The collection of Tunicata obtained during the trawling operations of the "Thetis" comprises twenty-five species, and most of these are familiar Australian forms. Three of the species appear to be new to science, and three are in such poor condition that they cannot be named with certainty. That no representatives of peculiar or exceptional genera were obtained is quite natural when we remember that the expedition was undertaken mainly for fisheries purposes, and that consequently the "Thetis" worked along the coasts of the State, north and south of Port Jackson, always within the 100 fathom line, and never more than thirty miles from shore. When we add that the Australian Tunicate fauna, and especially that of New South Wales, is one of the best known in the world, the small number of novelties found in this collection will cause no surprise. Believing, as we do, that the further elucidation of known forms is quite as important for science as the diagnosis of new species, we have not hesitated to add to this Report particulars ascertained from the "Thetis" specimens in regard to the structure and affinities of species already known to science.