The resemblances consist, in fact, not so much in the existence of one general facies running through the regions, as is the case with the northern flora, but in the presence of peculiar types, such ai those belonging to the families Restiaceae, Proteaceae, Ericaceae Mutisiaceac and Rutaceae.
In the Urals the marine facies is more fully developed and the fauna shows affinities with that of the Productus limestone of the Central Asian mountain belt.
As a rule the general facies as well as dimensions are remarkably uniform throughout a family, so that tropical species -often differ little in appearance from those inhabiting temperate regions.
Pure limestones do not frequently take on schistose facies.
Upper Silurian, having a strong relation to the Wenlock group of Britain, but with an American facies, and Lower Silurian, with a succession much the same as in British North America, are found on the shores of Smith Sound, and Nathorst has discovered them in King Oscar Fjord, but not as yet so far south as the Danish possessions.