The most apparent traces of a radical change of climate have been left by the period immediately preceding our own. It is the one known to geologists as the Quaternary, and more popularly as the glacial period. The reg is geologically young and belongs to the Quaternary stage; while the Egyptian serir, although a formation of analogous origin, dates back to some previous fluvial period so much more remote that all traces of its erosion have been obliterated. The elephant of Carthage then had already become a distinct species, degenerated and tending toward dwarfism, as would be natural in an animal belonging to a residual fauna. And for an animal species to become thus individualized requires a period of time infinitely exceeding the limits of human memory and experience, even though it be short in geological chronology.