132 BRITISH DESMIDIAOEJE. 



Lateral angles acute or rounded. 



95. C. pygmzeum. 



96. C. polygonum. 



97. C. pseiidobiremum. 



98. C. Mr erne. 



99. C. adoxum. 



100. C. Sinostegos. 

 Lateral angles emarginate. 



101. C. abruptum. 



%% Vertical view with no distinct central protuberance. 



102. C. sexangulare. 



103. C. pseudoprotuberans. 



104. C. abbreviatum. 

 ** Semicells subliexagonal or polygonal. 



t Angles of semicells produced. 



105. C. impressulum. 



106. C 1 '. umbilicatum. 



107. C. perpusillum. 



108. C. Eegnellii. 



109. C. MenegJiinii. 

 ft Angles of semicells not produced. 



110. C. angulosum. 



111. C. difficile. 



112. C. Clepsydra, 



*** Semicells rounded-polygonal, sometimes almost subcirctilar. 



113. C. 



SECTION G. Semicells obversely semicircular in outline, with 

 the lateral angles distinctly produced. 



114. C. monocliondrum . 



SECTION H. Cells subcylindrical or fusiform-cylindrical, with a 



> / 



very slight constriction. 

 * Cells subcylindrical. 



*t 



f Lateral margins subparallel. 



115. C. Thwaitesit. 



116. C. Cucurbita. 

 11 7. C. Palangula. 



118. C. 8ubpalangula. 



119. C. par v ulum. 



120. C. goniodes. 

 ft Lateral margins not parallel, generally convex. 



121. C. viride. 



122. C. oblongum. 



123. C. Hibernicum. 



124. C. turgidum. 



125. C. snbturgidum. 

 Cells fusiform-cylindrical. 



126. C. aitenuatum. 



