ABSTRACT
The Pleistocene period has been defined on a palaeontological basis: by the proportion of extinct to living mollusca in its marine faunas, and by the presence of Elephas, Equus and Bos in its land fauna. It has also been defined on the basis of certain changes of sea-level. Nevertheless, the most outstanding fact about the period is its broad coincidence with the Great Ice Age. Consequently the successive glaciations have provided the most obvious means of subdividing the period, particularly in the higher latitudes.
