Before returning to Calcutta the specimens described in his memoir “Ordovician and Silurian Fossils from Yun-nan” (1917, Palseont. Ind., N.S., vol. VI, Mem. 3), Dr. F. R. Cowper Reed very kindly lent to the Geological Department of the British Museum the figured cystids, in order that plaster casts of them might be made and kept there for reference. This was done, and a set of the casts was also furnished by the Department to the Sedgwick Museum, Cambridge. While preparing the specimens for the moulder, I had the opportunity of studying them with some care. Although Dr. Reed has published good figures, drawn with Mr. T. A. Brock's usual exactitude, and descriptions, on the fulness of which he will perhaps allow me to compliment him, nevertheless the notes made by me, when still unacquainted-with his valuable work or with the views therein expressed, do contain supplementary matter, which it seems better to publish now rather than to reserve for some revision in an uncertain future.