Page:Quarterly Journal of the Geological Society of London, vol. 28.djvu/508

414 north of the Alps and Pyrenees. It also corresponds with the Post-glacial period, as I have used the term, and covers the vast lapse of time, extending from the beginning of the era of intense cold down to the enormous break which separates the Pleistocene from the Prehistoric division of the Tertiary period.

The magnitude of the break in time between the Late Pleistocene and Prehistoric ages may be gathered not merely from the physical evidence, but also from the disappearance from Britain, in the interval, of the following species, of which the last five, and possibly the last seven, have become extinct.

All these animals were eliminated out of the fauna before the Prehistoric deposits were accumulated; and the remainder lived on through the Prehistoric down into the Historic period.

The middle division of the Pleistocene mammalia must now be examined, or that from which the characteristic Pliocene Cervidæ had vanished and were replaced by the invading forms from the temperate zones of Northern Asia, It is represented in Britain by the mammalia obtained from the Lower Brick-earths of the Thames-valley, at Crayford, Erith, Ilford, and Gray's Thurrock, by those from the deposit at Clacton, and most probably by those from the older deposit in Kent's Hole, and by the Rhinoceros megarhinus of Oreston. They consist of

The discovery, by the Rev. O. Fisher, of a flint-flake in the undisturbed Lower Brick-earths of Crayford, in the presence of the writer, in April 1872, proves that man was living at the time of the accumulation of these fluviatile strata.

If the mammalia from these deposits be compared with the Pre-