The material which has given occasion for the following notes was obtained from the Richmond River and tributary creeks, principally in the neighbourhood of Lismore, during the spring and summer of 1912-13. Lismore lies on the North arm of the river at the head of the navigable portion, and my richest gatherings were made in the short stretch of river, almost undisturbed by traffic, between the bridge and the boatshed. Here, on either side, were to be found huge beds of weed, chiefly Myriophyllum and Elodea, many yards in extent, and reaching right up to the surface of the water. The river remained undisturbed by heavy rains from the end of September, 1912, to the beginning of February, 1913, and the current being very slow indeed, the surface of these weed-beds became increasingly rich in both plant and animal life. Upon two occasions gatherings were made with silk plankton-nets, but these proved disappointing, nothing being obtained but Coscinodiscus lacustris and a few other diatoms, and as the weed-beds themselves constituted a very efficient filter, it was determined to rely altogether upon them.