132 BRITISH DESMIDIAOEJ]. 



SECTION E. Semicells more or less rectangular or subrectangular 

 (rarely subpyraniidate) in outline. 



* Margin of semicells entire. 



t Cells large or of medium size ; cell-wall strongly 



granulate. 

 + Semicells transversely subrectangular; cells 1-1 i 



times longer than broad. 



Granules large ; vertical view elliptic- oblong, 

 not tumid. 



229. C. coronatum. 



230. C. conspersum. 



231. C. margaritatum. 



232. C. quadrum. 



233. C. Pseudobroomei. 



Granules small; vertical view with a more or 



less marked protuberance on each side. 

 Vertical view only slightly tumid. 



234. C. Subbroomei. 

 /3 Vertical view strongly tumid. 



235. C. Broomei. 



236. C. biretum. 



++ Semicells elongate-rectangular ; cells about twice 

 as long as broad. 



237. C. amoenum. 



238. C. pseudamoenum. 

 ft Cells small ; cell- wall finely granulate. 



^239. C. latifrons. 



240. C. lepidum. 

 ** Margin of semicells undulate or crenate. 



241. C. promontorium. 



242. C. crenatum. 



243. C. Grantii. 



SECTION F. Semicells subcylindrical ; constriction of cells 

 slight. 



* Lateral margins of semicells subparallel ; cell- wall with 



nodules in distinct zones. 



244. C. annulatum. 



245. 0. elegautissimum. 

 Lateral margins not parallel. 



t Cell- wall granulate only at the apices of the semicells. 



246. C. tuber culatum. 

 ft Cell-wall granulate over entire surface. 



247. C. cylindricum. 



248. C. sub cylindricum. 



