62 DR. G. $. WEST ON THE ALGÆ OF 
latere visæ subcirculares; membrana punctata ; chromatophoris parietalibus 
circiter 8 in semicellula unaquaque, tænia unaquaque late et irregulare cum 
pyrenoide singulo. 
Long. 16-50 ш ; lat. 72-78 ш; lat. isthm. 16-175 ш; crass. 38 p. 
Hab. Yan Yean Reservoir, in the plankton and at the weedy margins 
throughout the greater part of the year. Among the weeds it was at its 
maximum abundanee in March. 
In general appearance Cosmarium achondroides somewhat resembles 
C. depressum var. achondrum, (Boldt) W. & G. S. West, especially some of 
the large forms which occur in the British freshwater plankton. It is distin- 
guished, however, by the form of the semicells, which have a more con- 
tinuously rounded ventral border, and by the peculiar chloroplasts. The 
latter are disposed as broad parietal bands, with irregular margins. One 
pyrenoid is present in each parietal chloroplast, but its position relative to the 
centre of the semicell is very variable. 
27. COSMARIUM PSEUDOPROTUBERANS, Kirchn. Alg. Schles. 1878, p. 150. 
Var. ancustius, .Vordst. т К. Sv. Vet.-Akad. Handl. xxii. по. 8 (1888), 
р. 98, t. 6. figs. 15, 16. 
Long. 28-35 ш; lat. 23-98 ш; lat. isthm. 6-8 ш. 
Hab. Yan Yean Reservoir, at the weedy margins (Dec. 1905 and Jan. 
1906). 
Many of the Desmids recorded as C. Elfeingii, Racib. (= С. heaagonum, 
Elfv. non Nordst.), should be transferred to this variety of С. pseudo- 
protuberans. The Victorian forms were delicately punctate as in the New 
Zealand specimens, and some of them possessed the minute papilla at the 
basal angles of the semicells described by Raciborski in his C. Elfvingii var. 
savonicum (vide Pamietnik. Wydz. matem.-przyr. Akad. Umiej. Krakow. 
xvii. (1889) p. 780, t. 5. fig. 14). 
28. COSMARIUM CAPITULUM, Roy $ Biss. in Journ. Bot. 1886, p. 195, 
t. 268. fig. 9. 
Var. AUSTRALE, G. 5. West, in Victorian Naturalist, xxii. (1905) p. 71 ; 
in Journ, Bot. xliii. (1905) p. 253. 
Var. ventre semicellulæ minore, angulis capitulis leviter sursum diver- 
gentibus, 
Long. 16-19 p ; lat. 20-28; lat. isthm. 575-6 p ; crass. 85-9 и. (PI. 5. 
fig. 6.) 
Hab, Yan Yean Reservoir, at the weedy margins and in the plankton 
from Nov. to July, sometimes very abundant. 
The upwardly diverging angles of this variety give the semicells a relatively 
