Plewotcenium] xi. desmidiace^ (West). 343 



2. P. Ehrenbergii De Bary, Conj. 75 (1858). 



Docidium Ehrenbergii Brib. (1844); Ralfs, Brit. Desm. 157, 



t. xxvi. f. 4 (1848) ; W. et G. S. West in Journ. Bot. 1897, p. 80. 



PuNGO Andongo.— In stagnis prope Anbilla (Condo) ; March 1857. 

 No. 177. 



3. P. maximum Lund, in Acta R. Soc. Scient. Ups. ser. 3, viii. 

 no. ii. 89 (1871) ; W. et G. S. West in Joiirn. Bot. 1897, p. 80. 



Docidium maodmum Reinsch in Abhandl. Senckenb. Naturforsch. 

 Gesellsch. vi. 140, t. xx. ii. f. 1-2 (1866-7); in Abhandl. 

 Naturhist. Gesellsch. zii NUrnberg, iii. 184, t. xii. f. 4 (1866). 



LlBONGC— Ad marlines flum. Lifune ; Sept. 1858. No. 204. 



The shorter semioells (which are sometimes only 175 jti in leagth) 

 have only one basal inflation ; the longer ones have two. 



7. ICHTHYOCERCUS W. et G. S. West in Journ. Bot. 1897, 

 p. 80. 



1. I. angolensis W. et G. S. West, I.e., t. 368, f, 26-31. 



HuiLLA. — In uliginosis editioribus prope Humpata. Erapalanca 

 et Lopollo, plagas spongiosas unaoum Eriooanloneia, Xyridibus et 

 Utriculariis constituens ; May 1860. No. 15. In graminosis paludosis 

 juxta rivulura de Lopollo ; April 1860. No. 180. Morro de Lopollo ; 

 May 1860. No. 182. 



This genus seems to be near Tetmemorus and Euastrum. It re- 

 sembles the former in its elongate form, in bning but slightly con- 

 stricted in the middle, and in possessing a circular (or very nearly 

 circular) vertical view ; it differs from it, however, in the absence of 

 the deep linear notch at the apex, in the presence of a spine at each 

 apical angle, and in the general conformation of the upper half of the 

 semicells, which are somewhat wedge-shaped, with convex surfaces. 

 From Euastrum it differs in its very slight constriction, its more 

 parallel sides in front view, and in its circular vertical view. 



The cell membrane appears to be much less firm than that of a 

 Tetmemorus. The punctulations on it are in some specimens dense 

 and in others distant from each other, and occasionally they are so 

 well developed at the apical angles as to give them a faintly rough 

 appearance. In one example the spine at one of the apical angles 

 was duplicated, the two spines being placed close together, and of 

 different lengths. 



It also approaches the genus Triploceros, but the delicate character 

 of the membrane, which is also destitute of warts, and the somewhat 

 different apex distinguish it. 



8. TETMEMORUS Ralfs (1844). 



1. T. granulatus Ralfs in Ann. Mag. Nat. Hist. xiv. 257, t. viii. 

 f. 2 (1844) ; Brit. Desm. 147, t. xxiv. f. 2, t. xxxiii. f. 1 (1848) ; 

 W. et G. 8. West in Journ. Bot. 1897, p. 81. 



Ghsterium granulatum Breb. (1839). 



H.TJILLA. — Inter Utriculariam cymbantham, Morro de Lopollo ; April 

 1860. No. 179. 



2. T. laevis Ralfs, Brit. Desm. 146, t. xxiv. f. 3 (1848). 

 Closterium Iceve KUtz. Pbyo. Germ. 132 (1845). 



