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.
The same deposits have also yielded remains of extinct types of kangaroo, some of gigantic size, constituting the genera Sthenurus, Procoptodon and Palorchestes.
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.