Tasmanian diatomaceae

The swiftly flowing South Esk River, confined to its narrow bed, in which numerous rock pools have been worn, the North Esk, a placid stream, subject to tidal influence for some miles; aud the Tamar River, formed by the junction of these two, with a 40-miles course to the sea, and a gradually increasing salinity, offer a specially favourable habitat for various genera aud species of the Diatomacae, and it is interesting to note the distribution of the genera — in some cases indifferent to most severe changes in conditious, in others susceptible to the slightest influences. Thus Actinocyclus Barkleyi I have found at the First Basin, a mile above the bridge, in fresh water, in company with Synedra splendens and Nitzchia rigida and Nitzchia viridis.