; frustxdes solitary or 

 during self-division in pairs, rarehj in greater numbers, 

 adherent or free, dispersed, or aggregated into a mucous 

 stratum. 



22 Genera. Epithemia, Eunotia, Cymbella, Amphora, Cocconeis, 

 Coscinodiscus, Eupodiscus, Actinocyclus, Arachnoi- 

 (hscus, Triceratium, Cyclotella, Campylodiscus, 

 Surirella, Tryblionella, Cymatoplevu'a, Nitzschia, 

 Amphiprora, Amphipleura, Navicula, Pinnularia, 

 Stauroneis, Plenrosigma. 



