Range-in-Time of Fossils in Australasian Sedimentary Rocks. _E.M., del._] ] [Illustration: =Fig. 14.--Skeleton of Diprotodon australis, Owen.= Uncovered in Morass at Lake Callabonna, South Australia. (_By permission of Dr. E. C. Stirling_). ] CHAPTER IV. HOW FOSSILS ARE FOUND: AND THE ROCKS THEY FORM. As already noticed, it is the hard parts of buried animals and plants that are generally preserved. We will now consider the groups of organisms, one by one, and note the particular parts of each which we may reasonably expect to find in the fossil state. MAMMALS.--The bones and teeth: as the _Diprotodon_ remains of Lake Callabonna in South Australia (Fig. 14), of West Melbourne Swamp, Victoria, and the Darling Downs, Queensland. Rarely the skin, as in the carcases of the frozen Mammoth of the tundras of Northern Siberia; or the dried remains of the _Grypotherium_ of South American caves. [Illustration: =Fig. 15.--Bird Bones.= Exposed on Sand-blow at Seal Bay, King Island. (_Photo by C. L. Barrett_). ] [Illustration: =Fig. 16.--Impression of a Bird's Feather in Ironstone.= About 2/3 nat. size. Of Cainozoic (? Janjukian) Age. Redruth, Victoria. (_Nat. Mus. Coll._) ] [Illustration: =Fig. 17.--Notochelone costata, Owen sp. (Anterior portion of carapace.)= About 1/4 nat. size. A Marine Turtle from the Lower Cretaceous of Flinders River, Queensland. (_Nat. Mus. Coll._) ] BIRDS:--Bones: as the Moa bones of New Zealand and the Emu bones of the King Island sand-dunes (Fig. 15). Very rarely the impressions of the feathers of birds are found, as in the ironstone occurring in the Wannon district of Victoria (Fig. 16), and others in fine clays and marls on the continent of Europe and in England. Fossil eggs of sea-birds are occasionally found in coastal sand-dunes of Holocene age. REPTILES.--Skeletons of fossil turtles (_Notochelone_) are found in Queensland (Fig. 17). Whole skeletons and the dermal armour (spines and bony plates) of the gigantic, specialised reptiles are found in Europe, North America, and in other parts of the world. FISHES.--Whole skeletons are sometimes found in sand and clay rocks, as in the Trias of Gosford, New South Wales (Fig. 18), and in the Jurassic of South Gippsland. The ganoid or enamel-scaled fishes are common fossils in the Devonian and Jurassic, notably in Germany, Scotland and Canada: and they also occur in the sandy mudstone of the Lower Carboniferous of Mansfield, Victoria.