34 
Transactions of the Royal Society of South Africa. 
Akad. Handl., viii, No. 18, 1884, p. 16, Tab. I, fig. 34 ; W. & O. S. West, 
loc. cit., p. 89, PL LXXII, fig. 25-28. 
Forma angulis lateralibus ca. in media loiigitudinis semicellulae, 
marginibus omnibus plus minus retusis, apice lata et exigue retusa. Long, 
cell., 15 /X ; lat. cell., 12 /x ; lat. isthm., 3 /x ; crass., 7 fx. (Fig. 13.)- 
Sample 327 (very rare). 
In front-view this is very much like var. minimum, Eichler and Grutwinski 
(' Eozprawy Akad. TJmiej. Wydz. Mat.-Przyr. Krakow,' ser. 2, viii, 1895, 
p. 164, Tab. IV, fig. 6), but this variety is described as having an end-view 
with a slight median inflation. There is also some resemblance with 
f . minor, Boldt, and with f. minima of C. sexangulare, Lund. ; in the latter, 
however, the lower parts of the lateral margins are not retuse. It is to be 
noted that these margins differed somewhat in the specimens examined. 
Fig. 13. — Cosmarium regnellii, Wille, forma, a, front-, h, side-, and c. end-views. 
X 1100. 
especially as regards their degree of divergence ; in some cases they were 
almost subparallel, and as a consequence the degree of projection of the 
lateral angles also varied considerably. 
10. Cosmarium meneghinii, Brcb. ; W. & Gr. S. West, loc. cit., p. 90, 
PI. LXXII, figs. 29-32. 
Sample 341 (very rare). 
Forma africana, n. f. {forma "marginibus lateralibus inferioribus leviter 
divergentibus ; alioqui typo et non var. nano, Wille similis est," Fritsch, 
loc. cit., p. 555). Long, cell., 18-24 /x ; lat. cell., 12-15 /x ; lat. isthm., 5 /x. 
Samples 64, 312 (in both cases rare). 
11. Cosmarium rectangulare, Grun. ; W. & Gr. S. West, loc. cit., p. 54, 
PI. LXX, figs. 1, 2. 
Forma ad var. africaiium, W. & S. Gr. West (" Alg. Centr. Afr.," ' Journ. 
Bot.,' xxxiv, 1896, p. 879, Tab. 361, fig. 14) accedens, sed apicibus 
angustioribus (et raro leviter retusis), semicellulis a vertice visis ellipticis. 
Long, cell., 24-33 ii ; lat. cell., 18-20 /x ; lat. isthm., 5-6 /x. (Fig. 11, G.) 
Sample 327 (rather rare). 
These specimens approach closely to some of the forms of C. laeve, 
Babenh., to be described below, and it is possible that they would best be 
regarded as extreme variations of this species. As shown in Fig. 11, G, 
