A reference to the chart will show that the Morumbidgee, from the first of the above positions, may be said to have entered the almost dead level of the interior. No elevation occurs to the westward for several hundreds of miles. A coarse grit occasionally traversed the beds of the rivers, and their lofty banks of clay or marl appear to be based on sandstone and granitic sand. The latter occurs in slabs of four inches in thickness, divided by a line of saffron-coloured sand, and seems to have been subjected to fusion, as if the particles or grains had been cemented together by fusion. The first decided break that takes place in the level of the interior occurs upon the right bank of the Murray, a little below the junction of the Rufus with it. A cliff of from 120 to 130 feet in perpendicular elevation here flanks the river for about 200 yards, when it recedes from it, and forms a spacious amphitheatre that is occupied by semicircular hillocks, that partake of the same character as the cliff itself; the face of which showed the various substances of which it was composed in horizontal lines, that if prolonged would cut the same substance in the hillocks. Based upon a soft white sandstone, a bed of clay formed the lowest part of the cliff; upon this bed of clay, a bed of chalk reposed; this chalk was superseded by a thick bed of saponaceous earth, whilst the summit of the cliff was composed of a bright red sand. Semi-opal and hydrate of silex were found in the chalk, and some beautiful specimens of brown menelite were collected from the upper stratum of the cliff. A little below this singular place, the country again declines, when a tertiary fossil formation shows itself, which, rising gradually as an inclined plain, ultimately attains an elevation of 300 feet. This formation continues to the very coast, since large masses of the rock were observed in the channel of communication between the lake and the ocean; and the hills to the left of the channel were based upon it. This great bank cannot, therefore, average less than from seventy to ninety miles in width. At its commencement, it strikingly resembled skulls piled one on the other, as well in colour as appearance. This effect had been produced by the constant rippling of water against the rock. The softer parts had been washed away, and the shells (a bed of Turritella) alone remained. Plate 1, Figures 1, 2, and 3, represent the selenite formation. Plate 2, represents a mass of the rock containing numerous kinds of shells, of which the following are the most conspicuous: Cardium Pectunculus Corbula Arca Conus, and Others unknown. * * * The following is a list of the fossils collected from various parts of this formation, from which it is evident that a closer examination would lead to the discovery of numberless species. TUNICATA. PLATE III. FIG.1 Eschara celleporacea. 2 ------- piriformis. 3 ------- UNNAMED.