the northern fauna could advance into England, either before its commencement, or towards its close; while the southern fauna would only penetrate into the country during the maximum period of its geniality. Professor Geikie informs us in the extract just quoted that "the valley- and cave-deposits are approximately contemporaneous," a statement which appears to me doubtful in the present state of our knowledge. The implements of the cave-dwellers are not only different in type from those of the valley gravels in Britain and on the Continent, but also the fauna of the former have considerably changed. Prior to the most flourishing phase of the reindeer period, the early elephants, rhinoceroses, hippopotamuses, some African species, and other characteristic fauna of the river gravels, disappeared from Central Europe. It would also appear that it was during this interglacial period, which was posterior to the boulder clay and its concomitant land submergence, that some of the southern fauna spread as far north as the Victoria cave and the Welsh caverns. It was then that Palæolithic Man first appeared on the scene in Western Europe; and it is to be particularly noted that his industrial remains, as disclosed by the gravel beds of the south of England, and the Chelléen and Acheuléen deposits of France, are almost identical. Subsequent to this warm epoch came another ice age, but of smaller dimensions, during which man was forced to take refuge in caverns and natural rock shelters. This corresponds with the Moustérien epoch and its cultural elements. The hunters of wild animals, who then took up their abode in the Dordogne, continued to make this favoured locality their headquarters till the close of the Palæolithic period and the disappearance of the reindeer from France.
Whatever may have been the exact physical and climatal conditions that brought these heterogeneous floras and faunas together on the plains of Central and Southern Europe, whether genial interglacial periods, or extremes of temperature in the summers and winters, I will not venture to decide. One thing, however, is certain, that the succession of such extreme changes in the climate taxed the life-capacity and power of endurance of the Pleistocene mammalia to a degree which ultimately became unbearable. Now they have nearly all dis-
