With regard to the geography of the region, it appears that the continent of India, at an early period of the Tertiary era, was a large island, situated in a bight, or bay, formed by the Himalayas and the Hindoo Koosh range. The valleys of the Ganges and Indus formed a long estuary, into which the drainage of the Himalayas poured its silt and alluvium. Later on, an upheaval took place, converting these straits into the plains of India, connecting them with the ancient island, and forming the existing continent. The large and varied forms whose remains now lie "sealed within the iron hills" then spread over the continent, from the Irrawaddi to the mouths of the Indus, two thousand miles; and north-west to the Jhelum, fifteen hundred miles. After a long interval of repose, another great upheaval took place, which threw up a strip of the plains of India, crumpled and ridged it up to form the Sivalik Hills, and at the same time increased the elevation of the Himalayas by many thousands of feet. It would be easy to show that such events as these must have been followed by changes in climate, for the climate of a region depends largely on its physical features--the proportion of land and water, the presence of hills and mountain ranges, and their height; and it is considered probable that the physical changes above mentioned helped to bring about the extinction of this most interesting and ancient fauna. Throughout the latter part of the Tertiary era it is well known to geologists that the climate of Europe was becoming gradually colder, until at last a glacial period, or "Ice Age," was experienced, during which Northern Europe was subjected to an arctic climate, and the great ice-sheet seems to have been slowly retiring and melting away in the early part of the Stone Age. But in India there has been no such decrease in temperature, and it enjoyed in Tertiary times as warm a climate as it now has, so that both animal and vegetable life continued to flourish vigorously. By the Sivalik (or Sewalik) Hills is meant that range of lower elevations which stretches along the south-west foot of the Himalayas, for the greater portion of their extent from the Indus to the Brahmapootra, where those rivers respectively debouche from the hills into the plains of India. It extends for nearly a thousand miles, and it appears to have been entirely built up of alluvial _débris_, washed down from the Himalayas into that sea which we have already referred to as having once separated the plains of India from the great range now forming its northern boundary. The strata thus formed were subsequently upheaved to form the Sivalik Hills. Thus we see that one mountain range may help to form another one running parallel to itself. The name is derived from Siva, or Mahadeo, the Hindoo god; these hills, as well as the Himalayas, being connected in Hindoo mythology in various ways with the history of Siva.