Pleurotcenium] xi. desmidiace^e (West). 343 



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



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

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



PiTNGO 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 Journ. Bot. 1897, p. 80. 



Docidium maximum Reinsch in Abhandl. Senckenb. Naturforsch. 

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

 Naturhist. Gesellsch. zu Niirnberg, iii. 184, t. xii. f. 4 (1866). 



LiBOXGO. — Ad margine.s flum. Lifune ; Sept. 1858. No. 204. 



The shorter semicells (which are sometimes only 175 /x in length) 

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



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

 p. 80. 



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



HuiLLA. — In uliginosis editioribus prope Humpata. Erapalanca 

 et Lopolio, plagas spongiosas unacnm Eriocauloneis, Xyridibus et 

 Utriculaiiis constituens ; May 1860. No. 15. In gi-amiiiosis paludosis 

 juxta rivulura de Lnpollo ; April 1860. No. 180. Morro de Lopolio ; 

 May 18G0. No. 182. 



This genu.s seems to be near Tetmemorus and Euastntm. It re- 

 sembles the former in its elongate form, in b-^ing 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 Euantruia 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 Trqdoceros, 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. S. West in Journ. Bot. 1897, p. 81. 



ClosteHum granulatum Breb. (1839). 



HuiLLA. — Inter Utricularlam cymbantham, Morro de Lopolio : April 

 1860. No. 179. 



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

 Closterium Iceve Kiitz. Phyc. Germ. 132 (1845). 



