2. That in which the characteristic pleiocene deer had disappeared. The even-toed ruminants are principally represented by the stag, the Irish elk, the roe, bison, and urus. _Elephas meridionalis_ and _Rhinoceros etruscus_ had retreated to the south. To this group belong the brick-earths of the lower valley of the Thames, the river-deposit at Clacton, the cave of Baume in the Jura, and a river-deposit in Auvergne. 3. The third division is that in which the true arctic mammalia were among the chief inhabitants of the region; and to it belong most of the ossiferous caves and river-deposits in middle and northern Europe. These three do not correspond with the preglacial, glacial, and postglacial divisions of the pleistocene strata, in central and north Britain; since there is reason to believe that all the animals which occupied Britain after the maximum cold had passed away, had arrived here in their southern advance before that maximum cold had been reached; or, in other words, were both pre- and postglacial. This classification does not apply to pleistocene river-strata south of the Alps and Pyrenees, into which the arctic mammalia never penetrated. _The Late Pleistocene Division._ The late pleistocene division corresponds in part with the reindeer period of M. Lartet; but it comprehends also his other three periods; for the spotted hyæna, the lion, the cave-bear, the mammoth, the woolly rhinoceros, the bison, the reindeer, and the urus are so associated together in the caves and river deposits of Great Britain and the continent that they do not afford a means of classification. The arctic division of the mammalia, defined in the preceding chapter, was then in full possession of the area north of the Alps and Pyrenees, and the _Rhinoceros megarhinus_ and _Elephas meridionalis_ had disappeared. With three exceptions, to be noticed presently, all the ossiferous caverns of France, Germany, and Britain, belong to this division of the pleistocene. _The Middle Pleistocene Division._ The middle division of the pleistocene mammalia may now be examined, or that from which the characteristic pleiocene deer 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 of the older deposit in Kent’s Hole, and by the _Rhinoceros megarhinus_ of Oreston.[268] They consist of--