Members of the allied order of the Radiolaria have a flinty shell ([Fig. 37]); and these organisms are often found building up siliceous rocks such as cherts ([Fig. 38]).
PLANTS.—The harder portions of plants which are found in the fossil state are,—the wood, the coarser vascular (vessel-bearing) tissue of the leaves, and the harder parts of fruits and seeds.
Fossil wood is of frequent occurrence in Palaeozoic, Mesozoic and Cainozoic strata in Australia, as, for instance, the wood of the trees called Araucarioxylon and Dadoxylon in the Coal measures of New South Wales (see antea, [Fig. 3]).
Fig. 38—Radiolaria in Siliceous Limestone.
× 40. Middle Devonian: Tamworth, New South Wales.
(From Prof. David’s Collection).
