The following are descriptions of two species of fresh-water Hemiptera, found commonly in the vicinity of Sydney, and which appear to be novelties. As opportunity occurs, the author hopes to supplement them with diagnoses of further species inhabiting the fresh-water creeks and ponds of New South Wales, and, if possible, of those of the neighbouring colonies :- Family Hydrometridae. Genus Hydrometra, Fab. Hydrometra Australis, sp. nov.