affect surface conditions. There are traces of periods of superabundant ice and snow, of “Glacial Ages,” that is, even in the Azoic period.
It was only towards the close of the Age of Fishes, in a period of extensive shallow seas and lagoons, that life spread itself out in any effectual way from the waters on to the land. No doubt the earlier types of the forms that now begin to appear in great abundance had already been developing in a rare and obscure manner for many scores of millions of years. But now came their opportunity.