In the external or upper part of the same cave, as shown in Plate 45, the floor consisted of the red dust, and was covered with loose fragments of rock, apparently fallen from conglomerated masses of limestone and breccia which also however extended under the red earth there.  Thus it would appear that traces remain in these caverns:  First, of an aqueous deposit in the red earth found below the stalagmite in one cavern, and beneath breccia in the other.  Secondly, of a long dry period, as appears in the thick crust of stalagmite covering the lowest deposit in the largest cavern, and during which some cavities were filled with breccia, even with the external surface.  Thirdly, of a subsidence in the breccia and associated rocks and, lastly, of a deposit of red earth similar to the first.

TRACES OF INUNDATION.

The present floor in both caves bears all the evidence of a deposition from water which probably filled the interior of the cavern to an unknown height.  It is clear that sediment deposited in this manner would, when the waters were drawn off, be left in the state of fine mud, and would become, on drying, a more or less friable earth.

STALAGMITIC CRUST.

Any water charged with carbonate of lime which might have been subsequently introduced would have deposited the calcareous matter in stalactites or stalagmites; but the general absence of these is accounted for in the dryness of the caves.  This sedimentary floor contained few or no bones except such as had previously belonged to the breccia, as was evident from the minuter cavities having been still filled with that substance.

I do not pretend to account for the phenomena presented by the caverns, yet it is evident, from the sediments of mud forming the extensive margins of the Darling, that at one period the waters of that spacious basin were of much greater volume than at present, and it is more than probable that the caves of Wellington Valley were twice immersed under temporary inundations.  I may therefore be permitted to suggest, from the evidence I am about to detail of changes of level on the coast, that the plains of the interior were formerly arms of the sea; and that inundations of greater height have twice penetrated into, or filled with water, the subterraneous cavities, and probably on their recession from higher parts of the land, parts of the surface have been altered and some additional channels of fluviatile drainage hollowed out.  The accumulation of animal remains very much broken and filling up hollow parts of the surface show at least that this surface has been modified since it was first inhabited; and these operations appear to have taken place subsequently to the extinction, in that part of Australia, of the species whose remains are found in the breccia; and previously to the existence, in at least the same districts, of the present species.

STATE OF THE BONES.

No entire skeleton has been discovered, and very rarely were any two bones of the same animal found together.  On the contrary even the corresponding fragments of a bone were frequently detected some yards apart (as for instance those in Figures 2 and 1 Plate 49).