Therefore, the tropical Atlantic waters must have been reduced to a lower temperature during a frigid age than the tropical waters of the Indian Ocean or the western part of the tropical Pacific, as a large portion of the great equatorial current of the latter oceans, during its western movement, was exposed to the rays of a tropical sun for a much longer time, after being replenished by the cold waters of the high latitudes, than the tropical currents of the Atlantic; and it is probable that, on account of tropical America possessing a colder climate than the tropical lands of the eastern continent during the frigid epoch, the cold of the western continent was more destructive to its fauna and flora than was the case in the tropical regions of the eastern continent. Professor Wright, in his valuable work on “The Ice Age of North America,” gives a good description of the “flight of plants and animals during the glacial epoch,” and also of the extermination of many superior species because of the frigid climate. The high lands of tropical Africa, above the altitude of three thousand feet, and situated in places of great precipitation, were probably covered with snow and ice during the glacial age. Travellers have reported that islands composed partly of granite bowlders are found in the lakes at the head-waters of the Nile. But the glaciers that invaded the tropical latitudes were of short duration compared with the ice-sheets that burdened the lands of the temperate zones. Besides, such tropical ice as flowed to the low lands was so near a melting condition that it made small impression on the rocks; but on steep mountain slopes, where the movement of the ice was comparatively rapid, it possessed considerable eroding power. The climate of the tropical zone on both continents during the perfection of an ice period was so cold that such animals as could not endure a low temperature retreated into the warmest regions of the equatorial latitudes, while many species who failed to reach such places perished. And especially was this the case with the pre-glacial fauna of the western continent. Mr. W. B. M. Davidson, in his treatise on Florida phosphates, says: “The great mammal hordes of the glacial epoch were driven into Florida in their flight southward for life and warmth, and there perished because of the deadly cold which ever moved southward. The Florida waters grew so icy cold, fishes, reptiles, and mammoth animals died, and added their frames and teeth to the valley of bones now found in that southern region.” Such species of the tropical fauna of the ocean as survived the ice age could have existed only in torrid seas with small connection with the cold oceans during the frigid epochs. For, with the diminished oceans of a cold period, it seems that the conditions were favorable for the maintenance of such seas in the region of the East India Islands.