On the whole, it appears to me, in accordance with the views of Professor Ramsay, M. Mortillet, Mr. Geikie, and others, that the abrading action of ice has formed some mountain tarns and many morainic lakes; but when it is a question of the origin of larger and deeper lakes, like those of Switzerland or the north of Italy, or inland fresh-water seas, like those of Canada, it will probably be found that ice has played a subordinate part in comparison with those movements by which changes of level in the earth’s crust are gradually brought about. [1] Jamieson, Quart. Geol. Journ., 1860, vol. xvi, p. 370. [2] Bryce, Quart. Geol. Journ., vol. xxi, p. 217, 1865. [3] Geikie, Trans. Geol. Soc. Glasgow, vol. i, part ii, p. 68, 1863. [4] Milne Home, Trans. Royal Soc. Edinburgh, vol. xxv, 1868-9. [5] Quart. Geol. Journ., 1852, vol. viii, p. 372. [6] Antiquity of Man, p. 313. [7] Travels in Central Caucasus, 1869, p. 452. [8] See Principles, vol. i, p. 420, 10th ed., 1867. TERTIARY OR CAINOZOIC PERIOD CHAPTER XIII. PLIOCENE PERIOD Glacial Formations of Pliocene Age. — Bridlington Beds. — Glacial Drifts of Ireland. — Drift of Norfolk Cliffs. — Cromer Forest-bed. — Aldeby and Chillesford Beds. — Norwich Crag. — Older Pliocene Strata. — Red Crag of Suffolk. — Coprolitic Bed of Red Crag. — White or Coralline Crag. — Relative Age, Origin, and Climate of the Crag Deposits. — Antwerp Crag. — Newer Pliocene Strata of Sicily. — Newer Pliocene Strata of the Upper Val d’Arno. — Older Pliocene of Italy. — Subapennine Strata. — Older Pliocene Flora of Italy. It will be seen in the description given in the last chapter of the Post-pliocene formations of the British Isles that they comprise a large proportion of those commonly termed glacial, characterised by shells which, although referable to living species, usually indicate a colder climate than that now belonging to the latitudes where they occur fossil. But in parts of England, more especially in Yorkshire, Norfolk, and Suffolk, there are superficial formations of clay with glaciated boulders, and of sand and pebbles, containing occasional, though rare, patches of shells, in which the marine fauna begins to depart from that now inhabiting the neighbouring sea, and comprises some species of mollusca not yet known as living, as well as extinct varieties of others, entitling us to class them as Newer Pliocene, although belonging to the close of that period and chronologically on the verge of the later or Post-pliocene epoch.