Towards the end of the period, however, during the deposition of the Portlandian beds, the sea again retreated, and in the early part of the Cretaceous period was limited (in France) to the catchment basins of the Sane and Rhnein the Paris basin the contemporaneous deposits were chiefly estuarine and were confined to the northern and eastern rim.
They are also preserved in basins on the western plateau, as shown by brown coal deposits passed through in the Lake Phillipson bore.
From the Oligocene deposits of France and southern England have been obtained numerous remains of opossums referable to the American family Didelphyidae.
The same deposits have yielded remains of small mammals whose dentition approximates more nearly to that of either polyprotodont marsupials or insectivores; and these may be conveniently noticed here without prejudice to their true affinities.
Cambrian rocks occur in each of these districts, and they are best developed in the South Australian high= lands, where they include a long belt of contemporary glacial deposits.
