Recent and Post-pliocene Periods. — Terms defined. — Formations of the Recent Period. — Modern littoral Deposits containing Works of Art near Naples. — Danish Peat and Shell-mounds. — Swiss Lake-dwellings. — Periods of Stone, Bronze, and Iron. — Post-pliocene Formations. — Coexistence of Man with extinct Mammalia. — Reindeer Period of South of France. — Alluvial Deposits of Paleolithic Age. — Higher and Lower-level Valley-gravels. — Loess or Inundation-mud of the Nile, Rhine, etc. — Origin of Caverns. — Remains of Man and extinct Quadrupeds in Cavern Deposits. — Cave of Kirkdale. — Australian Cave-breccias. — Geographical Relationship of the Provinces of living Vertebrata and those of extinct Post-pliocene Species. — Extinct struthious Birds of New Zealand. — Climate of the Post-pliocene Period. — Comparative Longevity of Species in the Mammalia and Testacea. — Teeth of Recent and Post-pliocene Mammalia. We have seen in the last chapter that the uppermost or newest strata are called Post-tertiary, as being more modern than the Tertiary. It will also be observed that the Post-tertiary formations are divided into two subordinate groups: the Recent, and Post-pliocene. In the former, or the Recent, the mammalia as well as the shells are identical with species now living: whereas in the Post-pliocene, the shells being all of living forms, a part, and often a considerable part, of the mammalia belonged to extinct species. To this nomenclature it may be objected that the term Post-pliocene should in strictness include all geological monuments posterior in date to the Pliocene; but when I have occasion to speak of the whole collectively, I shall call them Post-tertiary, and reserve the term Post-pliocene for the older Post-tertiary formations, while the Upper or newer ones will be called “Recent.” Cases will occur where it may be scarcely possible to draw the boundary line between the Recent and Post-pliocene deposits; and we must expect these difficulties to increase rather than diminish with every advance in our knowledge, and in proportion as gaps are filled up in the series of records. RECENT PERIOD It was stated in the sixth chapter, when I treated of denudation, that the dry land, or that part of the earth’s surface which is not covered by the waters of lakes or seas, is generally wasting away by the incessant action of rain and rivers, and in some cases by the undermining and removing power of waves and tides on the sea-coast. But the rate of waste is very unequal, since the level and gently sloping lands, where they are protected by a continuous covering of vegetation, escape nearly all wear and tear, so that they may remain for ages in a stationary condition, while the removal of matter is constantly widening and deepening the intervening ravines and valleys.