welwxtsch's afkican freshwater alg.e. 81 



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 Euastruiji, 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 cha- 

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

 somewhat different apex distinguish it. 



8. Tetmehorus Kalfs (1844). 



1. T. GRANULATUs (Breb.) Ealfs in Ann. Mag, Nat. Hist. xiv. 257, 

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

 Closteriiun fjranulatum Breb. (1839). Long. 19G /x; lat. 34 /x; lat. 

 isthm. 31 jj.. 



Huilla. Inter Utricnlaiiam ecalcaratam, Morro de LopoUo ; 

 April 18G0. No. 179. 



2. T. L^vis (Kiitz.) Ealfs, Brit. Desm. 146, t. xxiv. f. 3 (1848). 

 Closteriiun lave Kiitz. Phyc. Gerni. 132 (1845). 



Var. coNTiNuus Nordst. Ahj. Samlvic. 10 (1878). Long. 67 /* ; 

 lat. 25 II. 



Huilla. In paludibus exsiccaudis ; April 1860. No. 176. 



8. T. fissus, sp. n. (tab. 868, fig. 25). T. parvus, diametro 

 2^--plo longior, ad medium leviter constrictus ; semicellulfe breviter 

 oblongfc, lateribus convexis, apicibus incisura mediana profunda 

 late aperta fissis, lateribus iucisurje convexis, angulis apicalibus 

 obtuse acutis ; niembrana densissime et minutissime pauctata. 

 Long. 42 /x ; lat. max. 18 // ; lat. isthm. 15 /x. 



Huilla. In paludibus exsiccandis ; April 1860. No. 176. 



This small species has somewhat unique characters that readily 

 distinguish it from the otlier species of the genus. 



9. EuASTRUJi Ehrenb. (1832). 



1. E. acmon, sp. n. (tab. 366, ligs. 11, 12). E. subraediocre, 

 pa!ue Ifi-plo longius quam latins, profunde constrictum, sinu lineari 

 in parte niediiino, cxtremo ampliato, extrorsum aperto; scmiccllula) 

 trapezifornies lateribus multe concavis vel incadiformcs, apicibus et 

 basibus latitudine saba'(puilibus, apicibus late truncatis leviter retusis 

 ad medium ; a vertice vis;e rhomboideo-ellipticne polis subacutis ; a 

 latere visa^ rectangulares anguhs superioribus leviter rotundatis ; 

 membrana glabra. Long. 46 /x; lat. 28-31 /x; lat. apic. 23-27 /x ; 

 lat. constrict, sub apic. 15-17'5 /x ; lat. isthm. 8-9 /x ; crass. 18 /x. 

 Huilla. In uligiuosis editioribus propo Humpata, Empalanca 

 Journal of Botany. — Vol. 35. [M.\Rcn, 1897.] g 



