The Freshwater Algae of Africa. 547 



the striation and punctation of tlie membrane (Fig. 23, b) is that 

 characteristic of this species, and that the apices are very similar, ii 

 seems justified. C. pritchardianum, which is widely represented in 

 Suutl) Africa, is evidently very variable in size, since specimens have 

 been encountered from other localities attaining a length of 1700 /x 

 ( forma gigantissima). 



In sample 5 there also occurred individuals which approached some- 

 what to var. madagascariensis, P. E. Fritsch (Freshw. Alg. Mada- 

 gascar, Ann. (1. Biol, lacustre, Tab. Y1T, fasc. i), but differed from 

 it in two respects, viz. (a) in being in part shorter and propor- 

 tionally broader (long., 550 700 /j. ; lat., 48-55 fi), and (//) in the 

 almost straight ventral margin. .Such forms tend to link up var. 

 madagascariensis and also forma maxima, Nordstedt (Nonnullae alg. 

 aq. dulc. brasil., Ofvers. K. Sv. Vet.-Ak. Foerhandl., 1877, No. 3, 

 p. 16) with the type. 



Cenus PLEUEOTAENIUM Naegeli. 



4 •> 



1. Pleurotaenium ehrenbergii (Brtb.), De Bary, op. cit., p. 

 W. & a. S. West, op. cit, i, 1904, p. l><>5, PI. XXIX, figs. 9 11. 



Samples 3, 5. 



Previously recorded by Nordstedt from the Cape. 



2. Pleurotaenium ovatum, Nordstedt, Nonnull. alg. aq. dulc. brasil., 

 Ofvers. K. Sv. Vet.-Ak. Foerhandl., 1877, No. 3, p. 18. (Syn. : 

 Docidmm ovatum, Nordstedt, Desmid., in E. Warming, Symb. ad. fl. 

 Brasil.^centr. cogn., Vid. Med. Nat. Foren. Kjobenhavn, 1809, p. 205, 

 Tab. Ill, fig. 37). 



Sample 5. 



Previously recorded by Nordstedt from the Cape. 



Genus EUASTRUM Eheenberg. 



1. Euastrum cwpense, n. sp. (Fig. 24.) 



E. parvum, circiter 1^ plo longius quam latum, profunde constric- 

 tum, sinu angusto-lineari extremo paullo ampliato. Semieellulae 

 obscure trilobae, sinu late concavo inter lobos ; lobo polari lato, apice 

 phis minus convexo, incisura mediana non profunda extus ampliata, 

 marginibus lateralibus apicis plus minus concavis, angulis apicalibus 

 dente exiguo munitis, marginibus lateralibus lobi polaris subparallelis ; 

 lobis lateralibus bilobulatis, iis superioribus rotundatis, iis inferiori- 

 bus plus minus truncatis etiam leviter emarginatis, lobulo utroque 

 plerumque dente exiguo instructo; semicellulis plerumque granulis 



38 



