Contributions to Our Knowledge of the Freshwater Algae of Africa. 41 
30-33 /x; Lat., 24-29 (usually 27-29 /x, only specimen II being as narrow 
as 24 /x) ; lat. istlmi., 6-6*5 /x ; crass., 15-18 /x. The granules of these 
larger specimens are more numerous and apparently somewhat smaller than 
those of the others, whilst the central tumour is on the average less strongly 
developed — in fact, in some cases it is practically unrecognisable in side-view 
(Fig. 15, V). 
It appears that two main types are concerned, viz. («) a larger one 
(average length, 30-33 /x), with more or less convex lateral margins 
gradually converging from the base of the semicell to the apex, and rather 
numerous lateral crenations which are equal or subequal (Fig. 15, I, II, V), 
and (h) a smaller one (average length, 21-22 /x), with the lower parts of the 
lateral margins subparallel, and a pronounced larger, generally retuse, crest 
on the upper parts of the lateral margins (Fig. 15, VII-X). Transitions to 
Fig. 16. — Cosmarixims%ibiyrotumidiim,'^ov({s,t. A. Abnormal specimen, similar 
to that shown in Fig. 15, II. B. Almost typical semicell. x 750. 
type (6) are afforded by specimens III and IV, whilst transitions to type {a) 
are seen in VI and XI. It must be realised that there is no question of 
any sharp demarcation, however ; if occasion had offered for the presentation 
of still more numerous figures, a complete series of transitions could have 
been shown. 
It would seem to be best to include all these specimens in a subspecies 
simplex, characterised by feeble development of the central tumour, which 
lacks all special granulation, by uniform and generally concentric granula- 
tion of the entire semicells, and by a smooth truncate apex. I would 
include in this subspecies the form described by W. West {cf. above), and 
also 0. occultum, Schmidle. Brief diagnoses are given in the following : 
Cosmarium suh'protumiclimi, Nordst., subsp. simplex, F. E. Fritsch, nov. 
subsp. : Dift'ert a typo tumore centrali parvo sine granulis majoribus vel 
distincte dispositis ; granulis in tota superficie semicellularum aequalibus 
plerumque concentricis ; apicibus semicellularum planis truncatis. Long. 
