286 Sketch of the Infusoria of the family Bacillaria. 



The following analytical table of the genera of Bacillaria, is 

 translated from Ehrenberg. 



A. Carapace simple. 



A. Free. 



a. Univalve, .... Desmidiacea. 



a. Prismatic. 



1. Trilateral, Desmidium." 



2. Quadrilateral, Staurastrum.* 



3. Pentagonal, Peniastorias.* 



b. Round. 



1. Smooth. 



aa. Polypidoms moniliform, . . . Tessararthra. 



bb. " bacciform, . . . Sphserastrum. 



2. With projections, Xanthidium.* 



c. Flattened. 



1. In forms of bands. 



aa. Serrated, Arthrodesmus.* 



bb. Not serrated, Odontella.^ 



2. In form of discs or plates. 



aa. Several in each disc, .... Micrasterias.* 



bb. Two in each disc, .... Euastrum.* 



cc. Isolated in plates, .... Microtheca. 



b. Two or more valves, . . JYavicidacea. 



a. Round. 



1. Globular, Pyxidicula.* 



2. Forming polypidoms. 



aa. One cell, chain filiform, . . . Gallionclla.* 

 bb. Several concentric cells, . . . Actinocyclus.* 



b. Prismatic. 



1. Division perfect, never forming bands. 



aa. With six (?) openings, . . . Navicula.* 



bb. With four openings, .... Eunotia.* 



cc. With one opening, .... Cocconeis. 



2. Division imperfect, forming bands. 



aa. Articulated. 



aa. Prisms (" baguettes"), . . . Bacillaria.* 

 bb. Plates, Tessella.* 



bb. Without articulations. 



aa. Strait ribbands, .... Fragillaria.* 

 bb. Spiral ribbands, .... Meridion.* 



B. Fixed, .... Echinella. 



a. Wider than long, Isthmia. 



b. Longer than wide. 



a. Without a pedicel. 



1. Prismatic, Synedra.* 



2. Wedgeform, Podosphenia.* 



b. Supported by a pedicel. 



1. Wedgeform. 



aa. Dichotomous, Gomphonema.* 



bb. Verticillate, Echinella.* 



2. Fixed perpendicularly, . . . . Cocconema.* 



