Plate XV. 
Figs, 1a, 1b, 1c.—Xanthidium superbum, forma, Borge, x 740. 
Fig. 2.—Cosmarium excavatum, forma, Borge, x 740. 
Fig. 3.—Cosmarium venustum, forma, Borge, x 740. 
Fig. 4,—Cosmarium excavatum, forma, Borge, x 740. 
Figs, 5a, 5b, 5e,—Cosmarium Sectioubatce: Borge, b. sp., x 390. 
Fig. 6.—Cosmarium pseudobroomei, Wolle, x 390. 
Fig. 7a, 7c.—Cosmarium securiforme, Borge, n. sp., x 390. 
Figs. 8a, 8c.—Cosmarium pseudoprotuberans, forma, Borge, x 740. 
Figs. 9a, 9d.—Cosmarium Askenasyi, forma, Borye, x 390. 
Figs. 10a, 10d, 10¢.—Cosmarium dubium, Borge, n. sp., x 740. 
Figs. 11a, 11¢.—Cosmarium binum, var. australiensis, Borge, 1. vate, X 
Fig. 12.—Euastrum sp., Borge, x 740. = 
Fig. 13,—Micrasterias sp., Borge, x 740. 
Figs. 14a, 14d,—Cosmarium Askenasyi, forma, Borge, x 390. 
