114 SKETCH OF THE INFUSORIA 



EciiiNELLEA, with llic carapacc simple, fixed, (siliceous.) 

 Lacernata, with the carapace double, (siliceous, and envel- 

 oped in tubes or gelatine.) 



He separates the Closteria as a distinct family, but this genus 

 is so closely allied to Euastrum, that I cannot hesitate to follow 

 the example of most writers upon this subject, and to class them 

 with the Desmidiacece. 



The following analytical table of the genera of Bacillaria, is 

 translated from Elirenberg. 



A. Carapace simple. 

 A. Free. 



a. Univalve, Desmidiacea. 



a. Prismatic. 



1. Trilateral, Desmidium.* 



2. Quadrilateral, Staurastrum.* 



3. Pentagonal, Pentasterias.* 



h. Round. 



1. Smooth. 



aa. Polj-pidoms 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, Microlheca. 



b. Two or more valves, . . NoAncvlacea. 



a. Round. 



1. Globular, Pyxidicula.* 



2. Forming polypidoms. 



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



bb. Several concentrit cells, .... Actinocyclus.* 



b. Prismatic. 



1. Division perfect, never forming bands. 



aa. With si.x (?) 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.* 



