front-view sub-semicircular, basal angles slightly rounded; edges incised with numerous (eighteen to twenty on each) crenulations, of which the little elevations are truncate; cytioderm apparently slightly grooved just within the edge; in the centre of each segment a circular granuliferous inflation, the granules, arranged more or less concentrically, and connected by a network of fine rays; between the inflation and the edge are three concentric rows of granules. End-view elliptical, the edges crenulate, the median inflation conspicuous, sub-orbicular; on the surface are six rows of granules, arranged longitudinally. Long., 50 μ; lat., 33–36 μ; crass., 18 μ ex. inflat. Rutherford's Swamp, Otaki. This handsome plant is apparently an intermediate form between the original C. quadrifarium, and its varieties hexastichum, Lundell, and octastichum, Nordstedt. From the former it differs in having six rows of granules in end-view instead of four, and from the two latter in having the granules on the median inflation arranged more or less concentrically instead of in direct rows. The network of rays connecting these granules appears to be a character visible in the var. octastichum. The edges in end-view in my specimens do not exhibit such conspicuous “papillæ” as those figured by Lundell and Wolle, but have obscure crenulations. I have not seen the zygospore, which in C. quadrifarium is quadrate, a rather unusual form amongst Cosmaria. Genus Xanthidium, Ehrenberg. Xanthidium intermedium, sp. nov. Plate IV., fig. 33. Frond large; constriction deep, linear; segments in front-view sub-trapezoidal, widely and roundly inflated at the base, then tapering and slightly concave towards the ends, which are wide and straight, the angles very slightly dilated. Cytioderm punctate. On each segment are a number of strong simple spines, neither dilated nor forked: most of these are disposed in groups on the edges of the basal inflations in front-view, others in pairs or in threes on the ends and at the terminal angles, a few are scattered or in short rows on the surface. Median inflation not to be made out in front-view; granules none. End-view elliptical, with a very slight median inflation; the spines arranged in a longitudinal band, most numerous towards the two ends, and with a parallel row of only a few spines at each side of the band. Long., 89 μ; lat., 71.5 μ; crass., 35.5 μ; long. spin., 4.5 μ. Rutherford's Swamp, Otaki. The main distinction, it would seem, between the genera Cosmarium and Xanthidium lies in the usually truncate and granular projection which, in addition to the spines, occupies