The plant which I reported as “Cos. ralfsii, var. β” (“Trans.,” 1882, vol. xv., p. 239), may perhaps have been a still smaller form of the same plant; but I have not now any specimens to which to refer. * Cosmarium trilobulatum, Reinsch, var. basichondrum, Nordstedt. Plate II., fig. 19. Long., 18 μ; lat., 12 μ. Otaki. My measurements are a little less than those given by Professor Nordstedt (“Alg. of N.Z.,” p. 57). Cosmarium cordanum, Brébisson, forma minor. Plate II., fig. 20. Long., 30 μ; lat., 15 μ; crass., 12 μ. Rutherford's Swamp, Otaki. I have never seen the original figures of this plant, and have judged from those given of it by Wolle (“Fresh. Alg. of U.S.,” pl. lx.) and by Turner (“Journ. Roy. Micr. Soc.,” Dec., 1885). With these it agrees nearly in all but size, and perhaps a little more angular form in side-view. * Cosmarium repandum, Nordstedt. Plate II., fig. 21. I think my specimens have rather more sinuous sides than the type. Cosmarium speciosum, Lundell, forma genuina. Plate II., fig. 22. Long., 50 μ; lat., 26.8 μ; crass., 17 μ. Hawke's Bay. The dimensions of this plant seem to vary. Wolle says that the American forms are much larger than the Swedish. Cosmarium speciosum, Lundell, var. simplex, Nordstedt. Plate II., fig. 23. Long., 40–45 μ; lat., 28–32 μ; crass., 15–17 μ;. Hawke's Bay. This plant is less angular than the type; but I scarcely like to consider it at present as a new variety. Hereafter it may be separated on account of its rounder form. * Since completing this paper I have received from Dr. Nordstedt a tracing of C. speciosum, forma intermedia, Wille (“Desm. of Nov. Zemlya”), which appears to be perhaps nearer our plant than the var. simplex. * Cosmarium sub-speciosum, var. validius, Nordstedt. Plate II., fig. 24. This plant, in vol. xv. of our “Transactions,” I reported as C. speciosum, var. inflatum. Professor Nordstedt has placed it more correctly as above.