angular. Inflations doubtful, no specimen having been seen without endochrome. Long., 11.4 μ; lat., 13.2 μ; crass., 3.2 μ. Christchurch. If it were not for the concave ends and for the appearance in end-view, this plant would belong more properly to the genus Cosmarium. It is exceedingly minute, and not common. * Euastrum denticulatum, Kirchner. Plate II., fig. 11. This appears to be one of the innumerable varieties of E. binale, Ralfs. It is the plant of which a rough representation was given by me in 1880 (“Trans.,” vol. xiii., pl. xii., 26):. the present figure is more accurate. Nordstedt (“Alg. of N.Z.,” pl. iii., fig. 11) represents this plant as “sp. ad E. denticulatum accedens,” and in his fig. 9 he shows Kirchner's original type as a good deal smaller. The two sizes occur here together. I can detect only one median inflation on each segment in front-view. The side-view which I give is less “ornate” than that of Nordstedt (iii., 11c): it is taken from two specimens observed. Hawke's Bay; Christchurch. Euastrum binale, Ralfs, forma. Plate II., fig. 12. This seems to be nearer than the last to the original type, although it does not seem to fit it exactly. Christchurch. The variations of E. binale would appear to be endless. Ralfs, Lundell, Delponte, Wolle, all give figures which differ a good deal from each other. Especially Wolle describes and figures E. binale as distinguished by the “pouting” of the ends at each side of the terminal notch, this very character being a distinctive one of E. elegans. In fact, there is so much difference in these figures that one wonders why some of the plants have not been transferred to other species. My figure 12, which I take to be E. binale because its ends do not exhibit any “pouting,” is very similar to one of Wolle's exhibit any “pouting,” of U.S.,” pl. xxvii., 25) which he names E. elegans. Euastrum undulosum, sp. nov. Plate II., fig. 13. Frond moderate; constriction deep, linear; segments in front-view trapezoidal, tapering directly from the base to the rather wide ends; sides crenate, each with four equal crenations; ends wide, angles divergent, with minute terminal spines, slightly protuberant towards the middle and emarginate; notch conspicuous; at the base of each segment is a single median conspicuous inflation, and on the face of the frond a number of concentric verrucose undulations. In side-view the constriction is shallow and wide, the inflation visible;