INTRODUCTION. XXill 
When the eocene and other foundations of our present 
island had risen from the deep and become the seat of 
fresh-water lakes, receiving their tranquil deposits with 
the abundant shells of their testaceous colonies, and 
during the long progress of that slow and unequal eleva- 
tion which converted chains of lakes into river-courses, 
an extensive and varied Mammalian Fauna, as distinct 
from the miocene as this from the eocene series, ranged the 
banks or swam the waters of those ancient lakes and 
rivers. Of these pliocene Mammals, we have abundant 
evidence in the bones and teeth of successive generations 
which have been accumulated in the undisturbed stratified 
lacustrine and fluviatile formations. The like evidence is 
given by the existence of similar remains in local drifts, 
composed of gravel, exclusively derived from rocks in 
the immediate vicinity of such drift, without a single 
intermixture of any far transported fragments. Equally 
conclusive and more readily appreciable proof, that the now 
extinct pliocene and pleistocene Mammalia actually lived 
and died in this country, has been brought to light from 
the dark recesses of the caves which served as lurking- 
places for the predaceous species, and as charnel-houses to 
their prey. 
At the period indicated by those superficial stratified 
and unstratified deposits, the Mastodon had probably dis- 
appeared from England: but gigantic Elephants of nearly 
twice the bulk of the largest individuals that now exist in 
Ceylon and Africa, roamed here in herds, if we may judge 
from the abundance of their remains. Two-horned Rhi- 
noceroses, of at least two species, forced their way through 
the ancient forests, or wallowed in the swamps. The 
lakes and rivers were tenanted by Hippopotamuses as 
bulky and with as formidable tusks as those of Africa. 
