Relation of Pleistocene to Prehistoric Period.--Magnitude of the Interval.--Animals.--Physical changes.--Excavation and filling up of Valleys: Fisherton; Freshford.--Comparison of Deposits in Valleys with those of Caves.--Differences of Mineral Condition.--The Pleistocene Caves of Germany: Gailenreuth; Kühloch.--Of Great Britain.--The Caves of Yorkshire: Kirkdale.--Of Derbyshire: The Dream Cave.--Of North Wales, near St. Asaph.--Of South Wales, in counties of Glamorgan, Caermarthen, Pembroke.--Of Monmouth.--Of Gloucestershire.-- Of Somersetshire: Uphill, Banwell, Bleadon, Sandford Hill, Wookey Hole.--The District of Mendip higher in Pleistocene age than now.--The condition of bones gnawed by Hyænas.--The Caves of Devonshire: Oreston; Brixham; Kent’s Hole.--The probable age of the Machairodus of Kent’s Hole.--Those of Ireland, Shandon. _Relation of Pleistocene to Prehistoric Period._ We have seen, in the fifth and sixth chapters, that the caves offer valuable information as to the prehistoric ethnology of Europe, and that they prove the ancient neolithic population to stand directly related to the Basque and Celtic elements in the present inhabitants of Britain, France, and Spain. We shall discover in the course of this and the following chapters that no such continuity can be made out between the palæolithic man of the pleistocene age and any of the races now living in our quarter of the world; and we shall see that he is separated from his neolithic successor by an interval of time, the length of which cannot be measured in terms of years. Before the pleistocene group of caves be examined, it will be necessary to define the relation that exists between the prehistoric and the pleistocene periods. _The Animals--Magnitude of Interval._