It was observed both on the Macquarie river and the Morumbidgee, that the casuarinae ceased at a particular point. On the Macquarie particularly, these trees which had often excited our admiration from Wellington Valley downwards, ceased to occupy its banks below the cataract, nor were they again noticed until we arrived on the banks of the Castlereagh. The blue-gum trees, again, were never observed to extend beyond the secondary embankments of the rivers, occupying that ground alone which was subject to flood and covered with reeds. These trees waved over the marshes of the Macquarie, but were not observed to the westward of them for many miles; yet they re-appeared upon the banks of New-Year's Creek as suddenly as they had disappeared after we left the marshes, and grew along the line of the Darling to unusual size. But it is remarkable, that, even in the midst of the marshes, the blue-gum trees were strictly confined to the immediate flooded spaces on which the reeds prevailed, or to the very beds of the water-courses. Where the ground was elevated, or out of the reach of flood, the box (unnamed) alone occupied it; and, though the branches of these trees might be interwoven together, the one never left its wet and reedy bed, the other never descended from its more elevated position. The same singular distinction marked the acacia pendula, when it ceased to cover the interior plains of light earth, and was succeeded by another shrub of the same species. It continued to the banks of New-Year's Creek, a part of which it thickly lined. To the westward of the creek, another species of acacia was remarked for the first time. Both shrubs, like the blue-gum and the box, mixed their branches together, but the creek formed the line of separation between them. The acacia pendula was not afterwards seen, but that which had taken its place, as it were, was found to cover large tracts of country and to form extensive brushes. Many other peculiarities in the vegetation of the interior are noticed in the body of this work, but I have thought that these more striking ones deserved to be particularly remarked upon. GEOLOGICAL FEATURES.