30 
Transactions of the Royal Society of South Africa. 
prove to resemble those of 0. nitiduhirti, De Not., the former species would 
be better regarded as a variety of the latter. 
The membrane of var. tuberculatum often showed a minute granulation, 
but its presence was not always determinable. 
2. Cosmarium undulatum, Corda; W. & G. S. West, lac. cit., p, 148, 
PI. LIX, figs. 1-3, 5. 
var. crenulatum (Naeg.), Wittr. ; W. & G-. West, loc. cit., p. 150, 
PI. LIX, figs. 11, 12. (Syn. : Euastrum crenulatum, Naegeli, G-att. einzell. 
Alg., 1849, p. 120, Tab. VII, A, fig. 7.) (Fig. nostr. 11, A.) 
Sample 327 (rare). 
Long, cell., 21-22 /x; lat. cell., 16-17 ft; lat. isthm. 6 [x. The dimensions 
are rather less than those given in Messrs. West's monograph, but Nordstedt 
C Oefvers. K. Vet.-Akad. Foerhandl.,' Stockholm, 1872, No. 6, p. 32) has 
already recorded specimens of this variety measuring 24 /x in length and 
20 /X in breadth. 
3. Cosmaritmi hammeri, Eeinsch ; W. & G. S. West, loc. cit., p. 181, 
PI. LXII, figs. 20, 21. 
Sample 86 (rare). 
Long, cell., 45 /x ; lat. cell., 33 /x ; lat. isthm., 12 ju. 
var. africanum, F. E. Fritsch, nov. var. (Fig. 11, B). 
C. l^^-l^plo longius quam latum ; semicellulae apicibus truncatis vel 
leniter convexis (interdum obliquis), marginibus lateralibus superioribus 
late concavis, marginibus lateralibus inferioribus convexo-rotundatis vel 
raro subangularibus, interdum subrectis ; a vertice visae ellipticae, polis 
rotundatis, inflatione mediana distincta; a latere visae subcirculares vel 
elliptico-circulares. Membrana indistincte granulata. 
fl fJ. ft ^ fi fX 
Long. cell. . 27 . 27 . 27 . 28 . 30 . 30 
Lat. cell. . 21 . 23 . 24 . 24 . 24 . 25 
Lat. isthm., 6-8 /x. Lat. apic, 10-11 /x. Crass., 15 /x. 
Sample 86 (very rare), 327 (not uncommon). 
This variety appears to be rather widely distributed in South Africa, 
as it has also been observed in samples from other parts. The reference 
to 0. hammeri, Keinsch, seems correct, since in front-view there is much 
resemblance to var. homalodermum (Nordst.), W. & G. S. West, which is 
much bigger, and var. ^protuherans, W. & G. S. West, in which, however, 
to judge by the figures given by Messrs. West, the upper part of the lateral 
margins is not nearly so markedly concave. The new variety, however, 
differs from both of those just mentioned in the fact that the apex is 
truncate (Fig. 11, B, a, a") or even slightly convex (Fig. 11, B, a), 
and only very exceptionally faintly retuse; obliquity of the apex is not 
uncommon (Fig. 11, B, a), and, when pronounced, has a curious effect on 
the side-view, which then appears to bear an apical papilla. The granulation 
