20& 



81. Pleurosigma attenuatum. 



82. Synedra biceps. 



83. „ radians. 



84. „ fasciculata. 



85. „ ulna. 



86. „ capitata. 



87. „ delicatissima. 



88. „ Vancheriae ? 



89. Cocconema lanceolatum. 



90. ,, cymbiforme. 



91. „ Cistula. 



92. „ parvum. 



93. Gomphenema coronatum. 



94. „ constrictumr 



95. „ capitatum. 



96. „ dichotomum. 



97. „ acuminatum. 



98. „ Vibrio. 



99. „ tenellum. 



100. Himantidium majus. 



101. „ A re us. 



102. „ bidens. 



103. „ gracile. 



104. „ pectinale. 



105. „ undulatum. 



106. Fragiliaria capucina. 



107. Odontidium Tabellaria. 



108. Denticula tenuis. 



109. Tetracyclus lacustris. 



110. Tabellaria fenestrata. 



111. „ ventricosa. 



112. „ flocculosa. 



113. Melosira varians. 



114. „ arenaria. 



115. Orthosira nivalis. 



116. „ aurichalcea. 



117. Collatonema vulgare. 



118. Diatoma vulgare. 



The following are new to Britain, or now first distinguished from 

 others : — 



1. Eplthcmia gibberula. 



2. Eunotia bigibba, Kiitz. 



3. „ Camelus, Kiitz. 



4. „ depressa, Kiiu. 



5. Navicula laevissima. 



6. „ Trochus. 



7. Cocconema gibbum. 



8. Himantidium eziguum, Brib. 



Of these 8 species, figures were exhibited ; and in the case of 

 Eunotia bigibba a number of striking varieties were figured, and 

 compared with several varieties of Himantidium bidens, with which 

 it had hitherto been confounded. 



The author then proceeded to describe and illustrate by figures 

 the following species, most of which are new to science : — 



